Interaction of Munc18 and Syntaxin in the regulation of insulin secretion.
Syntaxin1A and Munc18-1 play essential roles in exocytosis. However, the molecular mechanism and the functional roles of their interaction in insulin secretion remain to be explored. Using membrane capacitance measurement, we examine effect of overexpressing Munc18-1 on exocytosis in pancreatic beta cells. The results show that Munc18-1 negatively regulates vesicle fusion. To probe the interaction between Munc18-1 and Syntaxin1A, Munc18-1-Tdimer2 and EGFP-Syntaxin1A were co-transfected into INS-1 cells. FRET measurement confirmed that Munc18-1 interacted with wild type Syntaxin 1A, but not the constitutively open form (DM) of Syntaxin1A. Overexpressing DM in primary pancreatic beta cells augmented insulin secretion, and this effect can overcome the inhibitory effect of Munc18-1 overexpression. We propose that Munc18-1 inhibitis the SNARE complex assembly by stabilizing Syntaxin1A in a closed conformation in vesicle priming process, therefore negatively regulates insulin secretion.
Dong
Yongming
Y
Joint Laboratory of the Institute of Biophysics & Huazhong University of Science and Technology, School of Life Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, PR China.
Wan
Qunfang
Q
Yang
Xiaofei
X
Bai
Li
L
Xu
Pingyong
P
D000818:Animals; D002478:Cells, Cultured; D031541:Fluorescence Resonance Energy Transfer; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008297:Male; D051938:Munc18 Proteins / Q000235:genetics / Q000378:metabolism*; D050765:Qa-SNARE Proteins / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D050827:Syntaxin 1 / Q000378:metabolism*
D007328:Insulin; D051938:Munc18 Proteins; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins; C494213:Stx1a protein, rat; C497939:Stxbp1 protein, rat; D050827:Syntaxin 1