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Zuriegat Q, Abubakar YS, Wang Z, Chen M, Zhang J. Emerging Roles of Exocyst Complex in Fungi: A Review. J Fungi (Basel) 2024; 10:614. [PMID: 39330374 PMCID: PMC11433146 DOI: 10.3390/jof10090614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2024] [Revised: 08/19/2024] [Accepted: 08/21/2024] [Indexed: 09/28/2024] Open
Abstract
The exocyst complex, an evolutionarily conserved octameric protein assembly, plays a central role in the targeted binding and fusion of vesicles at the plasma membrane. In fungal cells, this transport system is essential for polarized growth, morphogenesis, cell wall maintenance and virulence. Recent advances have greatly improved our understanding of the role and regulation of the exocyst complex in fungi. This review synthesizes these developments and focuses on the intricate interplay between the exocyst complex, specific fungal cargos and regulatory proteins. Insights into thestructure of the exocyst and its functional dynamics have revealed new dimensions of its architecture and its interactions with the cellular environment. Furthermore, the regulation of exocyst activity involves complex signaling pathways and interactions with cytoskeletal elements that are crucial for its role in vesicle trafficking. By exploring these emerging themes, this review provides a comprehensive overview of the multifaceted functions of the exocyst complex in fungal biology. Understanding these mechanisms offers potential avenues for novel therapeutic strategies against fungal pathogens and insights into the general principles of vesicle trafficking in eukaryotic cells. The review therefore highlights the importance of the exocyst complex in maintaining cellular functions and its broader implications in fungal pathogenicity and cell biology.
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Affiliation(s)
- Qussai Zuriegat
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (Q.Z.); (Y.S.A.); (Z.W.)
| | - Yakubu Saddeeq Abubakar
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (Q.Z.); (Y.S.A.); (Z.W.)
| | - Zonghua Wang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (Q.Z.); (Y.S.A.); (Z.W.)
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, College of Materials and Chemical Engineering, Minjiang University, Fuzhou 350108, China
| | - Meilian Chen
- Fujian Key Laboratory on Conservation and Sustainable Utilization of Marine Biodiversity, College of Materials and Chemical Engineering, Minjiang University, Fuzhou 350108, China
| | - Jun Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Ministerial and Provincial Joint Innovation Centre for Safety Production of Cross-Strait Crops, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, China; (Q.Z.); (Y.S.A.); (Z.W.)
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Zuo X, Kwon SH, Janech MG, Dang Y, Lauzon SD, Fogelgren B, Polgar N, Lipschutz JH. Primary cilia and the exocyst are linked to urinary extracellular vesicle production and content. J Biol Chem 2019; 294:19099-19110. [PMID: 31694916 PMCID: PMC6916495 DOI: 10.1074/jbc.ra119.009297] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Revised: 10/29/2019] [Indexed: 12/13/2022] Open
Abstract
The recently proposed idea of "urocrine signaling" hypothesizes that small secreted extracellular vesicles (EVs) contain proteins that transmit signals to distant cells. However, the role of renal primary cilia in EV production and content is unclear. We previously showed that the exocyst, a highly conserved trafficking complex, is necessary for ciliogenesis; that it is present in human urinary EVs; that knockdown (KD) of exocyst complex component 5 (EXOC5), a central exocyst component, results in very short or absent cilia; and that human EXOC5 overexpression results in longer cilia. Here, we show that compared with control Madin-Darby canine kidney (MDCK) cells, EXOC5 overexpression increases and KD decreases EV numbers. Proteomic analyses of isolated EVs from EXOC5 control, KD, and EXOC5-overexpressing MDCK cells revealed significant alterations in protein composition. Using immunoblotting to specifically examine the expression levels of ADP-ribosylation factor 6 (ARF6) and EPS8-like 2 (EPS8L2) in EVs, we found that EXOC5 KD increases ARF6 levels and decreases EPS8L2 levels, and that EXOC5 overexpression increases EPS8L2. Knockout of intraflagellar transport 88 (IFT88) confirmed that the changes in EV number/content were due to cilia loss: similar to EXOC5, the IFT88 loss resulted in very short or absent cilia, decreased EV numbers, increased EV ARF6 levels, and decreased Eps8L2 levels compared with IFT88-rescued EVs. Compared with control animals, urine from proximal tubule-specific EXOC5-KO mice contained fewer EVs and had increased ARF6 levels. These results indicate that perturbations in exocyst and primary cilia affect EV number and protein content.
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Affiliation(s)
- Xiaofeng Zuo
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Sang-Ho Kwon
- Department of Cellular Biology and Anatomy, Augusta University, Augusta, Georgia 30912
| | - Michael G Janech
- Department of Biology, College of Charleston, Charleston, South Carolina 29424
| | - Yujing Dang
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Steven D Lauzon
- Department of Public Health Sciences, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | - Noemi Polgar
- Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | - Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
- Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29425
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Abou-Fadel J, Vasquez M, Grajeda B, Ellis C, Zhang J. Systems-wide analysis unravels the new roles of CCM signal complex (CSC). Heliyon 2019; 5:e02899. [PMID: 31872111 PMCID: PMC6909108 DOI: 10.1016/j.heliyon.2019.e02899] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 10/17/2019] [Accepted: 11/18/2019] [Indexed: 12/20/2022] Open
Abstract
Cerebral cavernous malformations (CCMs) are characterized by abnormally dilated intracranial capillaries that result in increased susceptibility to stroke. Three genes have been identified as causes of CCMs; KRIT1 (CCM1), MGC4607 (CCM2) and PDCD10 (CCM3); one of them is disrupted in most CCM cases. It was demonstrated that both CCM1 and CCM3 bind to CCM2 to form a CCM signaling complex (CSC) to modulate angiogenesis. In this report, we deployed both RNA-seq and proteomic analysis of perturbed CSC after depletion of one of three CCM genes to generate interactomes for system-wide studies. Our results demonstrated a unique portrait detailing alterations in angiogenesis and vascular integrity. Interestingly, only in-direct overlapped alterations between RNA and protein levels were detected, supporting the existence of multiple layers of regulation in CSC cascades. Notably, this is the first report identifying that both β4 integrin and CAV1 signaling are downstream of CSC, conveying the angiogenic signaling. Our results provide a global view of signal transduction modulated by the CSC, identifies novel regulatory signaling networks and key cellular factors associated with CSC.
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Affiliation(s)
- Johnathan Abou-Fadel
- Department of Molecular and Translational Medicine (MTM), Texas Tech University Health Science Center El Paso, El Paso, TX, 79905, USA
| | - Mariana Vasquez
- Department of Molecular and Translational Medicine (MTM), Texas Tech University Health Science Center El Paso, El Paso, TX, 79905, USA
| | - Brian Grajeda
- Department of Molecular and Translational Medicine (MTM), Texas Tech University Health Science Center El Paso, El Paso, TX, 79905, USA
| | - Cameron Ellis
- Department of Molecular and Translational Medicine (MTM), Texas Tech University Health Science Center El Paso, El Paso, TX, 79905, USA
| | - Jun Zhang
- Department of Molecular and Translational Medicine (MTM), Texas Tech University Health Science Center El Paso, El Paso, TX, 79905, USA
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Boehm C, Field MC. Evolution of late steps in exocytosis: conservation and specialization of the exocyst complex. Wellcome Open Res 2019; 4:112. [PMID: 31633057 PMCID: PMC6784791 DOI: 10.12688/wellcomeopenres.15142.2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/18/2019] [Indexed: 01/09/2023] Open
Abstract
Background: The eukaryotic endomembrane system most likely arose
via paralogous expansions of genes encoding proteins that specify organelle identity, coat complexes and govern fusion specificity. While the majority of these gene families were established by the time of the last eukaryotic common ancestor (LECA), subsequent evolutionary events has moulded these systems, likely reflecting adaptations retained for increased fitness. As well as sequence evolution, these adaptations include loss of otherwise canonical components, the emergence of lineage-specific proteins and paralog expansion. The exocyst complex is involved in late exocytosis and additional trafficking pathways and a member of the complexes associated with tethering containing helical rods (CATCHR) tethering complex family. CATCHR includes the conserved oligomeric Golgi (COG) complex, homotypic fusion and vacuole protein sorting (HOPS)/class C core vacuole/endosome tethering (CORVET) complexes and several others. The exocyst is integrated into a complex GTPase signalling network in animals, fungi and other lineages. Prompted by discovery of Exo99, a non-canonical subunit in the excavate protist
Trypanosoma brucei, and availability of significantly increased genome sequence data, we re-examined evolution of the exocyst. Methods: We examined the evolution of exocyst components by comparative genomics, phylogenetics and structure prediction. Results: The exocyst composition is highly conserved, but with substantial losses of subunits in the Apicomplexa and expansions in Streptophyta plants, Metazoa and land plants, where for the latter, massive paralog expansion of Exo70 represents an extreme and unique example. Significantly, few taxa retain a partial complex, suggesting that, in general, all subunits are probably required for functionality. Further, the ninth exocyst subunit, Exo99, is specific to the Euglenozoa with a distinct architecture compared to the other subunits and which possibly represents a coat system. Conclusions: These data reveal a remarkable degree of evolutionary flexibility within the exocyst complex, suggesting significant diversity in exocytosis mechanisms.
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Affiliation(s)
- Cordula Boehm
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK
| | - Mark C Field
- School of Life Sciences, University of Dundee, Dow Street, Dundee, DD1 5EH, UK.,Biology Centre, Institute of Parasitology, Czech Academy of Sciences, České Budějovic, 37005, Czech Republic
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5
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Lipschutz JH. The role of the exocyst in renal ciliogenesis, cystogenesis, tubulogenesis, and development. Kidney Res Clin Pract 2019; 38:260-266. [PMID: 31284362 PMCID: PMC6727897 DOI: 10.23876/j.krcp.19.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 05/13/2019] [Accepted: 05/20/2019] [Indexed: 12/23/2022] Open
Abstract
The exocyst is a highly conserved eight-subunit protein complex (EXOC1–8) involved in the targeting and docking of exocytic vesicles translocating from the trans-Golgi network to various sites in renal cells. EXOC5 is a central exocyst component because it connects EXOC6, bound to the vesicles exiting the trans-Golgi network via the small GTPase RAB8, to the rest of the exocyst complex at the plasma membrane. In the kidney, the exocyst complex is involved in primary ciliognesis, cystogenesis, and tubulogenesis. The exocyst, and its regulators, have also been found in urinary extracellular vesicles, and may be centrally involved in urocrine signaling and repair following acute kidney injury. The exocyst is centrally involved in the development of other organs, including the eye, ear, and heart. The exocyst is regulated by many different small GTPases of the RHO, RAL, RAB, and ARF families. The small GTPases, and their guanine nucleotide exchange factors and GTPase-activating proteins, likely give the exocyst specificity of function. The recent development of a floxed Exoc5 mouse line will aid researchers in studying the role of the exocyst in multiple cells and organ types by allowing for tissue-specific knockout, in conjunction with Cre-driver mouse lines.
