1
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Gleason N, Williams CL, Kowluru A. Novel regulatory roles of small G protein GDP dissociation stimulator (smgGDS) in insulin secretion from pancreatic β-cells. Mol Cell Endocrinol 2024; 580:112104. [PMID: 38013223 PMCID: PMC10842139 DOI: 10.1016/j.mce.2023.112104] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 10/26/2023] [Accepted: 10/28/2023] [Indexed: 11/29/2023]
Abstract
Emerging evidence implicates novel roles for small G protein GDP dissociation stimulator (smgGDS) in G protein activation and subsequent targeting to relevant subcellular compartments for effector regulation. Given the well-established roles of small G proteins in insulin secretion, we undertook this investigation to determine the putative roles of smgGDS in insulin secretion. Immunoblotting studies revealed that both splice variants of smgGDS are expressed in human islets, rat islets and INS-1 832/13 cells. A significant inhibition (-52%) of glucose-stimulated insulin secretion (GSIS) was observed in INS-1 832/13 cells following siRNA-mediated depletion of smgGDS. In addition, insulin secretion elicited by a membrane depolarizing concentration of KCl (via increased calcium influx), forskolin (via increased cAMP generation) or IBMX (via inhibition of phosphodiesterase) was inhibited by -49%, -27%, and -28%, respectively. Subcellular distribution studies revealed no significant alterations in the abundance of smgGDS in the cytosolic and membrane fractions during the 45-min exposure of INS-1 832/13 cells to an insulinotropic concentration of glucose. Together, we present the first evidence of expression of smgGDS in human islets, rodent islets, and clonal β-cells. We also demonstrate novel regulatory roles of these proteins in insulin secretion derived from glucose metabolic events, including calcium- and cAMP-dependent signaling steps.
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Affiliation(s)
- Noah Gleason
- Research Service, John D. Dingell VA Medical Center, USA; Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, USA
| | - Carol L Williams
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Anjaneyulu Kowluru
- Research Service, John D. Dingell VA Medical Center, USA; Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI, USA.
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2
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Wells A, Mendes CC, Castellanos F, Mountain P, Wright T, Wainwright SM, Stefana MI, Harris AL, Goberdhan DCI, Wilson C. A Rab6 to Rab11 transition is required for dense-core granule and exosome biogenesis in Drosophila secondary cells. PLoS Genet 2023; 19:e1010979. [PMID: 37844085 PMCID: PMC10602379 DOI: 10.1371/journal.pgen.1010979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 10/26/2023] [Accepted: 09/17/2023] [Indexed: 10/18/2023] Open
Abstract
Secretory cells in glands and the nervous system frequently package and store proteins destined for regulated secretion in dense-core granules (DCGs), which disperse when released from the cell surface. Despite the relevance of this dynamic process to diseases such as diabetes and human neurodegenerative disorders, our mechanistic understanding is relatively limited, because of the lack of good cell models to follow the nanoscale events involved. Here, we employ the prostate-like secondary cells (SCs) of the Drosophila male accessory gland to dissect the cell biology and genetics of DCG biogenesis. These cells contain unusually enlarged DCGs, which are assembled in compartments that also form secreted nanovesicles called exosomes. We demonstrate that known conserved regulators of DCG biogenesis, including the small G-protein Arf1 and the coatomer complex AP-1, play key roles in making SC DCGs. Using real-time imaging, we find that the aggregation events driving DCG biogenesis are accompanied by a change in the membrane-associated small Rab GTPases which are major regulators of membrane and protein trafficking in the secretory and endosomal systems. Indeed, a transition from trans-Golgi Rab6 to recycling endosomal protein Rab11, which requires conserved DCG regulators like AP-1, is essential for DCG and exosome biogenesis. Our data allow us to develop a model for DCG biogenesis that brings together several previously disparate observations concerning this process and highlights the importance of communication between the secretory and endosomal systems in controlling regulated secretion.
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Affiliation(s)
- Adam Wells
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Cláudia C. Mendes
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Felix Castellanos
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Phoebe Mountain
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Tia Wright
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - S. Mark Wainwright
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - M. Irina Stefana
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Adrian L. Harris
- Department of Oncology, University of Oxford, Oxford, United Kingdom
| | | | - Clive Wilson
- Department of Physiology Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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3
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Han Y, Jin L, Wang L, Wei L, Tu C. Identification of PDK4 as Hub Gene for Diabetic Nephropathy Using Co-Expression Network Analysis. Kidney Blood Press Res 2023; 48:522-534. [PMID: 37385224 PMCID: PMC10619590 DOI: 10.1159/000531288] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Accepted: 05/15/2023] [Indexed: 07/01/2023] Open
Abstract
INTRODUCTION Diabetic nephropathy (DN) is related to type 1 and type 2 diabetes. They are the leading cause of end-stage renal disease, but the underling specific pathogenesis of DN is not yet clear. Our study was conducted to explore how DN changed the transcriptome profiles in the kidney. METHODS The gene expression profile of microdissected glomeruli of 41 type 2 DN patients and 20 healthy controls were included. The sample dataset GSE96804 was obtained from the GEO database. Differentially expressed genes (DEGs) were analyzed in R with the limma package and the important modules were found by weighted gene co-expression network analysis (WGCNA) clustering. The modules were then analyzed based on Gene Ontology (GO) gene set enrichment analysis, and the hub genes were found out. We next validated the hub gene, PDK4, in a cell model of DN. We also constructed the PDK4-related PPI network to investigate the correlation between PDK4 expression and other genes. RESULTS Heatmap and volcano map were drawn to illustrate the mRNA expression profile of 1,204 DEGs in both samples of DN patients and the control group. Using WGCNA, we selected the blue module in which genes showed the strongest correlation with the phenotype and the smallest p value. We also identified PDK4 as a hub gene. PDK4 expression was upregulated in human diabetic kidney tissue. Moreover, PDK4 was speculated to play a role in glomerular basement membrane development and kidney development according to the enrichment of functions and signaling pathways. Furthermore, PDK4 and two key genes GSTA2 and G6PC protein expression were verified highly expressed in the cell model of DN. CONCLUSION During the pathogenesis of DN, many genes may change expression in a coordinated manner. The discovery of PDK4 as key gene using WGCNA is of great significance for the development of new treatment strategies to block the development of DN.
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Affiliation(s)
- Yuanyuan Han
- Center of Tree Shrew Germplasm Resources, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, China
| | - Liangzi Jin
- Center of Tree Shrew Germplasm Resources, Institute of Medical Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Kunming, China
| | - Liangzhi Wang
- Department of Internal Medicine, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Lan Wei
- Department of Internal Medicine, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Chao Tu
- Department of Internal Medicine, The Third Affiliated Hospital of Soochow University, Changzhou, China
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4
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Barlow HR, Ahuja N, Bierschenk T, Htike Y, Fassetta L, Azizoglu DB, Flores J, Gao N, de la O S, Sneddon JB, Marciano DK, Cleaver O. Rab11 is essential to pancreas morphogenesis, lumen formation and endocrine mass. Dev Biol 2023; 499:59-74. [PMID: 37172642 DOI: 10.1016/j.ydbio.2023.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 04/21/2023] [Accepted: 05/09/2023] [Indexed: 05/15/2023]
Abstract
The molecular links between tissue-level morphogenesis and the differentiation of cell lineages in the pancreas remain elusive despite a decade of studies. We previously showed that in pancreas both processes depend on proper lumenogenesis. The Rab GTPase Rab11 is essential for epithelial lumen formation in vitro, however few studies have addressed its functions in vivo and none have tested its requirement in pancreas. Here, we show that Rab11 is critical for proper pancreas development. Co-deletion of the Rab11 isoforms Rab11A and Rab11B in the developing pancreatic epithelium (Rab11pancDKO) results in ∼50% neonatal lethality and surviving adult Rab11pancDKO mice exhibit defective endocrine function. Loss of both Rab11A and Rab11B in the embryonic pancreas results in morphogenetic defects of the epithelium, including defective lumen formation and lumen interconnection. In contrast to wildtype cells, Rab11pancDKO cells initiate the formation of multiple ectopic lumens, resulting in a failure to coordinate a single apical membrane initiation site (AMIS) between groups of cells. This results in a failure to form ducts with continuous lumens. Here, we show that these defects are due to failures in vesicle trafficking, as apical and junctional components remain trapped within Rab11pancDKO cells. Together, these observations suggest that Rab11 directly regulates epithelial lumen formation and morphogenesis. Our report links intracellular trafficking to organ morphogenesis in vivo and presents a novel framework for decoding pancreatic development.
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Affiliation(s)
- Haley R Barlow
- Department of Molecular Biology, Center for Regenerative Science and Medicine, USA.
| | - Neha Ahuja
- Department of Molecular Biology, Center for Regenerative Science and Medicine, USA
| | - Tyler Bierschenk
- Department of Molecular Biology, Center for Regenerative Science and Medicine, USA
| | - Yadanar Htike
- Department of Molecular Biology, Center for Regenerative Science and Medicine, USA
| | - Luke Fassetta
- Department of Molecular Biology, Center for Regenerative Science and Medicine, USA
| | - D Berfin Azizoglu
- Department of Developmental Biology, Beckman Center, 279 W. Campus Drive, B300, Stanford, CA, 94305, USA
| | - Juan Flores
- Rutgers University Microbiome Program, 679 Hoes Lane West, Piscataway, NJ, 08854, USA
| | - Nan Gao
- Rutgers University Microbiome Program, 679 Hoes Lane West, Piscataway, NJ, 08854, USA
| | - Sean de la O
- Department of Cell and Tissue Biology, Department of Anatomy, Diabetes Center, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, 94143, USA
| | - Julie B Sneddon
- Department of Cell and Tissue Biology, Department of Anatomy, Diabetes Center, Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, University of California, San Francisco, San Francisco, CA, 94143, USA
| | - Denise K Marciano
- Internal Medicine and Nephrology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX, 75390, USA
| | - Ondine Cleaver
- Department of Molecular Biology, Center for Regenerative Science and Medicine, USA.
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5
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Sultana P, Novotny J. Rab11 and Its Role in Neurodegenerative Diseases. ASN Neuro 2022; 14:17590914221142360. [PMID: 36464817 PMCID: PMC9726856 DOI: 10.1177/17590914221142360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022] Open
Abstract
Vesicles mediate the trafficking of membranes/proteins in the endocytic and secretory pathways. These pathways are regulated by small GTPases of the Rab family. Rab proteins belong to the Ras superfamily of GTPases, which are significantly involved in various intracellular trafficking and signaling processes in the nervous system. Rab11 is known to play a key role especially in recycling many proteins, including receptors important for signal transduction and preservation of functional activities of nerve cells. Rab11 activity is controlled by GEFs (guanine exchange factors) and GAPs (GTPase activating proteins), which regulate its function through modulating GTP/GDP exchange and the intrinsic GTPase activity, respectively. Rab11 is involved in the transport of several growth factor molecules important for the development and repair of neurons. Overexpression of Rab11 has been shown to significantly enhance vesicle trafficking. On the other hand, a reduced expression of Rab11 was observed in several neurodegenerative diseases. Current evidence appears to support the notion that Rab11 and its cognate proteins may be potential targets for therapeutic intervention. In this review, we briefly discuss the function of Rab11 and its related interaction partners in intracellular pathways that may be involved in neurodegenerative processes.
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Affiliation(s)
| | - Jiri Novotny
- Jiri Novotny, Department of Physiology, Faculty of Science, Charles University, Prague, Czech Republic.
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6
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Chang SJ, Hsu YT, Chen Y, Lin YY, Lara-Tejero M, Galan JE. Typhoid toxin sorting and exocytic transport from Salmonella Typhi-infected cells. eLife 2022; 11:e78561. [PMID: 35579416 PMCID: PMC9142146 DOI: 10.7554/elife.78561] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Accepted: 05/15/2022] [Indexed: 11/13/2022] Open
Abstract
Typhoid toxin is an essential virulence factor for Salmonella Typhi, the cause of typhoid fever in humans. This toxin has an unusual biology in that it is produced by Salmonella Typhi only when located within host cells. Once synthesized, the toxin is secreted to the lumen of the Salmonella-containing vacuole from where it is transported to the extracellular space by vesicle carrier intermediates. Here, we report the identification of the typhoid toxin sorting receptor and components of the cellular machinery that packages the toxin into vesicle carriers, and exports it to the extracellular space. We found that the cation-independent mannose-6-phosphate receptor serves as typhoid toxin sorting receptor and that the coat protein COPII and the GTPase Sar1 mediate its packaging into vesicle carriers. Formation of the typhoid toxin carriers requires the specific environment of the Salmonella Typhi-containing vacuole, which is determined by the activities of specific effectors of its type III protein secretion systems. We also found that Rab11B and its interacting protein Rip11 control the intracellular transport of the typhoid toxin carriers, and the SNARE proteins VAMP7, SNAP23, and Syntaxin 4 their fusion to the plasma membrane. Typhoid toxin's cooption of specific cellular machinery for its transport to the extracellular space illustrates the remarkable adaptation of an exotoxin to exert its function in the context of an intracellular pathogen.
