1
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Kang CJ, Guzmán-Clavel LE, Lei K, Koo M, To S, Roche JP. The exocyst subunit Sec15 is critical for proper synaptic development and function at the Drosophila NMJ. Mol Cell Neurosci 2024; 128:103914. [PMID: 38086519 DOI: 10.1016/j.mcn.2023.103914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2023] [Revised: 12/04/2023] [Accepted: 12/05/2023] [Indexed: 12/18/2023] Open
Abstract
The exocyst protein complex is important for targeted vesicle fusion in a variety of cell types, however, its function in neurons is still not entirely known. We found that presynaptic knockdown (KD) of the exocyst component sec15 by transgenic RNAi expression caused a number of unexpected morphological and physiological defects in the synapse. These include the development of active zones (AZ) devoid of essential presynaptic proteins, an increase in the branching of the presynaptic arbor, the appearance of satellite boutons, and a decrease in the amplitude of stimulated postsynaptic currents as well as a decrease in the frequency of spontaneous synaptic vesicle release. We also found the release of extracellular vesicles from the presynaptic neuron was greatly diminished in the Sec15 KDs. These effects were mimicked by presynaptic knockdown of Rab11, a protein known to interact with the exocyst. sec15 RNAi expression caused an increase in phosphorylated Mothers against decapentaplegic (pMad) in the presynaptic terminal, an indication of enhanced bone morphogenic protein (BMP) signaling. Some morphological phenotypes caused by Sec15 knockdown were reduced by attenuation of BMP signaling through knockdown of wishful thinking (Wit), while other phenotypes were unaffected. Individual knockdown of multiple proteins of the exocyst complex also displayed a morphological phenotype similar to Sec15 KD. We conclude that Sec15, functioning as part of the exocyst complex, is critically important for proper formation and function of neuronal synapses. We propose a model in which Sec15 is involved in the trafficking of vesicles from the recycling endosome to the cell membrane as well as possibly trafficking extracellular vesicles for presynaptic release and these processes are necessary for the correct structure and function of the synapse.
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Affiliation(s)
- Chris J Kang
- Neuroscience Program, Amherst College, Amherst, MA 01002, United States of America
| | - Luis E Guzmán-Clavel
- Neuroscience Program, Amherst College, Amherst, MA 01002, United States of America
| | - Katherine Lei
- Neuroscience Program, Amherst College, Amherst, MA 01002, United States of America
| | - Martin Koo
- Neuroscience Program, Amherst College, Amherst, MA 01002, United States of America
| | - Steven To
- Neuroscience Program, Amherst College, Amherst, MA 01002, United States of America
| | - John P Roche
- Neuroscience Program, Amherst College, Amherst, MA 01002, United States of America; Department of Biology, Amherst College, Amherst, MA 01002, United States of America.
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2
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Rossi G, Puller GC, Brennwald P. Asymmetric tethering by exocyst in vitro requires a Rab GTPase, an R-SNARE and a Sac1-sensitive phosphoinositide lipid. Mol Biol Cell 2024; 35:br8. [PMID: 38198574 PMCID: PMC10916868 DOI: 10.1091/mbc.e23-08-0311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 12/22/2023] [Accepted: 01/05/2024] [Indexed: 01/12/2024] Open
Abstract
Tethering factors play a critical role in deciphering the correct combination of vesicle and target membrane, before SNARE complex formation and membrane fusion. The exocyst plays a central role in tethering post-Golgi vesicles to the plasma membrane, although the mechanism by which this occurs is poorly understood. We recently established an assay for measuring exocyst-mediated vesicle tethering in vitro and we have adapted this assay to examine the ability of exocyst to tether vesicles in an asymmetric manner. We demonstrate that exocyst differs from another post-Golgi vesicle tethering protein, Sro7, in that it is fully capable of tethering vesicles with a functional Rab GTPase, Sec4, to vesicles lacking a functional Rab GTPase. Using this assay, we show that exocyst requires both the Rab and R-SNARE, Snc1, to be present on the same membrane surface. Using Sac1 phosphatase treatment, we demonstrate a likely role for phosphoinositides on the opposing Rab-deficient membrane. This suggests a specific model for exocyst orientation and its points of contact between membranes during heterotypic tethering of post-Golgi vesicles with the plasma membrane.
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Affiliation(s)
- Guendalina Rossi
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Gabrielle C. Puller
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
- Curriculum in Genetics and Molecular Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
| | - Patrick Brennwald
- Department of Cell Biology and Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
- Curriculum in Genetics and Molecular Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599
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3
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Guleria VS, Quadri N, Prasad K, Das R, Upadhyai P. Early insights into the role of Exoc6B associated with spondyloepimetaphyseal dysplasia with joint laxity type 3 in primary ciliogenesis and chondrogenic differentiation in vitro. Mol Biol Rep 2024; 51:274. [PMID: 38305850 DOI: 10.1007/s11033-023-09114-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 12/06/2023] [Indexed: 02/03/2024]
Abstract
BACKGROUND Spondyloepimetaphyseal dysplasia with joint laxity type 3 (SEMDJL3) is a rare skeletal dysplasia associated with EXOC6B, a component of the exocyst complex, involved in vesicle tethering and exocytosis at the plasma membrane. So far, EXOC6B and the pathomechanisms underlying SEMDJL3 remain obscure. METHODS AND RESULTS Exoc6b was detected largely at the perinuclear regions and the primary cilia base in ATDC5 prechondrocytes. Its shRNA lentiviral knockdown impeded primary ciliogenesis. In Exoc6b silenced prechondrocytes, Hedgehog signaling was attenuated, including when stimulated with Smoothened agonist. Exoc6b knockdown deregulated the mRNA and protein levels of Col2a1, a marker of chondrocyte proliferation at 7- and 14-days following differentiation. It led to the upregulation of Ihh another marker of proliferative chondrocytes. The levels of Col10a1, a marker of chondrocyte hypertrophy was enhanced at 14 days of differentiation. Congruently, Axin2, a canonical Wnt pathway modulator that inhibits chondrocyte hypertrophy was repressed. The expression of Mmp13 and Adamts4 that are terminal chondrocyte hypertrophy markers involved in extracellular matrix (ECM) remodelling were downregulated at 7 and 14 days of chondrogenesis. Bglap that encodes for the most abundant non-collagenous bone matrix constituent and promotes ECM calcification was suppressed at 14 days of chondrocyte differentiation. ECM mineralization was assessed by Alizarin Red staining. Gene expression and ciliogenesis were investigated by reverse transcription quantitative real-time PCR, immunoblotting, and immunocytochemistry. CONCLUSIONS These findings provide initial insights into the potential role of Exoc6b in primary ciliogenesis and chondrogenic differentiation, contributing towards a preliminary understanding of the molecular pathomechanisms underlying SEMDJL3.
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Affiliation(s)
- Vishal Singh Guleria
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Neha Quadri
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India
| | - Keshava Prasad
- Department of Cell and Molecular Biology, Manipal School of Life Sciences, Manipal Academy of Higher Education, Manipal, India
| | - Ranajit Das
- Division of Data Analytics, Bioinformatics and Structural Biology, Yenepoya Research Centre, Yenepoya (Deemed to be University), Mangalore, India
| | - Priyanka Upadhyai
- Department of Medical Genetics, Kasturba Medical College, Manipal, Manipal Academy of Higher Education, Manipal, India.
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4
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DAmico KA, Stanton AE, Shirkey JD, Travis SM, Jeffrey PD, Hughson FM. Structure of a membrane tethering complex incorporating multiple SNAREs. Nat Struct Mol Biol 2024; 31:246-254. [PMID: 38196032 PMCID: PMC10923073 DOI: 10.1038/s41594-023-01164-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Accepted: 10/26/2023] [Indexed: 01/11/2024]
Abstract
Most membrane fusion reactions in eukaryotic cells are mediated by multisubunit tethering complexes (MTCs) and SNARE proteins. MTCs are much larger than SNAREs and are thought to mediate the initial attachment of two membranes. Complementary SNAREs then form membrane-bridging complexes whose assembly draws the membranes together for fusion. Here we present a cryo-electron microscopy structure of the simplest known MTC, the 255-kDa Dsl1 complex of Saccharomyces cerevisiae, bound to the two SNAREs that anchor it to the endoplasmic reticulum. N-terminal domains of the SNAREs form an integral part of the structure, stabilizing a Dsl1 complex configuration with unexpected similarities to the 850-kDa exocyst MTC. The structure of the SNARE-anchored Dsl1 complex and its comparison with exocyst reveal what are likely to be common principles underlying MTC function. Our structure also implies that tethers and SNAREs can work together as a single integrated machine.
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Affiliation(s)
- Kevin A DAmico
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Abigail E Stanton
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Jaden D Shirkey
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Sophie M Travis
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
| | - Philip D Jeffrey
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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5
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Wang Y, Xiao T, Zhao C, Li G. The Regulation of Exosome Generation and Function in Physiological and Pathological Processes. Int J Mol Sci 2023; 25:255. [PMID: 38203424 PMCID: PMC10779122 DOI: 10.3390/ijms25010255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Revised: 12/16/2023] [Accepted: 12/21/2023] [Indexed: 01/12/2024] Open
Abstract
Exosomes, a type of extracellular vesicle with a diameter of approximately 100 nm that is secreted by all cells, regulate the phenotype and function of recipient cells by carrying molecules such as proteins, nucleic acids, and lipids and are important mediators of intercellular communication. Exosomes are involved in various physiological and pathological processes such as immunomodulation, angiogenesis, tumorigenesis, metastasis, and chemoresistance. Due to their excellent properties, exosomes have shown their potential application in the clinical diagnosis and treatment of disease. The functions of exosomes depend on their biogenesis, uptake, and composition. Thus, a deeper understanding of these processes and regulatory mechanisms can help to find new targets for disease diagnosis and therapy. Therefore, this review summarizes and integrates the recent advances in the regulatory mechanisms of the entire biological process of exosomes, starting from the formation of early-sorting endosomes (ESCs) by plasma membrane invagination to the release of exosomes by fusion of multivesicular bodies (MVBs) with the plasma membrane, as well as the regulatory process of the interactions between exosomes and recipient cells. We also describe and discuss the regulatory mechanisms of exosome production in tumor cells and the potential of exosomes used in cancer diagnosis and therapy.
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Affiliation(s)
| | | | | | - Guiying Li
- Key Laboratory for Molecular Enzymology and Engineering of the Ministry of Education, School of Life Sciences, Jilin University, Changchun 130012, China; (Y.W.); (T.X.); (C.Z.)
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6
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Liu DA, Tao K, Wu B, Yu Z, Szczepaniak M, Rames M, Yang C, Svitkina T, Zhu Y, Xu F, Nan X, Guo W. A phosphoinositide switch mediates exocyst recruitment to multivesicular endosomes for exosome secretion. Nat Commun 2023; 14:6883. [PMID: 37898620 PMCID: PMC10613218 DOI: 10.1038/s41467-023-42661-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Accepted: 10/17/2023] [Indexed: 10/30/2023] Open
Abstract
Exosomes are secreted to the extracellular milieu when multivesicular endosomes (MVEs) dock and fuse with the plasma membrane. However, MVEs are also known to fuse with lysosomes for degradation. How MVEs are directed to the plasma membrane for exosome secretion rather than to lysosomes is unclear. Here we report that a conversion of phosphatidylinositol-3-phosphate (PI(3)P) to phosphatidylinositol-4-phosphate (PI(4)P) catalyzed sequentially by Myotubularin 1 (MTM1) and phosphatidylinositol 4-kinase type IIα (PI4KIIα) on the surface of MVEs mediates the recruitment of the exocyst complex. The exocyst then targets the MVEs to the plasma membrane for exosome secretion. We further demonstrate that disrupting PI(4)P generation or exocyst function blocked exosomal secretion of Programmed death-ligand 1 (PD-L1), a key immune checkpoint protein in tumor cells, and led to its accumulation in lysosomes. Together, our study suggests that the PI(3)P to PI(4)P conversion on MVEs and the recruitment of the exocyst direct the exocytic trafficking of MVEs for exosome secretion.
