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Izumi T. In vivo Roles of Rab27 and Its Effectors in Exocytosis. Cell Struct Funct 2021; 46:79-94. [PMID: 34483204 PMCID: PMC10511049 DOI: 10.1247/csf.21043] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 08/31/2021] [Indexed: 11/11/2022] Open
Abstract
The monomeric GTPase Rab27 regulates exocytosis of a broad range of vesicles in multicellular organisms. Several effectors bind GTP-bound Rab27a and/or Rab27b on secretory vesicles to execute a series of exocytic steps, such as vesicle maturation, movement along microtubules, anchoring within the peripheral F-actin network, and tethering to the plasma membrane, via interactions with specific proteins and membrane lipids in a local milieu. Although Rab27 effectors generally promote exocytosis, they can also temporarily restrict it when they are involved in the rate-limiting step. Genetic alterations in Rab27-related molecules cause discrete diseases manifesting pigment dilution and immunodeficiency, and can also affect common diseases such as diabetes and cancer in complex ways. Although the function and mechanism of action of these effectors have been explored, it is unclear how multiple effectors act in coordination within a cell to regulate the secretory process as a whole. It seems that Rab27 and various effectors constitutively reside on individual vesicles to perform consecutive exocytic steps. The present review describes the unique properties and in vivo roles of the Rab27 system, and the functional relationship among different effectors coexpressed in single cells, with pancreatic beta cells used as an example.Key words: membrane trafficking, regulated exocytosis, insulin granules, pancreatic beta cells.
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Affiliation(s)
- Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma 371-8512, Japan
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2
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Fan F, Wu Y, Hara M, Rizk A, Ji C, Nerad D, Tamarina N, Lou X. Dynamin deficiency causes insulin secretion failure and hyperglycemia. Proc Natl Acad Sci U S A 2021; 118:e2021764118. [PMID: 34362840 PMCID: PMC8364113 DOI: 10.1073/pnas.2021764118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pancreatic β cells operate with a high rate of membrane recycling for insulin secretion, yet endocytosis in these cells is not fully understood. We investigate this process in mature mouse β cells by genetically deleting dynamin GTPase, the membrane fission machinery essential for clathrin-mediated endocytosis. Unexpectedly, the mice lacking all three dynamin genes (DNM1, DNM2, DNM3) in their β cells are viable, and their β cells still contain numerous insulin granules. Endocytosis in these β cells is severely impaired, resulting in abnormal endocytic intermediates on the plasma membrane. Although insulin granules are abundant, their release upon glucose stimulation is blunted in both the first and second phases, leading to hyperglycemia and glucose intolerance in mice. Dynamin triple deletion impairs insulin granule exocytosis and decreases intracellular Ca2+ responses and granule docking. The docking defect is correlated with reduced expression of Munc13-1 and RIM1 and reorganization of cortical F-actin in β cells. Collectively, these findings uncover the role of dynamin in dense-core vesicle endocytosis and secretory capacity. Insulin secretion deficiency in the absence of dynamin-mediated endocytosis highlights the risk of impaired membrane trafficking in endocrine failure and diabetes pathogenesis.
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Affiliation(s)
- Fan Fan
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226
| | - Yumei Wu
- HHMI, Yale University School of Medicine, New Haven, CT 06510
- Departments of Neuroscience and Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT 06510
| | - Manami Hara
- Section of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Chicago, Chicago, IL 60637
| | - Adam Rizk
- Section of Endocrinology, Diabetes and Metabolism, Department of Medicine, University of Chicago, Chicago, IL 60637
| | - Chen Ji
- Synapses and Circuits section, National Institute of Neurological Disorders and Stroke, Bethesda, MD 20892
| | - Dan Nerad
- Emergency Medicine, Carl R. Darnall Army Medical Center, Fort Hood, TX 76544
| | - Natalia Tamarina
- Department of Medicine, The Kovler Diabetes Center, University of Chicago, Chicago, IL 60637
| | - Xuelin Lou
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226;
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3
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Isolation and Proteomics of the Insulin Secretory Granule. Metabolites 2021; 11:metabo11050288. [PMID: 33946444 PMCID: PMC8147143 DOI: 10.3390/metabo11050288] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 04/28/2021] [Accepted: 04/28/2021] [Indexed: 12/21/2022] Open
Abstract
Insulin, a vital hormone for glucose homeostasis is produced by pancreatic beta-cells and when secreted, stimulates the uptake and storage of glucose from the blood. In the pancreas, insulin is stored in vesicles termed insulin secretory granules (ISGs). In Type 2 diabetes (T2D), defects in insulin action results in peripheral insulin resistance and beta-cell compensation, ultimately leading to dysfunctional ISG production and secretion. ISGs are functionally dynamic and many proteins present either on the membrane or in the lumen of the ISG may modulate and affect different stages of ISG trafficking and secretion. Previously, studies have identified few ISG proteins and more recently, proteomics analyses of purified ISGs have uncovered potential novel ISG proteins. This review summarizes the proteins identified in the current ISG proteomes from rat insulinoma INS-1 and INS-1E cell lines. Here, we also discuss techniques of ISG isolation and purification, its challenges and potential future directions.
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4
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Catz SD, McLeish KR. Therapeutic targeting of neutrophil exocytosis. J Leukoc Biol 2020; 107:393-408. [PMID: 31990103 PMCID: PMC7044074 DOI: 10.1002/jlb.3ri0120-645r] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2019] [Revised: 01/10/2020] [Accepted: 01/11/2020] [Indexed: 12/11/2022] Open
Abstract
Dysregulation of neutrophil activation causes disease in humans. Neither global inhibition of neutrophil functions nor neutrophil depletion provides safe and/or effective therapeutic approaches. The role of neutrophil granule exocytosis in multiple steps leading to recruitment and cell injury led each of our laboratories to develop molecular inhibitors that interfere with specific molecular regulators of secretion. This review summarizes neutrophil granule formation and contents, the role granule cargo plays in neutrophil functional responses and neutrophil-mediated diseases, and the mechanisms of granule release that provide the rationale for development of our exocytosis inhibitors. We present evidence for the inhibition of granule exocytosis in vitro and in vivo by those inhibitors and summarize animal data indicating that inhibition of neutrophil exocytosis is a viable therapeutic strategy.
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Affiliation(s)
- Sergio D. Catz
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA
| | - Kenneth R. McLeish
- Department of Medicine, University of Louisville School of Medicine, Louisville, KY
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Nguyen PM, Gandasi NR, Xie B, Sugahara S, Xu Y, Idevall-Hagren O. The PI(4)P phosphatase Sac2 controls insulin granule docking and release. J Cell Biol 2019; 218:3714-3729. [PMID: 31533953 PMCID: PMC6829663 DOI: 10.1083/jcb.201903121] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 06/20/2019] [Accepted: 08/08/2019] [Indexed: 12/12/2022] Open
Abstract
Insulin granule biogenesis involves transport to, and stable docking at, the plasma membrane before priming and fusion. Defects in this pathway result in impaired insulin secretion and are a hallmark of type 2 diabetes. We now show that the phosphatidylinositol 4-phosphate phosphatase Sac2 localizes to insulin granules in a substrate-dependent manner and that loss of Sac2 results in impaired insulin secretion. Sac2 operates upstream of granule docking, since loss of Sac2 prevented granule tethering to the plasma membrane and resulted in both reduced granule density and number of exocytic events. Sac2 levels correlated positively with the number of docked granules and exocytic events in clonal β cells and with insulin secretion in human pancreatic islets, and Sac2 expression was reduced in islets from type 2 diabetic subjects. Taken together, we identified a phosphoinositide switch on the surface on insulin granules that is required for stable granule docking at the plasma membrane and impaired in human type 2 diabetes.
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Affiliation(s)
- Phuoc My Nguyen
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Nikhil R Gandasi
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Beichen Xie
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden
| | - Sari Sugahara
- Department of Medical Cell Biology, Uppsala University, Uppsala, Sweden.,Laboratory of Health Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan
| | - Yingke Xu
- Department of Biomedical Engineering, Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang Provincial Key Laboratory of Cardio-Cerebral Vascular Detection Technology and Medicinal Effectiveness Appraisal, Zhejiang University, Hangzhou, China
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Luo Z, Wu F, Xue E, Huang L, Yan P, Pan X, Zhou Y. Hypoxia preconditioning promotes bone marrow mesenchymal stem cells survival by inducing HIF-1α in injured neuronal cells derived exosomes culture system. Cell Death Dis 2019; 10:134. [PMID: 30755595 PMCID: PMC6372680 DOI: 10.1038/s41419-019-1410-y] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Revised: 01/20/2019] [Accepted: 01/28/2019] [Indexed: 12/20/2022]
Abstract
Bone marrow derived stem cells (BMSCs) transplantation are viewed as a promising therapeutic candidate for spinal cord injury (SCI). However, the inflammatory microenvironment in the spinal cord following SCI limits the survival and efficacy of transplanted BMSCs. In this study, we investigate whether injured neuronal cells derived exosomes would influence the survival of transplanted BMSCs after SCI. In order to mimic the microenvironment in SCI that the neuronal cells or transplanted BMSCs suffer in vivo, PC12 cells conditioned medium and PC12 cell’s exosomes collected from H2O2-treated PC12 cell’s culture medium were cultured with BMSCs under oxidative stress in vitro. PC12 cells conditioned medium and PC12 cell’s exosomes significantly accelerated the apoptosis of BMSCs induced by H2O2. Moreover, the cleaved caspase-3, cytochrome (Cyt) C, lactate dehydrogenase (LDH) releases, and apoptotic percentage were increased, and the ratio of Bcl-2/Bax and cell viability were decreased. Inhibition of exosome secretion via Rab27a small interfering RNA prevented BMSCs apoptosis in vitro. In addition, hypoxia-preconditioned promoted the survival of BMSCs under oxidative stress both in vivo after SCI and in vitro. Our results also indicate that HIF-1α plays a central role in the survival of BMSCs in hypoxia pretreatment under oxidative stress conditions. siRNA-HIF-1α increased apoptosis of BMSCs; in contrast, HIF-1α inducer FG-4592 attenuated apoptosis of BMSCs. Taken together, we found that the injured PC12 cells derived exosomes accelerate BMSCs apoptosis after SCI and in vitro, hypoxia pretreatment or activating expression of HIF-1α to be important in the survival of BMSCs after transplantation, which provides a foundation for application of BMSCs in therapeutic potential for SCI.