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Affiliation(s)
- Joshua H Lipschutz
- Department of Medicine, Medical University of South Carolina, Charleston, SC, USA.,Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC, USA
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6
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Nihalani D, Solanki AK, Arif E, Srivastava P, Rahman B, Zuo X, Dang Y, Fogelgren B, Fermin D, Gillies CE, Sampson MG, Lipschutz JH. Disruption of the exocyst induces podocyte loss and dysfunction. J Biol Chem 2019; 294:10104-10119. [PMID: 31073028 PMCID: PMC6664173 DOI: 10.1074/jbc.ra119.008362] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/06/2019] [Indexed: 11/06/2022] Open
Abstract
Although the slit diaphragm proteins in podocytes are uniquely organized to maintain glomerular filtration assembly and function, little is known about the underlying mechanisms that participate in trafficking these proteins to the correct location for development and homeostasis. Identifying these mechanisms will likely provide novel targets for therapeutic intervention to preserve podocyte function following glomerular injury. Analysis of structural variation in cases of human nephrotic syndrome identified rare heterozygous deletions of EXOC4 in two patients. This suggested that disruption of the highly-conserved eight-protein exocyst trafficking complex could have a role in podocyte dysfunction. Indeed, mRNA profiling of injured podocytes identified significant exocyst down-regulation. To test the hypothesis that the exocyst is centrally involved in podocyte development/function, we generated homozygous podocyte-specific Exoc5 (a central exocyst component that interacts with Exoc4) knockout mice that showed massive proteinuria and died within 4 weeks of birth. Histological and ultrastructural analysis of these mice showed severe glomerular defects with increased fibrosis, proteinaceous casts, effaced podocytes, and loss of the slit diaphragm. Immunofluorescence analysis revealed that Neph1 and Nephrin, major slit diaphragm constituents, were mislocalized and/or lost. mRNA profiling of Exoc5 knockdown podocytes showed that vesicular trafficking was the most affected cellular event. Mapping of signaling pathways and Western blot analysis revealed significant up-regulation of the mitogen-activated protein kinase and transforming growth factor-β pathways in Exoc5 knockdown podocytes and in the glomeruli of podocyte-specific Exoc5 KO mice. Based on these data, we propose that exocyst-based mechanisms regulate Neph1 and Nephrin signaling and trafficking, and thus podocyte development and function.
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Affiliation(s)
- Deepak Nihalani
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425,
| | - Ashish K Solanki
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Ehtesham Arif
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Pankaj Srivastava
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Bushra Rahman
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Xiaofeng Zuo
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Yujing Dang
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Ben Fogelgren
- the Department of Anatomy, Biochemistry, and Physiology, University of Hawaii at Manoa, Honolulu, Hawaii 96813
| | | | | | - Matthew G Sampson
- the Department of Pediatrics-Nephrology and.,Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, and
| | - Joshua H Lipschutz
- From the Department of Medicine, Medical University of South Carolina, Charleston, South Carolina 29425.,the Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401
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7
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Zuo X, Lobo G, Fulmer D, Guo L, Dang Y, Su Y, Ilatovskaya DV, Nihalani D, Rohrer B, Body SC, Norris RA, Lipschutz JH. The exocyst acting through the primary cilium is necessary for renal ciliogenesis, cystogenesis, and tubulogenesis. J Biol Chem 2019; 294:6710-6718. [PMID: 30824539 DOI: 10.1074/jbc.ra118.006527] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 02/25/2019] [Indexed: 11/06/2022] Open
Abstract
The exocyst is a highly conserved protein complex found in most eukaryotic cells and is associated with many functions, including protein translocation in the endoplasmic reticulum, vesicular basolateral targeting, and ciliogenesis in the kidney. To investigate the exocyst functions, here we exchanged proline for alanine in the highly conserved VXPX ciliary targeting motif of EXOC5 (exocyst complex component 5), a central exocyst gene/protein, and generated stable EXOC5 ciliary targeting sequence-mutated (EXOC5CTS-m) Madin-Darby canine kidney (MDCK) cells. The EXOC5CTS-m protein was stable and could bind other members of the exocyst complex. Culturing stable control, EXOC5-overexpressing (OE), Exoc5-knockdown (KD), and EXOC5CTS-m MDCK cells on Transwell filters, we found that primary ciliogenesis is increased in EXOC5 OE cells and inhibited in Exoc5-KD and EXOC5CTS-m cells. Growing cells in collagen gels until the cyst stage, we noted that EXOC5-OE cells form mature cysts with single lumens more rapidly than control cysts, whereas Exoc5-KD and EXOC5CTS-m MDCK cells failed to form mature cysts. Adding hepatocyte growth factor to induce tubulogenesis, we observed that EXOC5-OE cell cysts form tubules more efficiently than control MDCK cell cysts, EXOC5CTS-m MDCK cell cysts form significantly fewer tubules than control cell cysts, and Exoc5-KD cysts did not undergo tubulogenesis. Finally, we show that EXOC5 mRNA almost completely rescues the ciliary phenotypes in exoc5-mutant zebrafish, unlike the EXOC5CTS-m mRNA, which could not efficiently rescue the phenotypes. Taken together, these results indicate that the exocyst, acting through the primary cilium, is necessary for renal ciliogenesis, cystogenesis, and tubulogenesis.
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Affiliation(s)
| | - Glenn Lobo
- From the Departments of Medicine.,Ophthalmology, and
| | - Diana Fulmer
- From the Departments of Medicine.,Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Lilong Guo
- From the Departments of Medicine.,Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina 29425
| | | | | | | | | | | | - Simon C Body
- the Department of Anesthesiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215
| | - Russell A Norris
- From the Departments of Medicine.,Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Joshua H Lipschutz
- From the Departments of Medicine, .,the Department of Medicine, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina 29401, and
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8
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Sec61β facilitates the maintenance of endoplasmic reticulum homeostasis by associating microtubules. Protein Cell 2017; 9:616-628. [PMID: 29168059 PMCID: PMC6019657 DOI: 10.1007/s13238-017-0492-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 11/13/2017] [Indexed: 10/25/2022] Open
Abstract
Sec61β, a subunit of the Sec61 translocon complex, is not essential in yeast and commonly used as a marker of endoplasmic reticulum (ER). In higher eukaryotes, such as Drosophila, deletion of Sec61β causes lethality, but its physiological role is unclear. Here, we show that Sec61β interacts directly with microtubules. Overexpression of Sec61β containing small epitope tags, but not a RFP tag, induces dramatic bundling of the ER and microtubule. A basic region in the cytosolic domain of Sec61β is critical for microtubule association. Depletion of Sec61β induces ER stress in both mammalian cells and Caenorhabditis elegans, and subsequent restoration of ER homeostasis correlates with the microtubule binding ability of Sec61β. Loss of Sec61β causes increased mobility of translocon complexes and reduced level of membrane-bound ribosomes. These results suggest that Sec61β may stabilize protein translocation by linking translocon complex to microtubule and provide insight into the physiological function of ER-microtubule interaction.
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9
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Anderson NS, Mukherjee I, Bentivoglio CM, Barlowe C. The Golgin protein Coy1 functions in intra-Golgi retrograde transport and interacts with the COG complex and Golgi SNAREs. Mol Biol Cell 2017; 28:mbc.E17-03-0137. [PMID: 28794270 PMCID: PMC5620376 DOI: 10.1091/mbc.e17-03-0137] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 07/12/2017] [Accepted: 07/31/2017] [Indexed: 01/09/2023] Open
Abstract
Extended coiled-coil proteins of the Golgin family play prominent roles in maintaining the structure and function of the Golgi complex. Here we further investigate the Golgin protein Coy1 and document its function in retrograde transport between early Golgi compartments. Cells that lack Coy1 displayed a reduced half-life of the Och1 mannosyltransferase, an established cargo of intra-Golgi retrograde transport. Combining the coy1Δ mutation with deletions in other putative retrograde Golgins (sgm1Δ and rud3Δ) caused strong glycosylation and growth defects and reduced membrane association of the Conserved Oligomeric Golgi complex. In contrast, overexpression of COY1 inhibited the growth of mutant strains deficient in fusion activity at the Golgi (sed5-1 and sly1-ts). To map Coy1 protein interactions, co-immunoprecipitation experiments revealed an association with the Conserved Oliogmeric Golgi (COG) complex and with intra-Golgi SNARE proteins. These physical interactions are direct, as Coy1 was efficiently captured in vitro by Lobe A of the COG complex and the purified SNARE proteins Gos1, Sed5 and Sft1. Thus, our genetic, in vivo, and biochemical data indicate a role for Coy1 in regulating COG complex-dependent fusion of retrograde-directed COPI vesicles.
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Affiliation(s)
- Nadine S Anderson
- Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Indrani Mukherjee
- Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Christine M Bentivoglio
- Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Charles Barlowe
- Department of Biochemistry & Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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10
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Tanaka T, Goto K, Iino M. Diverse Functions and Signal Transduction of the Exocyst Complex in Tumor Cells. J Cell Physiol 2016; 232:939-957. [DOI: 10.1002/jcp.25619] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 09/23/2016] [Indexed: 12/11/2022]
Affiliation(s)
- Toshiaki Tanaka
- Department of Anatomy and Cell Biology; School of Medicine; Yamagata University; Yamagata Japan
- Department of Dentistry, Oral and Maxillofacial Surgery; Plastic and Reconstructive Surgery; School of Medicine; Yamagata University; Yamagata Japan
| | - Kaoru Goto
- Department of Anatomy and Cell Biology; School of Medicine; Yamagata University; Yamagata Japan
| | - Mitsuyoshi Iino
- Department of Dentistry, Oral and Maxillofacial Surgery; Plastic and Reconstructive Surgery; School of Medicine; Yamagata University; Yamagata Japan
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11
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Lee AJ, Polgar N, Napoli JA, Lui VH, Tamashiro KK, Fujimoto BA, Thompson KS, Fogelgren B. Fibroproliferative response to urothelial failure obliterates the ureter lumen in a mouse model of prenatal congenital obstructive nephropathy. Sci Rep 2016; 6:31137. [PMID: 27511831 PMCID: PMC4980620 DOI: 10.1038/srep31137] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 07/12/2016] [Indexed: 01/02/2023] Open
Abstract
Congenital obstructive nephropathy (CON) is the most prevalent cause of pediatric chronic kidney disease and end-stage renal disease. The ureteropelvic junction (UPJ) region, where the renal pelvis transitions to the ureter, is the most commonly obstructed site in CON. The underlying causes of congenital UPJ obstructions remain poorly understood, especially when they occur in utero, in part due to the lack of genetic animal models. We previously showed that conditional inactivation of Sec10, a central subunit of the exocyst complex, in the epithelial cells of the ureter and renal collecting system resulted in late gestational bilateral UPJ obstructions with neonatal anuria and death. In this study, we show that without Sec10, the urothelial progenitor cells that line the ureter fail to differentiate into superficial cells, which are responsible for producing uroplakin plaques on the luminal surface. These Sec10-knockout urothelial cells undergo cell death by E17.5 and the urothelial barrier becomes leaky to luminal fluid. Also at E17.5, we measured increased expression of TGFβ1 and genes associated with myofibroblast activation, with evidence of stromal remodeling. Our findings support the model that a defective urothelial barrier allows urine to induce a fibrotic wound healing mechanism, which may contribute to human prenatal UPJ obstructions.