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Affiliation(s)
- Di-Ao Liu
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Kai Tao
- Program in Quantitative and Systems Biology, Department of Biomedical Engineering, Oregon Health and Science University, 2730 S. Moody Ave, Portland, OR, 97201, USA
| | - Bin Wu
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Ziyan Yu
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Malwina Szczepaniak
- Program in Quantitative and Systems Biology, Department of Biomedical Engineering, Oregon Health and Science University, 2730 S. Moody Ave, Portland, OR, 97201, USA
| | - Matthew Rames
- Cancer Early Detection Advanced Research Center, Knight Cancer Institute, Oregon Health and Science University, 2720 S. Moody Ave., Portland, OR, 97201, USA
| | - Changsong Yang
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Tatyana Svitkina
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Yueyao Zhu
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA
- Department of Pathology & Laboratory Medicine, Children's Hospital of Philadelphia Research Institute, Philadelphia, PA, 19104, USA
| | - Fengyuan Xu
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Xiaolin Nan
- Program in Quantitative and Systems Biology, Department of Biomedical Engineering, Oregon Health and Science University, 2730 S. Moody Ave, Portland, OR, 97201, USA
- Cancer Early Detection Advanced Research Center, Knight Cancer Institute, Oregon Health and Science University, 2720 S. Moody Ave., Portland, OR, 97201, USA
| | - Wei Guo
- Department of Biology, School of Arts & Sciences, University of Pennsylvania, Philadelphia, PA, 19104, USA.
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7
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Logue MJE, Farquhar RE, Eckhoff-Björngard Y, Cheung TT, Devor DC, McDonald FJ, Hamilton KL. The exocyst complex is required for the trafficking and delivery of KCa3.1 to the basolateral membrane of polarized epithelia. Am J Physiol Cell Physiol 2023; 324:C1249-C1262. [PMID: 37125772 PMCID: PMC10243536 DOI: 10.1152/ajpcell.00374.2022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 04/19/2023] [Accepted: 04/19/2023] [Indexed: 05/02/2023]
Abstract
Control of the movement of ions and water across epithelia is essential for homeostasis. Changing the number or activity of ion channels at the plasma membrane is a significant regulator of epithelial transport. In polarized epithelia, the intermediate-conductance calcium-activated potassium channel, KCa3.1 is delivered to the basolateral membrane where it generates and maintains the electrochemical gradients required for epithelial transport. The mechanisms that control the delivery of KCa3.1 to the basolateral membrane are still emerging. Herein, we investigated the role of the highly conserved tethering complex exocyst. In epithelia, exocyst is involved in the tethering of post-Golgi secretory vesicles with the basolateral membrane, which is required before membrane fusion. In our Fisher rat thyroid cell line that stably expresses KCa3.1, siRNA knockdown of either of the exocyst subunits Sec3, Sec6, or Sec8 significantly decreased KCa3.1-specific current. In addition, knockdown of exocyst complex subunits significantly reduced the basolateral membrane protein level of KCa3.1. Finally, co-immunoprecipitation experiments suggest associations between Sec6 and KCa3.1, but not between Sec8 and KCa3.1. Collectively, based on these data and our previous studies, we suggest that components of exocyst complex are crucially important in the tethering of KCa3.1 to the basolateral membrane. After which, Soluble N-ethylmaleimide-sensitive factor (SNF) Attachment Receptors (SNARE) proteins aid in the insertion of KCa3.1-containing vesicles into the basolateral membrane of polarized epithelia.NEW & NOTEWORTHY Our Ussing chamber and immunoblot experiments demonstrate that when subunits of the exocyst complex were transiently knocked down, this significantly reduced the basolateral population and functional expression of KCa3.1. These data suggest, combined with our protein association experiments, that the exocyst complex regulates the tethering of KCa3.1-containing vesicles to the basolateral membrane prior to the SNARE-dependent insertion of channels into the basolateral membrane of epithelial cells.
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Affiliation(s)
- Matthew J E Logue
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Rachel E Farquhar
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Yoakim Eckhoff-Björngard
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Tanya T Cheung
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Daniel C Devor
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States
| | - Fiona J McDonald
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Kirk L Hamilton
- Department of Physiology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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8
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Pereira C, Stalder D, Anderson GS, Shun-Shion AS, Houghton J, Antrobus R, Chapman MA, Fazakerley DJ, Gershlick DC. The exocyst complex is an essential component of the mammalian constitutive secretory pathway. J Cell Biol 2023; 222:e202205137. [PMID: 36920342 PMCID: PMC10041652 DOI: 10.1083/jcb.202205137] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 11/11/2022] [Accepted: 02/01/2023] [Indexed: 03/16/2023] Open
Abstract
Secreted proteins fulfill a vast array of functions, including immunity, signaling, and extracellular matrix remodeling. In the trans-Golgi network, proteins destined for constitutive secretion are sorted into post-Golgi carriers which fuse with the plasma membrane. The molecular machinery involved is poorly understood. Here, we have used kinetic trafficking assays and transient CRISPR-KO to study biosynthetic sorting from the Golgi to the plasma membrane. Depletion of all canonical exocyst subunits causes cargo accumulation in post-Golgi carriers. Exocyst subunits are recruited to and co-localize with carriers. Exocyst abrogation followed by kinetic trafficking assays of soluble cargoes results in intracellular cargo accumulation. Unbiased secretomics reveals impairment of soluble protein secretion after exocyst subunit knockout. Importantly, in specialized cell types, the loss of exocyst prevents constitutive secretion of antibodies in lymphocytes and of leptin in adipocytes. These data identify exocyst as the functional tether of secretory post-Golgi carriers at the plasma membrane and an essential component of the mammalian constitutive secretory pathway.
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Affiliation(s)
- Conceição Pereira
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Danièle Stalder
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | | | - Amber S. Shun-Shion
- Metabolic Research Laboratory, Wellcome-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Jack Houghton
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | - Robin Antrobus
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
| | | | - Daniel J. Fazakerley
- Metabolic Research Laboratory, Wellcome-Medical Research Council Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - David C. Gershlick
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
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9
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Miller BK, Rossi G, Hudson S, Cully D, Baker RW, Brennwald P. Allosteric regulation of exocyst: Discrete activation of tethering by two spatial signals. J Cell Biol 2023; 222:213852. [PMID: 36729146 PMCID: PMC9929655 DOI: 10.1083/jcb.202206108] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 11/17/2022] [Accepted: 01/05/2023] [Indexed: 02/03/2023] Open
Abstract
The exocyst imparts spatial control during exocytic vesicle tethering through its interactions with proteins and lipids on the vesicle and the plasma membrane. One such interaction is with the vesicle tether Sro7, although the outcome of this interaction is poorly understood. Here, we describe how Sro7 binding to the Exo84 subunit results in activation of the exocyst complex which leads to an increase in avidity for the Rab GTPase Sec4 and an increase in exocyst-mediated vesicle tethering. Gain-of-function (GOF) mutations in Exo84 that mimic Sro7 activation replicate these biochemical changes and result in allosteric changes within the complex. Direct comparison of GOF mutants which mimic Sro7- and Rho/Cdc42-activation of the exocyst reveals distinct mechanisms and outcomes. We propose a model by which these two activation pathways reside within the same tethering complex but remain insulated from one another. Structural modeling suggests a related mechanism for Sro7 activation of the exocyst in yeast and Ral GTPase activation of the exocyst in animal cells.
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Affiliation(s)
- Brittany K. Miller
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Guendalina Rossi
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Sara Hudson
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - David Cully
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Richard W. Baker
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina, Chapel Hill, NC, USA
| | - Patrick Brennwald
- https://ror.org/0130frc33Department of Cell Biology and Physiology, School of Medicine, University of North Carolina, Chapel Hill, NC, USA,Correspondence to Patrick Brennwald:
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10
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DAmico KA, Stanton AE, Shirkey JD, Travis SM, Jeffrey PD, Hughson FM. Structure of a Membrane Tethering Complex Incorporating Multiple SNAREs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.30.526244. [PMID: 36778436 PMCID: PMC9915479 DOI: 10.1101/2023.01.30.526244] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Most membrane fusion reactions in eukaryotic cells are mediated by membrane tethering complexes (MTCs) and SNARE proteins. MTCs are much larger than SNAREs and are thought to mediate the initial attachment of two membranes. Complementary SNAREs then form membrane-bridging complexes whose assembly draws the membranes together for fusion. Here, we present a cryo-EM structure of the simplest known MTC, the 255-kDa Dsl1 complex, bound to the two SNAREs that anchor it to the endoplasmic reticulum. N-terminal domains of the SNAREs form an integral part of the structure, stabilizing a Dsl1 complex configuration with remarkable and unexpected similarities to the 850-kDa exocyst MTC. The structure of the SNARE-anchored Dsl1 complex and its comparison with exocyst reveal what are likely to be common principles underlying MTC function. Our structure also implies that tethers and SNAREs can work together as a single integrated machine.
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Affiliation(s)
- Kevin A DAmico
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Abigail E Stanton
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Jaden D Shirkey
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Sophie M Travis
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Philip D Jeffrey
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
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11
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Mei K, Guo W. Modeling the Cryo-EM Structure of the Exocyst Complex. Methods Mol Biol 2023; 2557:247-262. [PMID: 36512220 DOI: 10.1007/978-1-0716-2639-9_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Multi-subunit tethering complexes (MTCs) are a family of evolutionarily conserved large protein complexes that function to tether intracellular vesicles from the donor compartments to the membrane of receptor compartments. The exocyst complex is an octameric MTC that tethers the post-Golgi secretory vesicles to the plasma membrane. To learn the function and regulation of the exocyst complex, it is crucial to understand the structure of the complex. We have solved the cryo-EM structure of the exocyst complex at 4.4 Angstrom (Å) resolution and detected the spatial relationship between the eight subunits using chemical cross-linking mass spectrometry. Here, we describe the method of modeling and validating the cryo-EM structure of the exocyst complex. This method could provide a guide for modeling of other protein complexes of which the structures are solved at medium to near-atomic resolution.
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Affiliation(s)
- Kunrong Mei
- School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, China.
| | - Wei Guo
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA.
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12
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Thibodeau MC, Harris NJ, Jenkins ML, Parson MAH, Evans JT, Scott MK, Shaw AL, Pokorný D, Leonard TA, Burke JE. Molecular basis for the recruitment of the Rab effector protein WDR44 by the GTPase Rab11. J Biol Chem 2023; 299:102764. [PMID: 36463963 PMCID: PMC9808001 DOI: 10.1016/j.jbc.2022.102764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2022] [Revised: 11/22/2022] [Accepted: 11/28/2022] [Indexed: 12/03/2022] Open
Abstract
The formation of complexes between Rab11 and its effectors regulates multiple aspects of membrane trafficking, including recycling and ciliogenesis. WD repeat-containing protein 44 (WDR44) is a structurally uncharacterized Rab11 effector that regulates ciliogenesis by competing with prociliogenesis factors for Rab11 binding. Here, we present a detailed biochemical and biophysical characterization of the WDR44-Rab11 complex and define specific residues mediating binding. Using AlphaFold2 modeling and hydrogen/deuterium exchange mass spectrometry, we generated a molecular model of the Rab11-WDR44 complex. The Rab11-binding domain of WDR44 interacts with switch I, switch II, and the interswitch region of Rab11. Extensive mutagenesis of evolutionarily conserved residues in WDR44 at the interface identified numerous complex-disrupting mutations. Using hydrogen/deuterium exchange mass spectrometry, we found that the dynamics of the WDR44-Rab11 interface are distinct from the Rab11 effector FIP3, with WDR44 forming a more extensive interface with the switch II helix of Rab11 compared with FIP3. The WDR44 interaction was specific to Rab11 over evolutionarily similar Rabs, with mutations defining the molecular basis of Rab11 specificity. Finally, WDR44 can be phosphorylated by Sgk3, with this leading to reorganization of the Rab11-binding surface on WDR44. Overall, our results provide molecular detail on how WDR44 interacts with Rab11 and how Rab11 can form distinct effector complexes that regulate membrane trafficking events.
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Affiliation(s)
- Matthew C Thibodeau
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Noah J Harris
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Matthew A H Parson
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - John T Evans
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Mackenzie K Scott
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada
| | - Alexandria L Shaw
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada; Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Daniel Pokorný
- Max Perutz Labs, Department of Structural and Computational Biology, Vienna, Austria; Department of Medical Biochemistry, Medical University of Vienna, Vienna, Austria
| | - Thomas A Leonard
- Max Perutz Labs, Department of Structural and Computational Biology, Vienna, Austria; Department of Medical Biochemistry, Medical University of Vienna, Vienna, Austria
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia, Canada; Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada.