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Affiliation(s)
- Zucheng Luo
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, 325000, P. R. China.,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, Zhejiang, 325000, P. R. China.,The Second School of Medicine, WenZhou Medical University, Wenzhou, Zhejiang, 325000, P. R. China
| | - Fangfang Wu
- The Second School of Medicine, WenZhou Medical University, Wenzhou, Zhejiang, 325000, P. R. China.,Emergency Department, The Second Affiliated Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, 325000, China
| | - Enxing Xue
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, 325000, P. R. China
| | - Linlin Huang
- The Second School of Medicine, WenZhou Medical University, Wenzhou, Zhejiang, 325000, P. R. China
| | - Ping Yan
- The Second School of Medicine, WenZhou Medical University, Wenzhou, Zhejiang, 325000, P. R. China
| | - Xiaoyun Pan
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, 325000, P. R. China. .,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, Zhejiang, 325000, P. R. China.
| | - Yulong Zhou
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, 325000, P. R. China. .,Zhejiang Provincial Key Laboratory of Orthpaedics, Wenzhou, Zhejiang, 325000, P. R. China.
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Koh J, Hogue JA, Roman SA, Scheri RP, Fradin H, Corcoran DL, Sosa JA. Transcriptional profiling reveals distinct classes of parathyroid tumors in PHPT. Endocr Relat Cancer 2018; 25:407-420. [PMID: 29475894 PMCID: PMC5826637 DOI: 10.1530/erc-17-0470] [Citation(s) in RCA: 6] [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: 01/23/2018] [Accepted: 02/01/2018] [Indexed: 12/20/2022]
Abstract
The clinical presentation of primary hyperparathyroidism (PHPT) varies widely, although the underlying mechanistic reasons for this disparity remain unknown. We recently reported that parathyroid tumors can be functionally segregated into two distinct groups on the basis of their relative responsiveness to ambient calcium, and that patients in these groups differ significantly in their likelihood of manifesting bone disability. To examine the molecular basis for this phenotypic variation in PHPT, we compared the global gene expression profiles of calcium-sensitive and calcium-resistant parathyroid tumors. RNAseq and proteomic analysis identified a candidate set of differentially expressed genes highly correlated with calcium-sensing capacity. Subsequent quantitative assessment of the expression levels of these genes in an independent cohort of parathyroid tumors confirmed that calcium-sensitive tumors cluster in a discrete transcriptional profile group. These data indicate that PHPT is not an etiologically monolithic disorder and suggest that divergent molecular mechanisms could drive the observed phenotypic differences in PHPT disease course, provenance, and outcome.
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Affiliation(s)
- James Koh
- Dept. of Surgery, Duke University Medical Center, Durham, NC
- Duke Clinical Research Institute, Duke University Medical Center
- To whom reprint requests should be addressed: James Koh, Ph.D., Department of Surgery, Duke University Medical Center, Durham, NC 27710, Phone: 919-684-0892, FAX: 919-681-6622,
| | - Joyce A. Hogue
- Dept. of Surgery, Duke University Medical Center, Durham, NC
| | | | | | | | | | - Julie A. Sosa
- Dept. of Surgery, Duke University Medical Center, Durham, NC
- Dept. of Medicine, Duke University
- Duke Cancer Institute, Duke University Medical Center
- Duke Clinical Research Institute, Duke University Medical Center
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8
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miR-124a expression contributes to the monophasic pattern of insulin secretion in islets from pregnant rats submitted to a low-protein diet. Eur J Nutr 2017; 57:1471-1483. [PMID: 28314963 DOI: 10.1007/s00394-017-1425-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 03/01/2017] [Indexed: 10/19/2022]
Abstract
PURPOSE To evaluate the role of miR-124a in the regulation of genes involved in insulin exocytosis and its effects on the kinetics of insulin secretion in pancreatic islets from pregnant rats submitted to a low-protein diet. METHODS Adult control non-pregnant (CNP) and control pregnant (CP) rats were fed a normal protein diet (17%), whereas low-protein non-pregnant (LPNP) and low-protein pregnant (LPP) rats were fed a low-protein diet (6%) from days 1 to 15 of pregnancy. Kinetics of the glucose-induced insulin release and measurement of [Ca2+]i in pancreatic islets were assessed by standard protocols. The miR-124a expression and gene transcriptions from pancreatic islets were determined by real-time polymerase chain reaction. RESULTS In islets from LPP rats, the first phase of insulin release was abrogated. The AUC [Ca2+]i from the LPP group was lower compared with the other groups. miR-124a expression was reduced by a low-protein diet. SNAP-25 mRNA, protein expression, and Rab3A protein content were lower in the LPP rats than in CP rats. Syntaxin 1A and Kir6.2 mRNA levels were decreased in islets from low-protein rats compared with control rats, whereas their protein content was reduced in islets from pregnant rats. CONCLUSIONS Loss of biphasic insulin secretion in islets from LPP rats appears to have resulted from reduced [Ca2+]i due, at least in part, to Kir6.2 underexpression and from the changes in exocytotic elements that are influenced either directly or indirectly by miR-124a.
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9
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Matsunaga K, Taoka M, Isobe T, Izumi T. Rab2a and Rab27a cooperatively regulate the transition from granule maturation to exocytosis through the dual effector Noc2. J Cell Sci 2016; 130:541-550. [PMID: 27927751 DOI: 10.1242/jcs.195479] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 11/28/2016] [Indexed: 11/20/2022] Open
Abstract
Exocytosis of secretory granules entails budding from the trans-Golgi network, sorting and maturation of cargo proteins, and trafficking and fusion to the plasma membrane. Rab27a regulates the late steps in this process, such as granule recruitment to the fusion site, whereas Rab2a functions in the early steps, such as granule biogenesis and maturation. Here, we demonstrate that these two small GTPases simultaneously bind to Noc2 (also known as RPH3AL) in a GTP-dependent manner, although Rab2a binds only after Rab27a has bound. In pancreatic β-cells, the ternary Rab2a-Noc2-Rab27a complex specifically localizes on perinuclear immature granules, whereas the binary Noc2-Rab27a complex localizes on peripheral mature granules. In contrast to the wild type, Noc2 mutants defective in binding to Rab2a or Rab27a fail to promote glucose-stimulated insulin secretion. Although knockdown of any component of the ternary complex markedly inhibits insulin secretion, only knockdown of Rab2a or Noc2, and not that of Rab27a, impairs cargo processing from proinsulin to insulin. These results suggest that the dual effector, Noc2, regulates the transition from Rab2a-mediated granule biogenesis to Rab27a-mediated granule exocytosis.
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Affiliation(s)
- Kohichi Matsunaga
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan
| | - Masato Taoka
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Toshiaki Isobe
- Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
| | - Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan .,Research Program for Signal Transduction, Division of Endocrinology, Metabolism and Signal Research, Gunma University Initiative for Advanced Research, Gunma University, Maebashi 371-8512, Japan
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10
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The tobacco-specific carcinogen-operated calcium channel promotes lung tumorigenesis via IGF2 exocytosis in lung epithelial cells. Nat Commun 2016; 7:12961. [PMID: 27666821 PMCID: PMC5052689 DOI: 10.1038/ncomms12961] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2016] [Accepted: 08/19/2016] [Indexed: 12/20/2022] Open
Abstract
Nicotinic acetylcholine receptors (nAChRs) binding to the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induces Ca2+ signalling, a mechanism that is implicated in various human cancers. In this study, we investigated the role of NNK-mediated Ca2+ signalling in lung cancer formation. We show significant overexpression of insulin-like growth factors (IGFs) in association with IGF-1R activation in human preneoplastic lung lesions in smokers. NNK induces voltage-dependent calcium channel (VDCC)-intervened calcium influx in airway epithelial cells, resulting in a rapid IGF2 secretion via the regulated pathway and thus IGF-1R activation. Silencing nAChR, α1 subunit of L-type VDCC, or various vesicular trafficking curators, including synaptotagmins and Rabs, or blockade of nAChR/VDCC-mediated Ca2+ influx significantly suppresses NNK-induced IGF2 exocytosis, transformation and tumorigenesis of lung epithelial cells. Publicly available database reveals inverse correlation between use of calcium channel blockers and lung cancer diagnosis. Our data indicate that NNK disrupts the regulated pathway of IGF2 exocytosis and promotes lung tumorigenesis. The binding of tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) to nicotinic acetylcholine receptors (nAChRs) induces calcium signalling. Here the authors show that NKK-induced calcium influx in airway epithelial cells triggers IGF2 secretion and tumourigenesis.