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Affiliation(s)
- Shu-Jung Chang
- Department of Microbial Pathogenesis, Yale University School of MedicineNew HavenUnited States
- Graduate Institute of Microbiology, College of Medicine, National Taiwan UniversityTaipeiTaiwan
| | - Yu-Ting Hsu
- Graduate Institute of Microbiology, College of Medicine, National Taiwan UniversityTaipeiTaiwan
| | - Yun Chen
- Graduate Institute of Microbiology, College of Medicine, National Taiwan UniversityTaipeiTaiwan
| | - Yen-Yi Lin
- Graduate Institute of Microbiology, College of Medicine, National Taiwan UniversityTaipeiTaiwan
| | - Maria Lara-Tejero
- Department of Microbial Pathogenesis, Yale University School of MedicineNew HavenUnited States
| | - Jorge E Galan
- Department of Microbial Pathogenesis, Yale University School of MedicineNew HavenUnited States
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7
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Hartman EJ, Asady B, Romano JD, Coppens I. The Rab11-Family Interacting Proteins reveal selective interaction of mammalian recycling endosomes with the Toxoplasma parasitophorous vacuole in a Rab11- and Arf6-dependent manner. Mol Biol Cell 2022; 33:ar34. [PMID: 35274991 PMCID: PMC9282008 DOI: 10.1091/mbc.e21-06-0284] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
After mammalian cell invasion, the parasite Toxoplasma multiplies in a self-made membrane-bound compartment, the parasitophorous vacuole (PV). We previously showed that Toxoplasma interacts with many host cell organelles, especially from recycling pathways, and sequestrates Rab11A and Rab11B vesicles into the PV. Here, we examine the specificity of host Rab11 vesicle interaction with the PV by focusing on the recruitment of subpopulations of Rab11 vesicles characterized by different effectors, for example, Rab11-family interacting roteins (FIPs) or Arf6. Our quantitative microscopic analysis illustrates the presence of intra-PV vesicles with FIPs from class I (FIP1C, FIP2, FIP5) and class II (FIP3, FIP4) but to various degrees. The intra-PV delivery of vesicles with class I, but not class II, FIPs is dependent on Rab11 binding. Cell depletion of Rab11A results in a significant decrease in intra-PV FIP5, but not FIP3 vesicles. Class II FIPs also bind to Arf6, and we observe vesicles associated with FIP3-Rab11A or FIP3-Arf6 complexes concomitantly within the PV. Abolishing FIP3 binding to both Rab11 and Arf6 reduces the number of intra-PV FIP3 vesicles. These data point to a selective process of mammalian Rab11 vesicle recognition and scavenging mediated by Toxoplasma, suggesting that specific parasite PV proteins may be involved in these processes.
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Affiliation(s)
- Eric J Hartman
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, 615N Wolfe Street, Baltimore, MD 21205, USA
| | - Beejan Asady
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, 615N Wolfe Street, Baltimore, MD 21205, USA
| | - Julia D Romano
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, 615N Wolfe Street, Baltimore, MD 21205, USA
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, Johns Hopkins School of Public Health, 615N Wolfe Street, Baltimore, MD 21205, USA
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8
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Neuman SD, Lee AR, Selegue JE, Cavanagh AT, Bashirullah A. A novel function for Rab1 and Rab11 during secretory granule maturation. J Cell Sci 2021; 134:jcs259037. [PMID: 34342349 PMCID: PMC8353522 DOI: 10.1242/jcs.259037] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 06/29/2021] [Indexed: 01/15/2023] Open
Abstract
Regulated exocytosis is an essential process whereby specific cargo proteins are secreted in a stimulus-dependent manner. Cargo-containing secretory granules are synthesized in the trans-Golgi network (TGN); after budding from the TGN, granules undergo modifications, including an increase in size. These changes occur during a poorly understood process called secretory granule maturation. Here, we leverage the Drosophila larval salivary glands as a model to characterize a novel role for Rab GTPases during granule maturation. We find that secretory granules increase in size ∼300-fold between biogenesis and release, and loss of Rab1 or Rab11 reduces granule size. Surprisingly, we find that Rab1 and Rab11 localize to secretory granule membranes. Rab11 associates with granule membranes throughout maturation, and Rab11 recruits Rab1. In turn, Rab1 associates specifically with immature granules and drives granule growth. In addition to roles in granule growth, both Rab1 and Rab11 appear to have additional functions during exocytosis; Rab11 function is necessary for exocytosis, while the presence of Rab1 on immature granules may prevent precocious exocytosis. Overall, these results highlight a new role for Rab GTPases in secretory granule maturation.
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Affiliation(s)
| | | | | | | | - Arash Bashirullah
- Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222, USA
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9
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Gendaszewska-Darmach E, Garstka MA, Błażewska KM. Targeting Small GTPases and Their Prenylation in Diabetes Mellitus. J Med Chem 2021; 64:9677-9710. [PMID: 34236862 PMCID: PMC8389838 DOI: 10.1021/acs.jmedchem.1c00410] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
A fundamental role
of pancreatic β-cells to maintain proper
blood glucose level is controlled by the Ras superfamily of small
GTPases that undergo post-translational modifications, including prenylation.
This covalent attachment with either a farnesyl or a geranylgeranyl
group controls their localization, activity, and protein–protein
interactions. Small GTPases are critical in maintaining glucose homeostasis
acting in the pancreas and metabolically active tissues such as skeletal
muscles, liver, or adipocytes. Hyperglycemia-induced upregulation
of small GTPases suggests that inhibition of these pathways deserves
to be considered as a potential therapeutic approach in treating T2D.
This Perspective presents how inhibition of various points in the
mevalonate pathway might affect protein prenylation and functioning
of diabetes-affected tissues and contribute to chronic inflammation
involved in diabetes mellitus (T2D) development. We also demonstrate
the currently available molecular tools to decipher the mechanisms
linking the mevalonate pathway’s enzymes and GTPases with diabetes.
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Affiliation(s)
- Edyta Gendaszewska-Darmach
- Institute of Molecular and Industrial Biotechnology, Faculty of Biotechnology and Food Sciences, Lodz University of Technology, Stefanowskiego Street 4/10, 90-924 Łódź, Poland
| | - Malgorzata A Garstka
- Core Research Laboratory, Department of Endocrinology, Department of Tumor and Immunology, Precision Medical Institute, Western China Science and Technology Innovation Port, School of Medicine, the Second Affiliated Hospital of Xi'an Jiaotong University, DaMingGong, Jian Qiang Road, Wei Yang district, Xi'an 710016, China
| | - Katarzyna M Błażewska
- Institute of Organic Chemistry, Faculty of Chemistry, Lodz University of Technology, Żeromskiego Street 116, 90-924 Łódź, Poland
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10
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Ma CIJ, Brill JA. Endosomal Rab GTPases regulate secretory granule maturation in Drosophila larval salivary glands. Commun Integr Biol 2021; 14:15-20. [PMID: 33628358 PMCID: PMC7889263 DOI: 10.1080/19420889.2021.1874663] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Secretory granules (SGs) are organelles responsible for regulated exocytosis of biologically active molecules in professional secretory cells. Maturation of SGs is a crucial process in which cargoes of SGs are processed and activated, allowing them to exert their function upon secretion. Nonetheless, the intracellular trafficking pathways required for SG maturation are not well defined. We recently performed an RNA interference (RNAi) screen in Drosophila larval salivary glands to identify trafficking components needed for SG maturation. From the screen, we identified several Rab GTPases (Rabs) that affect SG maturation. Expression of constitutively active (CA) and dominant-negative (DN) forms narrowed down the Rabs important for this process to Rab5, Rab9 and Rab11. However, none of these Rabs localizes to the limiting membrane of SGs. In contrast, examination of endogenously YFP-tagged Rabs (YRabs) in larval salivary glands revealed that YRab1 and YRab6 localize to the limiting membrane of immature SGs (iSGs) and SGs. These findings provide new insights into how Rab GTPases contribute to the process of SG maturation.
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Affiliation(s)
- Cheng-I Jonathan Ma
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Medical Sciences Building, Toronto, ON, Canada
| | - Julie A Brill
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Medical Sciences Building, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Medical Sciences Building, Toronto, ON, Canada
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11
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Yoon J, Garo J, Lee M, Sun J, Hwang YS, Daar IO. Rab11fip5 regulates telencephalon development via ephrinB1 recycling. Development 2021; 148:dev196527. [PMID: 33462110 PMCID: PMC7875491 DOI: 10.1242/dev.196527] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 12/25/2020] [Indexed: 12/12/2022]
Abstract
Rab11 family-interacting protein 5 (Rab11fip5) is an adaptor protein that binds to the small GTPase Rab11, which has an important function in endosome recycling and trafficking of cellular proteins to the plasma membrane. Rab11fip5 is involved in many cellular processes, such as cytoskeleton rearrangement, iron uptake and exocytosis in neuroendocrine cells, and is also known as a candidate gene for autism-spectrum disorder. However, the role of Rab11fip5 during early embryonic development is not clearly understood. In this study, we identified Rab11fip5 as a protein that interacts with ephrinB1, a transmembrane ligand for Eph receptors. The PDZ binding motif in ephrinB1 and the Rab-binding domain in Rab11fip5 are necessary for their interaction in a complex. EphrinB1 and Rab11fip5 display overlapping expression in the telencephalon of developing amphibian embryos. The loss of Rab11fip5 function causes a reduction in telencephalon size and a decrease in the expression level of ephrinB1. Moreover, morpholino oligonucleotide-mediated knockdown of Rab11fip5 decreases cell proliferation in the telencephalon. The overexpression of ephrinB1 rescues these defects, suggesting that ephrinB1 recycling by the Rab11/Rab11fip5 complex is crucial for proper telencephalon development.
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Affiliation(s)
- Jaeho Yoon
- Cancer and Developmental Biology Laboratory (CDBL), Center for Cancer Research (CCR) - Frederick, National Cancer Institute, Frederick, MD 21702, USA
| | - Jerlin Garo
- Cancer and Developmental Biology Laboratory (CDBL), Center for Cancer Research (CCR) - Frederick, National Cancer Institute, Frederick, MD 21702, USA
| | - Moonsup Lee
- Cancer and Developmental Biology Laboratory (CDBL), Center for Cancer Research (CCR) - Frederick, National Cancer Institute, Frederick, MD 21702, USA
| | - Jian Sun
- Cancer and Developmental Biology Laboratory (CDBL), Center for Cancer Research (CCR) - Frederick, National Cancer Institute, Frederick, MD 21702, USA
| | - Yoo-Seok Hwang
- Cancer and Developmental Biology Laboratory (CDBL), Center for Cancer Research (CCR) - Frederick, National Cancer Institute, Frederick, MD 21702, USA
| | - Ira O Daar
- Cancer and Developmental Biology Laboratory (CDBL), Center for Cancer Research (CCR) - Frederick, National Cancer Institute, Frederick, MD 21702, USA
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12
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Li D, Bradley T, Cain DW, Pedroza-Pacheco I, Aggelakopoulou M, Parks R, Barr M, Xia SM, Scearce R, Bowman C, Stevens G, Newman A, Hora B, Chen Y, Riebe K, Wang Y, Sempowski G, Saunders KO, Borrow P, Haynes BF. RAB11FIP5-Deficient Mice Exhibit Cytokine-Related Transcriptomic Signatures. Immunohorizons 2020; 4:713-728. [PMID: 33172842 PMCID: PMC8050958 DOI: 10.4049/immunohorizons.2000088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 10/23/2020] [Indexed: 11/19/2022] Open
Abstract
Rab11 recycling endosomes are involved in immunological synaptic functions, but the roles of Rab11 family–interacting protein 5 (Rab11Fip5), one of the Rab11 effectors, in the immune system remain obscure. Our previous study demonstrated that RAB11FIP5 transcripts are significantly elevated in PBMCs from HIV-1–infected individuals, making broadly HIV-1–neutralizing Abs compared with those without broadly neutralizing Abs; however, the role of Rab11FiP5 in immune functions remains unclear. In this study, a RAB11FIP5 gene knockout (RAB11FIP5−/−) mouse model was employed to study the role of Rab11Fip5 in immune responses. RAB11FIP5−/− mice exhibited no perturbation in lymphoid tissue cell subsets, and Rab11Fip5 was not required for serum Ab induction following HIV-1 envelope immunization, Ab transcytosis to mucosal sites, or survival after influenza challenge. However, differences were observed in multiple transcripts, including cytokine genes, in lymphocyte subsets from envelope-immunized RAB11FIP5−/− versus control mice. These included alterations in several genes in NK cells that mirrored observations in NKs from HIV-infected humans expressing less RAB11FIP5, although Rab11Fip5 was dispensable for NK cell cytolytic activity. Notably, immunized RAB11FIP5−/− mice had lower IL4 expression in CD4+ T follicular helper cells and showed lower TNF expression in CD8+ T cells. Likewise, TNF-α production by human CD8+ T cells correlated with PBMC RAB11FIP5 expression. These observations in RAB11FIP5−/− mice suggest a role for Rab11Fip5 in regulating cytokine responses.