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13
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Meyer C, Breitsprecher L, Bataille L, Vincent AJM, Drechsler M, Meyer H, Paululat A. Formation and function of a highly specialised type of organelle in cardiac valve cells. Development 2022; 149:276991. [DOI: 10.1242/dev.200701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 08/23/2022] [Indexed: 11/06/2022]
Abstract
ABSTRACT
Within a cell, vesicles play a crucial role in the transport of membrane material and proteins to a given target membrane, and thus regulate a variety of cellular functions. Vesicular transport occurs by means of, among others, endocytosis, where cargoes are taken up by the cell and are processed further upon vesicular trafficking, i.e. transported back to the plasma membrane via recycling endosomes or the degraded by fusion of the vesicles with lysosomes. During evolution, a variety of vesicles with individual functions arose, with some of them building up highly specialised subcellular compartments. In this study, we have analysed the biosynthesis of a new vesicular compartment present in the valve cells of Drosophila melanogaster. We show that the compartment is formed by invaginations of the plasma membrane and grows via re-routing of the recycling endosomal pathway. This is achieved by inactivation of other membrane-consuming pathways and a plasma membrane-like molecular signature of the compartment in these highly specialised heart cells.
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Affiliation(s)
- Christian Meyer
- University of Osnabrück 1 , Department of Biology and Chemistry, Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück , Germany
| | - Leonhard Breitsprecher
- University of Osnabrück 1 , Department of Biology and Chemistry, Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück , Germany
- Center of Cellular Nanoanalytics (CellNanOs), integrated Bioimaging Facility (iBiOs), University of Osnabrück 2 , Barbarastrasse 11, 49076 Osnabrück , Germany
| | - Laetitia Bataille
- Unité de Biologie Moléculaire et Cellulaire et du Développement (MCD), Centre de Biologie Intégrative (CBI) 3 , Université de Toulouse UMR 5077/CNRS, F-31062 Toulouse , France
| | - Alain J. M. Vincent
- Unité de Biologie Moléculaire et Cellulaire et du Développement (MCD), Centre de Biologie Intégrative (CBI) 3 , Université de Toulouse UMR 5077/CNRS, F-31062 Toulouse , France
| | - Maik Drechsler
- University of Osnabrück 1 , Department of Biology and Chemistry, Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück , Germany
| | - Heiko Meyer
- University of Osnabrück 1 , Department of Biology and Chemistry, Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück , Germany
- Center of Cellular Nanoanalytics (CellNanOs), integrated Bioimaging Facility (iBiOs), University of Osnabrück 2 , Barbarastrasse 11, 49076 Osnabrück , Germany
| | - Achim Paululat
- University of Osnabrück 1 , Department of Biology and Chemistry, Zoology and Developmental Biology, Barbarastraße 11, 49076 Osnabrück , Germany
- Center of Cellular Nanoanalytics (CellNanOs), integrated Bioimaging Facility (iBiOs), University of Osnabrück 2 , Barbarastrasse 11, 49076 Osnabrück , Germany
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14
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Chen M, Zhang Y, Jiang K, Wang W, Feng H, Zhen R, Moo C, Zhang Z, Shi J, Chen C. Grab regulates transferrin receptor recycling and iron uptake in developing erythroblasts. Blood 2022; 140:1145-1155. [PMID: 35820059 DOI: 10.1182/blood.2021015189] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 06/25/2022] [Indexed: 11/20/2022] Open
Abstract
Developing erythroblasts acquire massive amounts of iron through the transferrin (Tf) cycle, which involves endocytosis, sorting, and recycling of the Tf-Tf receptor (Tfrc) complex. Previous studies on the hemoglobin-deficit (hbd) mouse have shown that the exocyst complex is indispensable for the Tfrc recycling; however, the precise mechanism underlying the efficient exocytosis and recycling of Tfrc in erythroblasts remains unclear. Here, we identify the guanine nucleotide exchange factor Grab as a critical regulator of the Tf cycle and iron metabolism during erythropoiesis. Grab is highly expressed in differentiating erythroblasts. Loss of Grab diminishes the Tfrc recycling and iron uptake, leading to hemoglobinization defects in mouse primary erythroblasts, mammalian erythroleukemia cells, and zebrafish embryos. These defects can be alleviated by supplementing iron together with hinokitiol, a small-molecule natural compound that can mediate iron transport independent of the Tf cycle. Mechanistically, Grab regulates the exocytosis of Tfrc-associated vesicles by activating the GTPase Rab8, which subsequently promotes the recruitment of the exocyst complex and vesicle exocytosis. Our results reveal a critical role for Grab in regulating the Tf cycle and provide new insights into iron homeostasis and erythropoiesis.
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Affiliation(s)
- Mengying Chen
- Ministry of Education Key Laboratory of Biosystems Homeostasis and Protection, Institute of Cell and Developmental Biology, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Yuhan Zhang
- Ministry of Education Key Laboratory of Biosystems Homeostasis and Protection, Institute of Cell and Developmental Biology, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Kailun Jiang
- Ministry of Education Key Laboratory of Biosystems Homeostasis and Protection, Institute of Cell and Developmental Biology, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Weixi Wang
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
| | - He Feng
- Ministry of Education Key Laboratory of Biosystems Homeostasis and Protection, Institute of Cell and Developmental Biology, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Ru Zhen
- Ministry of Education Key Laboratory of Biosystems Homeostasis and Protection, Institute of Cell and Developmental Biology, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Chingyee Moo
- Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China
| | - Zhuonan Zhang
- Ministry of Education Key Laboratory of Biosystems Homeostasis and Protection, Institute of Cell and Developmental Biology, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Jiahai Shi
- Synthetic Biology Translational Research Programs, Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore; and
| | - Caiyong Chen
- Ministry of Education Key Laboratory of Biosystems Homeostasis and Protection, Institute of Cell and Developmental Biology, College of Life Sciences, Zhejiang University, Hangzhou, China
- Cancer Center, Zhejiang University, Hangzhou, China
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15
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Ebnet K, Gerke V. Rho and Rab Family Small GTPases in the Regulation of Membrane Polarity in Epithelial Cells. Front Cell Dev Biol 2022; 10:948013. [PMID: 35859901 PMCID: PMC9289151 DOI: 10.3389/fcell.2022.948013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Accepted: 06/14/2022] [Indexed: 11/27/2022] Open
Abstract
Membrane polarity, defined as the asymmetric distribution of lipids and proteins in the plasma membrane, is a critical prerequisite for the development of multicellular tissues, such as epithelia and endothelia. Membrane polarity is regulated by polarized trafficking of membrane components to specific membrane domains and requires the presence of intramembrane diffusion barriers that prevent the intermixing of asymmetrically distributed membrane components. This intramembrane diffusion barrier is localized at the tight junctions (TJs) in these cells. Both the formation of cell-cell junctions and the polarized traffic of membrane proteins and lipids are regulated by Rho and Rab family small GTPases. In this review article, we will summarize the recent developments in the regulation of apico-basal membrane polarity by polarized membrane traffic and the formation of the intramembrane diffusion barrier in epithelial cells with a particular focus on the role of Rho and Rab family small GTPases.
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Affiliation(s)
- Klaus Ebnet
- Institute-Associated Research Group: Cell Adhesion and Cell Polarity, Institute of Medical Biochemistry, ZMBE, University of Münster, Münster, Germany
- Interdisciplinary Clinical Research Center (IZKF), University of Münster, Münster, Germany
- Cells-In-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
- *Correspondence: Klaus Ebnet, ; Volker Gerke,
| | - Volker Gerke
- Institute-Associated Research Group: Cell Adhesion and Cell Polarity, Institute of Medical Biochemistry, ZMBE, University of Münster, Münster, Germany
- Interdisciplinary Clinical Research Center (IZKF), University of Münster, Münster, Germany
- Cells-In-Motion Cluster of Excellence (EXC1003-CiM), University of Münster, Münster, Germany
- *Correspondence: Klaus Ebnet, ; Volker Gerke,
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16
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Batystová K, Synek L, Klejchová M, Janková Drdová E, Sabol P, Potocký M, Žárský V, Hála M. Diversification of SEC15a and SEC15b isoforms of an exocyst subunit in seed plants is manifested in their specific roles in Arabidopsis sporophyte and male gametophyte. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 110:1382-1396. [PMID: 35306706 DOI: 10.1111/tpj.15744] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 03/07/2022] [Indexed: 06/14/2023]
Abstract
The exocyst complex is an octameric evolutionarily conserved tethering complex engaged in the regulation of polarized secretion in eukaryotic cells. Here, we focus on the systematic comparison of two isoforms of the SEC15 exocyst subunit, SEC15a and SEC15b. We infer that SEC15 gene duplication and diversification occurred in the common ancestor of seed plants (Spermatophytes). In Arabidopsis, SEC15a represents the main SEC15 isoform in the male gametophyte, and localizes to the pollen tube tip at the plasma membrane. Although pollen tubes of sec15a mutants are impaired, sporophytes show no phenotypic deviations. Conversely, SEC15b is the dominant isoform in the sporophyte and localizes to the plasma membrane in root and leaf cells. Loss-of-function sec15b mutants exhibit retarded elongation of hypocotyls and root hairs, a loss of apical dominance, dwarfed plant stature and reduced seed coat mucilage formation. Surprisingly, the sec15b mutants also exhibit compromised pollen tube elongation in vitro, despite its very low expression in pollen, suggesting a non-redundant role for the SEC15b isoform there. In pollen tubes, SEC15b localizes to distinct cytoplasmic structures. Reciprocally to this, SEC15a also functions in the sporophyte, where it accumulates at plasmodesmata. Importantly, although overexpressed SEC15a could fully complement the sec15b phenotypic deviations in the sporophyte, the pollen-specific overexpression of SEC15b was unable to fully compensate for the loss of SEC15a function in pollen. We conclude that the SEC15a and SEC15b isoforms evolved in seed plants, with SEC15a functioning mostly in pollen and SEC15b functioning mostly in the sporophyte.
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Affiliation(s)
- Klára Batystová
- Institute of Experimental Botany, Czech Academy of Sciences, Rozvojova 263, Prague, CZ-16502, Czech Republic
- Department of Experimental Plant Biology, Faculty of Science, Vinicna 5, Charles University, Prague, CZ-12844, Czech Republic
| | - Lukáš Synek
- Institute of Experimental Botany, Czech Academy of Sciences, Rozvojova 263, Prague, CZ-16502, Czech Republic
| | - Martina Klejchová
- Institute of Experimental Botany, Czech Academy of Sciences, Rozvojova 263, Prague, CZ-16502, Czech Republic
| | - Edita Janková Drdová
- Institute of Experimental Botany, Czech Academy of Sciences, Rozvojova 263, Prague, CZ-16502, Czech Republic
| | - Peter Sabol
- Department of Experimental Plant Biology, Faculty of Science, Vinicna 5, Charles University, Prague, CZ-12844, Czech Republic
| | - Martin Potocký
- Institute of Experimental Botany, Czech Academy of Sciences, Rozvojova 263, Prague, CZ-16502, Czech Republic
| | - Viktor Žárský
- Institute of Experimental Botany, Czech Academy of Sciences, Rozvojova 263, Prague, CZ-16502, Czech Republic
- Department of Experimental Plant Biology, Faculty of Science, Vinicna 5, Charles University, Prague, CZ-12844, Czech Republic
| | - Michal Hála
- Institute of Experimental Botany, Czech Academy of Sciences, Rozvojova 263, Prague, CZ-16502, Czech Republic
- Department of Experimental Plant Biology, Faculty of Science, Vinicna 5, Charles University, Prague, CZ-12844, Czech Republic
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17
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Tanasic D, Berns N, Riechmann V. Myosin V facilitates polarised E-cadherin secretion. Traffic 2022; 23:374-390. [PMID: 35575181 DOI: 10.1111/tra.12846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Revised: 05/09/2022] [Accepted: 05/09/2022] [Indexed: 11/30/2022]
Abstract
E-cadherin has a fundamental role in epithelial tissues by providing cell-cell adhesion. Polarised E-cadherin exocytosis to the lateral plasma membrane is central for cell polarity and epithelial homeostasis. Loss of E-cadherin secretion compromises tissue integrity and is a prerequisite for metastasis. Despite this pivotal role of E-cadherin secretion, the transport mechanism is still unknown. Here we identify Myosin V as the motor for E-cadherin secretion. Our data reveal that Myosin V and F-actin are required for the formation of a continuous apicolateral E-cadherin belt, the zonula adherens. We show by live imaging how Myosin V transports E-cadherin vesicles to the plasma membrane, and distinguish two distinct transport tracks: an apical actin network leading to the zonula adherens and parallel actin bundles leading to the basal-most region of the lateral membrane. E-cadherin secretion starts in endosomes, where Rab11 and Sec15 recruit Myosin V for transport to the zonula adherens. We also shed light on the endosomal sorting of E-cadherin by showing how Rab7 and Snx16 cooperate in moving E-cadherin into the Rab11 compartment. Thus, our data help to understand how polarised E-cadherin secretion maintains epithelial architecture and prevents metastasis. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Dajana Tanasic
- Department of Cell and Molecular Biology and Division of Signaling and Functional Genomics at the German Cancer Research Center (DKFZ), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Strasse 13-17, Mannheim, Germany
| | - Nicola Berns
- Department of Cell and Molecular Biology and Division of Signaling and Functional Genomics at the German Cancer Research Center (DKFZ), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Strasse 13-17, Mannheim, Germany
| | - Veit Riechmann
- Department of Cell and Molecular Biology and Division of Signaling and Functional Genomics at the German Cancer Research Center (DKFZ), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Strasse 13-17, Mannheim, Germany
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18
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Jones JH, Minshall RD. Endothelial Transcytosis in Acute Lung Injury: Emerging Mechanisms and Therapeutic Approaches. Front Physiol 2022; 13:828093. [PMID: 35431977 PMCID: PMC9008570 DOI: 10.3389/fphys.2022.828093] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 02/28/2022] [Indexed: 01/08/2023] Open
Abstract
Acute Lung Injury (ALI) is characterized by widespread inflammation which in its severe form, Acute Respiratory Distress Syndrome (ARDS), leads to compromise in respiration causing hypoxemia and death in a substantial number of affected individuals. Loss of endothelial barrier integrity, pneumocyte necrosis, and circulating leukocyte recruitment into the injured lung are recognized mechanisms that contribute to the progression of ALI/ARDS. Additionally, damage to the pulmonary microvasculature by Gram-negative and positive bacteria or viruses (e.g., Escherichia coli, SARS-Cov-2) leads to increased protein and fluid permeability and interstitial edema, further impairing lung function. While most of the vascular leakage is attributed to loss of inter-endothelial junctional integrity, studies in animal models suggest that transendothelial transport of protein through caveolar vesicles, known as transcytosis, occurs in the early phase of ALI/ARDS. Here, we discuss the role of transcytosis in healthy and injured endothelium and highlight recent studies that have contributed to our understanding of the process during ALI/ARDS. We also cover potential approaches that utilize caveolar transport to deliver therapeutics to the lungs which may prevent further injury or improve recovery.