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Kang SM, Nam KY, Jung SY, Song KH, Kho S, No KT, Choi HK, Song JY. Inhibition of cancer cell invasion by new ((3,4-dihydroxy benzylidene)hydrazinyl)pyridine-3-sulfonamide analogs. Bioorg Med Chem Lett 2015; 26:1322-8. [PMID: 26810259 DOI: 10.1016/j.bmcl.2015.12.093] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 11/23/2015] [Accepted: 12/28/2015] [Indexed: 01/24/2023]
Abstract
Rab GTPases regulate various types of intracellular membrane trafficking in all eukaryotes. Since Rab27a and its multiple effectors are involved in exocytosis of lysosome-related organelles and play a major role in malignancy, compounds targeting Rab27a could be likely used to inhibit invasive growth and tumor metastasis. Thus, we designed and synthesized several compounds based on the previously reported Rab27a-targeting synthetic compounds identified by virtual screening, and investigated their anti-metastatic effects in MDA-MB231 and A375 cells. Among the synthesized compounds, (E)-N-(3-chlorophenyl)-6-(2-(3,4-dihydroxy benzylidene)hydrazinyl)pyridine-3-sulfonamide (3d) and (E)-N-benzyl-6-(2-(3,4-dihydroxy benzylidene)hydrazinyl)-N-methylpyridine-3-sulfonamide (3f) significantly inhibited the invasiveness of both tumor cell lines. Compounds 3d and 3f also decreased the levels of signature extracellular matrix marker proteins (fibronectin, collagen, and α-smooth muscle actin) and representative mesenchymal cell markers (N-cadherin and vimentin). Taken together, our results suggest that novel sulfonamide analogs have anti-metastatic activity in breast and melanoma cancer cell lines and may be used as therapeutic agents to treat malignant cancer.
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Affiliation(s)
- Seong-Mook Kang
- Division of Radiation Cancer Research, Korea Institute of Radiological & Medical Sciences, Seoul 139-706, Republic of Korea
| | - Ky-Youb Nam
- Center for Development and Commercialization Anti-Cancer Therapeutics, Asan Medical Center, Seoul 138-736, Republic of Korea
| | - Seung-Youn Jung
- Division of Radiation Cancer Research, Korea Institute of Radiological & Medical Sciences, Seoul 139-706, Republic of Korea
| | - Kyung-Hee Song
- Division of Radiation Cancer Research, Korea Institute of Radiological & Medical Sciences, Seoul 139-706, Republic of Korea
| | - Seongho Kho
- Division of Radiation Cancer Research, Korea Institute of Radiological & Medical Sciences, Seoul 139-706, Republic of Korea
| | - Kyoung Tai No
- Department of Biotechnology, Yonsei University, Seoul 120-749, Republic of Korea
| | - Hyun Kyung Choi
- Department of Medicinal Chemistry, Jungwon University, Goesan 367-805, Republic of Korea.
| | - Jie-Young Song
- Division of Radiation Cancer Research, Korea Institute of Radiological & Medical Sciences, Seoul 139-706, Republic of Korea.
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Abstract
Noncoding RNA and especially microRNAs (miRs) have emerged as important regulators of key processes in cell biology, including development, differentiation, and survival. Currently, over 2,500 mature miRs have been reported in humans, and considering that each miR has multiple targets, the number of genes and pathways potentially affected is huge. Not surprisingly, many miRs have also been implicated in diabetes, and more recently, some have been discovered to play important roles in the pancreatic islet, including β-cell function, proliferation, and survival. The goal of this Perspective is to offer an overview of this rapidly evolving field and the miRs involved, reveal novel networks of β-cell miR signaling, and provide an outlook of the opportunities and challenges ahead.
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Affiliation(s)
- Stephen R Filios
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, The University of Alabama at Birmingham, Birmingham, AL
| | - Anath Shalev
- Comprehensive Diabetes Center and Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, The University of Alabama at Birmingham, Birmingham, AL
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13
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Koumanov F, Pereira VJ, Richardson JD, Sargent SL, Fazakerley DJ, Holman GD. Insulin regulates Rab3-Noc2 complex dissociation to promote GLUT4 translocation in rat adipocytes. Diabetologia 2015; 58:1877-86. [PMID: 26024738 PMCID: PMC4499112 DOI: 10.1007/s00125-015-3627-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 04/21/2015] [Indexed: 01/10/2023]
Abstract
AIMS/HYPOTHESIS The glucose transporter GLUT4 is present mainly in insulin-responsive tissues of fat, heart and skeletal muscle and is translocated from intracellular membrane compartments to the plasma membrane (PM) upon insulin stimulation. The transit of GLUT4 to the PM is known to be dependent on a series of Rab proteins. However, the extent to which the activity of these Rabs is regulated by the action of insulin action is still unknown. We sought to identify insulin-activated Rab proteins and Rab effectors that facilitate GLUT4 translocation. METHODS We developed a new photoaffinity reagent (Bio-ATB-GTP) that allows GTP-binding proteomes to be explored. Using this approach we screened for insulin-responsive GTP loading of Rabs in primary rat adipocytes. RESULTS We identified Rab3B as a new candidate insulin-stimulated G-protein in adipocytes. Using constitutively active and dominant negative mutants and Rab3 knockdown we provide evidence that Rab3 isoforms are key regulators of GLUT4 translocation in adipocytes. Insulin-stimulated Rab3 GTP binding is associated with disruption of the interaction between Rab3 and its negative effector Noc2. Disruption of the Rab3-Noc2 complex leads to displacement of Noc2 from the PM. This relieves the inhibitory effect of Noc2, facilitating GLUT4 translocation. CONCLUSIONS/INTERPRETATION The discovery of the involvement of Rab3 and Noc2 in an insulin-regulated step in GLUT4 translocation suggests that the control of this translocation process is unexpectedly similar to regulated secretion and particularly pancreatic insulin-vesicle release.
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Affiliation(s)
- Francoise Koumanov
- />Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY UK
| | - Vinit J. Pereira
- />Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY UK
| | | | - Samantha L. Sargent
- />Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY UK
| | - Daniel J. Fazakerley
- />Charles Perkins Centre, School of Molecular Bioscience, The University of Sydney, Sydney, NSW Australia
| | - Geoffrey D. Holman
- />Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY UK
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Chakraborty C, Doss CGP, Bandyopadhyay S, Agoramoorthy G. Influence of miRNA in insulin signaling pathway and insulin resistance: micro-molecules with a major role in type-2 diabetes. WILEY INTERDISCIPLINARY REVIEWS-RNA 2014; 5:697-712. [PMID: 24944010 DOI: 10.1002/wrna.1240] [Citation(s) in RCA: 177] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 04/12/2014] [Accepted: 04/17/2014] [Indexed: 12/25/2022]
Abstract
The prevalence of type-2 diabetes (T2D) is increasing significantly throughout the globe since the last decade. This heterogeneous and multifactorial disease, also known as insulin resistance, is caused by the disruption of the insulin signaling pathway. In this review, we discuss the existence of various miRNAs involved in regulating the main protein cascades in the insulin signaling pathway that affect insulin resistance. The influence of miRNAs (miR-7, miR-124a, miR-9, miR-96, miR-15a/b, miR-34a, miR-195, miR-376, miR-103, miR-107, and miR-146) in insulin secretion and beta (β) cell development has been well discussed. Here, we highlight the role of miRNAs in different significant protein cascades within the insulin signaling pathway such as miR-320, miR-383, miR-181b with IGF-1, and its receptor (IGF1R); miR-128a, miR-96, miR-126 with insulin receptor substrate (IRS) proteins; miR-29, miR-384-5p, miR-1 with phosphatidylinositol 3-kinase (PI3K); miR-143, miR-145, miR-29, miR-383, miR-33a/b miR-21 with AKT/protein kinase B (PKB) and miR-133a/b, miR-223, miR-143 with glucose transporter 4 (GLUT4). Insulin resistance, obesity, and hyperlipidemia (high lipid levels in the blood) have a strong connection with T2D and several miRNAs influence these clinical outcomes such as miR-143, miR-103, and miR-107, miR-29a, and miR-27b. We also corroborate from previous evidence how these interactions are related to insulin resistance and T2D. The insights highlighted in this review will provide a better understanding on the impact of miRNA in the insulin signaling pathway and insulin resistance-associated diagnostics and therapeutics for T2D.
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Affiliation(s)
- Chiranjib Chakraborty
- Department of Bio-informatics, School of Computer and Information Sciences, Galgotias University, Greater Noida, India
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15
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Fukuda M. Rab27 effectors, pleiotropic regulators in secretory pathways. Traffic 2013; 14:949-63. [PMID: 23678941 DOI: 10.1111/tra.12083] [Citation(s) in RCA: 153] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 05/13/2013] [Accepted: 05/16/2013] [Indexed: 12/18/2022]
Abstract
Rab27, a member of the small GTPase Rab family, is widely conserved in metazoan, and two Rab27 isoforms, Rab27A and Rab27B, are present in vertebrates. Rab27A was the first Rab protein whose dysfunction was found to cause a human hereditary disease, type 2 Griscelli syndrome, which is characterized by silvery hair and immunodeficiency. The discovery in the 21st century of three distinct types of mammalian Rab27A effectors [synaptotagmin-like protein (Slp), Slp homologue lacking C2 domains (Slac2), and Munc13-4] that specifically bind active Rab27A has greatly accelerated our understanding not only of the molecular mechanisms of Rab27A-mediated membrane traffic (e.g. melanosome transport and regulated secretion) but of the symptoms of Griscelli syndrome patients at the molecular level. Because Rab27B is widely expressed in various tissues together with Rab27A and has been found to have the ability to bind all of the Rab27A effectors that have been tested, Rab27A and Rab27B were initially thought to function redundantly by sharing common Rab27 effectors. However, recent evidence has indicated that by interacting with different Rab27 effectors Rab27A and Rab27B play different roles in special types of secretion (e.g. exosome secretion and mast cell secretion) even within the same cell type. In this review article, I describe the current state of our understanding of the functions of Rab27 effectors in secretory pathways.
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Affiliation(s)
- 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.
