Rab2a and Rab27a cooperatively regulate the transition from granule maturation to exocytosis through the dual effector Noc2

Matsunaga, Kohichi; Taoka, Masato; Isobe, Toshiaki; Izumi, Tetsuro

doi:10.1242/jcs.195479

Cited by 28 publications

(27 citation statements)

References 40 publications

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“…We also observed down-regulated gene expression for components of the exocytosis apparatus in β-cells, Snap-25 , Rph3al (Noc2), and Pclo (Piccolo) ( Figure 3F ). Noc2, an effector of the Rab3 and Rab27 GTPases, is an essential component of insulin granule exocytosis ( Matsumoto et al, 2004 ; Matsunaga et al, 2017 ). Piccolo is a scaffold protein that functions as a Ca 2+ sensor and links K ATP channels, L-type calcium channels and insulin granules into exocytosis-competent complexes ( Shibasaki et al, 2004 ), whereas Snap-25 is a t-SNARE protein that is critical for insulin granule fusion ( Wheeler et al, 1996 ).…”

Section: Resultsmentioning

confidence: 99%

Adrb2 controls glucose homeostasis by developmental regulation of pancreatic islet vasculature

Ceasrine

Lin

Lumelsky

et al. 2018

eLife

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A better understanding of processes controlling the development and function of pancreatic islets is critical for diabetes prevention and treatment. Here, we reveal a previously unappreciated function for pancreatic β2-adrenergic receptors (Adrb2) in controlling glucose homeostasis by restricting islet vascular growth during development. Pancreas-specific deletion of Adrb2 results in glucose intolerance and impaired insulin secretion in mice, and unexpectedly, specifically in females. The metabolic phenotypes were recapitulated by Adrb2 deletion from neonatal, but not adult, β-cells. Mechanistically, Adrb2 loss increases production of Vascular Endothelial Growth Factor-A (VEGF-A) in female neonatal β-cells and results in hyper-vascularized islets during development, which in turn, disrupts insulin production and exocytosis. Neonatal correction of islet hyper-vascularization, via VEGF-A receptor blockade, fully rescues functional deficits in glucose homeostasis in adult mutant mice. These findings uncover a regulatory pathway that functions in a sex-specific manner to control glucose metabolism by restraining excessive vascular growth during islet development.

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Section: Resultsmentioning

confidence: 99%

Adrb2 controls glucose homeostasis by developmental regulation of pancreatic islet vasculature

Ceasrine

Lin

Lumelsky

et al. 2018

eLife

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“…To understand the molecular mechanisms by which exophilin-8 functions, we investigated its interacting proteins, using the tandem affinity purification approach based on the Myc-TEV-FLAG (MEF) tag, as previously described (Ichimura et al, 2005; Matsunaga et al, 2009, 2017). Namely, we expressed exophilin-8 fused to the MEF tag at its amino terminus in MIN6 cells and recovered the bound proteins in successive purification steps.…”

Section: Resultsmentioning

confidence: 99%

“…The full-length and deleted cDNAs were subcloned into the pcDNA3-3×HA, EGFP-C2 (BD Biosciences, Franklin Lakes, NJ), pENTR3C-MEF, and pENTR3C-3×HA. They were also subcloned into the pCAG vector with or without an OSF tag (Morita et al, 2007; Matsunaga et al, 2017). Recombinant adenoviruses were prepared as described previously (Wang et al, 2013).…”

Section: Methodsmentioning

confidence: 99%

“…Guinea pig anti-porcine insulin serum was a gift from H. Kobayashi (Gunma University). The following commercially purchased antibodies were also used: rabbit polyclonal antibodies toward FLAG (F7425, Sigma-Aldrich, St. Louis, MO; RRID:AB_439687), myosin-Va (LF-18, Sigma-Aldrich; RRID:AB_260545), RIM-BP2 (15716–1-AP, Proteintech, Rosemont, IL), Munc13-1 (55053–1-AP, Proteintech), HA (561, MBL, Nagoya, Japan; RRID:AB_591839), green fluorescent protein (GFP; 598; MBL; RRID:AB_2313843), Rab27a/b (18975; IBL, Fujioka, Japan; RRID:AB_494635), PKA (ab26322; Abcam, Cambridge, United Kingdom), myosin-VIIa (ab3481; Abcam; RRID:AB_303841), Ca v 1.3 (ACC-005; Alomone Labs, Jerusalem, Israel; RRID:AB_2039775), RIM1/2 (140203; Synaptic Systems, Goettingen, Germany), and VAMP2 (627724; Calbiochem, San Diego, CA; RRID:AB_212589); and mouse monoclonal antibodies toward glyceraldehyde-3-phosphate dehydrogenase (GAPDH; 3H12; MBL), α-tubulin (T5168; Sigma-Aldrich; RRID:AB_477579), β-actin (A5316; Sigma-Aldrich; RRID:AB_476743), syntaxin1 (HPC-1; Sigma-Aldrich; RRID:AB_592786), Na + -K + ATPase (C464.6; Upstate Biotechnology, Lake Placid, NY; RRID:AB_309699), Sec6 (ADI-VAM-SV021; Assay Designs, Ann Arbor, MI), and SNAP25 (610366; BD Biosciences; RRID:AB_397752) Tissue extract preparation, immunoblotting, and immunoprecipitation were performed as described previously (Matsunaga et al, 2017). Each image resulting from immunoblotting is representative of at least three independent experiments.…”