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Affiliation(s)
- Dapeng Li
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710;
| | - Todd Bradley
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710.,Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Derek W Cain
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710.,Department of Medicine, Duke University School of Medicine, Durham, NC 27710
| | - Isabela Pedroza-Pacheco
- Nuffield Department of Clinical Medicine, University of Oxford, OX3 7FZ Oxford, United Kingdom
| | - Maria Aggelakopoulou
- Nuffield Department of Clinical Medicine, University of Oxford, OX3 7FZ Oxford, United Kingdom
| | - Robert Parks
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Maggie Barr
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Shi-Mao Xia
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Richard Scearce
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Cindy Bowman
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Grace Stevens
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Amanda Newman
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Bhavna Hora
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Yue Chen
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Kristina Riebe
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Yunfei Wang
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Gregory Sempowski
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710
| | - Kevin O Saunders
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710.,Department of Immunology, Duke University School of Medicine, Durham, NC 27710; and.,Department of Surgery, Duke University, Durham, NC 27710
| | - Persephone Borrow
- Nuffield Department of Clinical Medicine, University of Oxford, OX3 7FZ Oxford, United Kingdom
| | - Barton F Haynes
- Duke Human Vaccine Institute, Duke University School of Medicine, Durham, NC 27710; .,Department of Medicine, Duke University School of Medicine, Durham, NC 27710.,Department of Immunology, Duke University School of Medicine, Durham, NC 27710; and
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13
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Fan S, Kroeger B, Marie PP, Bridges EM, Mason JD, McCormick K, Zois CE, Sheldon H, Khalid Alham N, Johnson E, Ellis M, Stefana MI, Mendes CC, Wainwright SM, Cunningham C, Hamdy FC, Morris JF, Harris AL, Wilson C, Goberdhan DCI. Glutamine deprivation alters the origin and function of cancer cell exosomes. EMBO J 2020; 39:e103009. [PMID: 32720716 PMCID: PMC7429491 DOI: 10.15252/embj.2019103009] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2019] [Revised: 02/09/2020] [Accepted: 02/10/2020] [Indexed: 12/18/2022] Open
Abstract
Exosomes are secreted extracellular vesicles carrying diverse molecular cargos, which can modulate recipient cell behaviour. They are thought to derive from intraluminal vesicles formed in late endosomal multivesicular bodies (MVBs). An alternate exosome formation mechanism, which is conserved from fly to human, is described here, with exosomes carrying unique cargos, including the GTPase Rab11, generated in Rab11-positive recycling endosomal MVBs. Release of Rab11-positive exosomes from cancer cells is increased relative to late endosomal exosomes by reducing growth regulatory Akt/mechanistic Target of Rapamycin Complex 1 (mTORC1) signalling or depleting the key metabolic substrate glutamine, which diverts membrane flux through recycling endosomes. Vesicles produced under these conditions promote tumour cell proliferation and turnover and modulate blood vessel networks in xenograft mouse models in vivo. Their growth-promoting activity, which is also observed in vitro, is Rab11a-dependent, involves ERK-MAPK-signalling and is inhibited by antibodies against amphiregulin, an EGFR ligand concentrated on these vesicles. Therefore, glutamine depletion or mTORC1 inhibition stimulates release from Rab11a compartments of exosomes with pro-tumorigenic functions, which we propose promote stress-induced tumour adaptation.
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Affiliation(s)
- Shih‐Jung Fan
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Benjamin Kroeger
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Pauline P Marie
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Esther M Bridges
- Department of OncologyWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
| | - John D Mason
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Kristie McCormick
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Christos E Zois
- Department of OncologyWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
| | - Helen Sheldon
- Department of OncologyWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
| | - Nasullah Khalid Alham
- Institute of Biomedical EngineeringDepartment of Engineering ScienceUniversity of OxfordOxfordUK
- Nuffield Department of Surgical SciencesOxford NIHR Biomedical Research Centre (BRC)John Radcliffe HospitalUniversity of OxfordOxfordUK
| | - Errin Johnson
- Sir William Dunn School of PathologyUniversity of OxfordOxfordUK
| | - Matthew Ellis
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | | | - Cláudia C Mendes
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | | | - Christopher Cunningham
- Nuffield Department of Surgical SciencesJohn Radcliffe HospitalUniversity of OxfordOxfordUK
| | - Freddie C Hamdy
- Nuffield Department of Surgical SciencesJohn Radcliffe HospitalUniversity of OxfordOxfordUK
| | - John F Morris
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Adrian L Harris
- Department of OncologyWeatherall Institute of Molecular MedicineUniversity of OxfordOxfordUK
| | - Clive Wilson
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
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14
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Moreiras H, Pereira FJC, Neto MV, Bento-Lopes L, Festas TC, Seabra MC, Barral DC. The exocyst is required for melanin exocytosis from melanocytes and transfer to keratinocytes. Pigment Cell Melanoma Res 2019; 33:366-371. [PMID: 31665827 DOI: 10.1111/pcmr.12840] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 10/07/2019] [Accepted: 10/22/2019] [Indexed: 11/30/2022]
Abstract
Skin pigmentation involves the production of the pigment melanin by melanocytes, in melanosomes and subsequent transfer to keratinocytes. Within keratinocytes, melanin polarizes to the apical perinuclear region to form a protective cap, shielding the DNA from ultraviolet radiation-induced damage. Previously, we found evidence to support the exocytosis by melanocytes of the melanin core, termed melanocore, followed by endo/phagocytosis by keratinocytes as a main form of transfer, with Rab11b playing a key role in the process. Here, we report the requirement for the exocyst tethering complex in melanocore exocytosis and transfer to keratinocytes. We observed that the silencing of the exocyst subunits Sec8 or Exo70 impairs melanocore exocytosis from melanocytes, without affecting melanin synthesis. Moreover, we confirmed by immunoprecipitation that Rab11b interacts with Sec8 in melanocytes. Furthermore, we found that the silencing of Sec8 or Exo70 in melanocytes impairs melanin transfer to keratinocytes. These results support our model as melanocore exocytosis from melanocytes is essential for melanin transfer to keratinocytes and skin pigmentation and suggest that the role of Rab11b in melanocore exocytosis is mediated by the exocyst.
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Affiliation(s)
- Hugo Moreiras
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisboa, Portugal
| | - Francisco J C Pereira
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisboa, Portugal
| | - Matilde V Neto
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisboa, Portugal
| | - Liliana Bento-Lopes
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisboa, Portugal
| | - Tiago C Festas
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisboa, Portugal
| | - Miguel C Seabra
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisboa, Portugal
| | - Duarte C Barral
- CEDOC, NOVA Medical School, Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisboa, Portugal
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15
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Furber KL, Backlund PS, Yergey AL, Coorssen JR. Unbiased Thiol-Labeling and Top-Down Proteomic Analyses Implicate Multiple Proteins in the Late Steps of Regulated Secretion. Proteomes 2019; 7:proteomes7040034. [PMID: 31569819 PMCID: PMC6958363 DOI: 10.3390/proteomes7040034] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 09/20/2019] [Accepted: 09/23/2019] [Indexed: 12/12/2022] Open
Abstract
Regulated exocytosis enables temporal and spatial control over the secretion of biologically active compounds; however, the mechanism by which Ca2+ modulates different stages of exocytosis is still poorly understood. For an unbiased, top-down proteomic approach, select thiol- reactive reagents were used to investigate this process in release-ready native secretory vesicles. We previously characterized a biphasic effect of these reagents on Ca2+-triggered exocytosis: low doses potentiated Ca2+ sensitivity, whereas high doses inhibited Ca2+ sensitivity and extent of vesicle fusion. Capitalizing on this novel potentiating effect, we have now identified fluorescent thiol- reactive reagents producing the same effects: Lucifer yellow iodoacetamide, monobromobimane, and dibromobimane. Top-down proteomic analyses of fluorescently labeled proteins from total and cholesterol-enriched vesicle membrane fractions using two-dimensional gel electrophoresis coupled with mass spectrometry identified several candidate targets, some of which have been previously linked to the late steps of regulated exocytosis and some of which are novel. Initial validation studies indicate that Rab proteins are involved in the modulation of Ca2+ sensitivity, and thus the efficiency of membrane fusion, which may, in part, be linked to their previously identified upstream roles in vesicle docking.
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Affiliation(s)
- Kendra L Furber
- Northern Medical Program, University of Northern British Columbia, Prince George, BC V2N 4Z9, Canada.
| | - Peter S Backlund
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Alfred L Yergey
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Jens R Coorssen
- Department of Health Sciences, Faculty of Applied Health Sciences and Department of Biological Sciences, Faculty of Mathematics & Science, Brock University, St. Catharines, ON L2S 3A1, Canada.
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16
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Lo RW, Li L, Leung R, Pluthero FG, Kahr WHA. NBEAL2 (Neurobeachin-Like 2) Is Required for Retention of Cargo Proteins by α-Granules During Their Production by Megakaryocytes. Arterioscler Thromb Vasc Biol 2019; 38:2435-2447. [PMID: 30354215 DOI: 10.1161/atvbaha.118.311270] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective- Human and mouse megakaryocytes lacking NBEAL2 (neurobeachin-like 2) produce platelets where α-granules lack protein cargo. This cargo is mostly megakaryocyte-synthesized, but some proteins, including FGN (fibrinogen), are endocytosed. In this study, we examined the trafficking of both types of cargo within primary megakaryocytes cultured from normal and NBEAL2-null mice, to determine the role of NBEAL2 in α-granule maturation. We also examined the interaction of NBEAL2 with the granule-associated protein P-selectin in human megakaryocytes and platelets. Approach and Results- Fluorescence microscopy was used to compare uptake of labeled FGN by normal and NBEAL2-null mouse megakaryocytes, which was similar in both. NBEAL2-null cells, however, showed decreased FGN retention, and studies with biotinylated protein showed rapid loss rather than increased degradation. Intracellular tracking via fluorescence microscopy revealed that in normal megakaryocytes, endocytosed FGN sequentially associated with compartments expressing RAB5 (Ras-related protein in brain 5), RAB7 (Ras-related protein in brain 7), and P-selectin, where it was retained. A similar initial pattern was observed in NBEAL2-null megakaryocytes, but then FGN passed from the P-selectin compartment to RAB11 (Ras-related protein in brain 11)-associated endosomes before release. Megakaryocyte-synthesized VWF (Von Willebrand factor) was observed to follow the same route out of NBEAL2-null cells. Immunofluorescence microscopy revealed intracellular colocalization of NBEAL2 with P-selectin in human megakaryocytes, proplatelets, and platelets. Native NBEAL2 and P-selectin were coimmunoprecipitated from platelets and megakaryocytes. Conclusions- NBEAL2 is not required for FGN uptake by megakaryocytes. NBEAL2 is required for the retention of both endocytosed and megakaryocyte-synthesized proteins by maturing α-granules, and possibly by platelet-borne granules. This function may involve interaction of NBEAL2 with P-selectin.