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16
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Implications of microRNAs in the pathogenesis of diabetes. Arch Pharm Res 2013; 36:154-66. [DOI: 10.1007/s12272-013-0017-6] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2012] [Accepted: 12/24/2012] [Indexed: 01/30/2023]
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17
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Li J, Song J, Cassidy MG, Rychahou P, Starr ME, Liu J, Li X, Epperly G, Weiss HL, Townsend CM, Gao T, Evers BM. PI3K p110α/Akt signaling negatively regulates secretion of the intestinal peptide neurotensin through interference of granule transport. Mol Endocrinol 2012; 26:1380-93. [PMID: 22700584 DOI: 10.1210/me.2012-1024] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Neurotensin (NT), an intestinal peptide secreted from N cells in the small bowel, regulates a variety of physiological functions of the gastrointestinal tract, including secretion, gut motility, and intestinal growth. The class IA phosphatidylinositol 3-kinase (PI3K) family, which comprised of p110 catalytic (α, β and δ) and p85 regulatory subunits, has been implicated in the regulation of hormone secretion from endocrine cells. However, the underlying mechanisms remain poorly understood. In particular, the role of PI3K in intestinal peptide secretion is not known. Here, we show that PI3K catalytic subunit, p110α, negatively regulates NT secretion in vitro and in vivo. We demonstrate that inhibition of p110α, but not p110β, induces NT release in BON, a human endocrine cell line, which expresses NT mRNA and produces NT peptide in a manner analogous to N cells, and QGP-1, a pancreatic endocrine cell line that produces NT peptide. In contrast, overexpression of p110α decreases NT secretion. Consistently, p110α-inhibition increases plasma NT levels in mice. To further delineate the mechanisms contributing to this effect, we demonstrate that inhibition of p110α increases NT granule trafficking by up-regulating α-tubulin acetylation; NT secretion is prevented by overexpression of HDAC6, an α-tubulin deacetylase. Moreover, ras-related protein Rab27A (a small G protein) and kinase D-interacting substrate of 220 kDa (Kidins220), which are associated with NT granules, play a negative and positive role, respectively, in p110α-inhibition-induced NT secretion. Our findings identify the critical role and novel mechanisms for the PI3K signaling pathway in the control of intestinal hormone granule transport and release.
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Affiliation(s)
- Jing Li
- Department of Surgery, University of Kentucky, Lexington, Kentucky, USA
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18
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Abstract
Recent findings demonstrated the importance of microRNAs (miRNAs) in the vasculature and the orchestration of lipid metabolism and glucose homeostasis. MiRNA networks represent an additional layer of regulation for gene expression that absorbs perturbations and ensures the robustness of biological systems. This function is very elegantly demonstrated in cholesterol metabolism where miRNAs reducing cellular cholesterol export are embedded in the very same genes that increase cholesterol synthesis. Often their alteration does not affect normal development but changes under stress conditions and in disease. A detailed understanding of the molecular and cellular mechanisms of miRNA-mediated effects on metabolism and vascular pathophysiology could pave the way for the development of novel diagnostic markers and therapeutic approaches. In the first part of this review, we summarize the role of miRNAs in vascular and metabolic diseases and explore potential confounding effects by platelet miRNAs in preclinical models of cardiovascular disease. In the second part, we discuss experimental strategies for miRNA target identification and the challenges in attributing miRNA effects to specific cell types and single targets.
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Affiliation(s)
- Anna Zampetaki
- King's British Heart Foundation Centre, King’s College London, United Kingdom
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19
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Chen JS, Kuo YB, Chou YP, Chan CC, Fan CW, Chen KT, Huang YS, Chan EC. Detection of autoantibodies against Rabphilin-3A-like protein as a potential biomarker in patient's sera of colorectal cancer. Clin Chim Acta 2011; 412:1417-22. [PMID: 21536019 DOI: 10.1016/j.cca.2011.04.020] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 04/12/2011] [Accepted: 04/12/2011] [Indexed: 02/09/2023]
Abstract
BACKGROUND Rabphilin-3A-like (RPH3AL) protein functions in the regulation of hormone exocytosis, and mutations in the RPHA3L gene have been associated with tumorigenesis in colorectal cancer (CRC). We evaluated the potential use of anti-RPH3AL autoantibodies as a marker for CRC detection. METHODS Sera from 84 patients with CRC and 63 healthy controls were analysed for the presence of RPH3AL autoantibodies with a Western blotting assay. RESULTS The frequencies of RPH3AL autoantibodies in the early stage, advanced stage and all CRC patients were 64.7%, 78.0% and 72.6%, respectively. These values are significantly higher than the frequency of RPH3AL autoantibodies in healthy controls (15.9%, P<0.001). Although the presence of RPH3AL autoantibodies did not correlate with clinical parameters, RPH3AL autoantibodies were found in 69.4% (34/49) of CRC patients who were negative for carcinoembryonic antigen. The value of the area under the receiver operating characteristic curve of RPH3AL autoantibody was 0.84, which suggests that screening for these autoantibodies could potentially be used for CRC diagnosis. CONCLUSION Circulating RPH3AL autoantibodies are prevalent in patients with CRC, and detection of these autoantibodies might provide a novel non-invasive approach for CRC diagnosis.
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Affiliation(s)
- Jinn-Shiun Chen
- Department of Colorectal Surgery, Chang Gung Memorial Hospital, Tao Yuan, Taiwan
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20
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Abstract
Intracellular membrane traffic defines a complex network of pathways that connects many of the membrane-bound organelles of eukaryotic cells. Although each pathway is governed by its own set of factors, they all contain Rab GTPases that serve as master regulators. In this review, we discuss how Rabs can regulate virtually all steps of membrane traffic from the formation of the transport vesicle at the donor membrane to its fusion at the target membrane. Some of the many regulatory functions performed by Rabs include interacting with diverse effector proteins that select cargo, promoting vesicle movement, and verifying the correct site of fusion. We describe cascade mechanisms that may define directionality in traffic and ensure that different Rabs do not overlap in the pathways that they regulate. Throughout this review we highlight how Rab dysfunction leads to a variety of disease states ranging from infectious diseases to cancer.
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Affiliation(s)
- Alex H Hutagalung
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, California 92093, USA
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21
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Gu C, Stein GH, Pan N, Goebbels S, Hörnberg H, Nave KA, Herrera P, White P, Kaestner KH, Sussel L, Lee JE. Pancreatic beta cells require NeuroD to achieve and maintain functional maturity. Cell Metab 2010; 11:298-310. [PMID: 20374962 PMCID: PMC2855640 DOI: 10.1016/j.cmet.2010.03.006] [Citation(s) in RCA: 200] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 12/06/2009] [Accepted: 03/16/2010] [Indexed: 12/19/2022]
Abstract
NeuroD, a transactivator of the insulin gene, is critical for development of the endocrine pancreas, and NeuroD mutations cause MODY6 in humans. To investigate the role of NeuroD in differentiated beta cells, we generated mice in which neuroD is deleted in insulin-expressing cells. These mice exhibit severe glucose intolerance. Islets lacking NeuroD respond poorly to glucose and display a glucose metabolic profile similar to immature beta cells, featuring increased expression of glycolytic genes and LDHA, elevated basal insulin secretion and O2 consumption, and overexpression of NPY. Moreover, the mutant islets appear to have defective K(ATP) channel-mediated insulin secretion. Unexpectedly, virtually all insulin in the mutant mice is derived from ins2, whereas ins1 expression is almost extinguished. Overall, these results indicate that NeuroD is required for beta cell maturation and demonstrate the importance of NeuroD in the acquisition and maintenance of fully functional glucose-responsive beta cells.
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Affiliation(s)
- Chunyan Gu
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado at Boulder, Boulder, CO 80309-0347, USA
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22
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Kimura T, Taniguchi S, Toya K, Niki I. Glucose-induced translocation of coronin 3 regulates the retrograde transport of the secretory membrane in the pancreatic beta-cells. Biochem Biophys Res Commun 2010; 395:318-23. [PMID: 20362548 DOI: 10.1016/j.bbrc.2010.03.173] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2010] [Accepted: 03/30/2010] [Indexed: 12/16/2022]
Abstract
GTP-Rab27a is known to regulate insulin exocytosis. We have recently reported that coronin 3, which paradoxically binds GDP-Rab27a, participates in endocytosis of the insulin secretory membrane. Here, we demonstrate that glucose stimulation caused redistribution of coronin 3 in the vicinity of the plasma membrane, which was mimicked by overexpression of the GDP-Rab27a mutant or the Rab27a GAP. Glucose-induced translocation of coronin 3 was inhibited by Rab27a knock-down. The internalized phogrin, an insulin granule associated protein, located near the plasma membrane by the dominant-negative coronin 3, but the protein at the outer surface of the plasma membrane was decreased. These results indicate that glucose recruits coronin 3 near the plasma membrane, and that it regulates the retrograde transport of the secretory membrane in pancreatic beta-cells.
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Affiliation(s)
- Toshihide Kimura
- Department of Pharmacology, Oita University Faculty of Medicine, 1-1 Idaigaoka, Hasama, Yufu, Oita 879-5593, Japan
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23
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Abstract
Glucose-stimulated insulin secretion from the islet beta-cell involves a sequence of metabolic events and an interplay between a wide range of signaling pathways leading to the generation of second messengers (e.g., cyclic nucleotides, adenine and guanine nucleotides, soluble lipid messengers) and mobilization of calcium ions. Consequent to the generation of necessary signals, the insulin-laden secretory granules are transported from distal sites to the plasma membrane for fusion and release of their cargo into the circulation. The secretory granule transport underlies precise changes in cytoskeletal architecture involving a well-coordinated cross-talk between various signaling proteins, including small molecular mass GTP-binding proteins (G proteins) and their respective effector proteins. The purpose of this article is to provide an overview of current understanding of the identity of small G proteins (e.g., Cdc42, Rac1, and ARF-6) and their corresponding regulatory factors (e.g., GDP/GTP-exchange factors, GDP-dissociation inhibitors) in the pancreatic beta-cell. Plausible mechanisms underlying regulation of these signaling proteins by insulin secretagogues are also discussed. In addition to their positive modulatory roles, certain small G proteins also contribute to the metabolic dysfunction and demise of the islet beta-cell seen in in vitro and in vivo models of impaired insulin secretion and diabetes. Emerging evidence also suggests significant insulin secretory abnormalities in small G protein knockout animals, further emphasizing vital roles for these proteins in normal health and function of the islet beta-cell. Potential significance of these experimental observations from multiple laboratories and possible avenues for future research in this area of islet research are highlighted.