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Affiliation(s)
- Joshua H. Jones
- Department of Pharmacology, University of Illinois College of Medicine at Chicago, Chicago, IL, United States
| | - Richard D. Minshall
- Department of Pharmacology, University of Illinois College of Medicine at Chicago, Chicago, IL, United States,Department of Anesthesiology, University of Illinois College of Medicine at Chicago, Chicago, IL, United States,*Correspondence: Richard D. Minshall,
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19
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Pang L, Ma Z, Zhang X, Huang Y, Li R, Miao Y, Li R. The small GTPase RABA2a recruits SNARE proteins to regulate the secretory pathway in parallel with the exocyst complex in Arabidopsis. MOLECULAR PLANT 2022; 15:398-418. [PMID: 34798312 DOI: 10.1016/j.molp.2021.11.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 10/24/2021] [Accepted: 11/12/2021] [Indexed: 05/22/2023]
Abstract
Delivery of proteins to the plasma membrane occurs via secretion, which requires tethering, docking, priming, and fusion of vesicles. In yeast and mammalian cells, an evolutionarily conserved RAB GTPase activation cascade functions together with the exocyst and SNARE proteins to coordinate vesicle transport with fusion at the plasma membrane. However, it is unclear whether this is the case in plants. In this study, we show that the small GTPase RABA2a recruits and interacts with the VAMP721/722-SYP121-SNAP33 SNARE ternary complex for membrane fusion. Through immunoprecipitation coupled with mass spectrometry analysis followed by the validatation with a series of biochemical assays, we identified the SNARE proteins VAMP721 and SYP121 as the interactors and downstream effectors of RABA2a. Further expreiments showed that RABA2a interacts with all members of the SNARE complex in its GTP-bound form and modulates the assembly of the VAMP721/722-SYP121-SNAP33 SNARE ternary complex. Intriguingly, we did not observe the interaction of the exocyst subunits with either RABA2a or theSNARE proteins in several different experiments. Neither RABA2a inactivation affects the subcellular localization or assembly of the exocystnor the exocyst subunit mutant exo84b shows the disrupted RABA2a-SNARE association or SNARE assembly, suggesting that the RABA2a-SNARE- and exocyst-mediated secretory pathways are largely independent. Consistently, our live imaging experiments reveal that the two sets of proteins follow non-overlapping trafficking routes, and genetic and cell biologyanalyses indicate that the two pathways select different cargos. Finally, we demonstrate that the plant-specific RABA2a-SNARE pathway is essential for the maintenance of potassium homeostasis in Arabisopsis seedlings. Collectively, our findings imply that higher plants might have generated different endomembrane sorting pathways during evolution and may enable the highly conserved endomembrane proteins to participate in plant-specific trafficking mechanisms for adaptation to the changing environment.
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Affiliation(s)
- Lei Pang
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Zhiming Ma
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Xi Zhang
- College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China
| | - Yuanzhi Huang
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China
| | - Ruili Li
- College of Biological Sciences and Technology, Beijing Forestry University, Beijing 100083, China
| | - Yansong Miao
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Ruixi Li
- Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes, Institute of Plant and Food Science, School of Life Sciences, Southern University of Science and Technology, Shenzhen 518055, China.
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20
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Tunneling nanotubes and related structures: molecular mechanisms of formation and function. Biochem J 2021; 478:3977-3998. [PMID: 34813650 DOI: 10.1042/bcj20210077] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 10/12/2021] [Accepted: 11/01/2021] [Indexed: 12/13/2022]
Abstract
Tunneling nanotubes (TNTs) are F-actin-based, membrane-enclosed tubular connections between animal cells that transport a variety of cellular cargo. Over the last 15 years since their discovery, TNTs have come to be recognized as key players in normal cell communication and organism development, and are also exploited for the spread of various microbial pathogens and major diseases like cancer and neurodegenerative disorders. TNTs have also been proposed as modalities for disseminating therapeutic drugs between cells. Despite the rapidly expanding and wide-ranging relevance of these structures in both health and disease, there is a glaring dearth of molecular mechanistic knowledge regarding the formation and function of these important but enigmatic structures. A series of fundamental steps are essential for the formation of functional nanotubes. The spatiotemporally controlled and directed modulation of cortical actin dynamics would be required to ensure outward F-actin polymerization. Local plasma membrane deformation to impart negative curvature and membrane addition at a rate commensurate with F-actin polymerization would enable outward TNT elongation. Extrinsic tactic cues, along with cognate intrinsic signaling, would be required to guide and stabilize the elongating TNT towards its intended target, followed by membrane fusion to create a functional TNT. Selected cargoes must be transported between connected cells through the action of molecular motors, before the TNT is retracted or destroyed. This review summarizes the current understanding of the molecular mechanisms regulating these steps, also highlighting areas that deserve future attention.
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21
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Chan EHY, Zhou Y, Aerne BL, Holder MV, Weston A, Barry DJ, Collinson L, Tapon N. RASSF8-mediated transport of Echinoid via the exocyst promotes Drosophila wing elongation and epithelial ordering. Development 2021; 148:dev199731. [PMID: 34532737 PMCID: PMC8572004 DOI: 10.1242/dev.199731] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 09/13/2021] [Indexed: 01/14/2023]
Abstract
Cell-cell junctions are dynamic structures that maintain cell cohesion and shape in epithelial tissues. During development, junctions undergo extensive rearrangements to drive the epithelial remodelling required for morphogenesis. This is particularly evident during axis elongation, where neighbour exchanges, cell-cell rearrangements and oriented cell divisions lead to large-scale alterations in tissue shape. Polarised vesicle trafficking of junctional components by the exocyst complex has been proposed to promote junctional rearrangements during epithelial remodelling, but the receptors that allow exocyst docking to the target membranes remain poorly understood. Here, we show that the adherens junction component Ras Association domain family 8 (RASSF8) is required for the epithelial re-ordering that occurs during Drosophila pupal wing proximo-distal elongation. We identify the exocyst component Sec15 as a RASSF8 interactor. Loss of RASSF8 elicits cytoplasmic accumulation of Sec15 and Rab11-containing vesicles. These vesicles also contain the nectin-like homophilic adhesion molecule Echinoid, the depletion of which phenocopies the wing elongation and epithelial packing defects observed in RASSF8 mutants. Thus, our results suggest that RASSF8 promotes exocyst-dependent docking of Echinoid-containing vesicles during morphogenesis.
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Affiliation(s)
- Eunice H. Y. Chan
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Yanxiang Zhou
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Birgit L. Aerne
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Maxine V. Holder
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Anne Weston
- Electron Microscopy Science Technology Platform, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - David J. Barry
- Advanced Light Microscopy Science Technology Platform, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Lucy Collinson
- Electron Microscopy Science Technology Platform, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Nicolas Tapon
- Apoptosis and Proliferation Control Laboratory, The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
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22
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An SJ, Rivera-Molina F, Anneken A, Xi Z, McNellis B, Polejaev VI, Toomre D. An active tethering mechanism controls the fate of vesicles. Nat Commun 2021; 12:5434. [PMID: 34521845 PMCID: PMC8440521 DOI: 10.1038/s41467-021-25465-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 08/05/2021] [Indexed: 11/09/2022] Open
Abstract
Vesicle tethers are thought to underpin the efficiency of intracellular fusion by bridging vesicles to their target membranes. However, the interplay between tethering and fusion has remained enigmatic. Here, through optogenetic control of either a natural tether-the exocyst complex-or an artificial tether, we report that tethering regulates the mode of fusion. We find that vesicles mainly undergo kiss-and-run instead of full fusion in the absence of functional exocyst. Full fusion is rescued by optogenetically restoring exocyst function, in a manner likely dependent on the stoichiometry of tether engagement with the plasma membrane. In contrast, a passive artificial tether produces mostly kissing events, suggesting that kiss-and-run is the default mode of vesicle fusion. Optogenetic control of tethering further shows that fusion mode has physiological relevance since only full fusion could trigger lamellipodial expansion. These findings demonstrate that active coupling between tethering and fusion is critical for robust membrane merger.
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Affiliation(s)
- Seong J An
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Felix Rivera-Molina
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Alexander Anneken
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Zhiqun Xi
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Brian McNellis
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Vladimir I Polejaev
- International Science and Technology Center, Yale University School of Medicine, New Haven, CT, USA
| | - Derek Toomre
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.
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23
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Neuman SD, Lee AR, Selegue JE, Cavanagh AT, Bashirullah A. A novel function for Rab1 and Rab11 during secretory granule maturation. J Cell Sci 2021; 134:jcs259037. [PMID: 34342349 PMCID: PMC8353522 DOI: 10.1242/jcs.259037] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 06/29/2021] [Indexed: 01/15/2023] Open
Abstract
Regulated exocytosis is an essential process whereby specific cargo proteins are secreted in a stimulus-dependent manner. Cargo-containing secretory granules are synthesized in the trans-Golgi network (TGN); after budding from the TGN, granules undergo modifications, including an increase in size. These changes occur during a poorly understood process called secretory granule maturation. Here, we leverage the Drosophila larval salivary glands as a model to characterize a novel role for Rab GTPases during granule maturation. We find that secretory granules increase in size ∼300-fold between biogenesis and release, and loss of Rab1 or Rab11 reduces granule size. Surprisingly, we find that Rab1 and Rab11 localize to secretory granule membranes. Rab11 associates with granule membranes throughout maturation, and Rab11 recruits Rab1. In turn, Rab1 associates specifically with immature granules and drives granule growth. In addition to roles in granule growth, both Rab1 and Rab11 appear to have additional functions during exocytosis; Rab11 function is necessary for exocytosis, while the presence of Rab1 on immature granules may prevent precocious exocytosis. Overall, these results highlight a new role for Rab GTPases in secretory granule maturation.