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Affiliation(s)
- Richard W Lo
- From the Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, ON, Canada (R.W.L., L.L., R.L., F.G.P., W.H.A.K.).,Department of Biochemistry, University of Toronto, ON, Canada (R.W.L., W.H.A.K.)
| | - Ling Li
- From the Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, ON, Canada (R.W.L., L.L., R.L., F.G.P., W.H.A.K.)
| | - Richard Leung
- From the Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, ON, Canada (R.W.L., L.L., R.L., F.G.P., W.H.A.K.)
| | - Fred G Pluthero
- From the Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, ON, Canada (R.W.L., L.L., R.L., F.G.P., W.H.A.K.)
| | - Walter H A Kahr
- From the Cell Biology Program, Research Institute, Hospital for Sick Children, Toronto, ON, Canada (R.W.L., L.L., R.L., F.G.P., W.H.A.K.).,Department of Biochemistry, University of Toronto, ON, Canada (R.W.L., W.H.A.K.).,Division of Haematology/Oncology, Department of Paediatrics, University of Toronto and The Hospital for Sick Children, ON, Canada (W.H.A.K.)
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17
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RAB11FIP5 Expression and Altered Natural Killer Cell Function Are Associated with Induction of HIV Broadly Neutralizing Antibody Responses. Cell 2018; 175:387-399.e17. [PMID: 30270043 PMCID: PMC6176872 DOI: 10.1016/j.cell.2018.08.064] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 07/09/2018] [Accepted: 08/29/2018] [Indexed: 12/25/2022]
Abstract
HIV-1 broadly neutralizing antibodies (bnAbs) are difficult to induce with vaccines but are generated in ∼50% of HIV-1-infected individuals. Understanding the molecular mechanisms of host control of bnAb induction is critical to vaccine design. Here, we performed a transcriptome analysis of blood mononuclear cells from 47 HIV-1-infected individuals who made bnAbs and 46 HIV-1-infected individuals who did not and identified in bnAb individuals upregulation of RAB11FIP5, encoding a Rab effector protein associated with recycling endosomes. Natural killer (NK) cells had the highest differential expression of RAB11FIP5, which was associated with greater dysregulation of NK cell subsets in bnAb subjects. NK cells from bnAb individuals had a more adaptive/dysfunctional phenotype and exhibited impaired degranulation and cytokine production that correlated with RAB11FIP5 transcript levels. Moreover, RAB11FIP5 overexpression modulated the function of NK cells. These data suggest that NK cells and Rab11 recycling endosomal transport are involved in regulation of HIV-1 bnAb development. Elevated RAB11FIP5 expression is associated with HIV-1 bnAb induction NK cells show the highest differential RAB11FIP5 expression NK cell subsets are more dysregulated in individuals developing bnAbs Rab11Fip5 regulates NK cell function
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18
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Kumar AP, Lukman S. Allosteric binding sites in Rab11 for potential drug candidates. PLoS One 2018; 13:e0198632. [PMID: 29874286 PMCID: PMC5991966 DOI: 10.1371/journal.pone.0198632] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 05/22/2018] [Indexed: 12/19/2022] Open
Abstract
Rab11 is an important protein subfamily in the RabGTPase family. These proteins physiologically function as key regulators of intracellular membrane trafficking processes. Pathologically, Rab11 proteins are implicated in many diseases including cancers, neurodegenerative diseases and type 2 diabetes. Although they are medically important, no previous study has found Rab11 allosteric binding sites where potential drug candidates can bind to. In this study, by employing multiple clustering approaches integrating principal component analysis, independent component analysis and locally linear embedding, we performed structural analyses of Rab11 and identified eight representative structures. Using these representatives to perform binding site mapping and virtual screening, we identified two novel binding sites in Rab11 and small molecules that can preferentially bind to different conformations of these sites with high affinities. After identifying the binding sites and the residue interaction networks in the representatives, we computationally showed that these binding sites may allosterically regulate Rab11, as these sites communicate with switch 2 region that binds to GTP/GDP. These two allosteric binding sites in Rab11 are also similar to two allosteric pockets in Ras that we discovered previously.
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Affiliation(s)
- Ammu Prasanna Kumar
- Department of Chemistry, College of Arts and Sciences, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
| | - Suryani Lukman
- Department of Chemistry, College of Arts and Sciences, Khalifa University of Science and Technology, Abu Dhabi, United Arab Emirates
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19
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Liu X, Wang Z, Yang Y, Li Q, Zeng R, Kang J, Wu J. Rab1A mediates proinsulin to insulin conversion in β-cells by maintaining Golgi stability through interactions with golgin-84. Protein Cell 2018; 7:692-6. [PMID: 27502188 PMCID: PMC5003788 DOI: 10.1007/s13238-016-0298-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Affiliation(s)
- Xiaojing Liu
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China
- Clinical and Translational Research Center of Shanghai First Maternity and Infant Health Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, 200092, China
| | - Zhenguo Wang
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Ying Yang
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Qingrun Li
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Rong Zeng
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Jiuhong Kang
- Clinical and Translational Research Center of Shanghai First Maternity and Infant Health Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, Shanghai, 200092, China
| | - Jiarui Wu
- Key Laboratory of Systems Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200031, China.
- School of Life Science and Technology, ShanghaiTech University, Shanghai, 200031, China.
- Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai, 201210, China.
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20
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Rorsman P, Ashcroft FM. Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men. Physiol Rev 2018; 98:117-214. [PMID: 29212789 PMCID: PMC5866358 DOI: 10.1152/physrev.00008.2017] [Citation(s) in RCA: 445] [Impact Index Per Article: 74.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Revised: 05/30/2017] [Accepted: 06/18/2017] [Indexed: 12/14/2022] Open
Abstract
The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.
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Affiliation(s)
- Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Frances M Ashcroft
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Oxford, United Kingdom; Department of Neuroscience and Physiology, Metabolic Research Unit, Göteborg, Sweden; and Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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21
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Klein O, Roded A, Zur N, Azouz NP, Pasternak O, Hirschberg K, Hammel I, Roche PA, Yatsu A, Fukuda M, Galli SJ, Sagi-Eisenberg R. Rab5 is critical for SNAP23 regulated granule-granule fusion during compound exocytosis. Sci Rep 2017; 7:15315. [PMID: 29127297 PMCID: PMC5681557 DOI: 10.1038/s41598-017-15047-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 10/19/2017] [Indexed: 12/22/2022] Open
Abstract
Compound exocytosis is considered the most massive mode of exocytosis, during which the membranes of secretory granules (SGs) fuse with each other to form a channel through which the entire contents of their granules is released. The underlying mechanisms of compound exocytosis remain largely unresolved. Here we show that the small GTPase Rab5, a known regulator of endocytosis, is pivotal for compound exocytosis in mast cells. Silencing of Rab5 shifts receptor-triggered secretion from a compound to a full exocytosis mode, in which SGs individually fuse with the plasma membrane. Moreover, we show that Rab5 is essential for FcεRI-triggered association of the SNARE protein SNAP23 with the SGs. Direct evidence is provided for SNAP23 involvement in homotypic SG fusion that occurs in the activated cells. Finally, we show that this fusion event is prevented by inhibition of the IKKβ2 kinase, however, neither a phosphorylation-deficient nor a phosphomimetic mutant of SNAP23 can mediate homotypic SG fusion in triggered cells. Taken together our findings identify Rab5 as a heretofore-unrecognized regulator of compound exocytosis that is essential for SNAP23-mediated granule-granule fusion. Our results also implicate phosphorylation cycles in controlling SNAP23 SNARE function in homotypic SG fusion.
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Affiliation(s)
- Ofir Klein
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Amit Roded
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Neta Zur
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Nurit P Azouz
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel.,Division of Allergy and Immunology, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio, USA
| | - Olga Pasternak
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Koret Hirschberg
- Department of Pathology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Ilan Hammel
- Department of Pathology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Paul A Roche
- Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, 20892, USA
| | - Ayaka Yatsu
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai, Miyagi, 980-8578, Japan
| | - Mitsunori Fukuda
- Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai, Miyagi, 980-8578, Japan
| | - Stephen J Galli
- Departments of Pathology and of Microbiology and Immunology, and Sean N. Parker Center for Allergy and Asthma Research, Stanford University School of Medicine, Stanford, California, 94305-5176, USA
| | - Ronit Sagi-Eisenberg
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, 69978, Israel.
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22
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Guichard A, Jain P, Moayeri M, Schwartz R, Chin S, Zhu L, Cruz-Moreno B, Liu JZ, Aguilar B, Hollands A, Leppla SH, Nizet V, Bier E. Anthrax edema toxin disrupts distinct steps in Rab11-dependent junctional transport. PLoS Pathog 2017; 13:e1006603. [PMID: 28945820 PMCID: PMC5612732 DOI: 10.1371/journal.ppat.1006603] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 08/24/2017] [Indexed: 02/06/2023] Open
Abstract
Various bacterial toxins circumvent host defenses through overproduction of cAMP. In a previous study, we showed that edema factor (EF), an adenylate cyclase from Bacillus anthracis, disrupts endocytic recycling mediated by the small GTPase Rab11. As a result, cargo proteins such as cadherins fail to reach inter-cellular junctions. In the present study, we provide further mechanistic dissection of Rab11 inhibition by EF using a combination of Drosophila and mammalian systems. EF blocks Rab11 trafficking after the GTP-loading step, preventing a constitutively active form of Rab11 from delivering cargo vesicles to the plasma membrane. Both of the primary cAMP effector pathways -PKA and Epac/Rap1- contribute to inhibition of Rab11-mediated trafficking, but act at distinct steps of the delivery process. PKA acts early, preventing Rab11 from associating with its effectors Rip11 and Sec15. In contrast, Epac functions subsequently via the small GTPase Rap1 to block fusion of recycling endosomes with the plasma membrane, and appears to be the primary effector of EF toxicity in this process. Similarly, experiments conducted in mammalian systems reveal that Epac, but not PKA, mediates the activity of EF both in cell culture and in vivo. The small GTPase Arf6, which initiates endocytic retrieval of cell adhesion components, also contributes to junctional homeostasis by counteracting Rab11-dependent delivery of cargo proteins at sites of cell-cell contact. These studies have potentially significant practical implications, since chemical inhibition of either Arf6 or Epac blocks the effect of EF in cell culture and in vivo, opening new potential therapeutic avenues for treating symptoms caused by cAMP-inducing toxins or related barrier-disrupting pathologies. Recent anthrax outbreaks in Zambia and northern Russia and biodefense preparedness highlight the need for new therapies to counteract fatal late-stage pathologies in patients infected with Bacillus anthracis. Indeed, two toxins secreted by this pathogen—edema toxin (ET) and lethal toxin (LT)—can cause death in face of effective antibiotic treatment. ET, a potent adenylate cyclase, severely impacts host cells and tissues through an overproduction of the ubiquitous second messenger cAMP. Previously, we identified Rab11 as a key host factor inhibited by ET. Blockade of Rab11-dependent endocytic recycling resulted in the disruption of intercellular junctions, likely contributing to life threatening vascular effusion observed in anthrax patients. Here we present a multi-system analysis of the mechanism by which EF inhibits Rab11 and exocyst-dependent trafficking. Epistasis experiments in Drosophila reveal that over-activation of the cAMP effectors PKA and Epac/Rap1 interferes with Rab11-mediated trafficking at two distinct steps. We further describe conserved roles of Epac and the small GTPase Arf6 in ET-mediated disruption of vesicular trafficking and show how chemical inhibition of either pathway greatly alleviates ET-induced edema. Thus, our study defines Epac and Arf6 as promising drug targets for the treatment of infectious diseases and other pathologies involving cAMP overload or related barrier disruption.