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Affiliation(s)
- Anjaneyulu Kowluru
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, 259 Mack Avenue, Detroit, MI 48202-3489, USA.
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24
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Kasai H, Hatakeyama H, Ohno M, Takahashi N. Exocytosis in islet beta-cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 654:305-38. [PMID: 20217504 DOI: 10.1007/978-90-481-3271-3_14] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The development of technologies that allow for live optical imaging of exocytosis from beta-cells has greatly improved our understanding of insulin secretion. Two-photon imaging, in particular, has enabled researchers to visualize the exocytosis of large dense-core vesicles (LDCVs) containing insulin from beta-cells in intact islets of Langerhans. These studies have revealed that high glucose levels induce two phases of insulin secretion and that this release is dependent upon cytosolic Ca(2+) and cAMP. This technology has also made it possible to examine the spatial profile of insulin exocytosis in these tissues and compare that profile with those of other secretory glands. Such studies have led to the discovery of the massive exocytosis of synaptic-like microvesicles (SLMVs) in beta-cells. These imaging studies have also helped clarify facets of insulin exocytosis that cannot be properly addressed using the currently available electrophysiological techniques. This chapter provides a concise introduction to the field of optical imaging for those researchers who wish to characterize exocytosis from beta-cells in the islets of Langerhans.
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Affiliation(s)
- Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, The University of Tokyo, Hongo, Tokyo 113-0033, Japan.
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25
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Williams D, Vicôgne J, Zaitseva I, McLaughlin S, Pessin JE. Evidence that electrostatic interactions between vesicle-associated membrane protein 2 and acidic phospholipids may modulate the fusion of transport vesicles with the plasma membrane. Mol Biol Cell 2009; 20:4910-9. [PMID: 19812247 DOI: 10.1091/mbc.e09-04-0284] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The juxtamembrane domain of vesicle-associated membrane protein (VAMP) 2 (also known as synaptobrevin2) contains a conserved cluster of basic/hydrophobic residues that may play an important role in membrane fusion. Our measurements on peptides corresponding to this domain determine the electrostatic and hydrophobic energies by which this domain of VAMP2 could bind to the adjacent lipid bilayer in an insulin granule or other transport vesicle. Mutation of residues within the juxtamembrane domain that reduce the VAMP2 net positive charge, and thus its interaction with membranes, inhibits secretion of insulin granules in beta cells. Increasing salt concentration in permeabilized cells, which reduces electrostatic interactions, also results in an inhibition of insulin secretion. Similarly, amphipathic weak bases (e.g., sphingosine) that reverse the negative electrostatic surface potential of a bilayer reverse membrane binding of the positively charged juxtamembrane domain of a reconstituted VAMP2 protein and inhibit membrane fusion. We propose a model in which the positively charged VAMP and syntaxin juxtamembrane regions facilitate fusion by bridging the negatively charged vesicle and plasma membrane leaflets.
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Affiliation(s)
- Dumaine Williams
- Department of Medicine and Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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26
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Brunner Y, Schvartz D, Couté Y, Sanchez JC. Proteomics of regulated secretory organelles. MASS SPECTROMETRY REVIEWS 2009; 28:844-867. [PMID: 19301366 DOI: 10.1002/mas.20211] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Regulated secretory organelles are important subcellular structures of living cells that allow the release in the extracellular space of crucial compounds, such as hormones and neurotransmitters. Therefore, the regulation of biogenesis, trafficking, and exocytosis of regulated secretory organelles has been intensively studied during the last 30 years. However, due to the large number of different regulated secretory organelles, only a few of them have been specifically characterized. New insights into regulated secretory organelles open crucial perspectives for a better comprehension of the mechanisms that govern cell secretion. The combination of subcellular fractionation, protein separation, and mass spectrometry is also possible to study regulated secretory organelles at the proteome level. In this review, we present different strategies used to isolate regulated secretory organelles, separate their protein content, and identify the proteins by mass spectrometry. The biological significance of regulated secretory organelles-proteomic analysis is discussed as well.
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Affiliation(s)
- Yannick Brunner
- Biomedical Proteomics Research Group, University Medical Center, Geneva, Switzerland
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27
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Shanmugam C, Katkoori VR, Jhala NC, Grizzle WE, Manne U. Immunohistochemical expression of rabphilin-3A-like (Noc2) in normal and tumor tissues of human endocrine pancreas. Biotech Histochem 2009; 84:39-45. [PMID: 19212825 DOI: 10.1080/10520290902738878] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
Involvement of rabphilin-3A-like (RPH3AL), or Noc2, the potential effector of Ras-associated binding proteins Rab3A and Rab27A in the regulation of exocytotic processes in the endocrine pancreas has been demonstrated in experimental models. Noc2 expression together with other regulatory molecules of the exocytotic machinery in human tissues, however, has not been studied. We evaluated immunohistochemical expression of the key molecules of the exocytotic machinery, Noc2, Rab3A, Rab27A, and RIM2, together with the characteristic islet cell hormones, insulin and glucagon in normal and endocrine tumor tissues of human pancreas. Normal pancreatic islets were stained for all of these proteins and showed strong cytoplasmic localization. A similar pattern of strong cytoplasmic expression of these proteins was observed in the majority of endocrine tumors. By contrast, the exocrine portions of normal appearing pancreas completely lacked Rab27A staining and showed decreased expression of the proteins, Noc2, Rab3A, and RIM2. The staining pattern of Noc2 and Rab27A was similar to the staining pattern of glucagon-producing cells within the islets. The concomitant expression of Noc2 with these molecules suggests that Noc2 may serve as an effector for Rab3A and Rab27A and that it is involved in the regulation of exocytosis of the endocrine pancreas in humans.
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Affiliation(s)
- C Shanmugam
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294-7331, USA
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Brunner Y, Schvartz D, Priego-Capote F, Couté Y, Sanchez JC. Glucotoxicity and pancreatic proteomics. J Proteomics 2009; 71:576-91. [DOI: 10.1016/j.jprot.2008.10.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2008] [Revised: 09/29/2008] [Accepted: 10/18/2008] [Indexed: 02/02/2023]
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A newly identified isoform of Slp2a associates with Rab27a in cytotoxic T cells and participates to cytotoxic granule secretion. Blood 2008; 112:5052-62. [DOI: 10.1182/blood-2008-02-141069] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Abstract
Cytotoxic T lymphocytes (CTLs) and natural killer cells help control infections and tumors via a killing activity that is mediated by the release of cytotoxic granules. Granule secretion at the synapse formed between the CTL and the target cell leads to apoptosis of the latter. This process involves polarization of the CTL's secretory machinery and cytotoxic granules. The small GTPase Rab27a and the hMunc13-4 protein have been shown to be required for both granule maturation and granule docking and priming at the immunologic synapse. Using a tandem affinity purification technique, we identified a previously unknown hematopoietic form of Slp2a (Slp2a-hem) and determined that it is a specific effector of the active form of Rab27a. This interaction occurs in vivo in primary CTLs. We have shown that (1) Rab27a recruits Slp2a-hem on vesicular structures in peripheral CTLs and (2) following CTL-target cell conjugate formation, the Slp2a-hem/Rab27a complex colocalizes with perforin-containing granules at the immunologic synapse, where it binds to the plasma membrane through its C2 domains. The overexpression of a dominant-negative form of Slp2a-hem markedly impaired exocytosis of cytotoxic granules—indicating that Slp2a is required for cytotoxic granule docking at the immunologic synapse.
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Abstract
Plasma insulin levels are determined mainly by the rate of exocytosis of the insulin-containing large dense core vesicles (LDCVs) of pancreatic islet beta-cells. This process involves the recruitment of LDCVs to the plasma membrane, where they are docked by the assembly of multiprotein SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) complexes. However, fusion of the two membranes will proceed only in the presence of Ca(2+) ions, implicating a Ca(2+) sensor protein. The synaptotagmin gene family, comprising 15 members, was proposed to act as such Ca(2+) sensor in regulated exocytosis in neurons and neuroendocrine and endocrine cells. Herein, we review the physiological function of the various synaptotagmins with reference to their impact on insulin exocytosis. Cumulating evidence emphasizes the crucial role of synaptotagmin VII and IX as mediators of glucose-induced insulin secretion.
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Affiliation(s)
- Benoit R Gauthier
- Dept. of Cell Physiology and Metabolism, University Medical Center, 1211 Geneva 4, Switzerland.
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31
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Kimura T, Kaneko Y, Yamada S, Ishihara H, Senda T, Iwamatsu A, Niki I. The GDP-dependent Rab27a effector coronin 3 controls endocytosis of secretory membrane in insulin-secreting cell lines. J Cell Sci 2008; 121:3092-8. [PMID: 18768935 DOI: 10.1242/jcs.030544] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Rab27a is involved in the control of membrane traffic, a crucial step in the regulated secretion. Typically, the guanosine triphosphate (GTP)-bound form has been considered to be active and, therefore, searching for proteins binding to the GTP-form has been attempted to look for their effectors. Here, we have identified the actin-bundling protein coronin 3 as a novel Rab27a effector that paradoxically bound guanosine diphosphate (GDP)-Rab27a in the pancreatic beta-cell line MIN6. Coronin 3 directly bound GDP-Rab27a through its beta-propeller structure. The most important insulin secretagogue glucose promptly shifted Rab27a from the GTP- to GDP-bound form. Knockdown of coronin 3 by RNAi resulted in the inhibition of phogrin (an insulin-granule-associated protein) internalization and the uptake of FM4-64 (a marker of endocytosis). Similar results were reproduced by disruption of the coronin-3-GDP-Rab27a interaction with the dominant-negative coronin 3, and coexpression of the GDP-Rab27a mutant rescued these changes. Taken together, our results indicate that interaction of GDP-Rab27a and coronin 3 is important in stimulus-endocytosis coupling, and that GTP- and GDP-Rab27a regulates insulin membrane recycling at the distinct stages.