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Affiliation(s)
| | | | | | | | - Arash Bashirullah
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222, USA
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Escrevente C, Bento-Lopes L, Ramalho JS, Barral DC. Rab11 is required for lysosome exocytosis through the interaction with Rab3a, Sec15 and GRAB. J Cell Sci 2021; 134:jcs246694. [PMID: 34100549 PMCID: PMC8214760 DOI: 10.1242/jcs.246694] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 04/26/2021] [Indexed: 12/19/2022] Open
Abstract
Lysosomes are dynamic organelles, capable of undergoing exocytosis. This process is crucial for several cellular functions, namely plasma membrane repair. Nevertheless, the molecular machinery involved in this process is poorly understood. Here, we identify Rab11a and Rab11b as regulators of Ca2+-induced lysosome exocytosis. Interestingly, Rab11-positive vesicles transiently interact with lysosomes at the cell periphery, indicating that this interaction is required for the last steps of lysosome exocytosis. Additionally, we found that the silencing of the exocyst subunit Sec15, a Rab11 effector, impairs lysosome exocytosis, suggesting that Sec15 acts together with Rab11 in the regulation of lysosome exocytosis. Furthermore, we show that Rab11 binds the guanine nucleotide exchange factor for Rab3a (GRAB) as well as Rab3a, which we have previously described to be a regulator of the positioning and exocytosis of lysosomes. Thus, our study identifies new players required for lysosome exocytosis and suggest the existence of a Rab11-Rab3a cascade involved in this process.
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Affiliation(s)
| | | | | | - Duarte C. Barral
- iNOVA4Health, CEDOC, NOVA Medical School, NMS, Universidade NOVA de Lisboa, 1169-056 Lisboa, Portugal
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25
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Nonredundant roles of DIAPHs in primary ciliogenesis. J Biol Chem 2021; 296:100680. [PMID: 33872598 PMCID: PMC8122175 DOI: 10.1016/j.jbc.2021.100680] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 04/12/2021] [Accepted: 04/15/2021] [Indexed: 11/21/2022] Open
Abstract
Primary cilia are hubs for several signaling pathways, and disruption in cilia function and formation leads to a range of diseases collectively known as ciliopathies. Both ciliogenesis and cilia maintenance depend on vesicle trafficking along a network of microtubules and actin filaments toward the basal body. The DIAPH (Diaphanous-related) family of formins promote both actin polymerization and microtubule (MT) stability. Recently, we showed that the formin DIAPH1 is involved in ciliogenesis. However, the role of other DIAPH family members in ciliogenesis had not been investigated. Here we show that depletion of either DIAPH2 or DIAPH3 also disrupted ciliogenesis and cilia length. DIAPH3 depletion also reduced trafficking within cilia. To specifically examine the role of DIAPH3 at the base, we used fused full-length DIAPH3 to centrin, which targeted DIAPH3 to the basal body, causing increased trafficking to the ciliary base, an increase in cilia length, and formation of bulbs at the tips of cilia. Additionally, we confirmed that the microtubule-stabilizing properties of DIAPH3 are important for its cilia length functions and trafficking. These results indicate the importance of DIAPH proteins in regulating cilia maintenance. Moreover, defects in ciliogenesis caused by DIAPH depletion could only be rescued by expression of the specific family member depleted, indicating nonredundant roles for these proteins.
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Fais M, Sanna G, Galioto M, Nguyen TTD, Trần MUT, Sini P, Carta F, Turrini F, Xiong Y, Dawson TM, Dawson VL, Crosio C, Iaccarino C. LRRK2 Modulates the Exocyst Complex Assembly by Interacting with Sec8. Cells 2021; 10:203. [PMID: 33498474 PMCID: PMC7909581 DOI: 10.3390/cells10020203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 01/12/2021] [Accepted: 01/18/2021] [Indexed: 11/17/2022] Open
Abstract
Mutations in LRRK2 play a critical role in both familial and sporadic Parkinson's disease (PD). Up to date, the role of LRRK2 in PD onset and progression remains largely unknown. However, experimental evidence highlights a critical role of LRRK2 in the control of vesicle trafficking, likely by Rab phosphorylation, that in turn may regulate different aspects of neuronal physiology. Here we show that LRRK2 interacts with Sec8, one of eight subunits of the exocyst complex. The exocyst complex is an evolutionarily conserved multisubunit protein complex mainly involved in tethering secretory vesicles to the plasma membrane and implicated in the regulation of multiple biological processes modulated by vesicle trafficking. Interestingly, Rabs and exocyst complex belong to the same protein network. Our experimental evidence indicates that LRRK2 kinase activity or the presence of the LRRK2 kinase domain regulate the assembly of exocyst subunits and that the over-expression of Sec8 significantly rescues the LRRK2 G2019S mutant pathological effect. Our findings strongly suggest an interesting molecular mechanism by which LRRK2 could modulate vesicle trafficking and may have important implications to decode the complex role that LRRK2 plays in neuronal physiology.
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Affiliation(s)
- Milena Fais
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Giovanna Sanna
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Manuela Galioto
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Thi Thanh Duyen Nguyen
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Mai Uyên Thi Trần
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Paola Sini
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | | | - Franco Turrini
- Nurex Srl, 07100 Sassari, Italy; (F.C.); (F.T.)
- Department of Oncology, University of Turin, 10126 Turin, Italy
| | - Yulan Xiong
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ted M. Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Valina L. Dawson
- Neuroregeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; (Y.X.); (T.M.D.); (V.L.D.)
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Claudia Crosio
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
| | - Ciro Iaccarino
- Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy; (M.F.); (G.S.); (M.G.); (T.T.D.N.); (M.U.T.T.); (P.S.); (C.C.)
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Glutamatergic Receptor Trafficking and Delivery: Role of the Exocyst Complex. Cells 2020; 9:cells9112402. [PMID: 33153008 PMCID: PMC7693776 DOI: 10.3390/cells9112402] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 10/21/2020] [Accepted: 10/23/2020] [Indexed: 12/29/2022] Open
Abstract
Cells comprise several intracellular membrane compartments that allow them to function properly. One of these functions is cargo movement, typically proteins and membranes within cells. These cargoes ride microtubules through vesicles from Golgi and recycling endosomes to the plasma membrane in order to be delivered and exocytosed. In neurons, synaptic functions employ this cargo trafficking to maintain inter-neuronal communication optimally. One of the complexes that oversee vesicle trafficking and tethering is the exocyst. The exocyst is a protein complex containing eight subunits first identified in yeast and then characterized in multicellular organisms. This complex is related to several cellular processes, including cellular growth, division, migration, and morphogenesis, among others. It has been associated with glutamatergic receptor trafficking and tethering into the synapse, providing the molecular machinery to deliver receptor-containing vesicles into the plasma membrane in a constitutive manner. In this review, we discuss the evidence so far published regarding receptor trafficking and the exocyst complex in both basal and stimulated levels, comparing constitutive trafficking and long-term potentiation-related trafficking.
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28
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Chang YY, Stévenin V, Duchateau M, Giai Gianetto Q, Hourdel V, Rodrigues CD, Matondo M, Reiling N, Enninga J. Shigella hijacks the exocyst to cluster macropinosomes for efficient vacuolar escape. PLoS Pathog 2020; 16:e1008822. [PMID: 32866204 PMCID: PMC7485983 DOI: 10.1371/journal.ppat.1008822] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 09/11/2020] [Accepted: 07/20/2020] [Indexed: 12/15/2022] Open
Abstract
Shigella flexneri invades host cells by entering within a bacteria-containing vacuole (BCV). In order to establish its niche in the host cytosol, the bacterium ruptures its BCV. Contacts between S. flexneri BCV and infection-associated macropinosomes (IAMs) formed in situ have been reported to enhance BCV disintegration. The mechanism underlying S. flexneri vacuolar escape remains however obscure. To decipher the molecular mechanism priming the communication between the IAMs and S. flexneri BCV, we performed mass spectrometry-based analysis of the magnetically purified IAMs from S. flexneri-infected cells. While proteins involved in host recycling and exocytic pathways were significantly enriched at the IAMs, we demonstrate more precisely that the S. flexneri type III effector protein IpgD mediates the recruitment of the exocyst to the IAMs through the Rab8/Rab11 pathway. This recruitment results in IAM clustering around S. flexneri BCV. More importantly, we reveal that IAM clustering subsequently facilitates an IAM-mediated unwrapping of the ruptured vacuole membranes from S. flexneri, enabling the naked bacterium to be ready for intercellular spread via actin-based motility. Taken together, our work untangles the molecular cascade of S. flexneri-driven host trafficking subversion at IAMs to develop its cytosolic lifestyle, a crucial step en route for infection progression at cellular and tissue level.
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Affiliation(s)
- Yuen-Yan Chang
- Dynamics of Host-Pathogen Interactions Unit and CNRS UMR3691, Institut Pasteur, Paris, France
| | - Virginie Stévenin
- Dynamics of Host-Pathogen Interactions Unit and CNRS UMR3691, Institut Pasteur, Paris, France
| | - Magalie Duchateau
- Mass Spectrometry for Biology Unit, Proteomics Platform, Institut Pasteur, USR CNRS, Paris, France
| | - Quentin Giai Gianetto
- Mass Spectrometry for Biology Unit, Proteomics Platform, Institut Pasteur, USR CNRS, Paris, France
- Hub Bioinformatics et Biostatistics, Computational Biology Department, USR CNRS, Institut Pasteur, Paris, France
| | - Veronique Hourdel
- Mass Spectrometry for Biology Unit, Proteomics Platform, Institut Pasteur, USR CNRS, Paris, France
| | - Cristina Dias Rodrigues
- Dynamics of Host-Pathogen Interactions Unit and CNRS UMR3691, Institut Pasteur, Paris, France
| | - Mariette Matondo
- Mass Spectrometry for Biology Unit, Proteomics Platform, Institut Pasteur, USR CNRS, Paris, France
| | - Norbert Reiling
- Microbial Interface Biology, Research Center Borstel, Leibniz Lung Center, Borstel, Germany
- German Center for Infection Research (DZIF), Partner site Hamburg-Lübeck-Borstel, Borstel, Germany
| | - Jost Enninga
- Dynamics of Host-Pathogen Interactions Unit and CNRS UMR3691, Institut Pasteur, Paris, France
- * E-mail:
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29
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Nandy N, Roy JK. Rab11 is essential for lgl mediated JNK-Dpp signaling in dorsal closure and epithelial morphogenesis in Drosophila. Dev Biol 2020; 464:188-201. [PMID: 32562757 DOI: 10.1016/j.ydbio.2020.06.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 06/11/2020] [Accepted: 06/11/2020] [Indexed: 11/30/2022]
Abstract
Dorsal closure during Drosophila embryogenesis provides a robust genetic platform to study the basic cellular mechanisms that govern epithelial wound healing and morphogenesis. As dorsal closure proceeds, the lateral epithelial tissue (LE) adjacent to the dorsal opening advance contra-laterally, with a simultaneous retraction of the amnioserosa. The process involves a fair degree of coordinated cell shape changes in the dorsal most epithelial (DME) cells as well as a few penultimate rows of lateral epithelial (LE) cells (collectively referred here as Dorsolateral Epithelial (DLE) cells), lining the periphery of the amnioserosa, which in due course of time extend contra-laterally and ultimately fuse over the dorsal hole, giving rise to a dorsal epithelial continuum. The JNK-Dpp signaling in the dorsolateral epidermis, plays an instrumental role in guiding their fate during this process. A large array of genes have been reported to be involved in the regulation of this core signaling pathway, yet the mechanisms by which they do so is hitherto unclear, which forms the objective of our present study. Here we show a probable mechanism via which lgl, a conserved tumour suppressor gene, regulates the JNK-Dpp pathway during dorsal closure and epithelial morphogenesis. A conditional/targeted knock-down of lgl in the dorsolateral epithelium of embryos results in failure of dorsal closure. Interestingly, we also observed a similar phenotype in a Rab11 knockdown condition. Our experiment suggests Rab11 to be interacting with lgl as they seem to synergize in order to regulate the core JNK-Dpp signaling pathway during dorsal closure and also during adult thorax closure process.
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Affiliation(s)
- Nabarun Nandy
- Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221005, India
| | - Jagat Kumar Roy
- Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221005, India.