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Affiliation(s)
- Annabel Guichard
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Prashant Jain
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Mahtab Moayeri
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, United States of America
| | - Ruth Schwartz
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Stephen Chin
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Lin Zhu
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Beatriz Cruz-Moreno
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
| | - Janet Z. Liu
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, United States of America
| | - Bernice Aguilar
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, United States of America
- Division of Pediatric Infectious Diseases and the Immunobiology Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA 90048, United States of America
| | - Andrew Hollands
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, United States of America
| | - Stephen H. Leppla
- Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, MD, United States of America
| | - Victor Nizet
- Department of Pediatrics, University of California, San Diego, La Jolla, CA, United States of America
- Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA, United States of America
| | - Ethan Bier
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA, United States of America
- * E-mail:
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23
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Ramadass M, Catz SD. Molecular mechanisms regulating secretory organelles and endosomes in neutrophils and their implications for inflammation. Immunol Rev 2017; 273:249-65. [PMID: 27558339 DOI: 10.1111/imr.12452] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Neutrophils constitute the first line of cellular defense against invading microorganisms and modulate the subsequent innate and adaptive immune responses. In order to execute a rapid and precise response to infections, neutrophils rely on preformed effector molecules stored in a variety of intracellular granules. Neutrophil granules contain microbicidal factors, the membrane-bound components of the respiratory burst oxidase, membrane-bound adhesion molecules, and receptors that facilitate the execution of all neutrophil functions including adhesion, transmigration, phagocytosis, degranulation, and neutrophil extracellular trap formation. The rapid mobilization of intracellular organelles is regulated by vesicular trafficking mechanisms controlled by effector molecules that include small GTPases and their interacting proteins. In this review, we focus on recent discoveries of mechanistic processes that are at center stage of the regulation of neutrophil function, highlighting the discrete and selective pathways controlled by trafficking modulators. In particular, we describe novel pathways controlled by the Rab27a effectors JFC1 and Munc13-4 in the regulation of degranulation, reactive oxygen species and neutrophil extracellular trap production, and endolysosomal signaling. Finally, we discuss the importance of understanding these molecular mechanisms in order to design novel approaches to modulate neutrophil-mediated inflammatory processes in a targeted fashion.
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Affiliation(s)
- Mahalakshmi Ramadass
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
| | - Sergio D Catz
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
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24
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Paglialunga S, Simnett G, Robson H, Hoang M, Pillai R, Arkell AM, Simpson JA, Bonen A, Huising M, Joseph JW, Holloway GP. The Rab-GTPase activating protein, TBC1D1, is critical for maintaining normal glucose homeostasis and β-cell mass. Appl Physiol Nutr Metab 2017; 42:647-655. [DOI: 10.1139/apnm-2016-0585] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Tre-2/USP6, BUB2, cdc16 domain family, member 1 (TBC1D1), a Rab-GTPase activating protein, is a paralogue of AS160, and has been implicated in the canonical insulin-signaling cascade in peripheral tissues. More recently, TBC1D1 was identified in rat and human pancreatic islets; however, the islet function of TBC1D1 remains not fully understood. We examined the role of TBC1D1 in glucose homeostasis and insulin secretion utilizing a rat knockout (KO) model. Chow-fed TBC1D1 KO rats had improved insulin action but impaired glucose-tolerance tests (GTT) and a lower insulin response during an intraperitoneal GTT compared with wild-type (WT) rats. The in vivo data suggest there may be an islet defect. Glucose-stimulated insulin secretion was higher in isolated KO rat islets compared with WT animals, suggesting TBC1D1 is a negative regulator of insulin secretion. Moreover, KO rats displayed reduced β-cell mass, which likely accounts for the impaired whole-body glucose homeostasis. This β-cell mass reduction was associated with increased active caspase 3, and unaltered Ki67 or urocortin 3, suggesting the induction of apoptosis rather than decreased proliferation or dedifferentiation may account for the decline in islet mass. A similar phenotype was observed in TBC1D1 heterozygous animals, highlighting the sensitivity of the pancreas to subtle reductions in TBC1D1 protein. An 8-week pair-fed high-fat diet did not further alter β-cell mass or apoptosis in KO rats, suggesting that dietary lipids per se, do not lead to a further impairment in glucose homeostasis. The present study establishes a fundamental role for TBC1D1 in maintaining in vivo β-cell mass.
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Affiliation(s)
- Sabina Paglialunga
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd. East, Guelph, ON N1G 2W1, Canada
- School of Pharmacy, University of Waterloo, 10A Victoria Street South, Kitchener, ON N2G 1C5, Canada
| | - Genevieve Simnett
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd. East, Guelph, ON N1G 2W1, Canada
| | - Holly Robson
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd. East, Guelph, ON N1G 2W1, Canada
| | - Monica Hoang
- School of Pharmacy, University of Waterloo, 10A Victoria Street South, Kitchener, ON N2G 1C5, Canada
| | - Renjitha Pillai
- School of Pharmacy, University of Waterloo, 10A Victoria Street South, Kitchener, ON N2G 1C5, Canada
| | - Alicia M. Arkell
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd. East, Guelph, ON N1G 2W1, Canada
| | - Jeremy A. Simpson
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd. East, Guelph, ON N1G 2W1, Canada
| | - Arend Bonen
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd. East, Guelph, ON N1G 2W1, Canada
| | - Mark Huising
- Department of Neurobiology, Physiology & Behavior, College of Biological Sciences & Department of Physiology & Membrane Biology, School of Medicine, University of California, Davis, California, USA
| | - Jamie W. Joseph
- School of Pharmacy, University of Waterloo, 10A Victoria Street South, Kitchener, ON N2G 1C5, Canada
| | - Graham P. Holloway
- Department of Human Health & Nutritional Sciences, University of Guelph, 50 Stone Rd. East, Guelph, ON N1G 2W1, Canada
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25
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Sato H, Shiba Y, Tsuchiya Y, Saito M, Kohno K. 4μ8C Inhibits Insulin Secretion Independent of IRE1α RNase Activity. Cell Struct Funct 2017; 42:61-70. [PMID: 28321016 DOI: 10.1247/csf.17002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
IRE1α plays an important role in the unfolded protein response (UPR), which is activated by the accumulation of unfolded proteins in the endoplasmic reticulum. 4μ8C, a well-known inhibitor of IRE1α RNase activity, is commonly used to analyze IRE1α function during ER stress in cultured mammalian cells. However, the off-target effects of 4μ8C remain elusive. Pancreatic β-cells synthesize a large amount of insulin in response to high glucose stimulation, and IRE1α plays an important role in insulin secretion from pancreatic β-cells. Here, to analyze the role of IRE1α in pancreatic β-cells, we examined insulin secretion after 4μ8C treatment. Although 4μ8C inhibited insulin secretion within 2 hr, neither insulin synthesis nor maturation was inhibited by 4μ8C under the same conditions. This result prompted us to examine the precise effects of 4μ8C on insulin secretion in pancreatic β-cells. Unexpectedly, with just 5 min of treatment, 4μ8C blocked insulin secretion in cultured pancreatic β-cells as well as in pancreatic islets. Furthermore, insulin secretion was prevented by 4μ8C, even in pancreatic β-cells lacking the IRE1α RNase domain, suggesting that 4μ8C blocked the late stage of the insulin secretory process, independent of the IRE1α-XBP1 pathway. Our results indicate that 4μ8C has an off-target effect on insulin secretion in pancreatic β-cells. These findings inform the researchers in the field that the use of 4μ8C requires the special consideration for the future studies.Key words: 4μ8C, XBP1, insulin, IRE1α, pancreatic β-cells.
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Affiliation(s)
- Hitomi Sato
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology
| | - Yoko Shiba
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology.,Faculty of Science and Engineering, Iwate University
| | - Yuichi Tsuchiya
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology
| | - Michiko Saito
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology
| | - Kenji Kohno
- Laboratory of Molecular and Cell Genetics, Graduate School of Biological Sciences, Nara Institute of Science and Technology
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26
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Redhai S, Hellberg JEEU, Wainwright M, Perera SW, Castellanos F, Kroeger B, Gandy C, Leiblich A, Corrigan L, Hilton T, Patel B, Fan SJ, Hamdy F, Goberdhan DCI, Wilson C. Regulation of Dense-Core Granule Replenishment by Autocrine BMP Signalling in Drosophila Secondary Cells. PLoS Genet 2016; 12:e1006366. [PMID: 27727275 PMCID: PMC5065122 DOI: 10.1371/journal.pgen.1006366] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 09/16/2016] [Indexed: 11/19/2022] Open
Abstract
Regulated secretion by glands and neurons involves release of signalling molecules and enzymes selectively concentrated in dense-core granules (DCGs). Although we understand how many secretagogues stimulate DCG release, how DCG biogenesis is then accelerated to replenish the DCG pool remains poorly characterised. Here we demonstrate that each prostate-like secondary cell (SC) in the paired adult Drosophila melanogaster male accessory glands contains approximately ten large DCGs, which are loaded with the Bone Morphogenetic Protein (BMP) ligand Decapentaplegic (Dpp). These DCGs can be marked in living tissue by a glycophosphatidylinositol (GPI) lipid-anchored form of GFP. In virgin males, BMP signalling is sporadically activated by constitutive DCG secretion. Upon mating, approximately four DCGs are typically released immediately, increasing BMP signalling, primarily via an autocrine mechanism. Using inducible knockdown specifically in adult SCs, we show that secretion requires the Soluble NSF Attachment Protein, SNAP24. Furthermore, mating-dependent BMP signalling not only promotes cell growth, but is also necessary to accelerate biogenesis of new DCGs, restoring DCG number within 24 h. Our analysis therefore reveals an autocrine BMP-mediated feedback mechanism for matching DCG release to replenishment as secretion rates fluctuate, and might explain why in other disease-relevant systems, like pancreatic β-cells, BMP signalling is also implicated in the control of secretion.
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Affiliation(s)
- Siamak Redhai
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | | | - Mark Wainwright
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Sumeth W. Perera
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Felix Castellanos
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Benjamin Kroeger
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Carina Gandy
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Aaron Leiblich
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
- Nuffield Department of Surgical Sciences, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Laura Corrigan
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Thomas Hilton
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Benjamin Patel
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Shih-Jung Fan
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Freddie Hamdy
- Nuffield Department of Surgical Sciences, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Deborah C. I. Goberdhan
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Clive Wilson
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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27
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Rab11 and phosphoinositides: A synergy of signal transducers in the control of vesicular trafficking. Adv Biol Regul 2016; 63:132-139. [PMID: 27658318 DOI: 10.1016/j.jbior.2016.09.002] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 09/13/2016] [Indexed: 12/11/2022]
Abstract
Rab11 and phosphoinositides are signal transducers able to direct the delivery of membrane components to the cell surface. Rab11 is a small GTPase that, by cycling from an active to an inactive state, controls key events of vesicular transport, while phosphoinositides are major determinants of membrane identity, modulating compartmentalized small GTPase function. By sharing common effectors, these two signal transducers synergistically direct vesicular traffic to specific intracellular membranes. This review focuses on the latest advances regarding the mechanisms that ensure the compartmentalized regulation of Rab11 function through its interaction with phosphoinositides.
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28
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Reynier M, Allart S, Gaspard E, Moga A, Goudounèche D, Serre G, Simon M, Leprince C. Rab11a Is Essential for Lamellar Body Biogenesis in the Human Epidermis. J Invest Dermatol 2016; 136:1199-1209. [DOI: 10.1016/j.jid.2016.02.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 11/05/2015] [Accepted: 12/08/2015] [Indexed: 12/11/2022]
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29
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Johnson JL, He J, Ramadass M, Pestonjamasp K, Kiosses WB, Zhang J, Catz SD. Munc13-4 Is a Rab11-binding Protein That Regulates Rab11-positive Vesicle Trafficking and Docking at the Plasma Membrane. J Biol Chem 2015; 291:3423-38. [PMID: 26637356 DOI: 10.1074/jbc.m115.705871] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Indexed: 11/06/2022] Open
Abstract
The small GTPase Rab11 and its effectors control trafficking of recycling endosomes, receptor replenishment and the up-regulation of adhesion and adaptor molecules at the plasma membrane. Despite recent advances in the understanding of Rab11-regulated mechanisms, the final steps mediating docking and fusion of Rab11-positive vesicles at the plasma membrane are not fully understood. Munc13-4 is a docking factor proposed to regulate fusion through interactions with SNAREs. In hematopoietic cells, including neutrophils, Munc13-4 regulates exocytosis in a Rab27a-dependent manner, but its possible regulation of other GTPases has not been explored in detail. Here, we show that Munc13-4 binds to Rab11 and regulates the trafficking of Rab11-containing vesicles. Using a novel Time-resolved Fluorescence Resonance Energy Transfer (TR-FRET) assay, we demonstrate that Munc13-4 binds to Rab11a but not to dominant negative Rab11a. Immunoprecipitation analysis confirmed the specificity of the interaction between Munc13-4 and Rab11, and super-resolution microscopy studies support the interaction of endogenous Munc13-4 with Rab11 at the single molecule level in neutrophils. Vesicular dynamic analysis shows the common spatio-temporal distribution of Munc13-4 and Rab11, while expression of a calcium binding-deficient mutant of Munc13-4 significantly affected Rab11 trafficking. Munc13-4-deficient neutrophils showed normal endocytosis, but the trafficking, up-regulation, and retention of Rab11-positive vesicles at the plasma membrane was significantly impaired. This correlated with deficient NADPH oxidase activation at the plasma membrane in response to Rab11 interference. Our data demonstrate that Munc13-4 is a Rab11-binding partner that regulates the final steps of Rab11-positive vesicle docking at the plasma membrane.