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Affiliation(s)
- Amanda J Lee
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, HI 96813, USA
| | - Noemi Polgar
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, HI 96813, USA
| | - Josephine A Napoli
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, HI 96813, USA
| | - Vanessa H Lui
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, HI 96813, USA
| | - Kadee-Kalia Tamashiro
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, HI 96813, USA
| | - Brent A Fujimoto
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, HI 96813, USA
| | - Karen S Thompson
- Department of Pathology, John A. Burns School of Medicine, University of Hawaii at Manoa, HI 96813, USA
| | - Ben Fogelgren
- Department of Anatomy, Biochemistry and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, HI 96813, USA
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12
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Disrupted-in-schizophrenia-1 (DISC1) Regulates Endoplasmic Reticulum Calcium Dynamics. Sci Rep 2015; 5:8694. [PMID: 25732993 PMCID: PMC4346799 DOI: 10.1038/srep08694] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 02/02/2015] [Indexed: 11/22/2022] Open
Abstract
Disrupted-in-schizophrenia-1 (DISC1) has emerged as a convincing susceptibility gene for multiple mental disorders, but its mechanistic link to the pathogenesis of schizophrenia related psychiatric conditions is yet to be further understood. Here, we showed that DISC1 localizes to the outer surface of the endoplasmic reticulum (ER). EXOC1, a subunit of the exocyst complex, interacted with DISC1 and affected its recruitment to inositol-1,4,5-trisphosphate receptor 1 (IP3R1). Notably, knockdown of DISC1 and EXOC1 elicited an exaggerated ER calcium response upon stimulation of IP3R agonists. Similar abnormal ER calcium responses were observed in hippocampal neurons from DISC1-deficient mutant mice. Moreover, perturbation of ER calcium dynamics upon DISC1 knockdown was effectively reversed by treatment with antipsychotic drugs, such as clozapine and haloperidol. These results collectively indicate that DISC1 is a regulatory factor in ER calcium dynamics, linking a perturbed intracellular calcium signaling and schizophrenia pathogenesis.
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Chacon-Heszele MF, Choi SY, Zuo X, Baek JI, Ward C, Lipschutz JH. The exocyst and regulatory GTPases in urinary exosomes. Physiol Rep 2014; 2:2/8/e12116. [PMID: 25138791 PMCID: PMC4246586 DOI: 10.14814/phy2.12116] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Cilia, organelles that function as cellular antennae, are central to the pathogenesis of “ciliopathies”, including various forms of polycystic kidney disease (PKD). To date, however, the molecular mechanisms controlling ciliogenesis and ciliary function remain incompletely understood. A recently proposed model of cell–cell communication, called “urocrine signaling”, hypothesizes that a subset of membrane bound vesicles that are secreted into the urinary stream (termed exosome‐like vesicles, or ELVs), carry cilia‐specific proteins as cargo, interact with primary cilia, and affect downstream cellular functions. This study was undertaken to determine the role of the exocyst, a highly conserved eight‐protein trafficking complex, in the secretion and/or retrieval of ELVs. We used Madin–Darby canine kidney (MDCK) cells expressing either Sec10‐myc (a central component of the exocyst complex) or Smoothened‐YFP (a ciliary protein found in ELVs) in experiments utilizing electron gold microscopy and live fluorescent microscopy, respectively. Additionally, human urinary exosomes were isolated via ultracentrifugation and subjected to mass‐spectrometry‐based proteomics analysis to determine the composition of ELVs. We found, as determined by EM, that the exocyst localizes to primary cilia, and is present in vesicles attached to the cilium. Furthermore, the entire exocyst complex, as well as most of its known regulatory GTPases, are present in human urinary ELVs. Finally, in living MDCK cells, ELVs appear to interact with primary cilia using spinning disc confocal microscopy. These data suggest that the exocyst complex, in addition to its role in ciliogenesis, is centrally involved in the secretion and/or retrieval of urinary ELVs. Our data suggest that the exocyst complex, in addition to its role in ciliogenesis that we previously described, is centrally involved in the secretion and/or retrieval of urinary exosomes. These results could have important implications for PKD, other renal diseases, as well as normal kidney homeostasis.
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Affiliation(s)
- Maria F Chacon-Heszele
- Renal, Electrolyte and Hypertension Division, Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Soo Young Choi
- Renal Division, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Xiaofeng Zuo
- Renal Division, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Jeong-In Baek
- Renal Division, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Chris Ward
- Division of Nephrology and Hypertension, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, Kansas
| | - Joshua H Lipschutz
- Renal Division, Department of Medicine, Medical University of South Carolina, Charleston, South Carolina Department of Medicine, Ralph H. Johnson VAMC, Charleston, South Carolina
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Huang L, Lipschutz JH. Cilia and polycystic kidney disease, kith and kin. ACTA ACUST UNITED AC 2014; 102:174-85. [PMID: 24898006 DOI: 10.1002/bdrc.21066] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/07/2014] [Indexed: 11/11/2022]
Abstract
In the past decade, cilia have been found to play important roles in renal cystogenesis. Many genes, such as PKD1 and PKD2 which, when mutated, cause autosomal dominant polycystic kidney disease (ADPKD), have been found to localize to primary cilia. The cilium functions as a sensor to transmit extracellular signals into the cell. Abnormal cilia structure and function are associated with the development of polyscystic kidney disease (PKD). Cilia assembly includes centriole migration to the apical surface of the cell, ciliary vesicle docking and fusion with the cell membrane at the intended site of cilium outgrowth, and microtubule growth from the basal body. This review summarizes the most recent advances in cilia and PKD research, with special emphasis on the mechanisms of cytoplasmic and intraciliary protein transport during ciliogenesis.
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Affiliation(s)
- Liwei Huang
- Department of Medicine, Eastern Virginia Medical School, Norfolk, Virginia
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15
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Chacon-Heszele MF, Zuo X, Hellman NE, McKenna S, Choi SY, Huang L, Tobias JW, Park KM, Lipschutz JH. Novel MAPK-dependent and -independent tubulogenes identified via microarray analysis of 3D-cultured Madin-Darby canine kidney cells. Am J Physiol Renal Physiol 2014; 306:F1047-58. [PMID: 24573390 DOI: 10.1152/ajprenal.00589.2013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Cystogenesis and tubulogenesis are basic building blocks for many epithelial organs, including the kidney. Most researchers have used two-dimensional (2D) cell culture to investigate signaling pathways downstream of hepatocyte growth factor (HGF). We hypothesize that three-dimensional (3D) collagen-grown Madin-Darby canine kidney (MDCK) cells, which form cysts and then tubulate in response to HGF, are a much more in vivo-like system for the identification of novel tubulogenes. With the use of a canine microarray containing over 20,000 genes, 2,417 genes were identified as potential tubulogenes that were differentially regulated, exclusively in 3D-grown MDCK cells. Among these, 840 were dependent on MAPK signaling. Importantly, this work shows that many putative tubulogenes, previously identified via microarray analysis of 2D cultures, including by us, do not change in 3D culture and vice versa. The use of a 3D-culture system allowed for the identification of novel MAPK-dependent and -independent genes that regulate early renal tubulogenesis in vitro, e.g., matrix metalloproteinase 1 (MMP1). Knockdown of MMP1 led to defects in cystogenesis and tubulogenesis in 3D-grown MDCK cells, most likely due to problems establishing normal polarity. We suggest that data obtained from 2D cultures, even those using MDCK cells treated with HGF, should not be automatically extrapolated to factors important for cystogenesis and tubulogenesis. Instead, 3D culture, which more closely replicates the biological environment and is therefore a more accurate model for identifying tubulogenes, is preferred. Results from the present analysis will be used to build a more accurate model of the signaling pathways that control cystogenesis and tubulogenesis.
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Affiliation(s)
- Maria F Chacon-Heszele
- Renal, Electrolyte and Hypertension Division, Rm. 405C, Clinical Research Bldg., Univ. of Pennsylvania, Philadelphia, PA 19104.
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16
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Zárský V, Kulich I, Fendrych M, Pečenková T. Exocyst complexes multiple functions in plant cells secretory pathways. CURRENT OPINION IN PLANT BIOLOGY 2013; 16:726-33. [PMID: 24246229 DOI: 10.1016/j.pbi.2013.10.013] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 10/21/2013] [Accepted: 10/22/2013] [Indexed: 05/18/2023]
Abstract
The exocyst is a complex of proteins mediating first contact (tethering) between secretory vesicles and the target membrane. Discovered in yeast as an effector of RAB and RHO small GTPases, it was also found to function in land plants. Plant cells and tissues rely on targeted exocytosis and this implies that the exocyst is involved in regulation of cell polarity and morphogenesis, including cytokinesis, plasma membrane protein recycling (including PINs, the auxin efflux carriers), cell wall biogenesis, fertilization, stress and biotic interactions including defence against pathogens. The dramatic expansion of the EXO70 subunit gene family, of which individual members are likely responsible for exocyst complex targeting, implies that there are specialized functions of different exocysts with different EXO70s. One of these functions comprises a role in autophagy-related Golgi independent membrane trafficking into the vacuole or apoplast. It is also possible, that some EXO70 paralogues have been recruited into exocyst independent functions. The exocyst has the potential to function as an important regulatory hub to coordinate endomembrane dynamics in plants.
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Affiliation(s)
- Viktor Zárský
- Department of Experimental Plant Biology, Faculty of Sciences, Charles University, Viničná 5, Prague 2, 128 43, Czech Republic; Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Rozvojová 263, Prague 6, 165 02, Czech Republic.
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17
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Choi SY, Chacon-Heszele MF, Huang L, McKenna S, Wilson FP, Zuo X, Lipschutz JH. Cdc42 deficiency causes ciliary abnormalities and cystic kidneys. J Am Soc Nephrol 2013; 24:1435-50. [PMID: 23766535 DOI: 10.1681/asn.2012121236] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Ciliogenesis and cystogenesis require the exocyst, a conserved eight-protein trafficking complex that traffics ciliary proteins. In culture, the small GTPase Cdc42 co-localizes with the exocyst at primary cilia and interacts with the exocyst component Sec10. The role of Cdc42 in vivo, however, is not well understood. Here, knockdown of cdc42 in zebrafish produced a phenotype similar to sec10 knockdown, including tail curvature, glomerular expansion, and mitogen-activated protein kinase (MAPK) activation, suggesting that cdc42 and sec10 cooperate in ciliogenesis. In addition, cdc42 knockdown led to hydrocephalus and loss of photoreceptor cilia. Furthermore, there was a synergistic genetic interaction between zebrafish cdc42 and sec10, suggesting that cdc42 and sec10 function in the same pathway. Mice lacking Cdc42 specifically in kidney tubular epithelial cells died of renal failure within weeks of birth. Histology revealed cystogenesis in distal tubules and collecting ducts, decreased ciliogenesis in cyst cells, increased tubular cell proliferation, increased apoptosis, increased fibrosis, and led to MAPK activation, all of which are features of polycystic kidney disease, especially nephronophthisis. Taken together, these results suggest that Cdc42 localizes the exocyst to primary cilia, whereupon the exocyst targets and docks vesicles carrying ciliary proteins. Abnormalities in this pathway result in deranged ciliogenesis and polycystic kidney disease.
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Affiliation(s)
- Soo Young Choi
- Department of Medicine, University of Pennsylvania, Philadelphia, USA
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Osman MA, Sarkar FH, Rodriguez-Boulan E. A molecular rheostat at the interface of cancer and diabetes. Biochim Biophys Acta Rev Cancer 2013; 1836:166-76. [PMID: 23639840 DOI: 10.1016/j.bbcan.2013.04.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Accepted: 04/23/2013] [Indexed: 12/17/2022]
Abstract
Epidemiology studies revealed the connection between several types of cancer and type 2 diabetes (T2D) and suggested that T2D is both a symptom and a risk factor of pancreatic cancer. High level of circulating insulin (hyperinsulinemia) in obesity has been implicated in promoting aggressive types of cancers. Insulin resistance, a symptom of T2D, pressures pancreatic β-cells to increase insulin secretion, leading to hyperinsulinemia, which in turn leads to a gradual loss of functional β-cell mass, thus indicating a fine balance and interplay between β-cell function and mass. While the mechanisms of these connections are unclear, the mTORC1-Akt signaling pathway has been implicated in controlling β-cell function and mass, and in mediating the link of cancer and T2D. However, incomplete understating of how the pathway is regulated and how it integrates body metabolism has hindered its efficacy as a clinical target. The IQ motif containing GTPase activating protein 1 (IQGAP1)-Exocyst axis is a growth factor- and nutrient-sensor that couples cell growth and division. Here we discuss how IQGAP1-Exocyst, through differential interactions with Rho-type of small guanosine triphosphatases (GTPases), acts as a rheostat that modulates the mTORC1-Akt and MAPK signals, and integrates β-cell function and mass with insulin signaling, thus providing a molecular mechanism for cancer initiation in diabetes. Delineating this regulatory pathway may have the potential of contributing to optimizing the efficacy and selectivity of future therapies for cancer and diabetes.