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30
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Venugopal K, Chehade S, Werkmeister E, Barois N, Periz J, Lafont F, Tardieux I, Khalife J, Langsley G, Meissner M, Marion S. Rab11A regulates dense granule transport and secretion during Toxoplasma gondii invasion of host cells and parasite replication. PLoS Pathog 2020; 16:e1008106. [PMID: 32463830 PMCID: PMC7255593 DOI: 10.1371/journal.ppat.1008106] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 02/10/2020] [Indexed: 12/31/2022] Open
Abstract
Toxoplasma gondii possesses an armada of secreted virulent factors that enable parasite invasion and survival into host cells. These factors are contained in specific secretory organelles, the rhoptries, micronemes and dense granules that release their content upon host cell recognition. Dense granules are secreted in a constitutive manner during parasite replication and play a crucial role in modulating host metabolic and immune responses. While the molecular mechanisms triggering rhoptry and microneme release upon host cell adhesion have been well studied, constitutive secretion remains a poorly explored aspect of T. gondii vesicular trafficking. Here, we investigated the role of the small GTPase Rab11A, a known regulator of exocytosis in eukaryotic cells. Our data revealed an essential role of Rab11A in promoting the cytoskeleton driven transport of dense granules and the release of their content into the vacuolar space. Rab11A also regulates transmembrane protein trafficking and localization during parasite replication, indicating a broader role of Rab11A in cargo exocytosis at the plasma membrane. Moreover, we found that Rab11A also regulates extracellular parasite motility and adhesion to host cells. In line with these findings, MIC2 secretion was altered in Rab11A-defective parasites, which also exhibited severe morphological defects. Strikingly, by live imaging we observed a polarized accumulation of Rab11A-positive vesicles and dense granules at the apical pole of extracellular motile and invading parasites suggesting that apically polarized Rab11A-dependent delivery of cargo regulates early secretory events during parasite entry into host cells. Toxoplasma gondii (T. gondii) is a highly prevalent parasite infecting a wide range of animals as well as humans. T. gondii secretes numerous virulent factors contained in specific organelles, termed the rhoptries, micronemes and dense granules. These factors are released upon host cell recognition and enable parasite invasion and subsequent development into an intracellular vacuole. In particular, dense granules contain critical effectors that modulate intrinsic defenses of infected host cells ensuring parasite survival and dissemination. The mechanisms regulating dense granule secretion have not been elucidated. In this study, we unraveled a novel role for the T. gondii GTPase Rab11A in promoting dense granule transport along the parasite cytoskeleton and their content release into the vacuolar space during parasite replication. We also found that T. gondii Rab11A regulates extracellular parasite motility and adhesion to host cells suggesting a broader role in distinct secretory pathways essential for parasite virulence.
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Affiliation(s)
- Kannan Venugopal
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 9017—CIIL—Center for Infection and Immunity of Lille, Lille, France
| | - Sylia Chehade
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 9017—CIIL—Center for Infection and Immunity of Lille, Lille, France
| | - Elisabeth Werkmeister
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 9017—CIIL—Center for Infection and Immunity of Lille, Lille, France
| | - Nicolas Barois
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 9017—CIIL—Center for Infection and Immunity of Lille, Lille, France
| | - Javier Periz
- Department of Veterinary Sciences, Experimental Parasitology, Ludwig-Maximilians-Universität, Munich, Germany
| | - Frank Lafont
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 9017—CIIL—Center for Infection and Immunity of Lille, Lille, France
| | - Isabelle Tardieux
- Institute for Advanced Biosciences (IAB), Membrane Dynamics of Parasite-Host Cell Interactions, CNRS UMR5309, INSERM U1209, Université Grenoble Alpes, Grenoble, France
| | - Jamal Khalife
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 9017—CIIL—Center for Infection and Immunity of Lille, Lille, France
| | - Gordon Langsley
- Laboratoire de Biologie Comparative des Apicomplexes, Faculté de Médicine, Université Paris Descartes—Sorbonne Paris Cité, France, INSERM U1016, CNRS UMR8104, Institut Cochin, Paris, France
| | - Markus Meissner
- Department of Veterinary Sciences, Experimental Parasitology, Ludwig-Maximilians-Universität, Munich, Germany
| | - Sabrina Marion
- Univ. Lille, CNRS, Inserm, CHU Lille, Institut Pasteur de Lille, U1019—UMR 9017—CIIL—Center for Infection and Immunity of Lille, Lille, France
- * E-mail:
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31
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Ganesan SJ, Feyder MJ, Chemmama IE, Fang F, Rout MP, Chait BT, Shi Y, Munson M, Sali A. Integrative structure and function of the yeast exocyst complex. Protein Sci 2020; 29:1486-1501. [PMID: 32239688 DOI: 10.1002/pro.3863] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 12/13/2022]
Abstract
Exocyst is an evolutionarily conserved hetero-octameric tethering complex that plays a variety of roles in membrane trafficking, including exocytosis, endocytosis, autophagy, cell polarization, cytokinesis, pathogen invasion, and metastasis. Exocyst serves as a platform for interactions between the Rab, Rho, and Ral small GTPases, SNARE proteins, and Sec1/Munc18 regulators that coordinate spatial and temporal fidelity of membrane fusion. However, its mechanism is poorly described at the molecular level. Here, we determine the molecular architecture of the yeast exocyst complex by an integrative approach, based on a 3D density map from negative-stain electron microscopy (EM) at ~16 Å resolution, 434 disuccinimidyl suberate and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride cross-links from chemical-crosslinking mass spectrometry, and partial atomic models of the eight subunits. The integrative structure is validated by a previously determined cryo-EM structure, cross-links, and distances from in vivo fluorescence microscopy. Our subunit configuration is consistent with the cryo-EM structure, except for Sec5. While not observed in the cryo-EM map, the integrative model localizes the N-terminal half of Sec3 near the Sec6 subunit. Limited proteolysis experiments suggest that the conformation of Exo70 is dynamic, which may have functional implications for SNARE and membrane interactions. This study illustrates how integrative modeling based on varied low-resolution structural data can inform biologically relevant hypotheses, even in the absence of high-resolution data.
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Affiliation(s)
- Sai J Ganesan
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA.,Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, USA
| | - Michael J Feyder
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Ilan E Chemmama
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA.,Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, USA
| | - Fei Fang
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Michael P Rout
- Laboratory of Cellular and Structural Biology, The Rockefeller University, New York, New York, USA
| | - Brian T Chait
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, New York, USA
| | - Yi Shi
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, San Francisco, California, USA.,Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California, USA
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32
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Wen P, Zhang F, Fu Y, Zhu JY, Han Z. Exocyst Genes Are Essential for Recycling Membrane Proteins and Maintaining Slit Diaphragm in Drosophila Nephrocytes. J Am Soc Nephrol 2020; 31:1024-1034. [PMID: 32238475 DOI: 10.1681/asn.2019060591] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 02/17/2020] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Studies have linked mutations in genes encoding the eight-protein exocyst protein complex to kidney disease, but the underlying mechanism is unclear. Because Drosophila nephrocytes share molecular and structural features with mammalian podocytes, they provide an efficient model for studying this issue. METHODS We silenced genes encoding exocyst complex proteins specifically in Drosophila nephrocytes and studied the effects on protein reabsorption by lacuna channels and filtration by the slit diaphragm. We performed nephrocyte functional assays, carried out super-resolution confocal microscopy of slit diaphragm proteins, and used transmission electron microscopy to analyze ultrastructural changes. We also examined the colocalization of slit diaphragm proteins with exocyst protein Sec15 and with endocytosis and recycling regulators Rab5, Rab7, and Rab11. RESULTS Silencing exocyst genes in nephrocytes led to profound changes in structure and function. Abolition of cellular accumulation of hemolymph proteins with dramatically reduced lacuna channel membrane invaginations offered a strong indication of reabsorption defects. Moreover, the slit diaphragm's highly organized surface structure-essential for filtration-was disrupted, and key proteins were mislocalized. Ultrastructural analysis revealed that exocyst gene silencing led to the striking appearance of novel electron-dense structures that we named "exocyst rods," which likely represent accumulated membrane proteins following defective exocytosis or recycling. The slit diaphragm proteins partially colocalized with Sec15, Rab5, and Rab11. CONCLUSIONS Our findings suggest that the slit diaphragm of Drosophila nephrocytes requires balanced endocytosis and recycling to maintain its structural integrity and that impairment of the exocyst complex leads to disruption of the slit diaphragm and nephrocyte malfunction. This model may help identify therapeutic targets for treating kidney diseases featuring molecular defects in vesicle endocytosis, exocytosis, and recycling.
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Affiliation(s)
- Pei Wen
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland.,Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Fujian Zhang
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Yulong Fu
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Jun-Yi Zhu
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland.,Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
| | - Zhe Han
- Center for Precision Disease Modeling, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland .,Division of Endocrinology, Diabetes and Nutrition, Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
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33
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Plutoni C, Keil S, Zeledon C, Delsin LEA, Decelle B, Roux PP, Carréno S, Emery G. Misshapen coordinates protrusion restriction and actomyosin contractility during collective cell migration. Nat Commun 2019; 10:3940. [PMID: 31477736 PMCID: PMC6718686 DOI: 10.1038/s41467-019-11963-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 07/19/2019] [Indexed: 11/09/2022] Open
Abstract
Collective cell migration is involved in development, wound healing and metastasis. In the Drosophila ovary, border cells (BC) form a small cluster that migrates collectively through the egg chamber. To achieve directed motility, the BC cluster coordinates the formation of protrusions in its leader cell and contractility at the rear. Restricting protrusions to leader cells requires the actin and plasma membrane linker Moesin. Herein, we show that the Ste20-like kinase Misshapen phosphorylates Moesin in vitro and in BC. Depletion of Misshapen disrupts protrusion restriction, thereby allowing other cells within the cluster to protrude. In addition, we show that Misshapen is critical to generate contractile forces both at the rear of the cluster and at the base of protrusions. Together, our results indicate that Misshapen is a key regulator of BC migration as it coordinates two independent pathways that restrict protrusion formation to the leader cells and induces contractile forces.
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Affiliation(s)
- Cédric Plutoni
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada
| | - Sarah Keil
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada
| | - Carlos Zeledon
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada
| | - Lara Elis Alberici Delsin
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada
| | - Barbara Decelle
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada
| | - Philippe P Roux
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada.,Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Sébastien Carréno
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada.,Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada
| | - Gregory Emery
- Institute for Research in Immunology and Cancer (IRIC), Université de Montréal, Montréal, QC, Canada. .,Department of Pathology and Cell Biology, Faculty of Medicine, Université de Montréal, Montréal, QC, Canada.
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34
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Bhuin T, Roy JK. Developmental expression, co-localization and genetic interaction of exocyst component Sec15 with Rab11 during Drosophila development. Exp Cell Res 2019; 381:94-104. [PMID: 31071318 DOI: 10.1016/j.yexcr.2019.04.038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 04/17/2019] [Accepted: 04/30/2019] [Indexed: 12/13/2022]
Abstract
Sec15, a component of an evolutionarily conserved octomeric exocyst complex, has been identified as an interactor of GTP-bound Rab11 in mammals and Drosophila which shows its role in secretion in yeast and intracellular vesicle transport. Here, we report the expression patterns of Drosophila Sec15 (DSec15) transcript and Sec15 protein during Drosophila development. At early embryonic stages, a profound level of maternally loaded DSec15 transcript and protein is found. At cellular blastoderm cells (stage 5 embryos); the expression is seen in pole cells, apical membrane and sub-apical region. The transcript is predominantly accumulated in mesoderm, tracheal pits, gut, LE cells, trachea, and ventral nerve cord as development proceeds. While, a robust expression of Sec15 is seen in amnioserosa (AS), lateral epidermis (LAE), developing trachea, gut, ventral nerve cord and epithelial cells. During larval development, the transcript is also found in all imaginal discs with a distinguished accumulation in the morphogenetic furrow of eye disc, gut, proventriculus and gastric ceacae, garland cells/nephrocytes, malpighian tubules, ovary and testis. Further, we show that Sec15 co-localizes with Rab11 during Drosophila embryonic and larval development. Finally, using a genetic approach, we demonstrate that Sec15 interacts with Rab11 in producing blister during Drosophila wing development.