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Affiliation(s)
| | - Jing He
- From the Department of Molecular and Experimental Medicine and
| | | | - Kersi Pestonjamasp
- Cancer Center Microscopy Shared Resource, University of California San Diego, La Jolla, California 92093
| | - William B Kiosses
- Light Microscopy Core Facility, The Scripps Research Institute, La Jolla, California 92037 and
| | - Jinzhong Zhang
- From the Department of Molecular and Experimental Medicine and
| | - Sergio D Catz
- From the Department of Molecular and Experimental Medicine and
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30
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Boal F, Hodgson LR, Reed SE, Yarwood SE, Just VJ, Stephens DJ, McCaffrey MW, Tavaré JM. Insulin promotes Rip11 accumulation at the plasma membrane by inhibiting a dynamin- and PI3-kinase-dependent, but Akt-independent, internalisation event. Cell Signal 2015; 28:74-82. [PMID: 26515129 PMCID: PMC4678287 DOI: 10.1016/j.cellsig.2015.10.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 10/23/2015] [Indexed: 12/11/2022]
Abstract
Rip11 is a Rab11 effector protein that has been shown to be important in controlling the trafficking of several intracellular cargoes, including the fatty acid transporter FAT/CD36, V-ATPase and the glucose transporter GLUT4. We have previously demonstrated that Rip11 translocates to the plasma membrane in response to insulin and here we examine the basis of this regulated phenomenon in more detail. We show that Rip11 rapidly recycles between the cell interior and surface, and that the ability of insulin to increase the appearance of Rip11 at the cell surface involves an inhibition of Rip11 internalisation from the plasma membrane. By contrast the hormone has no effect on the rate of Rip11 translocation towards the plasma membrane. The ability of insulin to inhibit Rip11 internalisation requires dynamin and class I PI3-kinases, but is independent of the activation of the protein kinase Akt; characteristics which are very similar to the mechanism by which insulin inhibits GLUT4 endocytosis.
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Affiliation(s)
- Frédéric Boal
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Lorna R Hodgson
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Sam E Reed
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Sophie E Yarwood
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Victoria J Just
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - David J Stephens
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK
| | - Mary W McCaffrey
- Molecular Cell Biology Laboratory, School of Biochemistry and Cell Biology, Biosciences Institute, University College Cork, Cork, Ireland
| | - Jeremy M Tavaré
- School of Biochemistry, University of Bristol, Bristol, BS8 1TD, UK.
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31
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Abstract
Postsynaptic AMPA-type glutamate receptors (AMPARs) are among the major determinants of synaptic strength and can be trafficked into and out of synapses. Neuronal activity regulates AMPAR trafficking during synaptic plasticity to induce long-term changes in synaptic strength, including long-term potentiation (LTP) and long-term depression (LTD). Rab family GTPases regulate most membrane trafficking in eukaryotic cells; particularly, Rab11 and its effectors are implicated in mediating postsynaptic AMPAR insertion during LTP. To explore the synaptic function of Rab11Fip5, a neuronal Rab11 effector and a candidate autism-spectrum disorder gene, we performed shRNA-mediated knock-down and genetic knock-out (KO) studies. Surprisingly, we observed robust shRNA-induced synaptic phenotypes that were rescued by a Rab11Fip5 cDNA but that were nevertheless not observed in conditional KO neurons. Both in cultured neurons and acute slices, KO of Rab11Fip5 had no significant effect on basic parameters of synaptic transmission, indicating that Rab11Fip5 is not required for fundamental synaptic operations, such as neurotransmitter release or postsynaptic AMPAR insertion. KO of Rab11Fip5 did, however, abolish hippocampal LTD as measured both in acute slices or using a chemical LTD protocol in cultured neurons but did not affect hippocampal LTP. The Rab11Fip5 KO mice performed normally in several behavioral tasks, including fear conditioning, but showed enhanced contextual fear extinction. These are the first findings to suggest a requirement for Rab11Fip5, and presumably Rab11, during LTD.
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32
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New insight into the intracellular roles of class II phosphoinositide 3-kinases. Biochem Soc Trans 2015; 42:1378-82. [PMID: 25233418 DOI: 10.1042/bst20140140] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In the last few years, an increased attention to class II isoforms of phosphoinositide 3-kinase (PI3K) has emerged, mainly fuelled by evidence suggesting a distinct non-redundant role for these enzymes compared with other PI3Ks. Despite this renewed interest, many questions remain on the specific functions regulated by these isoforms and their mechanism of activation and action. In the present review, we discuss results from recent studies that have provided some answers to these questions.
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Glutamate acts as a key signal linking glucose metabolism to incretin/cAMP action to amplify insulin secretion. Cell Rep 2014; 9:661-73. [PMID: 25373904 PMCID: PMC4536302 DOI: 10.1016/j.celrep.2014.09.030] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 08/19/2014] [Accepted: 09/15/2014] [Indexed: 11/29/2022] Open
Abstract
Incretins, hormones released by the gut after meal ingestion, are essential for maintaining systemic glucose homeostasis by stimulating insulin secretion. The effect of incretins on insulin secretion occurs only at elevated glucose concentrations and is mediated by cAMP signaling, but the mechanism linking glucose metabolism and cAMP action in insulin secretion is unknown. We show here, using a metabolomics-based approach, that cytosolic glutamate derived from the malate-aspartate shuttle upon glucose stimulation underlies the stimulatory effect of incretins and that glutamate uptake into insulin granules mediated by cAMP/PKA signaling amplifies insulin release. Glutamate production is diminished in an incretin-unresponsive, insulin-secreting β cell line and pancreatic islets of animal models of human diabetes and obesity. Conversely, a membrane-permeable glutamate precursor restores amplification of insulin secretion in these models. Thus, cytosolic glutamate represents the elusive link between glucose metabolism and cAMP action in incretin-induced insulin secretion. Glutamate is derived from the malate-aspartate shuttle upon glucose stimulation Shuttle-derived glutamate is crucial for incretin-induced insulin secretion Cytosolic glutamate is transported into insulin granules via cAMP/PKA signaling Glutamate production by glucose is defective in incretin-unresponsive β cells
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34
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Chutna O, Gonçalves S, Villar-Piqué A, Guerreiro P, Marijanovic Z, Mendes T, Ramalho J, Emmanouilidou E, Ventura S, Klucken J, Barral DC, Giorgini F, Vekrellis K, Outeiro TF. The small GTPase Rab11 co-localizes with α-synuclein in intracellular inclusions and modulates its aggregation, secretion and toxicity. Hum Mol Genet 2014; 23:6732-45. [PMID: 25092884 DOI: 10.1093/hmg/ddu391] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Alpha-synuclein (aSyn) misfolding and aggregation are pathological features common to several neurodegenerative diseases, including Parkinson's disease (PD). Mounting evidence suggests that aSyn can be secreted and transferred from cell to cell, participating in the propagation and spreading of pathological events. Rab11, a small GTPase, is an important regulator in both endocytic and secretory pathways. Here, we show that Rab11 is involved in regulating aSyn secretion. Rab11 knockdown or overexpression of either Rab11a wild-type (Rab11a WT) or Rab11a GDP-bound mutant (Rab11a S25N) increased secretion of aSyn. Furthermore, we demonstrate that Rab11 interacts with aSyn and is present in intracellular inclusions together with aSyn. Moreover, Rab11 reduces aSyn aggregation and toxicity. Our results suggest that Rab11 is involved in modulating the processes of aSyn secretion and aggregation, both of which are important mechanisms in the progression of aSyn pathology in PD and other synucleinopathies.
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Affiliation(s)
- Oldriska Chutna
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal
| | - Susana Gonçalves
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal
| | - Anna Villar-Piqué
- Department of Neurodegeneration and Restorative Research, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
| | - Patrícia Guerreiro
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal Department of Neurodegeneration and Restorative Research, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
| | - Zrinka Marijanovic
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal
| | - Tiago Mendes
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal
| | - José Ramalho
- CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
| | | | - Salvador Ventura
- Institut de Biotecnologia i Biomedicina Departament de Bioquimica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
| | - Jochen Klucken
- Department of Molecular Neurology, University Hospital, Erlangen, Germany
| | - Duarte C Barral
- CEDOC, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Flaviano Giorgini
- Department of Genetics, University of Leicester, University Road, Leicester, UK and
| | - Kostas Vekrellis
- Biomedical Research Foundation of the Academy of Athens, Athens, Greece
| | - Tiago F Outeiro
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Lisbon, Portugal Department of Neurodegeneration and Restorative Research, Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany Instituto de Fisiologia, Faculdade de Medicina da Universidade de Lisboa, Lisbon, Portugal
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Soares H, Henriques R, Sachse M, Ventimiglia L, Alonso MA, Zimmer C, Thoulouze MI, Alcover A. Regulated vesicle fusion generates signaling nanoterritories that control T cell activation at the immunological synapse. ACTA ACUST UNITED AC 2013; 210:2415-33. [PMID: 24101378 PMCID: PMC3804939 DOI: 10.1084/jem.20130150] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The assembly of signaling nanoterritories at the T cell immunological synapse is controlled by the coordinated trafficking and fusion of specific vesicles containing the signaling molecules Lck, LAT, and TCRζ. How the vesicular traffic of signaling molecules contributes to T cell receptor (TCR) signal transduction at the immunological synapse remains poorly understood. In this study, we show that the protein tyrosine kinase Lck, the TCRζ subunit, and the adapter LAT traffic through distinct exocytic compartments, which are released at the immunological synapse in a differentially regulated manner. Lck vesicular release depends on MAL protein. Synaptic Lck, in turn, conditions the calcium- and synaptotagmin-7–dependent fusion of LAT and TCRζ containing vesicles. Fusion of vesicles containing TCRζ and LAT at the synaptic membrane determines not only the nanoscale organization of phosphorylated TCRζ, ZAP70, LAT, and SLP76 clusters but also the presence of phosphorylated LAT and SLP76 in interacting signaling nanoterritories. This mechanism is required for priming IL-2 and IFN-γ production and may contribute to fine-tuning T cell activation breadth in response to different stimulatory conditions.
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Affiliation(s)
- Helena Soares
- Institut Pasteur, Department of Immunology, Lymphocyte Cell Biology Unit, F-75724 Paris, France
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36
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Uenishi E, Shibasaki T, Takahashi H, Seki C, Hamaguchi H, Yasuda T, Tatebe M, Oiso Y, Takenawa T, Seino S. Actin dynamics regulated by the balance of neuronal Wiskott-Aldrich syndrome protein (N-WASP) and cofilin activities determines the biphasic response of glucose-induced insulin secretion. J Biol Chem 2013; 288:25851-25864. [PMID: 23867458 DOI: 10.1074/jbc.m113.464420] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Actin dynamics in pancreatic β-cells is involved in insulin secretion. However, the molecular mechanisms of the regulation of actin dynamics by intracellular signals in pancreatic β-cells and its role in phasic insulin secretion are largely unknown. In this study, we elucidate the regulation of actin dynamics by neuronal Wiskott-Aldrich syndrome protein (N-WASP) and cofilin in pancreatic β-cells and demonstrate its role in glucose-induced insulin secretion (GIIS). N-WASP, which promotes actin polymerization through activation of the actin nucleation factor Arp2/3 complex, was found to be activated by glucose stimulation in insulin-secreting clonal pancreatic β-cells (MIN6-K8 β-cells). Introduction of a dominant-negative mutant of N-WASP, which lacks G-actin and Arp2/3 complex-binding region VCA, into MIN6-K8 β-cells or knockdown of N-WASP suppressed GIIS, especially the second phase. We also found that cofilin, which severs F-actin in its dephosphorylated (active) form, is converted to the phosphorylated (inactive) form by glucose stimulation in MIN6-K8 β-cells, thereby promoting F-actin remodeling. In addition, the dominant-negative mutant of cofilin, which inhibits activation of endogenous cofilin, or knockdown of cofilin reduced the second phase of GIIS. However, the first phase of GIIS occurs in the G-actin predominant state, in which cofilin activity predominates over N-WASP activity. Thus, actin dynamics regulated by the balance of N-WASP and cofilin activities determines the biphasic response of GIIS.