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Affiliation(s)
- Mahasin A Osman
- Warren Alpert Medical School, Division of Biology and Medicine, Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI 02912, USA.
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19
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Abstract
During oogenesis in Drosophila melanogaster, the cells in the follicular epithelium of the ovary undergo a transition from a cuboidal to a squamous shape. In this issue, Gomez et al. (2012. J. Cell Biol.http://dx.doi.org/10.1083/jcb.201207150) show that the kinase Tao promotes the endocytosis of the cell adhesion molecule Fasciclin 2 from the lateral surface of the cell and is critical for the cuboidal to squamous cell shape transition. Their results indicate that Tao is rising as a regulator of cell height.
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Affiliation(s)
- Liang Cai
- State Key Laboratory of Genetic Engineering, Department of Biochemistry, School of Life Sciences, Fudan University, Shanghai 200433, China
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20
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Abstract
The compartmentalization of cellular functions in complex membranous organelles is a key feature of eukaryotic cells. To cope with the enormous complexity of trafficking pathways that connect these compartments, new approaches need to be considered and introduced into the field of cell biology. We exploit the advantages of the "micropatterning technique," which is to bring cells to adopt a highly reproducible shape, and probabilistic density mapping, which quantifies spatial organization of trafficking compartments, to study regulatory mechanisms of intracellular trafficking. Here, we provide a protocol to analyze and quantify alterations in trafficking compartments upon cellular manipulation. We demonstrate how this approach can be employed to study the regulation of Rab6-labeled transport carriers by the cytoskeleton.
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21
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Soromani C, Zeng N, Hollemeyer K, Heinzle E, Klein MC, Tretter T, Seaman MNJ, Römisch K. N-acetylation and phosphorylation of Sec complex subunits in the ER membrane. BMC Cell Biol 2012; 13:34. [PMID: 23237413 PMCID: PMC3541991 DOI: 10.1186/1471-2121-13-34] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Accepted: 12/11/2012] [Indexed: 12/01/2022] Open
Abstract
Background Covalent modifications of proteins provide a mechanism to control protein function. Here, we have investigated modifications of the heptameric Sec complex which is responsible for post-translational protein import into the endoplasmic reticulum (ER). It consists of the Sec61 complex (Sec61p, Sbh1p, Sss1p) which on its own mediates cotranslational protein import into the ER and the Sec63 complex (Sec63p, Sec62p, Sec71p, Sec72p). Little is known about the biogenesis and regulation of individual Sec complex subunits. Results We show that Sbh1p when it is part of the Sec61 complex is phosphorylated on T5 which is flanked by proline residues. The phosphorylation site is conserved in mammalian Sec61ß, but only partially in birds, and not in other vertebrates or unicellular eukaryotes, suggesting convergent evolution. Mutation of T5 to A did not affect the ability of mutant Sbh1p to complement the growth defect in a Δsbh1Δsbh2 strain, and did not result in a hypophosphorylated protein which shows that alternate sites can be used by the T5 kinase. A survey of yeast phosphoproteome data shows that Sbh1p can be phosphorylated on multiple sites which are organized in two patches, one at the N-terminus of its cytosolic domain, the other proximal to the transmembrane domain. Surprisingly, although N-acetylation has been shown to interfere with ER targeting, we found that both Sbh1p and Sec62p are cotranslationally N-acetylated by NatA, and N-acetyl-proteome data indicate that Sec61p is modified by the same enzyme. Mutation of the N-acetylation site, however, did not affect Sec62p function in posttranslational protein import into the ER. Disabling NatA resulted in growth retardation, but not in co- or posttranslational translocation defects or instability of Sec62p or Sbh1p. Conclusions We conclude that N-acetylation of transmembrane and tail-anchored proteins does not interfere with their ER-targeting, and that Sbh1p phosphorylation on T5, which is not present in Sbh2p, plays a non-essential role specific to the Sec61 complex.
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Affiliation(s)
- Christina Soromani
- Department of Clinical Biochemistry, University College London Hospital, London, UK
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22
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Choi SY, Fogelgren B, Zuo X, Huang L, McKenna S, Lingappa VR, Lipschutz JH. Exocyst Sec10 is involved in basolateral protein translation and translocation in the endoplasmic reticulum. Nephron Clin Pract 2012; 120:e134-40. [PMID: 23037926 DOI: 10.1159/000342366] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 07/23/2012] [Indexed: 01/29/2023] Open
Abstract
BACKGROUND Protein translation and translocation at the rough endoplasmic reticulum (RER) are the first steps in the secretory pathway. The translocon through which newly made proteins are translocated into or across the RER membrane consists of three main subunits: Sec61α, -β, and -γ. Sec61β facilitates translocation, and we and others have shown that the highly conserved eight-protein exocyst complex interacts with Sec61β. We have also shown that the exocyst is involved in basolateral, not apical, protein synthesis and delivery. Recently, however, exocyst involvement in apical protein delivery has been reported. Furthermore, we have shown that the exocyst is necessary for formation of primary cilia, organelles found on the apical surface. METHODS GST pulldown was performed on lysate of renal tubule cells to investigate biochemical interactions. Cell-free assays consisting of cell-free extracts from rabbit reticulocytes, pancreatic endoplasmic reticulum (ER) microsomal membranes, transcripts of cDNA from apical and basolateral proteins, ATP/GTP, amino acids, and (35)S-methionine for protein detection were used to investigate the role of the exocyst in synthesis of polarized proteins. P(32)-orthophosphate and immunoprecipitation with antibody against Sec61β was used to investigate Sec61β phosphorylation in exocyst Sec10-overexpressing cells. RESULTS Sec10 biochemically interacts with Sec61β using GST pulldown. Using cell-free assays, there is enhanced exocyst recruitment to endoplasmic reticulum membranes following exocyst depletion and basolateral G protein of vesicular stomatitis virus protein translation, compared to apical hemagglutinin of influenza virus protein translation. Finally, Sec10 overexpression increases Sec61β phosphorylation. CONCLUSION These data confirm that the exocyst is preferentially involved in basolateral protein translation and translocation, and may well act through the phosphorylation of Sec61β.
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Affiliation(s)
- Soo Young Choi
- Department of Medicine, University of Pennsylvania, Philadelphia, Pa., USA
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Mukerji J, Olivieri KC, Misra V, Agopian KA, Gabuzda D. Proteomic analysis of HIV-1 Nef cellular binding partners reveals a role for exocyst complex proteins in mediating enhancement of intercellular nanotube formation. Retrovirology 2012; 9:33. [PMID: 22534017 PMCID: PMC3382630 DOI: 10.1186/1742-4690-9-33] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 04/25/2012] [Indexed: 12/16/2022] Open
Abstract
Background HIV-1 Nef protein contributes to pathogenesis via multiple functions that include enhancement of viral replication and infectivity, alteration of intracellular trafficking, and modulation of cellular signaling pathways. Nef stimulates formation of tunneling nanotubes and virological synapses, and is transferred to bystander cells via these intercellular contacts and secreted microvesicles. Nef associates with and activates Pak2, a kinase that regulates T-cell signaling and actin cytoskeleton dynamics, but how Nef promotes nanotube formation is unknown. Results To identify Nef binding partners involved in Pak2-association dependent Nef functions, we employed tandem mass spectrometry analysis of Nef immunocomplexes from Jurkat cells expressing wild-type Nef or Nef mutants defective for the ability to associate with Pak2 (F85L, F89H, H191F and A72P, A75P in NL4-3). We report that wild-type, but not mutant Nef, was associated with 5 components of the exocyst complex (EXOC1, EXOC2, EXOC3, EXOC4, and EXOC6), an octameric complex that tethers vesicles at the plasma membrane, regulates polarized exocytosis, and recruits membranes and proteins required for nanotube formation. Additionally, Pak2 kinase was associated exclusively with wild-type Nef. Association of EXOC1, EXOC2, EXOC3, and EXOC4 with wild-type, but not mutant Nef, was verified by co-immunoprecipitation assays in Jurkat cells. Furthermore, shRNA-mediated depletion of EXOC2 in Jurkat cells abrogated Nef-mediated enhancement of nanotube formation. Using bioinformatic tools, we visualized protein interaction networks that reveal functional linkages between Nef, the exocyst complex, and the cellular endocytic and exocytic trafficking machinery. Conclusions Exocyst complex proteins are likely a key effector of Nef-mediated enhancement of nanotube formation, and possibly microvesicle secretion. Linkages revealed between Nef and the exocyst complex suggest a new paradigm of exocyst involvement in polarized targeting for intercellular transfer of viral proteins and viruses.
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Affiliation(s)
- Joya Mukerji
- Department of Cancer Immunology and AIDS, Dana Farber Cancer Institute, Boston, MA, USA
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Abada PB, Larson CA, Manorek G, Adams P, Howell SB. Sec61β controls sensitivity to platinum-containing chemotherapeutic agents through modulation of the copper-transporting ATPase ATP7A. Mol Pharmacol 2012; 82:510-20. [PMID: 22710939 DOI: 10.1124/mol.112.079822] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The Sec61 protein translocon is a multimeric complex that transports proteins across lipid bilayers. We discovered that the Sec61β subunit modulates cellular sensitivity to chemotherapeutic agents, particularly the platinum drugs. To investigate the mechanism, expression of Sec61β was constitutively knocked down in 2008 ovarian cancer cells. Sec61β knockdown (KD) resulted in 8-, 16.8-, and 9-fold resistance to cisplatin (cDDP), carboplatin, and oxaliplatin, respectively. Sec61β KD reduced the cellular accumulation of cDDP to 67% of that in parental cells. Baseline copper levels, copper uptake, and copper cytotoxicity were also reduced. Because copper transporters and chaperones regulate platinum drug accumulation and efflux, their expression in 2008 Sec61β-KD cells was analyzed; ATP7A was found to be 2- to 3-fold overexpressed, whereas there was no change in ATP7B, ATOX1, CTR1, or CTR2 levels. Cells lacking ATP7A did not exhibit increased cDDP resistance upon knockdown of Sec61β. Sec61β-KD cells also exhibited altered ATP7A cellular distribution. We conclude that Sec61β modulates the cytotoxicity of many chemotherapeutic agents, with the largest effect being on the platinum drugs. This modulation occurs through effects of Sec61β on the expression and distribution of ATP7A, which was shown previously to control platinum drug sequestration and cytotoxicity.
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Affiliation(s)
- Paolo B Abada
- Moores UCSD Cancer Center, La Jolla, CA 92093-0819, USA.