Section: Methodsmentioning

confidence: 99%

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Exophilin-8 assembles secretory granules for exocytosis in the actin cortex via interaction with RIM-BP2 and myosin-VIIa

Fan

Matsunaga

Wang

et al. 2017

eLife

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Exophilin-8 has been reported to play a role in anchoring secretory granules within the actin cortex, due to its direct binding activities to Rab27 on the granule membrane and to F-actin and its motor protein, myosin-Va. Here, we show that exophilin-8 accumulates granules in the cortical F-actin network not by direct interaction with myosin-Va, but by indirect interaction with a specific form of myosin-VIIa through its previously unknown binding partner, RIM-BP2. RIM-BP2 also associates with exocytic machinery, Cav1.3, RIM, and Munc13-1. Disruption of the exophilin-8–RIM-BP2–myosin-VIIa complex by ablation or knockdown of each component markedly decreases both the peripheral accumulation and exocytosis of granules. Furthermore, exophilin-8-null mouse pancreatic islets lose polarized granule localization at the β-cell periphery and exhibit impaired insulin secretion. This newly identified complex acts as a physical and functional scaffold and provides a mechanism supporting a releasable pool of granules within the F-actin network beneath the plasma membrane.DOI: http://dx.doi.org/10.7554/eLife.26174.001

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“…CircRPH3AL was also upregulated in diabetic islets. Linear transcripts from RPH3AL are highly expressed in β-cells and have roles in calciumdependent exocytosis during granule maturation and insulin secretion [34].…”

Section: Discussionmentioning

confidence: 99%

Islet-expressed circular RNAs are associated with type 2 diabetes status in human primary islets and in peripheral blood

et al. 2020

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Background: Circular RNAs are non-coding RNA molecules with gene regulatory potential that have been associated with several human diseases. They are stable and present in the circulation, making them excellent candidates for biomarkers of disease. Despite their promise as biomarkers or future therapeutic targets, information on their expression and functionality in human pancreatic islets is a relatively unexplored subject. Methods: Here we aimed to produce an enriched circRNAome profile for human pancreatic islets by CircleSeq, and to explore the relationship between circRNA expression, diabetes status, genotype at T2D risk loci and measures of glycaemia (insulin secretory index; SI and HbA1c) in human islet preparations from healthy control donors and donors with type 2 diabetes using ANOVA or linear regression as appropriate. We also assessed the effect of elevated glucose, cytokine and lipid and hypoxia on circRNA expression in the human beta cell line EndoC-βH1. Results: We identified over 2600 circRNAs present in human islets. Of the five most abundant circRNAs in human islets, four (circCIRBP, circZKSCAN, circRPH3AL and circCAMSAP1) demonstrated marked associations with diabetes status. CircCIRBP demonstrated an association with insulin secretory index in isolated human islets and circCIRBP and circRPH3AL displayed altered expression with elevated fatty acid in treated EndoC-βH1 cells. CircCAMSAP1 was also noted to be associated with T2D status in human peripheral blood. No associations between circRNA expression and genotype at T2D risk loci were identified in our samples. Conclusions: Our data suggest that circRNAs are abundantly expressed in human islets, and that some are differentially regulated in the islets of donors with type 2 diabetes. Some islet circRNAs are also expressed in peripheral blood and the expression of one, circCAMSAP1, correlates with diabetes status. These findings highlight the potential of circRNAs as biomarkers for T2D.

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Rab2a and Rab27a cooperatively regulate the transition from granule maturation to exocytosis through the dual effector Noc2

Cited by 28 publications

References 40 publications

Adrb2 controls glucose homeostasis by developmental regulation of pancreatic islet vasculature

Adrb2 controls glucose homeostasis by developmental regulation of pancreatic islet vasculature

Exophilin-8 assembles secretory granules for exocytosis in the actin cortex via interaction with RIM-BP2 and myosin-VIIa

Islet-expressed circular RNAs are associated with type 2 diabetes status in human primary islets and in peripheral blood

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