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Affiliation(s)
- Eita Uenishi
- From the Division of Cellular and Molecular Medicine,; the Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya 466-8550, and
| | | | | | - Chihiro Seki
- From the Division of Cellular and Molecular Medicine
| | | | - Takao Yasuda
- From the Division of Cellular and Molecular Medicine
| | - Masao Tatebe
- From the Division of Cellular and Molecular Medicine
| | - Yutaka Oiso
- the Department of Endocrinology and Diabetes, Nagoya University Graduate School of Medicine, Nagoya 466-8550, and
| | - Tadaomi Takenawa
- Division of Lipid Biochemistry, and; the Integrated Center for Mass Spectrometry, Kobe University Graduate School of Medicine, Kobe 650-0017
| | - Susumu Seino
- From the Division of Cellular and Molecular Medicine,; the Integrated Center for Mass Spectrometry, Kobe University Graduate School of Medicine, Kobe 650-0017,; Division of Molecular and Metabolic Medicine,; the Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Corp., Kawaguchi, Saitama 332-0012, Japan.
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Abstract
Comprising over 60 members, Rab proteins constitute the largest branch of the Ras superfamily of low-molecular-mass G-proteins. This protein family have been primarily implicated in various aspects of intracellular membrane trafficking processes. On the basis of distinct subfamily-specific sequence motifs, many Rabs have been grouped into subfamilies. The Rab11 GTPase subfamily comprises three members: Rab11a, Rab11b and Rab25/Rab11c, which, between them, have been demonstrated to bind more than 30 proteins. In the present paper, we review the function of the Rab11 subfamily. We describe their localization and primary functional roles within the cell and their implication, to date, in disease processes. We also summarize the protein machinery currently known to regulate or mediate their functions and the cargo molecules which they have been shown to transport.
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Cheng K, Agarwal R, Mitra S, Mills G. Rab25 Small GTPase Mediates Secretion of Tumor Necrosis Factor Receptor Superfamily Member 11b (osteoprotegerin) Protecting Cancer Cells from Effects of TRAIL. ACTA ACUST UNITED AC 2013; 4. [PMID: 25520884 PMCID: PMC4266180 DOI: 10.4172/2157-7412.1000153] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Expression of Rab25, which is located in the 1q amplicon present at high frequency in many cancer lineages, promotes cancer cell survival under multiple stress conditions. While Rab proteins play essential roles in all stages of vesicle trafficking, the functions and endogenous cargoes for Rab25 remain to be fully elucidated. Osteoprotegerin (OPG) is a secreted glycoprotein that binds the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) thus preventing it from activating the TNF-family death receptors. In the present study, we demonstrated that Rab25 regulates OPG at both the transcription and secretion level. METHODS The effect of Rab25 on OPG expression and its effect on TRAIL-induced cell were examined in both ovarian and breast cells. Signal transduction pathways regulation of OPG expression was examined in cells using pharmacogenetic approaches. RESULTS Expression of Rab25 to levels similar to those in tumors with RAB25 amplification, increased OPG mRNA expression and secretion from ovarian and breast cancer cell lines, whereas down regulation with Rab25 specific siRNA decreased OPG secretion and sensitized cells to TRAIL-induced cell death. Critically, exogenous OPG mimicked the effects of Rab25 on cell death supporting the contention that Rab25-induced accumulation of OPG protects cancer cells from the effects of TRAIL. Rab25 cooperates with EGFR-mediated MAPK signaling to increase TRAIL production and release. Importantly, priming cells with EGFR inhibitors increased sensitivity to TRAIL-induced cells death regardless of the Rab25 background. CONCLUSION Increased OPG expression induced by Rab25 may provide a mechanistic advantage for cancer development and progression.
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Affiliation(s)
- Kw Cheng
- Department of Systems Biology, the University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - R Agarwal
- Department of Surgery & Cancer, Institute of Reproductive and Developmental Biology, Imperial College London, London, W12 0NN, UK
| | - S Mitra
- Department of Systems Biology, the University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Gb Mills
- Department of Systems Biology, the University of Texas MD Anderson Cancer Center, Houston, Texas, USA
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Bogan JS, Xu Y, Hao M. Cholesterol accumulation increases insulin granule size and impairs membrane trafficking. Traffic 2012; 13:1466-80. [PMID: 22889194 DOI: 10.1111/j.1600-0854.2012.01407.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 08/09/2012] [Accepted: 08/13/2012] [Indexed: 11/28/2022]
Abstract
The formation of mature secretory granules is essential for proper storage and regulated release of hormones and neuropeptides. In pancreatic β cells, cholesterol accumulation causes defects in insulin secretion and may participate in the pathogenesis of type 2 diabetes. Using a novel cholesterol analog, we show for the first time that insulin granules are the major sites of intracellular cholesterol accumulation in live β cells. This is distinct from other, non-secretory cell types, in which cholesterol is concentrated in the recycling endosomes and the trans-Golgi network. Excess cholesterol was delivered specifically to insulin granules, which caused granule enlargement and retention of syntaxin 6 and VAMP4 in granule membranes, with concurrent depletion of these proteins from the trans-Golgi network. Clathrin also accumulated in the granules of cholesterol-overloaded cells, consistent with a possible defect in the last stage of granule maturation, during which clathrin-coated vesicles bud from the immature granules. Excess cholesterol also reduced the docking and fusion of insulin granules at the plasma membrane. Together, the data support a model in which cholesterol accumulation in insulin secretory granules impairs the ability of these vesicles to respond to stimuli, and thus reduces insulin secretion.
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Affiliation(s)
- Jonathan S Bogan
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
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Zografou S, Basagiannis D, Papafotika A, Shirakawa R, Horiuchi H, Auerbach D, Fukuda M, Christoforidis S. A complete Rab screening reveals novel insights in Weibel-Palade body exocytosis. J Cell Sci 2012; 125:4780-90. [PMID: 22899725 DOI: 10.1242/jcs.104174] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Weibel-Palade bodies (WPBs) are endothelial-cell-specific organelles that, upon fusion with the plasma membrane, release cargo molecules that are essential in blood vessel abnormalities, such as thrombosis and inflammation, as well as in angiogenesis. Despite the importance of WPBs, the basic mechanisms that mediate their secretion are only poorly understood. Rab GTPases play fundamental role in the trafficking of intracellular organelles. Yet, the only known WPB-associated Rabs are Rab27a and Rab3d. To determine the full spectrum of WPB-associated Rabs we performed a complete Rab screening by analysing the localisation of all Rabs in WPBs and their involvement in the secretory process in endothelial cells. Apart from Rab3 and Rab27, we identified three additional Rabs, Rab15 (a previously reported endocytic Rab), Rab33 and Rab37, on the WPB limiting membrane. A knockdown approach using siRNAs showed that among these five WPB Rabs only Rab3, Rab27 and Rab15 are required for exocytosis. Intriguingly, we found that Rab15 cooperates with Rab27a in WPB secretion. Furthermore, a specific effector of Rab27, Munc13-4, appears to be also an effector of Rab15 and is required for WPB exocytosis. These data indicate that WPB secretion requires the coordinated function of a specific group of Rabs and that, among them, Rab27a and Rab15, as well as their effector Munc13-4, cooperate to drive exocytosis.
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Affiliation(s)
- Sofia Zografou
- Institute of Molecular Biology and Biotechnology, Department of Ioannina/Foundation for Research and Technology Hellas, Ioannina, Greece
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41
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Seino S. Cell signalling in insulin secretion: the molecular targets of ATP, cAMP and sulfonylurea. Diabetologia 2012; 55:2096-108. [PMID: 22555472 DOI: 10.1007/s00125-012-2562-9] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 03/09/2012] [Indexed: 12/25/2022]
Abstract
Clarification of the molecular mechanisms of insulin secretion is crucial for understanding the pathogenesis and pathophysiology of diabetes and for development of novel therapeutic strategies for the disease. Insulin secretion is regulated by various intracellular signals generated by nutrients and hormonal and neural inputs. In addition, a variety of glucose-lowering drugs including sulfonylureas, glinide-derivatives, and incretin-related drugs such as dipeptidyl peptidase IV (DPP-4) inhibitors and glucagon-like peptide 1 (GLP-1) receptor agonists are used for glycaemic control by targeting beta cell signalling for improved insulin secretion. There has been a remarkable increase in our understanding of the basis of beta cell signalling over the past two decades following the application of molecular biology, gene technology, electrophysiology and bioimaging to beta cell research. This review discusses cell signalling in insulin secretion, focusing on the molecular targets of ATP, cAMP and sulfonylurea, an essential metabolic signal in glucose-induced insulin secretion (GIIS), a critical signal in the potentiation of GIIS, and the commonly used glucose-lowering drug, respectively.
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Affiliation(s)
- S Seino
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, 650-0017, Japan.
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42
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Straub SG, Sharp GWG. Evolving insights regarding mechanisms for the inhibition of insulin release by norepinephrine and heterotrimeric G proteins. Am J Physiol Cell Physiol 2012; 302:C1687-98. [PMID: 22492651 DOI: 10.1152/ajpcell.00282.2011] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Norepinephrine has for many years been known to have three major effects on the pancreatic β-cell which lead to the inhibition of insulin release. These are activation of K(+) channels to hyperpolarize the cell and prevent the gating of voltage-dependent Ca(2+) channels that increase intracellular Ca(2+) concentration ([Ca(2+)](i)) and trigger release; inhibition of adenylyl cyclases, thus preventing the augmentation of stimulated insulin release by cyclic AMP; and a "distal" effect that occurs downstream of increased [Ca(2+)](i) to inhibit exocytosis. All three are mediated by the pertussis toxin (PTX)-sensitive heterotrimeric Gi and Go proteins. The distal inhibitory effect on exocytosis is now known to be due to the binding of G protein βγ subunits to the synaptosomal-associated protein of 25 kDa (SNAP-25) on the soluble NSF attachment protein receptor (SNARE) complex. Recent studies have uncovered two more actions of norepinephrine on the β-cell: 1) retardation of the refilling of the readily releasable granule pool after it has been discharged, an action that is mediated by Gαi(1) and/or Gαi(2); and 2) inhibition of endocytosis that is mediated by Gz. Of importance also are new findings that Gαo regulates the number of docked granules in the β-cell, and that Gαo(2) maintains a tonic inhibitory influence on secretion. The latter provides another explanation as to why PTX, which blocks the effect of Gαo(2), was initially called "islet activating protein." Finally, there is clear evidence that overexpression of α(2A)-adrenergic receptors in β-cells can cause type 2 diabetes.
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Affiliation(s)
- Susanne G Straub
- Department of Molecular Medicine, Cornell University, Ithaca, New York 14853-6401, USA
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43
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Larsson S, Resjö S, Gomez MF, James P, Holm C. Characterization of the lipid droplet proteome of a clonal insulin-producing β-cell line (INS-1 832/13). J Proteome Res 2012; 11:1264-73. [PMID: 22268682 DOI: 10.1021/pr200957p] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Lipids are known to play a crucial role both in the normal control of insulin release and in the deterioration of β-cell function, as observed in type 2 diabetes. Despite this established dual role of lipids, little is known about lipid storage and handling in β-cells. Here, we isolated lipid droplets from oleate-incubated INS-1 832/13 cells and characterized the lipid droplet proteome. In a total of four rounds of droplet isolation and proteomic analysis by HPLC-MS/MS, we identified 96 proteins that were specific to droplets. The proteins fall into six categories based on function or previously observed localization: metabolism, endoplasmic reticulum/ribosomes, mitochondria, vesicle formation and transport, signaling, and miscellaneous. The protein profile reinforces the emerging picture of the lipid droplet as an active and dynamic organelle involved in lipid homeostasis and intracellular trafficking. Proteins belonging to the category mitochondria were highly represented, suggesting that the β-cell mitochondria and lipid droplets form a metabolic unit of potential relevance for insulin secretion.
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Affiliation(s)
- Sara Larsson
- Department of Experimental Medical Science, Division of Diabetes, Metabolism and Endocrinology, Lund Univeristy , BMC C11, SE-221 84 Lund, Sweden.