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25
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Naydenov NG, Brown B, Harris G, Dohn MR, Morales VM, Baranwal S, Reynolds AB, Ivanov AI. A membrane fusion protein αSNAP is a novel regulator of epithelial apical junctions. PLoS One 2012; 7:e34320. [PMID: 22485163 PMCID: PMC3317505 DOI: 10.1371/journal.pone.0034320] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 02/28/2012] [Indexed: 12/31/2022] Open
Abstract
Tight junctions (TJs) and adherens junctions (AJs) are key determinants of the structure and permeability of epithelial barriers. Although exocytic delivery to the cell surface is crucial for junctional assembly, little is known about the mechanisms controlling TJ and AJ exocytosis. This study was aimed at investigating whether a key mediator of exocytosis, soluble N-ethylmaleimide sensitive factor (NSF) attachment protein alpha (αSNAP), regulates epithelial junctions. αSNAP was enriched at apical junctions in SK-CO15 and T84 colonic epithelial cells and in normal human intestinal mucosa. siRNA-mediated knockdown of αSNAP inhibited AJ/TJ assembly and establishment of the paracellular barrier in SK-CO15 cells, which was accompanied by a significant down-regulation of p120-catenin and E-cadherin expression. A selective depletion of p120 catenin effectively disrupted AJ and TJ structure and compromised the epithelial barrier. However, overexpression of p120 catenin did not rescue the defects of junctional structure and permeability caused by αSNAP knockdown thereby suggesting the involvement of additional mechanisms. Such mechanisms did not depend on NSF functions or induction of cell death, but were associated with disruption of the Golgi complex and down-regulation of a Golgi-associated guanidine nucleotide exchange factor, GBF1. These findings suggest novel roles for αSNAP in promoting the formation of epithelial AJs and TJs by controlling Golgi-dependent expression and trafficking of junctional proteins.
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Affiliation(s)
- Nayden G. Naydenov
- Department of Medicine, University of Rochester, Rochester, New York, United States of America
| | - Bryan Brown
- Department of Medicine, University of Rochester, Rochester, New York, United States of America
| | - Gianni Harris
- Department of Medicine, University of Rochester, Rochester, New York, United States of America
| | - Michael R. Dohn
- Department of Cancer Biology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Victor M. Morales
- Department of Medicine, University of Rochester, Rochester, New York, United States of America
| | - Somesh Baranwal
- Department of Medicine, University of Rochester, Rochester, New York, United States of America
| | - Albert B. Reynolds
- Department of Cancer Biology, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Andrei I. Ivanov
- Department of Medicine, University of Rochester, Rochester, New York, United States of America
- * E-mail:
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26
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Naydenov NG, Harris G, Brown B, Schaefer KL, Das SK, Fisher PB, Ivanov AI. Loss of soluble N-ethylmaleimide-sensitive factor attachment protein α (αSNAP) induces epithelial cell apoptosis via down-regulation of Bcl-2 expression and disruption of the Golgi. J Biol Chem 2011; 287:5928-41. [PMID: 22194596 DOI: 10.1074/jbc.m111.278358] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Intracellular trafficking represents a key mechanism that regulates cell fate by participating in either prodeath or prosurvival signaling. Soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein α (αSNAP) is a well known component of vesicle trafficking machinery that mediates intermembrane fusion. αSNAP increases cell resistance to cytotoxic stimuli, although mechanisms of its prosurvival function are poorly understood. In this study, we found that either siRNA-mediated knockdown of αSNAP or expression of its dominant negative mutant induced epithelial cell apoptosis. Apoptosis was not caused by activation of the major prodeath regulators Bax and p53 and was independent of a key αSNAP binding partner, NSF. Instead, death of αSNAP-depleted cells was accompanied by down-regulation of the antiapoptotic Bcl-2 protein; it was mimicked by inhibition and attenuated by overexpression of Bcl-2. Knockdown of αSNAP resulted in impairment of Golgi to endoplasmic reticulum (ER) trafficking and fragmentation of the Golgi. Moreover, pharmacological disruption of ER-Golgi transport by brefeldin A and eeyarestatin 1 or siRNA-mediated depletion of an ER/Golgi-associated p97 ATPase recapitulated the effects of αSNAP inhibition by decreasing Bcl-2 level and triggering apoptosis. These results reveal a novel role for αSNAP in promoting epithelial cell survival by unique mechanisms involving regulation of Bcl-2 expression and Golgi biogenesis.
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Affiliation(s)
- Nayden G Naydenov
- Department of Medicine, University of Rochester, Rochester, New York 14642, USA
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27
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Dellago H, Löscher M, Ajuh P, Ryder U, Kaisermayer C, Grillari-Voglauer R, Fortschegger K, Gross S, Gstraunthaler A, Borth N, Eisenhaber F, Lamond AI, Grillari J. Exo70, a subunit of the exocyst complex, interacts with SNEV(hPrp19/hPso4) and is involved in pre-mRNA splicing. Biochem J 2011; 438:81-91. [PMID: 21639856 PMCID: PMC3708444 DOI: 10.1042/bj20110183] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The Cdc5L (cell division cycle 5-like) complex is a spliceosomal subcomplex that also plays a role in DNA repair. The complex contains the splicing factor hPrp19, also known as SNEV or hPso4, which is involved in cellular life-span regulation and proteasomal breakdown. In a recent large-scale proteomics analysis for proteins associated with this complex, proteins involved in transcription, cell-cycle regulation, DNA repair, the ubiquitin-proteasome system, chromatin remodelling, cellular aging, the cytoskeleton and trafficking, including four members of the exocyst complex, were identified. In the present paper we report that Exo70 interacts directly with SNEV(hPrp19/hPso4) and shuttles to the nucleus, where it associates with the spliceosome. We mapped the interaction site to the N-terminal 100 amino acids of Exo70, which interfere with pre-mRNA splicing in vitro. Furthermore, Exo70 influences the splicing of a model substrate as well as of its own pre-mRNA in vivo. In addition, we found that Exo70 is alternatively spliced in a cell-type- and cell-age- dependent way. These results suggest a novel and unexpected role of Exo70 in nuclear mRNA splicing, where it might signal membrane events to the splicing apparatus.
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Affiliation(s)
- Hanna Dellago
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Marlies Löscher
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Paul Ajuh
- Department of Gene Expression and Regulation, University of Dundee, Dundee, Scotland, U.K
| | - Ursula Ryder
- Department of Gene Expression and Regulation, University of Dundee, Dundee, Scotland, U.K
| | - Christian Kaisermayer
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
| | | | - Klaus Fortschegger
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Stefan Gross
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Anna Gstraunthaler
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Nicole Borth
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Frank Eisenhaber
- Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, Singapore 138671
- Department of Biological Sciences (DBS), National University of Singapore (NUS), 8 Medical Drive, Singapore 117597
- School of Computater Engineering (SCE), Nanyang Technological University (NTU), 50 Nanyang Drive, Singapore 637553
| | - Angus I. Lamond
- Department of Gene Expression and Regulation, University of Dundee, Dundee, Scotland, U.K
| | - Johannes Grillari
- Department of Biotechnology, University of Natural Resources and Life Sciences, Vienna, Austria
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Lynes EM, Simmen T. Urban planning of the endoplasmic reticulum (ER): how diverse mechanisms segregate the many functions of the ER. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2011; 1813:1893-905. [PMID: 21756943 PMCID: PMC7172674 DOI: 10.1016/j.bbamcr.2011.06.011] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Revised: 06/22/2011] [Accepted: 06/23/2011] [Indexed: 12/21/2022]
Abstract
The endoplasmic reticulum (ER) is the biggest organelle in most cell types, but its characterization as an organelle with a continuous membrane belies the fact that the ER is actually an assembly of several, distinct membrane domains that execute diverse functions. Almost 20 years ago, an essay by Sitia and Meldolesi first listed what was known at the time about domain formation within the ER. In the time that has passed since, additional ER domains have been discovered and characterized. These include the mitochondria-associated membrane (MAM), the ER quality control compartment (ERQC), where ER-associated degradation (ERAD) occurs, and the plasma membrane-associated membrane (PAM). Insight has been gained into the separation of nuclear envelope proteins from the remainder of the ER. Research has also shown that the biogenesis of peroxisomes and lipid droplets occurs on specialized membranes of the ER. Several studies have shown the existence of specific marker proteins found on all these domains and how they are targeted there. Moreover, a first set of cytosolic ER-associated sorting proteins, including phosphofurin acidic cluster sorting protein 2 (PACS-2) and Rab32 have been identified. Intra-ER targeting mechanisms appear to be superimposed onto ER retention mechanisms and rely on transmembrane and cytosolic sequences. The crucial roles of ER domain formation for cell physiology are highlighted with the specific targeting of the tumor metastasis regulator gp78 to ERAD-mediating membranes or of the promyelocytic leukemia protein to the MAM.
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Affiliation(s)
- Emily M Lynes
- Department of Cell Biology, University of Alberta, Alberta, Canada
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Forsmark A, Rossi G, Wadskog I, Brennwald P, Warringer J, Adler L. Quantitative proteomics of yeast post-Golgi vesicles reveals a discriminating role for Sro7p in protein secretion. Traffic 2011; 12:740-53. [PMID: 21477180 DOI: 10.1111/j.1600-0854.2011.01186.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We here report the first comparative proteomics of purified yeast post-Golgi vesicles (PGVs). Vesicle samples isolated from PGV-accumulating sec6-4 mutants were treated with isobaric tags (iTRAQ) for subsequent quantitative tandem mass spectrometric analysis of protein content. After background subtraction, a total of 66 vesicle-associated proteins were identified, including known or assumed vesicle residents as well as a fraction not previously known to be PGV associated. Vesicles isolated from cells lacking the polarity protein Sro7p contained essentially the same catalogue of proteins but showed a reduced content of a subset of cargo proteins, in agreement with a previously shown selective role for Sro7p in cargo sorting.
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Affiliation(s)
- Annabelle Forsmark
- Department of Cell and Molecular Biology, Microbiology, University of Gothenburg, Box 462, SE-405 30 Gothenburg, Sweden
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Fogelgren B, Lin SY, Zuo X, Jaffe KM, Park KM, Reichert RJ, Bell PD, Burdine RD, Lipschutz JH. The exocyst protein Sec10 interacts with Polycystin-2 and knockdown causes PKD-phenotypes. PLoS Genet 2011; 7:e1001361. [PMID: 21490950 PMCID: PMC3072367 DOI: 10.1371/journal.pgen.1001361] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 03/02/2011] [Indexed: 01/26/2023] Open
Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is characterized by formation of renal cysts that destroy the kidney. Mutations in PKD1 and PKD2, encoding polycystins-1 and -2, cause ADPKD. Polycystins are thought to function in primary cilia, but it is not well understood how these and other proteins are targeted to cilia. Here, we provide the first genetic and biochemical link between polycystins and the exocyst, a highly-conserved eight-protein membrane trafficking complex. We show that knockdown of exocyst component Sec10 yields cellular phenotypes associated with ADPKD, including loss of flow-generated calcium increases, hyperproliferation, and abnormal activation of MAPK. Sec10 knockdown in zebrafish phenocopies many aspects of polycystin-2 knockdown-including curly tail up, left-right patterning defects, glomerular expansion, and MAPK activation-suggesting that the exocyst is required for pkd2 function in vivo. We observe a synergistic genetic interaction between zebrafish sec10 and pkd2 for many of these cilia-related phenotypes. Importantly, we demonstrate a biochemical interaction between Sec10 and the ciliary proteins polycystin-2, IFT88, and IFT20 and co-localization of the exocyst and polycystin-2 at the primary cilium. Our work supports a model in which the exocyst is required for the ciliary localization of polycystin-2, thus allowing for polycystin-2 function in cellular processes.