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Affiliation(s)
- Tanmay Bhuin
- Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221 005, India; Department of Zoology, The University of Burdwan, Golapbag, Burdwan, 713104, India.
| | - Jagat K Roy
- Cytogenetics Laboratory, Department of Zoology, Banaras Hindu University, Varanasi, 221 005, India
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35
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Fu D, Cardona P, Ho H, Watkins PB, Brouwer KLR. Novel Mechanisms of Valproate Hepatotoxicity: Impaired Mrp2 Trafficking and Hepatocyte Depolarization. Toxicol Sci 2019; 171:431-442. [PMID: 31368504 PMCID: PMC6760262 DOI: 10.1093/toxsci/kfz154] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 07/02/2019] [Accepted: 07/03/2019] [Indexed: 12/14/2022] Open
Abstract
Drug-induced liver injury (DILI) remains a major challenge in drug development. Although numerous mechanisms for DILI have been identified, few studies have focused on loss of hepatocyte polarization as a DILI mechanism. The current study investigated the effects of valproate, an antiepileptic drug with DILI risk, on the cellular mechanisms responsible for loss of hepatocyte polarization. Fully polarized collagen sandwich-cultured rat hepatocytes were treated with valproate (1-20mM) for specified times (3-24hr). Hepatocyte viability was significantly decreased by 10mM and 20mM valproate. Valproate depolarized hepatocytes, even at non-cytotoxic concentrations (=5mM). Depolarization was associated with significantly decreased canalicular levels of multidrug resistance-associated protein 2 (Mrp2) resulting in reduced canalicular excretion of the Mrp2 substrate carboxydichlorofluorescein. The decreased canalicular Mrp2 was associated with intracellular accumulation of Mrp2 in Rab11-positive recycling endosomes and early endosomes. Mechanistic studies suggested that valproate inhibited canalicular trafficking of Mrp2. This effect of valproate on Mrp2 appeared to be selective in that valproate had less impact on canalicular levels of the bile salt export pump (Bsep) and no detectable effect on P-glycoprotein (P-gp) canalicular levels. Treatment with valproate for 24hr also significantly downregulated levels of tight junction-associated protein, zonula occludens 2 (ZO2), but appeared to have no effect on the levels of tight junction proteins claudin 1, claudin 2, occludin, ZO1 and ZO3. These findings reveal that two novel mechanisms may contribute to valproate hepatotoxicity: impaired canalicular trafficking of Mrp2 and disruption of ZO2-associated hepatocyte polarization.
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Affiliation(s)
- Dong Fu
- UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Panli Cardona
- UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Henry Ho
- UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Paul B Watkins
- UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Kim L R Brouwer
- UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC
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36
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Kumar H, Pushpa K, Kumari A, Verma K, Pergu R, Mylavarapu SVS. The exocyst complex and Rab5 are required for abscission by localizing ESCRT III subunits to the cytokinetic bridge. J Cell Sci 2019; 132:jcs226001. [PMID: 31221728 PMCID: PMC6679584 DOI: 10.1242/jcs.226001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 06/14/2019] [Indexed: 01/26/2023] Open
Abstract
Cytokinesis is the final step of cell division following chromosome segregation that generates two daughter cells. The conserved exocyst complex is required for scission of the intercellular cytokinetic bridge, although the molecular mechanisms it employs in this process are unclear. We identify and validate the early endocytic GTPase Rab5 as interacting with the exocyst complex in mammalian cells. Rab5 localizes in the cytokinetic bridge and on the midbody ring in a manner similar to the exocyst complex. Depletion of Rab5 led to delayed abscission. Caenorhabditis elegans orthologs of both exocyst complex subunits and Rab5 localize along the cleavage furrow and are required for cytokinesis in early embryos. Cytokinetic cells depleted of either Rab5 or the exocyst subunits Exoc3 and Exoc4 showed impaired deposition of the endosomal sorting complexes required for transport (ESCRT) III subunits CHMP2B and/or CHMP4B near the midbody ring. The study reveals an evolutionarily conserved role for the early endocytic marker Rab5 in cytokinetic abscission. In addition, it uncovers a key requirement of the exocyst and Rab5 for the delivery of components of the membrane-severing ESCRT III machinery to complete cytokinesis.
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Affiliation(s)
- Harsh Kumar
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone Faridabad-Gurgaon Expressway, Faridabad, Haryana 121001, India
- Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Kumari Pushpa
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone Faridabad-Gurgaon Expressway, Faridabad, Haryana 121001, India
| | - Amrita Kumari
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone Faridabad-Gurgaon Expressway, Faridabad, Haryana 121001, India
- Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Kuldeep Verma
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone Faridabad-Gurgaon Expressway, Faridabad, Haryana 121001, India
| | - Rajaiah Pergu
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone Faridabad-Gurgaon Expressway, Faridabad, Haryana 121001, India
- Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
| | - Sivaram V S Mylavarapu
- Laboratory of Cellular Dynamics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, 3rd Milestone Faridabad-Gurgaon Expressway, Faridabad, Haryana 121001, India
- Manipal Academy of Higher Education, Manipal, Karnataka 576104, India
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37
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Nishida‐Fukuda H. The Exocyst: Dynamic Machine or Static Tethering Complex? Bioessays 2019; 41:e1900056. [DOI: 10.1002/bies.201900056] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 05/14/2019] [Indexed: 01/15/2023]
Affiliation(s)
- Hisayo Nishida‐Fukuda
- Department of Genome Editing, Institute of Biomedical ScienceKansai Medical University2‐5‐1 Shin‐machi, Hirakata Osaka 5731010 Japan
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38
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Live-Cell Structural Biology to Solve Biological Mechanisms: The Case of the Exocyst. Structure 2019; 27:886-892. [DOI: 10.1016/j.str.2019.04.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 04/01/2019] [Accepted: 04/18/2019] [Indexed: 01/24/2023]
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39
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Ungermann C, Kümmel D. Structure of membrane tethers and their role in fusion. Traffic 2019; 20:479-490. [DOI: 10.1111/tra.12655] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 04/26/2019] [Accepted: 05/03/2019] [Indexed: 12/27/2022]
Affiliation(s)
- Christian Ungermann
- Biochemistry Section, Department of Biology/ChemistryUniversity of Osnabrück Osnabrück Germany
- Center for Cellular Nanoanalytics (CellNanOs)University of Osnabrück Osnabrück Germany
| | - Daniel Kümmel
- Biochemistry & Structural Biology Section, Institute of BiochemistryUniversity of Münster Münster Germany
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40
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Zhu S, Bhat S, Syan S, Kuchitsu Y, Fukuda M, Zurzolo C. Rab11a-Rab8a cascade regulates the formation of tunneling nanotubes through vesicle recycling. J Cell Sci 2018; 131:jcs.215889. [PMID: 30209134 DOI: 10.1242/jcs.215889] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 08/29/2018] [Indexed: 01/02/2023] Open
Abstract
Tunneling nanotubes (TNTs) are actin-enriched membranous channels enabling cells to communicate over long distances. TNT-like structures form between various cell types and mediate the exchange of different cargos, such as ions, vesicles, organelles and pathogens; thus, they may play a role in physiological conditions and diseases (e.g. cancer and infection). TNTs also allow the intercellular passage of protein aggregates related to neurodegenerative diseases, thus propagating protein misfolding. Understanding the mechanism of TNT formation is mandatory in order to reveal the mechanism of disease propagation and to uncover their physiological function. Vesicular transport controlled by the small GTPases Rab11a and Rab8a can promote the formation of different plasma membrane protrusions (filopodia, cilia and neurites). Here, we report that inhibiting membrane recycling reduces the number of TNT-connected cells and that overexpression of Rab11a and Rab8a increases the number of TNT-connected cells and the propagation of vesicles between cells in co-culture. We demonstrate that these two Rab GTPases act in a cascade in which Rab11a activation of Rab8a is independent of Rabin8. We also show that VAMP3 acts downstream of Rab8a to regulate TNT formation.
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Affiliation(s)
- Seng Zhu
- Unit of Membrane Trafficking and Pathogenesis, Department of Cell Biology and Infection, Pasteur Institute, Paris 75015, France
| | - Shaarvari Bhat
- Unit of Membrane Trafficking and Pathogenesis, Department of Cell Biology and Infection, Pasteur Institute, Paris 75015, France
| | - Sylvie Syan
- Unit of Membrane Trafficking and Pathogenesis, Department of Cell Biology and Infection, Pasteur Institute, Paris 75015, France
| | - Yoshihiko Kuchitsu
- Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Mitsunori Fukuda
- Department of Integrative Life Sciences, Graduate School of Life Sciences, Tohoku University, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Chiara Zurzolo
- Unit of Membrane Trafficking and Pathogenesis, Department of Cell Biology and Infection, Pasteur Institute, Paris 75015, France
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41
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Arasaki K, Kimura H, Tagaya M, Roy CR. Legionella remodels the plasma membrane-derived vacuole by utilizing exocyst components as tethers. J Cell Biol 2018; 217:3863-3872. [PMID: 30275106 PMCID: PMC6219717 DOI: 10.1083/jcb.201801208] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 07/10/2018] [Accepted: 08/31/2018] [Indexed: 12/15/2022] Open
Abstract
Legionella pneumophila enters cells in a vacuole derived from the plasma membrane, which then sequesters vesicles from the ER in order to support parasite growth and immune evasion. Arasaki et al. now reveal that the Legionella effector DrrA recruits components of the exocyst to promote tethering of host vesicles with the LCV. During the initial stage of infection, Legionella pneumophila secretes effectors that promote the fusion of endoplasmic reticulum (ER)–derived vesicles with the Legionella-containing vacuole (LCV). This fusion leads to a remodeling of the plasma membrane (PM)–derived LCV into a specialized ER-like compartment that supports bacterial replication. Although the effector DrrA has been shown to activate the small GTPase Rab1, it remains unclear how DrrA promotes the tethering of host vesicles with the LCV. Here, we show that Sec5, Sec15, and perhaps Sec6, which are subunits of the exocyst that functions in the tethering of exocytic vesicles with the PM, are required for DrrA-mediated, ER-derived vesicle recruitment to the PM-derived LCV. These exocyst components were found to interact specifically with a complex containing DrrA, and the loss of Sec5 or Sec15 significantly suppressed the recruitment of ER-derived vesicles to the LCV and inhibited intracellular replication of Legionella. Importantly, Sec15 is recruited to the LCV, and Rab1 activation is necessary for this recruitment.
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Affiliation(s)
- Kohei Arasaki
- Department of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, New Haven, CT .,School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Hana Kimura
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Mitsuo Tagaya
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
| | - Craig R Roy
- Department of Microbial Pathogenesis, Yale University School of Medicine, Boyer Center for Molecular Medicine, New Haven, CT
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42
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Lepore DM, Martínez-Núñez L, Munson M. Exposing the Elusive Exocyst Structure. Trends Biochem Sci 2018; 43:714-725. [PMID: 30055895 PMCID: PMC6108956 DOI: 10.1016/j.tibs.2018.06.012] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 06/18/2018] [Accepted: 06/29/2018] [Indexed: 11/18/2022]
Abstract
A major challenge for a molecular understanding of membrane trafficking has been the elucidation of high-resolution structures of large, multisubunit tethering complexes that spatially and temporally control intracellular membrane fusion. Exocyst is a large hetero-octameric protein complex proposed to tether secretory vesicles at the plasma membrane to provide quality control of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated membrane fusion. Breakthroughs in methodologies, including sample preparation, biochemical characterization, fluorescence microscopy, and single-particle cryoelectron microscopy, are providing critical insights into the structure and function of the exocyst. These studies now pose more questions than answers for understanding fundamental functional mechanisms, and they open wide the door for future studies to elucidate interactions with protein and membrane partners, potential conformational changes, and molecular insights into tethering reactions.
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Affiliation(s)
- Dante M Lepore
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Leonora Martínez-Núñez
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Mary Munson
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.
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43
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Polgar N, Fogelgren B. Regulation of Cell Polarity by Exocyst-Mediated Trafficking. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a031401. [PMID: 28264817 DOI: 10.1101/cshperspect.a031401] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
One requirement for establishing polarity within a cell is the asymmetric trafficking of intracellular vesicles to the plasma membrane. This tightly regulated process creates spatial and temporal differences in both plasma membrane composition and the membrane-associated proteome. Asymmetric membrane trafficking is also a critical mechanism to regulate cell differentiation, signaling, and physiology. Many eukaryotic cell types use the eight-protein exocyst complex to orchestrate polarized vesicle trafficking to certain membrane locales. Members of the exocyst were originally discovered in yeast while screening for proteins required for the delivery of secretory vesicles to the budding daughter cell. The same eight exocyst genes are conserved in mammals, in which the specifics of exocyst-mediated trafficking are highly cell-type-dependent. Some exocyst members bind to certain Rab GTPases on intracellular vesicles, whereas others localize to the plasma membrane at the site of exocytosis. Assembly of the exocyst holocomplex is responsible for tethering these vesicles to the plasma membrane before their soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated exocytosis. In this review, we will focus on the role and regulation of the exocyst complex in targeted vesicular trafficking as related to the establishment and maintenance of cellular polarity. We will contrast exocyst function in apicobasal epithelial polarity versus front-back mesenchymal polarity, and the dynamic regulation of exocyst-mediated trafficking during cell phenotype transitions.