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Affiliation(s)
- Toshihide Kimura
- Department of Pharmacology, Oita University Faculty of Medicine, Hasama, Yufu, Oita 879-5593, Japan
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Merrins MJ, Stuenkel EL. Kinetics of Rab27a-dependent actions on vesicle docking and priming in pancreatic beta-cells. J Physiol 2008; 586:5367-81. [PMID: 18801842 PMCID: PMC2655366 DOI: 10.1113/jphysiol.2008.158477] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Accepted: 09/18/2008] [Indexed: 12/26/2022] Open
Abstract
The small GTPase Rab27a, along with the isoforms of Rab3, is present on insulin secretory granules and has been implicated in regulation of Ca(2+)-triggered exocytosis. We have used membrane capacitance measurements to define the role of Rab27a in regulating the size and refilling of distinct pools of insulin granules by comparison of evoked secretory responses from Rab27a-null ashen and strain-matched wild-type control pancreatic beta-cells. We find that ashen beta-cells display a kinetic defect in refilling of readily releasable and immediately releasable vesicle pools (RRP and IRP, respectively) in response to depolarization-evoked Ca(2+) influx. The deficit in IRP refilling was not observed in the presence of stimulatory glucose concentrations (16.7 mm), though incomplete refilling of the RRP persisted. Comparatively, beta-cells from Rab3a(-/-) mice exhibited complete refilling of the IRP and RRP, demonstrating that Rab27a and Rab3a exert distinct roles in the insulin granule secretory pathway. Further, depletion of the RRP in ashen beta-cells was twofold faster than that of control beta-cells. These deficits in refilling and exocytotic rate in ashen beta-cells were absent when cAMP-regulatory pathways were activated. Elevated cAMP increased the RRP pool size, and complete refilling of the RRP occurred in ashen beta-cells; responses were comparable to wild-type controls. These effects of cAMP were largely eliminated by Rp-cAMP inhibition of PKA, indicating that PKA acts on vesicle priming downstream or via pathways independent of Rab27a. In summary, Rab27a exerts dual roles in glucose-mediated insulin granule exocytosis, facilitating refilling of releasable granule pools while also limiting the rate of release from these pools.
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Affiliation(s)
- Matthew J Merrins
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109-0622, USA
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Handley MTW, Burgoyne RD. The Rab27 effector Rabphilin, unlike Granuphilin and Noc2, rapidly exchanges between secretory granules and cytosol in PC12 cells. Biochem Biophys Res Commun 2008; 373:275-81. [PMID: 18573236 DOI: 10.1016/j.bbrc.2008.06.043] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 06/05/2008] [Indexed: 11/29/2022]
Abstract
Rab proteins are GTPases that transit between GTP- and GDP-bound states. In the GTP-bound form they can recruit specific effector to membrane domains. It is possible that the exchange of Rab effectors between membranes and cytosol would be determined by the exchange of the particular Rab partner. We have compared the cycling of three Rab3/27 effectors, Granuphilin, Noc2, and Rabphilin, in PC12 cells using fluorescence recovery after photobleaching of EGFP-tagged proteins. All three effectors become localised to secretory granules. Granuphilin and Noc2 showed little or no exchange between secretory granules and cytosol whereas Rabphilin showed rapid and complete exchange. Both Noc2 and Rabphilin were found to be recruited to granules by Rab27 but the data suggest that Rabphilin did not form stable complexes with Rab27 on secretory granules and so Rab effector cycling between membranes and cytosol can be independent of that of the Rab protein.
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Affiliation(s)
- Mark T W Handley
- The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L693BX, UK
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Review: Molecular mechanism of docking of dense-core vesicles to the plasma membrane in neuroendocrine cells. Med Mol Morphol 2008; 41:68-75. [DOI: 10.1007/s00795-008-0400-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2008] [Accepted: 03/04/2008] [Indexed: 02/06/2023]
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Yuan QX, Teng LP, Zhou JY, Liu CP, Guo J, Liu LJ, De W, Liu C. Characterization of Munc13-1 and insulin secretion during pancreatic development in rats. J Endocrinol Invest 2008; 31:630-5. [PMID: 18787382 DOI: 10.1007/bf03345615] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Munc13-1 may be a key factor in regulating insulin exocytosis, but its exact expression and role have not been clarified yet, especially during pancreatic development. We attempted to investigate the expression and function of Munc13-1 during embryonic pancreatic development in rats and determine the effects on insulin secretion. In the present study, pancreata of rats at embryonic day 12.5 (E12.5), E15.5, E18.5, new-born, 21 after birth (P21), and adult stage were dissected under microscope. The rat model of intrauterine growth retardation (IUGR) was made by 50% calorie restriction in pregnant rats from gestational day 15 until term. The expression of Munc13-1 and insulin secretion was studied by the techniques of RTPCR, real-time PCR, Western blot, and enzyme-linked immunosorbent assay. Immunohistochemistry and immunofluorescence were used to define the location of Munc13- 1. We found that Munc13-1 was located at islet along with insulin. Insulin- and Munc13-1-specific mRNA were not detected until E12.5 and E15.5, respectively, and increased with the development of the fetus. Western blot showed that Munc13-1 was low at E15.5 and E18.5 and increased later. The blood insulin level and Munc13-1 were reduced simultaneously in IUGR newborn rats compared with normal ones. These results suggest that Munc13-1 exists in pancreas islets during fetus development and its deficiency in the pancreas, as occurs in IUGR, was in accordance with decreased blood insulin level. Munc13-1 may play an essential role in insulin exocytosis.
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Affiliation(s)
- Q X Yuan
- Department of Endocrinology, First Affiliated Hospital, Nanjing Medical University, Nanjing, 210029, China
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36
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Saegusa C, Kanno E, Itohara S, Fukuda M. Expression of Rab27B-binding protein Slp1 in pancreatic acinar cells and its involvement in amylase secretion. Arch Biochem Biophys 2008; 475:87-92. [PMID: 18477466 DOI: 10.1016/j.abb.2008.04.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Accepted: 04/18/2008] [Indexed: 12/16/2022]
Abstract
Slp1 is a putative Rab27 effector protein and implicated in intracellular membrane transport; however, the precise tissue distribution and function of Slp1 protein remain largely unknown. In this study we investigated the tissue distribution of Slp1 in mice and found that Slp1 is abundantly expressed in the pancreas, especially in the apical region of pancreatic acinar cells. Slp1 interacted with Rab27B in vivo and both proteins were co-localized on zymogen granules. Morphological analysis of fasted Slp1 knockout mice showed an increased number of zymogen granules in the pancreatic acinar cells, indicating that Slp1 is part of the machinery of amylase secretion by the exocrine pancreas.
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Affiliation(s)
- Chika Saegusa
- Fukuda Initiative Research Unit, RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
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37
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Lovis P, Gattesco S, Regazzi R. Regulation of the expression of components of the exocytotic machinery of insulin-secreting cells by microRNAs. Biol Chem 2008; 389:305-12. [DOI: 10.1515/bc.2008.026] [Citation(s) in RCA: 214] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Abstract
Fine-tuning of insulin secretion from pancreatic β-cells participates in blood glucose homeostasis. Defects in this process can lead to chronic hyperglycemia and diabetes mellitus. Several proteins controlling insulin exocytosis have been identified, but the mechanisms regulating their expression remain poorly understood. Here, we show that two non-coding microRNAs, miR124a and miR96, modulate the expression of proteins involved in insulin exocytosis and affect secretion of the β-cell line MIN6B1. miR124a increases the levels of SNAP25, Rab3A and synapsin-1A and decreases those of Rab27A and Noc2. Inhibition of Rab27A expression is mediated by direct binding to the 3′-untranslated region of Rab27A mRNA. The effect on the other genes is indirect and linked to changes in mRNA levels. Over-expression of miR124a leads to exaggerated hormone release under basal conditions and a reduction in glucose-induced secretion. miR96 increases mRNA and protein levels of granuphilin, a negative modulator of insulin exocytosis, and decreases the expression of Noc2, resulting in lower capacity of MIN6B1 cells to respond to secretagogues. Our data identify miR124a and miR96 as novel regulators of the expression of proteins playing a critical role in insulin exocytosis and in the release of other hormones and neurotransmitters.
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Maris M, Overbergh L, Mathieu C. Type 2 diabetes: Gaining insight into the disease process using proteomics. Proteomics Clin Appl 2008; 2:312-26. [PMID: 21136836 DOI: 10.1002/prca.200780093] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Indexed: 12/30/2022]
Abstract
The incidence of diabetes mellitus is growing rapidly, with an increasing disease related morbidity and mortality. This is caused by macro- and microvascular complications, as a consequence of the often late diagnosis of type 2 diabetes (T2D), but especially by the difficulties to control glucose homeostasis due to the progressive nature of the disease. T2D is moreover a dual disease, with components of beta-cell failure and components of insulin resistance in peripheral organs, such as liver, fat, and muscle. Understanding the pathogenesis of the disease by gaining insight into the molecular pathways involved in both phenomena is one of the major assets of proteomic approaches. Moreover, proteomics and peptidomics may provide us with robust biomarkers for beta-cell failure, insulin resistance in pheripheral organs, but also for the development of diabetic complications. This review focuses on the knowledge gained by use of proteomic and peptidomic techniques in the study of the pathophysiology of T2D and in the attempts to discover new therapeutic targets.