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Affiliation(s)
- Ben Fogelgren
- Department of Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania, United States of America
| | - Shin-Yi Lin
- Department of Molecular Biology, Princeton University, Princeton, New
Jersey, United States of America
| | - Xiaofeng Zuo
- Department of Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania, United States of America
| | - Kimberly M. Jaffe
- Department of Molecular Biology, Princeton University, Princeton, New
Jersey, United States of America
| | - Kwon Moo Park
- Department of Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania, United States of America
- Department of Anatomy and BK 21 Project, Kyungpook National University,
Daegu, Republic of Korea
| | - Ryan J. Reichert
- Department of Medicine, Medical University of South Carolina, Charleston,
South Carolina, United States of America
| | - P. Darwin Bell
- Department of Medicine, Medical University of South Carolina, Charleston,
South Carolina, United States of America
| | - Rebecca D. Burdine
- Department of Molecular Biology, Princeton University, Princeton, New
Jersey, United States of America
| | - Joshua H. Lipschutz
- Department of Medicine, University of Pennsylvania, Philadelphia,
Pennsylvania, United States of America
- Department of Medicine, Philadelphia Veterans Affairs Medical Center,
Philadelphia, Pennsylvania, United States of America
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31
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Ishikawa H, Barber GN. The STING pathway and regulation of innate immune signaling in response to DNA pathogens. Cell Mol Life Sci 2010; 68:1157-65. [PMID: 21161320 PMCID: PMC3056141 DOI: 10.1007/s00018-010-0605-2] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Revised: 11/19/2010] [Accepted: 11/25/2010] [Indexed: 12/24/2022]
Abstract
The innate immune system has evolved a variety of sensing mechanisms to detect and counter microbial invasion. These include the Toll-like receptor (TLR), cytoplasmic, nucleotide binding oligomerization domain (NOD)-like receptor and RIG-I-like helicase (RLH) pathways. However, how the cell detects pathogen-associated DNA to trigger host defense, including the production of interferon, remains to be fully clarified. Understanding these processes could have profound implications into how we understand and treat a variety of microbial-related disease, including viral-associated cancers, as well as autoimmune disorders. Recently, an endoplasmic reticulum-associated molecule referred to as STING (for stimulator of interferon genes) was isolated and shown to be critical for regulating the production of IFN in response to cytoplasmic DNA. Here, we review recent discoveries relating to the detection of foreign DNA, including the importance of the STING and inflammasome pathways and the triggering of innate signaling processes.
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Affiliation(s)
- Hiroki Ishikawa
- Department of Medicine and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Rm 511 Papanicolaou Building [M700], 1550 NW 10th Ave, Miami, FL 33136 USA
| | - Glen N. Barber
- Department of Medicine and Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Rm 511 Papanicolaou Building [M700], 1550 NW 10th Ave, Miami, FL 33136 USA
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Abstract
IQGAP1, an effector of CDC42p GTPase, is a widely conserved, multifunctional protein that bundles F-actin through its N-terminus and binds microtubules through its C-terminus to modulate the cell architecture. It has emerged as a potential oncogene associated with diverse human cancers. Therefore, IQGAP1 has been heavily investigated; regardless, its precise cellular function remains unclear. Work from yeast suggests that IQGAP1 plays an important role in directed cell growth, which is a conserved feature crucial to morphogenesis, division axis, and body plan determination. New evidence suggests a conserved role for IQGAP1 in protein synthesis and membrane traffic, which may help to explain the diversity of its cellular functions. Membrane traffic mediates infections by intracellular pathogens and a range of degenerative human diseases arise from dysfunctions in intracellular traffic; thus, elucidating the mechanisms of cellular traffic will be important in order to understand the basis of a wide range of inherited and acquired human diseases. Recent evidence suggests that IQGAP1 plays its role in cell growth through regulating the conserved mTOR pathway. The mTOR signaling cascade has been implicated in membrane traffic and is activated in nearly all human cancers, but clinical response to the mTOR-specific inhibitor rapamycin has been disappointing. Thus, understanding the regulators of this pathway will be crucial in order to identify predictors of rapamycin sensitivity. In this review, I discuss emerging evidence that supports a potential role of IQGAP1 in regulating membrane traffic via regulating the mTOR pathway.
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Affiliation(s)
- Mahasin Osman
- Department of Molecular Pharmacology, Physiology and Biotechnology, Division of Biology and Medicine, Alpert School of Medicine, Brown University, Providence, RI, USA.
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Hillenmeyer ME, Ericson E, Davis RW, Nislow C, Koller D, Giaever G. Systematic analysis of genome-wide fitness data in yeast reveals novel gene function and drug action. Genome Biol 2010; 11:R30. [PMID: 20226027 PMCID: PMC2864570 DOI: 10.1186/gb-2010-11-3-r30] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2010] [Revised: 01/09/2010] [Accepted: 03/12/2010] [Indexed: 02/07/2023] Open
Abstract
The relationship between co-fitness and co-inhibition of genes in chemicogenomic yeast screens provides insights into gene function and drug target prediction. We systematically analyzed the relationships between gene fitness profiles (co-fitness) and drug inhibition profiles (co-inhibition) from several hundred chemogenomic screens in yeast. Co-fitness predicted gene functions distinct from those derived from other assays and identified conditionally dependent protein complexes. Co-inhibitory compounds were weakly correlated by structure and therapeutic class. We developed an algorithm predicting protein targets of chemical compounds and verified its accuracy with experimental testing. Fitness data provide a novel, systems-level perspective on the cell.
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Affiliation(s)
- Maureen E Hillenmeyer
- Biomedical Informatics, 251 Campus Drive, MSOB, Stanford University, Stanford, CA 94305, USA.
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Park KM, Fogelgren B, Zuo X, Kim J, Chung DC, Lipschutz JH. Exocyst Sec10 protects epithelial barrier integrity and enhances recovery following oxidative stress, by activation of the MAPK pathway. Am J Physiol Renal Physiol 2010; 298:F818-26. [PMID: 20053792 DOI: 10.1152/ajprenal.00596.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Cell-cell contacts are essential for epithelial cell function, and disruption is associated with pathological conditions including ischemic kidney injury. We hypothesize that the exocyst, a highly-conserved eight-protein complex that targets secretory vesicles carrying membrane proteins, is involved in maintaining renal epithelial barrier integrity. Accordingly, increasing exocyst expression in renal tubule cells may protect barrier function from oxidative stress resulting from ischemia and reperfusion (I/R) injury. When cultured on plastic, Madin-Darby canine kidney (MDCK) cells overexpressing Sec10, a central exocyst component, formed domes showing increased resistance to hydrogen peroxide (H2O2). Transepithelial electric resistance (TER) of Sec10-overexpressing MDCK cells grown on Transwell filters was higher than in control MDCK cells, and the rate of TER decrease following H2O2 treatment was less in Sec10-overexpressing MDCK cells compared with control MDCK cells. After removal of H2O2, TER returned to normal more rapidly in Sec10-overexpressing compared with control MDCK cells. In collagen culture MDCK cells form cysts, and H2O2 treatment damaged Sec10-overexpressing MDCK cell cysts less than control MDCK cell cysts. The MAPK pathway has been shown to protect animals from I/R injury. Levels of active ERK, the final MAPK pathway step, were higher in Sec10-overexpressing compared with control MDCK cells. U0126 inhibited ERK activation, exacerbated the H2O2-induced decrease in TER and cyst disruption, and delayed recovery of TER following H2O2 removal. Finally, in mice with renal I/R injury, exocyst expression decreased early and returned to normal concomitant with functional recovery, suggesting that the exocyst may be involved in the recovery following I/R injury.
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Affiliation(s)
- Kwon Moo Park
- Department of Medicine, University of Pennsylvania, and the Veterans Administration Medical Center, Philadelphia, Pennsylvania, USA
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35
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Chong YT, Gidda SK, Sanford C, Parkinson J, Mullen RT, Goring DR. Characterization of the Arabidopsis thaliana exocyst complex gene families by phylogenetic, expression profiling, and subcellular localization studies. THE NEW PHYTOLOGIST 2010; 185:401-19. [PMID: 19895414 DOI: 10.1111/j.1469-8137.2009.03070.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
*The exocyst is a complex of eight proteins (Sec3p, Sec5p, Sec6p, Sec8p, Sec10p, Sec15p, Exo70p and Exo84p) involved in tethering vesicles to the plasma membrane during regulated or polarized secretion. Here, the plant exocyst complex was explored in phylogenetic, expression, and subcellular localization studies. *Evolutionary relationships of predicted exocyst subunits were examined in the complete genomes of Arabidopsis thaliana, Oryza sativa, Populus trichocarpa and Physcomitrella patens. Furthermore, detailed expression profiling of the A. thaliana microarray databases was performed and subcellular localization patterns were studied. *Several plant exocyst subunit genes appear to have undergone gene expansion in a common ancestor and subsequent duplication events in independent plant lineages. Expression profiling revealed that the A. thaliana Exo70 gene family exhibits dynamic expression patterns, while the remaining exocyst subunit genes displayed more static profiles. Subcellular localization patterns for A. thaliana exocyst subunits ranged from cytosolic to endosomal compartments (with enrichment in the early endosomes and the trans-Golgi network). Interestingly, two endosomal-localized AtExo70 proteins also recruited other exocyst subunits to these compartments. *Overall subcellular localization patterns were observed that were also found in yeast and animal cells, and this, coupled with the evolutionary relationships, suggests that the exocyst may perform similar conserved functions in plants.
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Affiliation(s)
- Yolanda T Chong
- Department of Cell & Systems Biology and the Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada M5S 3B2
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Andersen NJ, Yeaman C. Sec3-containing exocyst complex is required for desmosome assembly in mammalian epithelial cells. Mol Biol Cell 2009; 21:152-64. [PMID: 19889837 PMCID: PMC2801709 DOI: 10.1091/mbc.e09-06-0459] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
In epithelial cells, Sec3 associates with Exocyst complexes enriched at desmosomes and centrosomes, distinct from Sec6/8 complexes at the apical junctional complex. RNAi-mediated suppression of Sec3 alters trafficking of desmosomal cadherins and impairs desmosome morphology and function, without noticeable effect on adherens junctions. The Exocyst is a conserved multisubunit complex involved in the docking of post-Golgi transport vesicles to sites of membrane remodeling during cellular processes such as polarization, migration, and division. In mammalian epithelial cells, Exocyst complexes are recruited to nascent sites of cell–cell contact in response to E-cadherin–mediated adhesive interactions, and this event is an important early step in the assembly of intercellular junctions. Sec3 has been hypothesized to function as a spatial landmark for the development of polarity in budding yeast, but its role in epithelial cells has not been investigated. Here, we provide evidence in support of a function for a Sec3-containing Exocyst complex in the assembly or maintenance of desmosomes, adhesive junctions that link intermediate filament networks to sites of strong intercellular adhesion. We show that Sec3 associates with a subset of Exocyst complexes that are enriched at desmosomes. Moreover, we found that membrane recruitment of Sec3 is dependent on cadherin-mediated adhesion but occurs later than that of the known Exocyst components Sec6 and Sec8 that are recruited to adherens junctions. RNA interference-mediated suppression of Sec3 expression led to specific impairment of both the morphology and function of desmosomes, without noticeable effect on adherens junctions. These results suggest that two different exocyst complexes may function in basal–lateral membrane trafficking and will enable us to better understand how exocytosis is spatially organized during development of epithelial plasma membrane domains.