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Affiliation(s)
- Noemi Polgar
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii 96813
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44
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Mei K, Li Y, Wang S, Shao G, Wang J, Ding Y, Luo G, Yue P, Liu JJ, Wang X, Dong MQ, Wang HW, Guo W. Cryo-EM structure of the exocyst complex. Nat Struct Mol Biol 2018; 25:139-146. [PMID: 29335562 PMCID: PMC5971111 DOI: 10.1038/s41594-017-0016-2] [Citation(s) in RCA: 93] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2017] [Accepted: 12/07/2017] [Indexed: 12/22/2022]
Abstract
The exocyst is an evolutionarily conserved octameric protein complex that mediates the tethering of post-Golgi secretory vesicles to the plasma membrane during exocytosis and is implicated in many cellular processes such as cell polarization, cytokinesis, ciliogenesis and tumor invasion. Using cryo-EM and chemical cross-linking MS (CXMS), we solved the structure of the Saccharomyces cerevisiae exocyst complex at an average resolution of 4.4 Å. Our model revealed the architecture of the exocyst and led to the identification of the helical bundles that mediate the assembly of the complex at its core. Sequence analysis suggests that these regions are evolutionarily conserved across eukaryotic systems. Additional cell biological data suggest a mechanism for exocyst assembly that leads to vesicle tethering at the plasma membrane.
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Affiliation(s)
- Kunrong Mei
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Yan Li
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China.,School of Life Sciences, Tsinghua University, Beijing, China.,Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Shaoxiao Wang
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Guangcan Shao
- National Institute of Biological Sciences, Beijing, China
| | - Jia Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China.,School of Life Sciences, Tsinghua University, Beijing, China.,Tsinghua-Peking Joint Center for Life Sciences, Beijing, China
| | - Yuehe Ding
- National Institute of Biological Sciences, Beijing, China
| | - Guangzuo Luo
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Peng Yue
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA
| | - Jun-Jie Liu
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China.,School of Life Sciences, Tsinghua University, Beijing, China.,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Xinquan Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China.,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China.,School of Life Sciences, Tsinghua University, Beijing, China
| | - Meng-Qiu Dong
- National Institute of Biological Sciences, Beijing, China
| | - Hong-Wei Wang
- Ministry of Education Key Laboratory of Protein Sciences, Tsinghua University, Beijing, China. .,Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, China. .,School of Life Sciences, Tsinghua University, Beijing, China. .,Tsinghua-Peking Joint Center for Life Sciences, Beijing, China.
| | - Wei Guo
- Department of Biology, University of Pennsylvania, Philadelphia, PA, USA.
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45
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Abstract
Polarized exocytosis is generally considered as the multistep vesicular trafficking process in which membrane-bounded carriers are transported from the Golgi or endosomal compartments to specific sites of the plasma membrane. Polarized exocytosis in cells is achieved through the coordinated actions of membrane trafficking machinery and cytoskeleton orchestrated by signaling molecules such as the Rho family of small GTPases. Elucidating the molecular mechanisms of polarized exocytosis is essential to our understanding of a wide range of pathophysiological processes from neuronal development to tumor invasion.
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Affiliation(s)
- Jingwen Zeng
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
| | - Shanshan Feng
- Key Laboratory for Regenerative Medicine of Ministry of Education and Department of Developmental & Regenerative Biology, Jinan University, Guangzhou 510632, P.R. China
| | - Bin Wu
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
| | - Wei Guo
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6018
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46
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Bernabé-Rubio M, Alonso MA. Routes and machinery of primary cilium biogenesis. Cell Mol Life Sci 2017; 74:4077-4095. [PMID: 28624967 PMCID: PMC11107551 DOI: 10.1007/s00018-017-2570-5] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 06/01/2017] [Accepted: 06/13/2017] [Indexed: 02/06/2023]
Abstract
Primary cilia are solitary, microtubule-based protrusions of the cell surface that play fundamental roles as photosensors, mechanosensors and biochemical sensors. Primary cilia dysfunction results in a long list of developmental and degenerative disorders that combine to give rise to a large spectrum of human diseases affecting almost any major body organ. Depending on the cell type, primary ciliogenesis is initiated intracellularly, as in fibroblasts, or at the cell surface, as in renal polarized epithelial cells. In this review, we have focused on the routes of primary ciliogenesis placing particular emphasis on the recently described pathway in renal polarized epithelial cells by which the midbody remnant resulting from a previous cell division event enables the centrosome for initiation of primary cilium assembly. The protein machinery implicated in primary cilium formation in epithelial cells, including the machinery best known for its involvement in establishing cell polarity and polarized membrane trafficking, is also discussed.
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Affiliation(s)
- Miguel Bernabé-Rubio
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Nicolás Cabrera 1, Cantoblanco, 28049, Madrid, Spain
| | - Miguel A Alonso
- Department of Cell Biology and Immunology, Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Nicolás Cabrera 1, Cantoblanco, 28049, Madrid, Spain.
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47
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Guichard A, Jain P, Moayeri M, Schwartz R, Chin S, Zhu L, Cruz-Moreno B, Liu JZ, Aguilar B, Hollands A, Leppla SH, Nizet V, Bier E. Anthrax edema toxin disrupts distinct steps in Rab11-dependent junctional transport. PLoS Pathog 2017; 13:e1006603. [PMID: 28945820 PMCID: PMC5612732 DOI: 10.1371/journal.ppat.1006603] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 08/24/2017] [Indexed: 02/06/2023] Open
Abstract
Various bacterial toxins circumvent host defenses through overproduction of cAMP. In a previous study, we showed that edema factor (EF), an adenylate cyclase from Bacillus anthracis, disrupts endocytic recycling mediated by the small GTPase Rab11. As a result, cargo proteins such as cadherins fail to reach inter-cellular junctions. In the present study, we provide further mechanistic dissection of Rab11 inhibition by EF using a combination of Drosophila and mammalian systems. EF blocks Rab11 trafficking after the GTP-loading step, preventing a constitutively active form of Rab11 from delivering cargo vesicles to the plasma membrane. Both of the primary cAMP effector pathways -PKA and Epac/Rap1- contribute to inhibition of Rab11-mediated trafficking, but act at distinct steps of the delivery process. PKA acts early, preventing Rab11 from associating with its effectors Rip11 and Sec15. In contrast, Epac functions subsequently via the small GTPase Rap1 to block fusion of recycling endosomes with the plasma membrane, and appears to be the primary effector of EF toxicity in this process. Similarly, experiments conducted in mammalian systems reveal that Epac, but not PKA, mediates the activity of EF both in cell culture and in vivo. The small GTPase Arf6, which initiates endocytic retrieval of cell adhesion components, also contributes to junctional homeostasis by counteracting Rab11-dependent delivery of cargo proteins at sites of cell-cell contact. These studies have potentially significant practical implications, since chemical inhibition of either Arf6 or Epac blocks the effect of EF in cell culture and in vivo, opening new potential therapeutic avenues for treating symptoms caused by cAMP-inducing toxins or related barrier-disrupting pathologies. Recent anthrax outbreaks in Zambia and northern Russia and biodefense preparedness highlight the need for new therapies to counteract fatal late-stage pathologies in patients infected with Bacillus anthracis. Indeed, two toxins secreted by this pathogen—edema toxin (ET) and lethal toxin (LT)—can cause death in face of effective antibiotic treatment. ET, a potent adenylate cyclase, severely impacts host cells and tissues through an overproduction of the ubiquitous second messenger cAMP. Previously, we identified Rab11 as a key host factor inhibited by ET. Blockade of Rab11-dependent endocytic recycling resulted in the disruption of intercellular junctions, likely contributing to life threatening vascular effusion observed in anthrax patients. Here we present a multi-system analysis of the mechanism by which EF inhibits Rab11 and exocyst-dependent trafficking. Epistasis experiments in Drosophila reveal that over-activation of the cAMP effectors PKA and Epac/Rap1 interferes with Rab11-mediated trafficking at two distinct steps. We further describe conserved roles of Epac and the small GTPase Arf6 in ET-mediated disruption of vesicular trafficking and show how chemical inhibition of either pathway greatly alleviates ET-induced edema. Thus, our study defines Epac and Arf6 as promising drug targets for the treatment of infectious diseases and other pathologies involving cAMP overload or related barrier disruption.
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Affiliation(s)
- Annabel Guichard
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Prashant Jain
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Mahtab Moayeri
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, United States of America
| | - Ruth Schwartz
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Stephen Chin
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Lin Zhu
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Beatriz Cruz-Moreno
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Janet Z. Liu
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, United States of America
| | - Bernice Aguilar
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, United States of America
- Division of Pediatric Infectious Diseases and the Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, United States of America
| | - Andrew Hollands
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, United States of America
| | - Stephen H. Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, United States of America
| | - Victor Nizet
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, United States of America
- Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, United States of America
| | - Ethan Bier
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
- * E-mail:
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Inoshita M, Mima J. Human Rab small GTPase- and class V myosin-mediated membrane tethering in a chemically defined reconstitution system. J Biol Chem 2017; 292:18500-18517. [PMID: 28939769 DOI: 10.1074/jbc.m117.811356] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 09/21/2017] [Indexed: 12/13/2022] Open
Abstract
Membrane tethering is a fundamental process essential for the compartmental specificity of intracellular membrane trafficking in eukaryotic cells. Rab-family small GTPases and specific sets of Rab-interacting effector proteins, including coiled-coil tethering proteins and multisubunit tethering complexes, are reported to be responsible for membrane tethering. However, whether and how these key components directly and specifically tether subcellular membranes remains enigmatic. Using chemically defined proteoliposomal systems reconstituted with purified human Rab proteins and synthetic liposomal membranes to study the molecular basis of membrane tethering, we established here that Rab-family GTPases have a highly conserved function to directly mediate membrane tethering, even in the absence of any types of Rab effectors such as the so-called tethering proteins. Moreover, we demonstrate that membrane tethering mediated by endosomal Rab11a is drastically and selectively stimulated by its cognate Rab effectors, class V myosins (Myo5A and Myo5B), in a GTP-dependent manner. Of note, Myo5A and Myo5B exclusively recognized and cooperated with the membrane-anchored form of their cognate Rab11a to support membrane tethering mediated by trans-Rab assemblies on opposing membranes. Our findings support the novel concept that Rab-family proteins provide a bona fide membrane tether to physically and specifically link two distinct lipid bilayers of subcellular membranes. They further indicate that Rab-interacting effector proteins, including class V myosins, can regulate these Rab-mediated membrane-tethering reactions.
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Affiliation(s)
- Motoki Inoshita
- From the Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
| | - Joji Mima
- From the Institute for Protein Research, Osaka University, Suita, Osaka 565-0871, Japan
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The In Vivo Architecture of the Exocyst Provides Structural Basis for Exocytosis. Cell 2017; 168:400-412.e18. [PMID: 28129539 DOI: 10.1016/j.cell.2017.01.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 10/18/2016] [Accepted: 01/05/2017] [Indexed: 11/21/2022]
Abstract
The structural characterization of protein complexes in their native environment is challenging but crucial for understanding the mechanisms that mediate cellular processes. We developed an integrative approach to reconstruct the 3D architecture of protein complexes in vivo. We applied this approach to the exocyst, a hetero-octameric complex of unknown structure that is thought to tether secretory vesicles during exocytosis with a poorly understood mechanism. We engineered yeast cells to anchor the exocyst on defined landmarks and determined the position of its subunit termini at nanometer precision using fluorescence microscopy. We then integrated these positions with the structural properties of the subunits to reconstruct the exocyst together with a vesicle bound to it. The exocyst has an open hand conformation made of rod-shaped subunits that are interlaced in the core. The exocyst architecture explains how the complex can tether secretory vesicles, placing them in direct contact with the plasma membrane.
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50
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Crystal structure of Sec10, a subunit of the exocyst complex. Sci Rep 2017; 7:40909. [PMID: 28098232 PMCID: PMC5241887 DOI: 10.1038/srep40909] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Accepted: 12/13/2016] [Indexed: 12/22/2022] Open
Abstract
The exocyst complex is a heterooctameric protein complex composed of Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70 and Exo84. This complex plays an essential role in trafficking secretory vesicles to the plasma membrane through its interaction with phosphatidylinositol 4,5-bisphosphate and small GTPases. To date, the near-full-length structural information of each subunit has been limited to Exo70, although the C-terminal half structures of Sec6, Sec15 and Exo84 and the structures of the small GTPase-binding domains of Sec3, Sec5 and Exo84 have been reported. Here, we report the crystal structure of the near-full-length zebrafish Sec10 (zSec10) at 2.73 Å resolution. The structure of zSec10 consists of tandem antiparallel helix bundles that form a straight rod, like helical core regions of other exocyst subunits. This structure provides the first atomic details of Sec10, which may be useful for future functional and structural studies of this subunit and the exocyst complex.
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