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Affiliation(s)
- Michael Maris
- Laboratory for Experimental Medicine and Endocrinology (LEGENDO), Catholic University of Leuven, Leuven, Belgium
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Katkoori VR, Jia X, Chatla C, Kumar S, Ponnazhagan S, Callens T, Messiaen L, Grizzle WE, Manne U. Clinical significance of a novel single nucleotide polymorphism in the 5' untranslated region of the Rabphillin-3A-Like gene in colorectal adenocarcinoma. FRONT BIOSCI-LANDMRK 2008; 13:1050-61. [PMID: 17981610 DOI: 10.2741/2742] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The recently identified human ortholog of the Rabphillin-3A-Like (RPH3AL) gene, located at the 17p13.3 locus, has been assessed for its mutational status and clinical significance in colorectal adenocarcinoma (CRC). Prospectively collected 95 frozen CRCs and their matching benign colonic epithelial tissues were evaluated for mutations and mRNA expression. Since, we observed a higher incidence of a single nucleotide polymorphism (SNP) at the -25 position in the 5'untranslated region (5'UTR-25) of RPH3AL, we performed the genotyping analysis of this SNP in a retrospective CRC cohort (n=134) to assess their clinical importance. Univariate and multivariate outcome analyses were performed. The cDNA analysis has detected point mutations in 6 CRCs, coding region SNPs in 14 CRCs, and non-coding region SNPs in 38 CRCs. Combined analyses of both cohorts has demonstrated that the incidence of SNP at 5'UTR-25 was 41% (95 of 229), and its A/A genotype (9%, 20 of 229) was observed exclusively in non-Hispanic Caucasians, and 19 of these cases were diagnosed with nodal metastasis. Patients who exhibited homozygous for A or C alleles had a significantly decreased levels of mRNA expression, increased risk of CRC recurrence and mortality. Therefore, these findings have significant clinical implications in assessing the aggressiveness of CRC.
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Affiliation(s)
- Venkat R Katkoori
- Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294-7331, USA
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40
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Min L, Leung YM, Tomas A, Watson RT, Gaisano HY, Halban PA, Pessin JE, Hou JC. Dynamin is functionally coupled to insulin granule exocytosis. J Biol Chem 2007; 282:33530-33536. [PMID: 17848579 DOI: 10.1074/jbc.m703402200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The insulin granule integral membrane protein marker phogrin-green fluorescent protein was co-localized with insulin in Min6B1 beta-cell secretory granules but did not undergo plasma membrane translocation following glucose stimulation. Surprisingly, although expression of a dominant-interfering dynamin mutant (Dyn/K44A) inhibited transferrin receptor endocytosis, it had no effect on phogringreen fluorescent protein localization in the basal or secretagogue-stimulated state. By contrast, co-expression of Dyn/K44A with human growth hormone as an insulin secretory marker resulted in a marked inhibition of human growth hormone release by glucose, KCl, and a combination of multiple secretagogues. Moreover, serial pulse depolarization stimulated an increase in cell surface capacitance that was also blocked in cells expressing Dyn/K44A. Similarly, small interference RNA-mediated knockdown of dynamin resulted in marked inhibition of glucose-stimulated insulin secretion. Together, these data suggest the presence of a selective kiss and run mechanism of insulin release. Moreover, these data indicate a coupling between endocytosis and exocytosis in the regulation of beta-cell insulin secretion.
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Affiliation(s)
- Le Min
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794
| | - Yuk M Leung
- Departments of Medicine and Physiology, University of Toronto, Toronto M5S 1A8, Canada; Department of Physiology, China Medical University, Taichung 404, Taiwan
| | - Alejandra Tomas
- Department of Genetic Medicine and Development, Centre Médical Universitaire, 1 rue Michel-Servet, 1211 Geneva, Switzerland
| | - Robert T Watson
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794
| | - Herbert Y Gaisano
- Departments of Medicine and Physiology, University of Toronto, Toronto M5S 1A8, Canada
| | - Philippe A Halban
- Department of Genetic Medicine and Development, Centre Médical Universitaire, 1 rue Michel-Servet, 1211 Geneva, Switzerland
| | - Jeffrey E Pessin
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794
| | - June Chunqiu Hou
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, New York 11794.
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41
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Brunner Y, Couté Y, Iezzi M, Foti M, Fukuda M, Hochstrasser DF, Wollheim CB, Sanchez JC. Proteomics analysis of insulin secretory granules. Mol Cell Proteomics 2007; 6:1007-17. [PMID: 17317658 DOI: 10.1074/mcp.m600443-mcp200] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin secretory granules (ISGs) are cytoplasmic organelles of pancreatic beta-cells. They are responsible for the storage and secretion of insulin. To date, only about 30 different proteins have been clearly described to be associated with these organelles. However, data from two-dimensional gel electrophoresis analyses suggested that almost 150 different polypeptides might be present within ISGs. The elucidation of the identity and function of the ISG proteins by proteomics strategies would be of considerable help to further understand some of the underlying mechanisms implicated in ISG biogenesis and trafficking. Furthermore it should give the bases to the comprehension of impaired insulin secretion observed during diabetes. A proteomics analysis of an enriched insulin granule fraction from the rat insulin-secreting cell line INS-1E was performed. The efficacy of the fractionation procedure was assessed by Western blot and electron microscopy. Proteins of the ISG fraction were separated by SDS-PAGE, excised from consecutive gel slices, and tryptically digested. Peptides were analyzed by nano-LC-ESI-MS/MS. This strategy identified 130 different proteins that were classified into four structural groups including intravesicular proteins, membrane proteins, novel proteins, and other proteins. Confocal microscopy analysis demonstrated the association of Rab37 and VAMP8 with ISGs in INS-1E cells. In conclusion, the present study identified 130 proteins from which 110 are new proteins associated with ISGs. The elucidation of their role will further help in the understanding of the mechanisms governing impaired insulin secretion during diabetes.
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Affiliation(s)
- Yannick Brunner
- Biomedical Proteomics Research Group, University Medical Center, 1211 Geneva 4, Switzerland
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42
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Straub SG, Sharp GWG. Inhibition of insulin secretion by cerulenin might be due to impaired glucose metabolism. Diabetes Metab Res Rev 2007; 23:146-51. [PMID: 16705622 DOI: 10.1002/dmrr.649] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Cerulenin, an inhibitor of protein acylation, has been used as a tool to study the potential role of protein acylation in a variety of activities in different cells, and in stimulus-secretion coupling in pancreatic islets and clonal beta-cells. METHODS In the present study we investigated its effects on stimulated insulin secretion, glucose metabolism and utilization, oxygen consumption and ATP levels. RESULTS In isolated rat pancreatic islets, cerulenin pre-treatment (100 microM) inhibited insulin secretion in response to glucose, and to the non-hydrolysable analogue of leucine, aminobicyclo-[2,2,1]heptane-2-carboxylic acid (BCH). These data are in accord with the hypothesis that protein acylation could be involved in the stimulation of insulin secretion. However, we also found that cerulenin profoundly decreased glucose oxidation, glucose utilization, oxygen consumption and ATP levels. Consequently, decreased metabolism provides an alternative mechanism to inhibition of protein acylation that could explain the inhibition of insulin secretion by cerulenin. CONCLUSIONS Inhibition of insulin secretion by cerulenin can no longer be taken as evidence in favour of a role for protein acylation in the control of insulin release. As protein acylation is known to be involved in the normal functioning of proteins in stimulus-secretion coupling and exocytosis, more direct approaches to understand its role(s) are required.
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Affiliation(s)
- Susanne G Straub
- The Department of Molecular Medicine, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
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43
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Abstract
The mechanisms by which insulin-containing dense core secretory vesicles approach and finally fuse with the plasma membrane are of considerable current interest: defects in these processes may be one of the contributing factors to Type 2 diabetes. In this review, we discuss the molecular mechanisms involved in vesicle trafficking within the pancreatic beta-cell and the mechanisms whereby these may be regulated. We then go on to describe recent evidence that suggests that vesicle fusion at the plasma membrane is a partly reversible process ("kiss and run" or "cavity recapture"). We propose that vesicles may participate in a exo-endocytotic cycle in which a proportion of those that have already undergone an interaction with the plasma membrane may exchange exocytotic machinery with maturing vesicles.
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Affiliation(s)
- Guy A Rutter
- Department of Biochemistry, School of Medical Sciences, University Walk University of Bristol, Bristol, United Kingdom.
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44
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Ducibella T, Matson S. Secretory mechanisms and Ca2+ signaling in gametes: similarities to regulated neuroendocrine secretion in somatic cells and involvement in emerging pathologies. Endocr Pathol 2007; 18:191-203. [PMID: 18247164 DOI: 10.1007/s12022-007-0015-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Recent studies demonstrate that regulated secretion in probably all mammalian cells, from gonadotropes to gametes, utilizes similar signaling systems, intracellular Ca(2+) regulation, Ca(2+)-dependent proteins, cytoskeletal participation, and SNARE-mediated fusion. Thus, highly specialized cells, like sperm and eggs, should no longer be considered to have evolved a cell-type specific secretory mechanism. In gametes, Ca(2+)-dependent proteins and enzymes transduce elevations of intracellular Ca(2+) into secretory events, i.e., exocytosis of the acrosome in sperm and cortical granules in the egg. Just as secretory deficiencies have clinical consequences in endocrine and exocrine cells, failure of secretion of cortical granules or the acrosome can result in failure of normal fertilization or fertilization followed by abnormal development. With the advent of human in vitro fertilization, such gamete pathologies have been recently identified and have led to new clinical procedures to achieve normal fertilization and pregnancies. A better understanding of the common Ca(2+)-dependent secretory pathways in both gametes and somatic cells should be beneficial to investigating mis-regulation in either cell type.
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Affiliation(s)
- Tom Ducibella
- Sackler School of Biomedical Sciences, Program in Cell, Molecular, and Developmental Biology, Tufts University School of Medicine, Boston, MA, 0211, USA.