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37
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Zhao X, Jäntti J. Functional characterization of the trans-membrane domain interactions of the Sec61 protein translocation complex beta-subunit. BMC Cell Biol 2009; 10:76. [PMID: 19857245 PMCID: PMC2770995 DOI: 10.1186/1471-2121-10-76] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Accepted: 10/26/2009] [Indexed: 01/19/2023] Open
Abstract
Background In eukaryotic cells co- and post-translational protein translocation is mediated by the trimeric Sec61 complex. Currently, the role of the Sec61 complex β-subunit in protein translocation is poorly understood. We have shown previously that in Saccharomyces cerevisiae the trans-membrane domain alone is sufficient for the function of the β-subunit Sbh1p in co-translational protein translocation. In addition, Sbh1p co-purifies not only with the protein translocation channel subunits Sec61p and Sss1p, but also with the reticulon family protein Rtn1p. Results We used random mutagenesis to generate novel Sbh1p mutants in order to functionally map the Sbh1p trans-membrane domain. These mutants were analyzed for their interactions with Sec61p and how they support co-translational protein translocation. The distribution of mutations identifies one side of the Sbh1p trans-membrane domain α-helix that is involved in interactions with Sec61p and that is important for Sbh1p function in protein translocation. At the same time, these mutations do not affect Sbh1p interaction with Rtn1p. Furthermore we show that Sbh1p is found in protein complexes containing not only Rtn1p, but also the two other reticulon-like proteins Rtn2p and Yop1p. Conclusion Our results identify functionally important amino acids in the Sbh1p trans-membrane domain. In addition, our results provide additional support for the involvement of Sec61β in processes unlinked to protein translocation.
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Affiliation(s)
- Xueqiang Zhao
- Research Program in Cell and Molecular Biology, Institute of Biotechnology, P,O, Box 56, 00014 University of Helsinki, Finland.
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38
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Barral PM, Sarkar D, Su ZZ, Barber GN, DeSalle R, Racaniello VR, Fisher PB. Functions of the cytoplasmic RNA sensors RIG-I and MDA-5: key regulators of innate immunity. Pharmacol Ther 2009; 124:219-34. [PMID: 19615405 DOI: 10.1016/j.pharmthera.2009.06.012] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2009] [Accepted: 06/22/2009] [Indexed: 12/13/2022]
Abstract
The innate immune system responds within minutes of infection to produce type I interferons and pro-inflammatory cytokines. Interferons induce the synthesis of cell proteins with antiviral activity, and also shape the adaptive immune response by priming T cells. Despite the discovery of interferons over 50 years ago, only recently have we begun to understand how cells sense the presence of a virus infection. Two families of pattern recognition receptors have been shown to distinguish unique molecules present in pathogens, such as bacterial and fungal cell wall components, viral RNA and DNA, and lipoproteins. The first family includes the membrane-bound toll-like receptors (TLRs). Studies of the signaling pathways that lead from pattern recognition to cytokine induction have revealed extensive and overlapping cascades that involve protein-protein interactions and phosphorylation, and culminate in activation of transcription proteins that control the transcription of genes encoding interferons and other cytokines. A second family of pattern recognition receptors has recently been identified, which comprises the cytoplasmic sensors of viral nucleic acids, including MDA-5, RIG-I, and LGP2. In this review we summarize the discovery of these cytoplasmic sensors, how they recognize nucleic acids, the signaling pathways leading to cytokine synthesis, and viral countermeasures that have evolved to antagonize the functions of these proteins. We also consider the function of these cytoplasmic sensors in apoptosis, development and differentiation, and diabetes.
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Affiliation(s)
- Paola M Barral
- Department of Human and Molecular Genetics, Virginia Commonwealth University, School of Medicine, Richmond, VA, USA.
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Sec24- and ARFGAP1-dependent trafficking of GABA transporter-1 is a prerequisite for correct axonal targeting. J Neurosci 2009; 28:12453-64. [PMID: 19020038 DOI: 10.1523/jneurosci.3451-08.2008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The GABA transporter-1 (GAT1) is a prototypical protein of the synaptic specialization. Export of GAT1 from the endoplasmic reticulum (ER) is contingent on its interaction with the COPII (coatomer protein-II) coat subunit Sec24D. Here we show that silencing all four Sec24 isoforms strongly inhibits transport of GAT1 to the cell surface. In contrast, transport of GAT1-RL/AS, a mutant that is deficient in Sec24D recruitment, was not inhibited, suggesting a nonconventional, COPII-independent pathway. However, ARFGAP1 bound directly to the C terminus of both GAT1-RL/AS and wild-type GAT1. Surface expression of GAT1-RL/AS involved ARFGAP1. GAT1-RL/AS appeared to bypass the ER-Golgi-intermediate compartment, but its pathway to the plasma membrane still involved passage through the Golgi. Thus, the GAT1-RL/AS mutant allowed to test whether COPII-dependent ER-export is required for correct sorting of GAT1 to the axon terminal in neuronal cells. In contrast to wild-type GAT1, GAT1-RL/AS failed to be specifically enriched at the tip of neurite extensions of CAD.a cells (a neuroblastoma cell line that can be differentiated into a neuron-like phenotype) and in the axon terminals of hippocampal neurons. These findings indicate that correct sorting to the axon is contingent on ER export via the COPII machinery and passage through the ER-Golgi-intermediate compartment.
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40
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Caudron F, Barral Y. Septins and the lateral compartmentalization of eukaryotic membranes. Dev Cell 2009; 16:493-506. [PMID: 19386259 DOI: 10.1016/j.devcel.2009.04.003] [Citation(s) in RCA: 229] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Eukaryotic cells from neurons and epithelial cells to unicellular fungi frequently rely on cellular appendages such as axons, dendritic spines, cilia, and buds for their biology. The emergence and differentiation of these appendages depend on the formation of lateral diffusion barriers at their bases to insulate their membranes from the rest of the cell. Here, we review recent progress regarding the molecular mechanisms and functions of such barriers. This overview underlines the importance and conservation of septin-dependent diffusion barriers, which coordinately compartmentalize both plasmatic and internal membranes. We discuss their role in memory establishment and the control of cellular aging.
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Affiliation(s)
- Fabrice Caudron
- Institute of Biochemistry, Department of Biology, ETH Zurich, Zurich, Switzerland
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Zuo X, Guo W, Lipschutz JH. The exocyst protein Sec10 is necessary for primary ciliogenesis and cystogenesis in vitro. Mol Biol Cell 2009; 20:2522-9. [PMID: 19297529 DOI: 10.1091/mbc.e08-07-0772] [Citation(s) in RCA: 141] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Primary cilia are found on many epithelial cell types, including renal tubular epithelial cells, in which they are felt to participate in flow sensing and have been linked to the pathogenesis of cystic renal disorders such as autosomal dominant polycystic kidney disease. We previously localized the exocyst, an eight-protein complex involved in membrane trafficking, to the primary cilium of Madin-Darby canine kidney cells and showed that it was involved in cystogenesis. Here, using short hairpin RNA (shRNA) to knockdown exocyst expression and stable transfection to induce exocyst overexpression, we show that the exocyst protein Sec10 regulates primary ciliogenesis. Using immunofluorescence, scanning, and transmission electron microscopy, primary cilia containing only basal bodies are seen in the Sec10 knockdown cells, and increased ciliogenesis is seen in Sec10-overexpressing cells. These phenotypes do not seem to be because of gross changes in cell polarity, as apical, basolateral, and tight junction proteins remain properly localized. Sec10 knockdown prevents normal cyst morphogenesis when the cells are grown in a collagen matrix, whereas Sec10 overexpression results in increased cystogenesis. Transfection with human Sec10 resistant to the canine shRNA rescues the phenotype, demonstrating specificity. Finally, Par3 was recently shown to regulate primary cilia biogenesis. Par3 and the exocyst colocalized by immunofluorescence and coimmunoprecipitation, consistent with a role for the exocyst in targeting and docking vesicles carrying proteins necessary for primary ciliogenesis.
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Affiliation(s)
- Xiaofeng Zuo
- Department of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Kelkar A, Dobberstein B. Sec61beta, a subunit of the Sec61 protein translocation channel at the endoplasmic reticulum, is involved in the transport of Gurken to the plasma membrane. BMC Cell Biol 2009; 10:11. [PMID: 19226464 PMCID: PMC2653466 DOI: 10.1186/1471-2121-10-11] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2008] [Accepted: 02/18/2009] [Indexed: 11/22/2022] Open
Abstract
Background Protein translocation across the membrane of the Endoplasmic Reticulum (ER) is the first step in the biogenesis of secretory and membrane proteins. Proteins enter the ER by the Sec61 translocon, a proteinaceous channel composed of three subunits, α, β and γ. While it is known that Sec61α forms the actual channel, the function of the other two subunits remains to be characterized. Results In the present study we have investigated the function of Sec61β in Drosophila melanogaster. We describe its role in the plasma membrane traffic of Gurken, the ligand for the Epidermal Growth Factor (EGF) receptor in the oocyte. Germline clones of the mutant allele of Sec61β show normal translocation of Gurken into the ER and transport to the Golgi complex, but further traffic to the plasma membrane is impeded. The defect in plasma membrane traffic due to absence of Sec61β is specific for Gurken and is not due to a general trafficking defect. Conclusion Based on our study we conclude that Sec61β, which is part of the ER protein translocation channel affects a post-ER step during Gurken trafficking to the plasma membrane. We propose an additional role of Sec61β beyond protein translocation into the ER.
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Affiliation(s)
- Anshuman Kelkar
- Zentrum für Molekulare Biologie Universitat Heidelberg, Heidelberg, Germany.
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Leroux A, Rokeach LA. Inter-species complementation of the translocon beta subunit requires only its transmembrane domain. PLoS One 2008; 3:e3880. [PMID: 19057642 PMCID: PMC2586087 DOI: 10.1371/journal.pone.0003880] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Accepted: 11/13/2008] [Indexed: 11/18/2022] Open
Abstract
In eukaryotes, proteins enter the secretory pathway through the translocon pore of the endoplasmic reticulum. This protein translocation channel is composed of three major subunits, called Sec61alpha, beta and gamma in mammals. Unlike the other subunits, the beta subunit is dispensable for translocation and cell viability in all organisms studied. Intriguingly, the knockout of the Sec61beta encoding genes results in different phenotypes in different species. Nevertheless, the beta subunit shows a high level of sequence homology across species, suggesting the conservation of a biological function that remains ill-defined. To address its cellular roles, we characterized the homolog of Sec61beta in the fission yeast Schizosaccharomyces pombe (Sbh1p). Here, we show that the knockout of sbh1(+) results in severe cold sensitivity, increased sensitivity to cell-wall stress, and reduced protein secretion at 23 degrees C. Sec61beta homologs from Saccharomyces cerevisiae and human complement the knockout of sbh1(+) in S. pombe. As in S. cerevisiae, the transmembrane domain (TMD) of S. pombe Sec61beta is sufficient to complement the phenotypes resulting from the knockout of the entire encoding gene. Remarkably, the TMD of Sec61beta from S. cerevisiae and human also complement the gene knockouts in both yeasts. Together, these observations indicate that the TMD of Sec61beta exerts a cellular function that is conserved across species.