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Pavarotti M, Capmany A, Vitale N, Colombo MI, Damiani MT. Rab11 is phosphorylated by classical and novel protein kinase C isoenzymes upon sustained phorbol ester activation. Biol Cell 2012; 104:102-15. [PMID: 22188018 DOI: 10.1111/boc.201100062] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Accepted: 11/29/2011] [Indexed: 01/06/2023]
Abstract
BACKGROUND INFORMATION Rab11 is a small GTPase that controls diverse intracellular trafficking pathways. However, the molecular machinery that regulates the participation of Rab11 in those different transport events is poorly understood. In resting cells, Rab11 localizes at the endocytic recycling compartment (ERC), whereas the different protein kinase C (PKC) isoforms display a cytosolic distribution. RESULTS Sustained phorbol ester stimulation induces the translocation of the classical PKCα and PKCβII isoenzymes to the ERC enriched in Rab11, and results in transferrin recycling inhibition. In contrast, novel PKCε and atypical PKCζ isoenzymes neither redistribute to the perinucleus nor modify transferrin recycling transport after phorbol ester stimulation. Although several Rabs have been shown to be phosphorylated, there is to date no evidence indicating Rab11 as a kinase substrate. In this report, we show that Rab11 appears phosphorylated in vivo in phorbol ester-stimulated cells. A bioinformatic analysis of Rab11 allowed us to identify several high-probability Ser/Thr kinase phosphorylation sites. Our results demonstrate that classical PKC (PKCα and PKCβII but not PKCβI) directly phosphorylate Rab11 in vitro. In addition, novel PKCε and PKCη but not PKCδ isoenzymes also phosphorylate Rab11. Mass spectrometry analysis revealed that Ser 177 is the Rab11 residue to be phosphorylated in vitro by either PKCβII or PKCε. In agreement, the phosphomimetic mutant, Rab11 S177D, retains transferrin at the ERC in the absence of phorbol-12-myristate-13-acetate stimulus. CONCLUSIONS This report shows for the first time that Rab11 is differentially phosphorylated by distinct PKC isoenzymes and that this post-translational modification might be a regulatory mechanism of intracellular trafficking.
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Affiliation(s)
- Martín Pavarotti
- IHEM-CONICET, National Research Council, School of Medicine, University of Cuyo, Mendoza, Argentina
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45
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Zemskov EA, Mikhailenko I, Hsia RC, Zaritskaya L, Belkin AM. Unconventional secretion of tissue transglutaminase involves phospholipid-dependent delivery into recycling endosomes. PLoS One 2011; 6:e19414. [PMID: 21556374 PMCID: PMC3083433 DOI: 10.1371/journal.pone.0019414] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 04/04/2011] [Indexed: 12/20/2022] Open
Abstract
Although endosomal compartments have been suggested to play a role in unconventional protein secretion, there is scarce experimental evidence for such involvement. Here we report that recycling endosomes are essential for externalization of cytoplasmic secretory protein tissue transglutaminase (tTG). The de novo synthesized cytoplasmic tTG does not follow the classical ER/Golgi-dependent secretion pathway, but is targeted to perinuclear recycling endosomes, and is delivered inside these vesicles prior to externalization. On its route to the cell surface tTG interacts with internalized β1 integrins inside the recycling endosomes and is secreted as a complex with recycled β1 integrins. Inactivation of recycling endosomes, blocking endosome fusion with the plasma membrane, or downregulation of Rab11 GTPase that controls outbound trafficking of perinuclear recycling endosomes, all abrogate tTG secretion. The initial recruitment of cytoplasmic tTG to recycling endosomes and subsequent externalization depend on its binding to phosphoinositides on endosomal membranes. These findings begin to unravel the unconventional mechanism of tTG secretion which utilizes the long loop of endosomal recycling pathway and indicate involvement of endosomal trafficking in non-classical protein secretion.
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Affiliation(s)
- Evgeny A. Zemskov
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Irina Mikhailenko
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Ru-Ching Hsia
- Core Imaging Facility, University of Maryland Dental School, Baltimore, Maryland, United States of America
| | - Liubov Zaritskaya
- Applied and Developmental Research Support Program, Science Applications International Corporation, Frederick, Maryland, United States of America
| | - Alexey M. Belkin
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Center for Vascular and Inflammatory Diseases, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Center for Stem Cell Biology and Regenerative Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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Beaumont KA, Hamilton NA, Moores MT, Brown DL, Ohbayashi N, Cairncross O, Cook AL, Smith AG, Misaki R, Fukuda M, Taguchi T, Sturm RA, Stow JL. The recycling endosome protein Rab17 regulates melanocytic filopodia formation and melanosome trafficking. Traffic 2011; 12:627-43. [PMID: 21291502 DOI: 10.1111/j.1600-0854.2011.01172.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Rab GTPases including Rab27a, Rab38 and Rab32 function in melanosome maturation or trafficking in melanocytes. A screen to identify additional Rabs involved in these processes revealed the localization of GFP-Rab17 on recycling endosomes (REs) and melanosomes in melanocytic cells. Rab17 mRNA expression is regulated by microphthalmia transcription factor (MITF), a characteristic of known pigmentation genes. Rab17 siRNA knockdown in melanoma cells quantitatively increased melanosome concentration at the cell periphery. Rab17 knockdown did not inhibit melanosome maturation nor movement, but it caused accumulation of melanin inside cells. Double knockdown of Rab17 and Rab27a indicated that Rab17 acts on melanosomes downstream of Rab27a. Filopodia are known to play a role in melanosome transfer, and in Rab17 knockdown cells filopodia formation was inhibited. Furthermore, we show that stimulation of melanoma cells with α-melanocyte-stimulating hormone induces filopodia formation, supporting a role for filopodia in melanosome release. Cell stimulation also caused redistribution of REs to the periphery, and knockdown of additional RE-associated Rabs 11a and 11b produced a similar accumulation of melanosomes and melanin to that seen after loss of Rab17. Our findings reveal new functions for RE and Rab17 in pigmentation through a distal step in the process of melanosome release via filopodia.
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Affiliation(s)
- Kimberley A Beaumont
- Institute for Molecular Bioscience, The University of Queensland, Brisbane 4072 QLD, Australia
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Oehlke O, Martin HW, Osterberg N, Roussa E. Rab11b and its effector Rip11 regulate the acidosis-induced traffic of V-ATPase in salivary ducts. J Cell Physiol 2010; 226:638-51. [DOI: 10.1002/jcp.22388] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Yasuda T, Shibasaki T, Minami K, Takahashi H, Mizoguchi A, Uriu Y, Numata T, Mori Y, Miyazaki JI, Miki T, Seino S. Rim2alpha determines docking and priming states in insulin granule exocytosis. Cell Metab 2010; 12:117-29. [PMID: 20674857 DOI: 10.1016/j.cmet.2010.05.017] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Revised: 04/23/2010] [Accepted: 05/26/2010] [Indexed: 12/20/2022]
Abstract
Insulin secretion is essential for maintenance of glucose homeostasis, but the mechanism of insulin granule exocytosis, the final step of insulin secretion, is largely unknown. Here, we investigated the role of Rim2alpha in insulin granule exocytosis, including the docking, priming, and fusion steps. We found that interaction of Rim2alpha and Rab3A is required for docking, which is considered a brake on fusion events, and that docking is necessary for K(+)-induced exocytosis, but not for glucose-induced exocytosis. Furthermore, we found that dissociation of the Rim2alpha/Munc13-1 complex by glucose stimulation activates Syntaxin1 by Munc13-1, indicating that Rim2alpha primes insulin granules for fusion. Thus, Rim2alpha determines docking and priming states in insulin granule exocytosis depending on its interacting partner, Rab3A or Munc13-1, respectively. Because Rim2alpha(-/-) mice exhibit impaired secretion of various hormones stored as dense-core granules, including glucose-dependent insulinotropic polypeptide, growth hormone, and epinephrine, Rim2alpha plays a critical role in exocytosis of these dense-core granules.
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Affiliation(s)
- Takao Yasuda
- Division of Cellular and Molecular Medicine, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Hyogo 650-0017, Japan
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Chepurny OG, Kelley GG, Dzhura I, Leech CA, Roe MW, Dzhura E, Li X, Schwede F, Genieser HG, Holz GG. PKA-dependent potentiation of glucose-stimulated insulin secretion by Epac activator 8-pCPT-2'-O-Me-cAMP-AM in human islets of Langerhans. Am J Physiol Endocrinol Metab 2010; 298:E622-33. [PMID: 20009023 PMCID: PMC2838523 DOI: 10.1152/ajpendo.00630.2009] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Potential insulin secretagogue properties of an acetoxymethyl ester of a cAMP analog (8-pCPT-2'-O-Me-cAMP-AM) that activates the guanine nucleotide exchange factors Epac1 and Epac2 were assessed using isolated human islets of Langerhans. RT-QPCR demonstrated that the predominant variant of Epac expressed in human islets was Epac2, although Epac1 was detectable. Under conditions of islet perifusion, 8-pCPT-2'-O-Me-cAMP-AM (10 microM) potentiated first- and second-phase 10 mM glucose-stimulated insulin secretion (GSIS) while failing to influence insulin secretion measured in the presence of 3 mM glucose. The insulin secretagogue action of 8-pCPT-2'-O-Me-cAMP-AM was associated with depolarization and an increase of [Ca(2+)](i) that reflected both Ca(2+) influx and intracellular Ca(2+) mobilization in islet beta-cells. As expected for an Epac-selective cAMP analog, 8-pCPT-2'-O-Me-cAMP-AM (10 microM) failed to stimulate phosphorylation of PKA substrates CREB and Kemptide in human islets. Furthermore, 8-pCPT-2'-O-Me-cAMP-AM (10 microM) had no significant ability to activate AKAR3, a PKA-regulated biosensor expressed in human islet cells by viral transduction. Unexpectedly, treatment of human islets with an inhibitor of PKA activity (H-89) or treatment with a cAMP antagonist that blocks PKA activation (Rp-8-CPT-cAMPS) nearly abolished the action of 8-pCPT-2'-O-Me-cAMP-AM to potentiate GSIS. It is concluded that there exists a permissive role for PKA activity in support of human islet insulin secretion that is both glucose dependent and Epac regulated. This permissive action of PKA may be operative at the insulin secretory granule recruitment, priming, and/or postpriming steps of Ca(2+)-dependent exocytosis.
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Affiliation(s)
- Oleg G Chepurny
- Departments of Medicine, State University of New York, Syracuse, 13210, USA
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Wang Z, Thurmond DC. Differential phosphorylation of RhoGDI mediates the distinct cycling of Cdc42 and Rac1 to regulate second-phase insulin secretion. J Biol Chem 2009; 285:6186-97. [PMID: 20028975 DOI: 10.1074/jbc.m109.072421] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cdc42 cycling through GTP/GDP states is critical for its function in the second/granule mobilization phase of insulin granule exocytosis in pancreatic islet beta cells, although the identities of the Cdc42 cycling proteins involved remain incomplete. Using a tandem affinity purification-based mass spectrometry screen for Cdc42 cycling factors in beta cells, RhoGDI was identified. RNA interference-mediated depletion of RhoGDI from isolated islets selectively amplified the second phase of insulin release, consistent with the role of RhoGDI as a Cdc42 cycling factor. Replenishment of RhoGDI to RNA interference-depleted cells normalized secretion, confirming the action of RhoGDI to be that of a negative regulator of Cdc42 activation. Given that RhoGDI also regulates Rac1 activation in beta cells, and that Rac1 activation occurs in a Cdc42-dependent manner, the question as to how the beta cell utilized RhoGDI for differential Cdc42 and Rac1 cycling was explored. Co-immunoprecipitation was used to determine that RhoGDI-Cdc42 complexes dissociated upon stimulation of beta cells with glucose for 3 min, correlating with the timing of glucose-induced Cdc42 activation and the onset of RhoGDI tyrosine phosphorylation. Glucose-induced disruption of RhoGDI-Rac1 complexes occurred subsequent to this, coincident with Rac1 activation, which followed the onset of RhoGDI serine phosphorylation. RhoGDI-Cdc42 complex dissociation was blocked by mutation of RhoGDI residue Tyr-156, whereas RhoGDI-Rac1 dissociation was blocked by RhoGDI mutations Y156F and S101A/S174A. Finally, expression of a triple Y156F/S101A/S174A-RhoGDI mutant specifically inhibited only the second/granule mobilization phase of glucose-stimulated insulin secretion, overall supporting the integration of RhoGDI into the activation cycling mechanism of glucose-responsive small GTPases.
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Affiliation(s)
- Zhanxiang Wang
- Herman B Wells Center for Pediatric Research, Basic Diabetes Research Group, Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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