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45
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Uchida T, Iwashita N, Ohara-Imaizumi M, Ogihara T, Nagai S, Choi JB, Tamura Y, Tada N, Kawamori R, Nakayama KI, Nagamatsu S, Watada H. Protein Kinase Cδ Plays a Non-redundant Role in Insulin Secretion in Pancreatic β Cells. J Biol Chem 2007; 282:2707-16. [PMID: 17135234 DOI: 10.1074/jbc.m610482200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Protein kinase C (PKC) is considered to modulate glucose-stimulated insulin secretion. Pancreatic beta cells express multiple isoforms of PKCs; however, the role of each isoform in glucose-stimulated insulin secretion remains controversial. In this study we investigated the role of PKCdelta, a major isoform expressed in pancreatic beta cells on beta cell function. Here, we showed that PKCdelta null mice manifested glucose intolerance with impaired insulin secretion. Insulin tolerance test showed no decrease in insulin sensitivity in PKCdelta null mice. Studies using islets isolated from these mice demonstrated decreased glucose- and KCl-stimulated insulin secretion. Perifusion studies indicated that mainly the second phase of insulin secretion was decreased. On the other hand, glucose-induced influx of Ca2+ into beta cells was not altered. Immunohistochemistry using total internal reflection fluorescence microscopy and electron microscopic analysis showed an increased number of insulin granules close to the plasma membrane in beta cells of PKCdelta null mice. Although PKC is thought to phosphorylate Munc18-1 and facilitate soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors complex formation, the phosphorylation of Munc18-1 by glucose stimulation was decreased in islets of PKCdelta null mice. We conclude that PKCdelta plays a non-redundant role in glucose-stimulated insulin secretion. The impaired insulin secretion in PKCdelta null mice is associated with reduced phosphorylation of Munc18-1.
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Affiliation(s)
- Toyoyoshi Uchida
- Department of Medicine, Metabolism and Endocrinology, Juntendo University School of Medicine, 2-1-1, Tokyo 113-8421, Japan
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46
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Fukuda M. Rab27 and its effectors in secretory granule exocytosis: a novel docking machinery composed of a Rab27·effector complex. Biochem Soc Trans 2006; 34:691-5. [PMID: 17052176 DOI: 10.1042/bst0340691] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
A small GTPase Rab27 is present on secretory granules in a wide variety of secretory cells and on melanosomes in melanocytes, and it is involved in controlling the trafficking of these organelles through interaction with a cell-type- or tissue-specific Rab27 effector(s). Slps (synaptotagmin-like proteins) and rabphilin contain an N-terminal Rab27-binding domain and C-terminal tandem C2 domains, and some of the Rab27-binding proteins have recently been shown to promote docking of Rab27-bound organelles to the plasma membrane. This mini-review presents a model for how the Rab27·effector complex controls the docking step in the trafficking of Rab27-bound organelles. Our results indicate that Slp2-a, Slp4-a/granuphilin-a and rabphilin are capable of interacting with the plasma membrane directly or indirectly, and thus that these Rab27 effectors form a bridge between Rab27-bound organelles and the plasma membrane.
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Affiliation(s)
- M Fukuda
- Fukuda Initiative Research Unit, RIKEN (The Institute of Physical and Chemical Research), 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
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47
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Imai A, Yoshie S, Nashida T, Shimomura H, Fukuda M. Functional involvement of Noc2, a Rab27 effector, in rat parotid acinar cells. Arch Biochem Biophys 2006; 455:127-35. [PMID: 17067543 DOI: 10.1016/j.abb.2006.09.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Revised: 09/17/2006] [Accepted: 09/18/2006] [Indexed: 11/23/2022]
Abstract
Noc2 has recently been proposed to regulate exocytosis in both endocrine and exocrine cells; however, protein expression, subcellular localization and function of Noc2 in exocrine cells have never been elucidated. In this study, we investigated whether Noc2, a Rab27 effector, is involved in isoproterenol (IPR)-stimulated amylase release from acinar cells. Rab27 was detected in the apical plasma membrane (APM) and secretory granule membrane (SGM) fractions, and was translocated to the APM after IPR stimulation for 5 min, but was detected at lower levels in the APM after 30 min. In contrast, although Noc2 was expressed in SGM bound to Rab27, Noc2 was not translocated to APM and the Noc2/Rab27 complex was disrupted after stimulation with IPR for short time. In addition, the anti-Noc2-Rab-binding-domain antibody inhibited IPR-stimulated amylase release from streptolysin O-permeabilized parotid acinar cells. Our results suggest that the Noc2/Rab27 complex is an important constituent of the early stages of IPR-stimulated amylase release.
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Affiliation(s)
- Akane Imai
- Department of Biochemistry, The Nippon Dental University, School of Life Dentistry at Niigata, 1-8 Hamaura-cho, Niigata 951-8580, Japan.
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Cheviet S, Bezzi P, Ivarsson R, Renström E, Viertl D, Kasas S, Catsicas S, Regazzi R. Tomosyn-1 is involved in a post-docking event required for pancreatic β-cell exocytosis. J Cell Sci 2006; 119:2912-20. [PMID: 16787939 DOI: 10.1242/jcs.03037] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Although the assembly of a ternary complex between the SNARE proteins syntaxin-1, SNAP25 and VAMP2 is known to be crucial for insulin exocytosis, the mechanisms controlling this key event are poorly understood. We found that pancreatic β-cells express different isoforms of tomosyn-1, a syntaxin-1-binding protein possessing a SNARE-like motif. Using atomic force microscopy we show that the SNARE-like domain of tomosyn-1 can form a complex with syntaxin-1 and SNAP25 but displays binding forces that are weaker than those observed for VAMP2 (237±13 versus 279±3 pN). In pancreatic β-cells tomosyn-1 was found to be concentrated in cellular compartments enriched in insulin-containing secretory granules. Silencing of tomosyn-1 in the rat β-cell line INS-1E by RNA interference did not affect the number of secretory granules docked at the plasma membrane but led to a reduction in stimulus-induced exocytosis. Replacement of endogenous tomosyn-1 with mouse tomosyn-1, which differs in the nucleotide sequence from its rat homologue and escapes silencing, restored a normal secretory rate. Taken together, our data suggest that tomosyn-1 is involved in a post-docking event that prepares secretory granules for fusion and is necessary to sustain exocytosis of pancreatic β-cells in response to insulin secretagogues.
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Affiliation(s)
- Séverine Cheviet
- Department of Cell Biology and Morphology, Rue du Bugnon 9, University of Lausanne, 1005 Lausanne, Switzerland
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Teramae H, Fujimoto W, Seino S, Iwanaga T. Cellular expression of Noc2, a Rab effector protein, in endocrine and exocrine tissues in the mouse. Histochem Cell Biol 2006; 127:1-11. [PMID: 16835753 DOI: 10.1007/s00418-006-0207-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2006] [Indexed: 12/21/2022]
Abstract
Noc2 is a Rab effector which participates in regulated exocytosis. It is expressed abundantly in endocrine cells but at low levels in exocrine tissues. Noc2-deficient mice, however, exhibit marked accumulation of secretory granules in exocrine cells rather than endocrine cells. In the present study, we investigated localization of Noc2 immunohistochemically in various endocrine and exocrine tissues in normal mice. Western blotting detected a Noc2-immunoreactive band of 38 kDa in isolated pancreatic islets, the adrenal gland, pituitary gland, and thyroid gland. Immunostaining for Noc2 labeled endocrine cells in the adrenal medulla and adenohypophysis, pancreatic islet cells, thyroid parafollicular cells, and gut endocrine cells, supporting the notion that Noc2 is a Rab effector protein shared by amine/peptide-secreting endocrine cells. Besides endocrine tissues, granular ducts in salivary glands contained Noc2. Although immunostaining failed to detect Noc2 in acinar cells of all exocrine glands examined, reverse transcriptase-polymerase chain reaction analysis detected the mRNA expression in exocrine pancreas. Ultrastructurally, Noc2 immunoreactivity was associated with the limiting membrane of granules in both pancreatic endocrine and salivary duct exocrine cells. The cellular and subcellular localizations of Noc2 should yield key information on its functional significance as well as account for the phenotype in Noc2-deficient mice.
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Affiliation(s)
- Hiroki Teramae
- Laboratory of Histology and Cytology, Graduate School of Medicine, Hokkaido University, Kita-15 Nishi-7, Sapporo 060-8638, Japan
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50
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Plaisance V, Abderrahmani A, Perret-Menoud V, Jacquemin P, Lemaigre F, Regazzi R. MicroRNA-9 controls the expression of Granuphilin/Slp4 and the secretory response of insulin-producing cells. J Biol Chem 2006; 281:26932-42. [PMID: 16831872 DOI: 10.1074/jbc.m601225200] [Citation(s) in RCA: 290] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Insulin release from pancreatic beta-cells plays an essential role in blood glucose homeostasis. Several proteins controlling insulin exocytosis have been identified, but the factors determining the expression of the components of the secretory machinery of beta-cells remain largely unknown. MicroRNAs are newly discovered small non-coding RNAs acting as repressors of gene expression. We found that overexpression of mir-9 in insulin-secreting cells causes a reduction in exocytosis elicited by glucose or potassium. We show that mir-9 acts by diminishing the expression of the transcription factor Onecut-2 and, in turn, by increasing the level of Granuphilin/Slp4, a Rab GTPase effector associated with beta-cell secretory granules that exerts a negative control on insulin release. Indeed, electrophoretic mobility shift assays, chromatin immunoprecipitation, and transfection experiments demonstrated that Onecut-2 is able to bind to the granuphilin promoter and to repress its transcriptional activity. Moreover, we show that silencing of Onecut-2 by RNA interference increases Granuphilin expression and mimics the effect of mir-9 on stimulus-induced exocytosis. Our data provide evidence that in insulin-producing cells adequate levels of mir-9 are mandatory for maintaining appropriate Granuphilin levels and optimal secretory capacity.
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Affiliation(s)
- Valérie Plaisance
- Department of Cell Biology and Morphology, University of Lausanne, and Department of Internal Medicine, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
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