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Affiliation(s)
- Alexandre Leroux
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
| | - Luis A. Rokeach
- Department of Biochemistry, Université de Montréal, Montréal, Québec, Canada
- * E-mail:
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45
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STING is an endoplasmic reticulum adaptor that facilitates innate immune signalling. Nature 2008; 455:674-8. [PMID: 18724357 PMCID: PMC2804933 DOI: 10.1038/nature07317] [Citation(s) in RCA: 2415] [Impact Index Per Article: 150.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 08/06/2008] [Indexed: 11/17/2022]
Abstract
We report here the identification, following expression cloning, of a molecule, STING (STimulator of INterferon Genes) that regulates innate immune signaling processes. STING, comprising 5 putative transmembrane (TM) regions, predominantly resides in the endoplasmic reticulum (ER) and is able to activate both NF-κB and IRF3 transcription pathways to induce type I IFN and exert a potent anti-viral state following expression. In contrast, loss of STING rendered murine embryonic fibroblasts (STING −/−MEFs) extremely susceptible to negative-stranded virus infection, including vesicular stomatitis virus, VSV. Further, STING ablation abrogated the ability of intracellular B-form DNA, as well as members of the herpes virus family, to induce IFNβ, but did not significantly affect the Toll-like receptor (TLR pathway). Yeast-two hybrid and co-immunprecipitation studies indicated that STING interacts with RIG-I and with Ssr2/TRAPβ, a member of the translocon-associated protein (TRAP) complex required for protein translocation across the ER membrane following translation[1, 2]. RNAi ablation of TRAPβ and translocon adaptor Sec61β was subsequently found to inhibit STING’s ability to stimulate IFNβ. Thus, aside from identifying a novel regulator of innate immune signaling, this data implicates for the first time a potential role for the translocon in innate signaling pathways activated by select viruses as well as intracellular DNA.
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Rittmeyer EN, Daniel S, Hsu SC, Osman MA. A dual role for IQGAP1 in regulating exocytosis. J Cell Sci 2008; 121:391-403. [PMID: 18216334 DOI: 10.1242/jcs.016881] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Polarized secretion is a tightly regulated event generated by conserved, asymmetrically localized multiprotein complexes, and the mechanism(s) underlying its temporal and spatial regulation are only beginning to emerge. Although yeast Iqg1p has been identified as a positional marker linking polarity and exocytosis cues, studies on its mammalian counterpart, IQGAP1, have focused on its role in organizing cytoskeletal architecture, for which the underlying mechanism is unclear. Here, we report that IQGAP1 associates and co-localizes with the exocyst-septin complex, and influences the localization of the exocyst and the organization of septin. We further show that activation of CDC42 GTPase abolishes this association and inhibits secretion in pancreatic beta-cells. Whereas the N-terminus of IQGAP1 binds the exocyst-septin complex, enhances secretion and abrogates the inhibition caused by CDC42 or the depletion of IQGAP1, the C-terminus, which binds CDC42, inhibits secretion. Pulse-chase experiments indicate that IQGAP1 influences protein-synthesis rates, thus regulating exocytosis. We propose and discuss a model in which IQGAP1 serves as a conformational switch to regulate exocytosis.
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Affiliation(s)
- Eric N Rittmeyer
- Department of Microbiology, Cornell University, Ithaca, NY 14853-2703, USA
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Hellman NE, Spector J, Robinson J, Zuo X, Saunier S, Antignac C, Tobias JW, Lipschutz JH. Matrix metalloproteinase 13 (MMP13) and tissue inhibitor of matrix metalloproteinase 1 (TIMP1), regulated by the MAPK pathway, are both necessary for Madin-Darby canine kidney tubulogenesis. J Biol Chem 2007; 283:4272-82. [PMID: 18039671 DOI: 10.1074/jbc.m708027200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
A classic model of tubulogenesis utilizes Madin-Darby canine kidney (MDCK) cells. MDCK cells form monoclonal cysts in three-dimensional collagen and tubulate in response to hepatocyte growth factor, which activates multiple signaling pathways, including the mitogen-activated protein kinase (MAPK) pathway. It was shown previously that MAPK activation is necessary and sufficient to induce the first stage of tubulogenesis, the partial epithelial to mesenchymal transition (p-EMT), whereas matrix metalloproteinases (MMPs) are necessary for the second redifferentiation stage. To identify specific MMP genes, their regulators, tissue inhibitors of matrix metalloproteinases (TIMPs), and the molecular pathways by which they are activated, we used two distinct MAPK inhibitors and a technique we have termed subtraction pathway microarray analysis. Of the 19 MMPs and 3 TIMPs present on the Canine Genome 2.0 Array, MMP13 and TIMP1 were up-regulated 198- and 169-fold, respectively, via the MAPK pathway. This was confirmed by two-dimensional and three-dimensional real time PCR, as well as in MDCK cells inducible for the MAPK gene Raf. Knockdown of MMP13 using short hairpin RNA prevented progression past the initial phase of p-EMT. Knockdown of TIMP1 prevented normal cystogenesis, although the initial phase of p-EMT did occasionally occur. The MMP13 knockdown phenotype is likely because of decreased collagenase activity, whereas the TIMP1 knockdown phenotype appears due to increased apoptosis. These data suggest a model, which may also be important for development of other branched organs, whereby the MAPK pathway controls both MDCK p-EMT and redifferentiation, in part by activating MMP13 and TIMP1.
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Affiliation(s)
- Nathan E Hellman
- Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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48
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Oztan A, Silvis M, Weisz OA, Bradbury NA, Hsu SC, Goldenring JR, Yeaman C, Apodaca G. Exocyst requirement for endocytic traffic directed toward the apical and basolateral poles of polarized MDCK cells. Mol Biol Cell 2007; 18:3978-92. [PMID: 17686995 PMCID: PMC1995710 DOI: 10.1091/mbc.e07-02-0097] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Revised: 07/24/2007] [Accepted: 07/26/2007] [Indexed: 12/24/2022] Open
Abstract
The octameric exocyst complex is associated with the junctional complex and recycling endosomes and is proposed to selectively tether cargo vesicles directed toward the basolateral surface of polarized Madin-Darby canine kidney (MDCK) cells. We observed that the exocyst subunits Sec6, Sec8, and Exo70 were localized to early endosomes, transferrin-positive common recycling endosomes, and Rab11a-positive apical recycling endosomes of polarized MDCK cells. Consistent with its localization to multiple populations of endosomes, addition of function-blocking Sec8 antibodies to streptolysin-O-permeabilized cells revealed exocyst requirements for several endocytic pathways including basolateral recycling, apical recycling, and basolateral-to-apical transcytosis. The latter was selectively dependent on interactions between the small GTPase Rab11a and Sec15A and was inhibited by expression of the C-terminus of Sec15A or down-regulation of Sec15A expression using shRNA. These results indicate that the exocyst complex may be a multipurpose regulator of endocytic traffic directed toward both poles of polarized epithelial cells and that transcytotic traffic is likely to require Rab11a-dependent recruitment and modulation of exocyst function, likely through interactions with Sec15A.
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Affiliation(s)
- Asli Oztan
- *Laboratory of Epithelial Cell Biology/Renal Electrolyte Division of the Department of Medicine and
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Mark Silvis
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Ora A. Weisz
- *Laboratory of Epithelial Cell Biology/Renal Electrolyte Division of the Department of Medicine and
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261
| | - Neil A. Bradbury
- Department of Physiology and Biophysics, Chicago Medical School, Chicago, IL 60064
| | - Shu-Chan Hsu
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854
| | - James R. Goldenring
- Department of Surgery and Cell and Developmental Biology, Vanderbilt University and the Nashville Veterans Affairs Medical Center, Nashville, TN 37212; and
| | - Charles Yeaman
- Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242
| | - Gerard Apodaca
- *Laboratory of Epithelial Cell Biology/Renal Electrolyte Division of the Department of Medicine and
- Department of Cell Biology and Physiology, University of Pittsburgh, Pittsburgh, PA 15261
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Feng D, Zhao X, Soromani C, Toikkanen J, Römisch K, Vembar SS, Brodsky JL, Keränen S, Jäntti J. The transmembrane domain is sufficient for Sbh1p function, its association with the Sec61 complex, and interaction with Rtn1p. J Biol Chem 2007; 282:30618-28. [PMID: 17699516 PMCID: PMC2361393 DOI: 10.1074/jbc.m701840200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Sec61 protein translocation complex in the endoplasmic reticulum (ER) membrane is composed of three subunits. The alpha-subunit, called Sec61p in yeast, is a multispanning membrane protein that forms the protein conducting channel. The functions of the smaller, carboxyl-terminally tail-anchored beta subunit Sbh1p, its close homologue Sbh2p, and the gamma subunit Sss1p are not well understood. Here we show that co-translational protein translocation into the ER is reduced in sbh1Delta sbh2Delta cells, whereas there is a limited reduction of post-translational translocation and no effect on export of a mutant form of alpha-factor precursor for ER-associated degradation in the cytosol. The translocation defect and the temperature-sensitive growth phenotype of sbh1Delta sbh2Delta cells were rescued by expression of the transmembrane domain of Sbh1p alone, and the Sbh1p transmembrane domain was sufficient for coimmunoprecipitation with Sec61p and Sss1p. Furthermore, we show that Sbh1p co-precipitates with the ER transmembrane protein Rtn1p. Sbh1p-Rtn1p complexes do not appear to contain Sss1p and Sec61p. Our results define the transmembrane domain as the minimal functional domain of the Sec61beta homologue Sbh1p in ER translocation, identify a novel interaction partner for Shb1p, and imply that Sbh1p has additional functions that are not directly linked to protein translocation in association with the Sec61 complex.
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Affiliation(s)
- Dejiang Feng
- VTT Biotechnology, FI-02044 VTT, Espoo, Finland
- Institute of Biotechnology, P. O. Box 56, 00014 University of Helsinki, Helsinki, Finland
| | - Xueqiang Zhao
- Institute of Biotechnology, P. O. Box 56, 00014 University of Helsinki, Helsinki, Finland
| | - Christina Soromani
- University of Cambridge, Cambridge Institute for Medical Research and Department of Clinical Biochemistry, Hills Road, Cambridge CB2 2XY, United Kingdom
| | | | - Karin Römisch
- University of Cambridge, Cambridge Institute for Medical Research and Department of Clinical Biochemistry, Hills Road, Cambridge CB2 2XY, United Kingdom
| | - Shruthi S. Vembar
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
| | | | - Jussi Jäntti
- VTT Biotechnology, FI-02044 VTT, Espoo, Finland
- Institute of Biotechnology, P. O. Box 56, 00014 University of Helsinki, Helsinki, Finland
- To whom correspondence should be addressed: Institute of Biotechnology, P.O. Box 56, 00014 University of Helsinki, Helsinki, Finland. Tel.: 358-9-19159722; Fax: 358-9-19159570; E-mail:
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50
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Abstract
In higher eukaryotic cells pleiomorphic compartments composed of vacuoles, tubules and vesicles move from the endoplasmic reticulum (ER) and the plasma membrane to the cell center, operating in early biosynthetic trafficking and endocytosis, respectively. Besides transporting cargo to the Golgi apparatus and lysosomes, a major task of these compartments is to promote extensive membrane recycling. The endocytic membrane system is traditionally divided into early (sorting) endosomes, late endosomes and the endocytic recycling compartment (ERC). Recent studies on the intermediate compartment (IC) between the ER and the Golgi apparatus suggest that it also consists of peripheral ("early") and centralized ("late") structures, as well as a third component, designated here as the biosynthetic recycling compartment (BRC). We propose that the ERC and the BRC exist as long-lived "mirror compartments" at the cell center that also share the ability to expand and become mobilized during cell activation. These considerations emphasize the functional symmetry of endomembrane compartments, which provides a basis for the membrane rearrangements taking place during cell division, polarization, and differentiation.
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Affiliation(s)
- Jaakko Saraste
- *Section of Anatomy and Cell Biology, Department of Biomedicine, University of Bergen, N-5009 Bergen, Norway; and
| | - Bruno Goud
- Centre National de la Recherche Scientifique Unité Mixte de Recherche 144, Institut Curie, Section de Recherche, 75248 Paris Cedex 05, France
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