PMID- 25762204
OWN - NLM
STAT- MEDLINE
DCOM- 20160310
LR  - 20231213
IS  - 1432-0428 (Electronic)
IS  - 0012-186X (Linking)
VI  - 58
IP  - 6
DP  - 2015 Jun
TI  - Syntaxin-4 mediates exocytosis of pre-docked and newcomer insulin granules 
      underlying biphasic glucose-stimulated insulin secretion in human pancreatic beta 
      cells.
PG  - 1250-9
LID - 10.1007/s00125-015-3545-4 [doi]
AB  - AIMS/HYPOTHESIS: Of the four exocytotic syntaxins (Syns), much is now known about 
      the role of Syn-1A (pre-docked secretory granules [SGs]) and Syn-3 (newcomer SGs) 
      in insulin exocytosis. Some work was reported on Syn-4's role in biphasic 
      glucose-stimulated insulin secretion (GSIS), but its precise role in insulin SG 
      exocytosis remains unclear. In this paper we examine this role in human beta 
      cells. METHODS: Endogenous function of Syn-4 in human islets was assessed by 
      knocking down its expression with lentiviral single hairpin RNA 
      (lenti-shRNA)-RFP. Biphasic GSIS was determined by islet perifusion assay. 
      Single-cell analysis of exocytosis of red fluorescent protein (RFP)-positive beta 
      cells (exhibiting near-total depletion of Syn-4) was by patch clamp capacitance 
      measurements (Cm) and total internal reflection fluorescence microscopy (TIRFM), 
      the latter to further assess single SG behaviour. Co-immunoprecipitations were 
      conducted on INS-1 cells to assess exocytotic complexes. RESULTS: Syn-4 knockdown 
      (KD) of 77% in human islets caused a concomitant reduction in cognate Munc18c 
      expression (46%) without affecting expression of other exocytotic proteins; this 
      resulted in reduction of GSIS in the first phase (by 42%) and the second phase 
      (by 40%). Cm of RFP-tagged Syn-4-KD beta cells showed severe inhibition in the 
      readily releasable pool (by 71%) and mobilisation from reserve pools (by 63%). 
      TIRFM showed that Syn-4-KD-induced inhibition of first-phase GSIS was attributed 
      to reduction in exocytosis of both pre-docked and newcomer SGs (which undergo 
      minimal residence or docking time at the plasma membrane before fusion). 
      Second-phase inhibition was attributed to reduction in newcomer SGs. Stx-4 
      co-immunoprecipitated Munc18c, VAMP2 and VAMP8, suggesting that these exocytotic 
      complexes may be involved in exocytosis of pre-docked and newcomer SGs. 
      CONCLUSIONS/INTERPRETATION: Syn-4 is involved in distinct molecular machineries 
      that influence exocytosis of both pre-docked and newcomer SGs in a manner 
      functionally redundant to Syn-1A and Syn-3, respectively; this underlies Syn-4's 
      role in mediating portions of first-phase and second-phase GSIS.
FAU - Xie, Li
AU  - Xie L
AD  - Department of Medicine, Faculty of Medicine, University of Toronto, Medical 
      Sciences Building, 1 King's College Circle, Toronto, ON, Canada, M5S 1A8.
FAU - Zhu, Dan
AU  - Zhu D
FAU - Dolai, Subhankar
AU  - Dolai S
FAU - Liang, Tao
AU  - Liang T
FAU - Qin, Tairan
AU  - Qin T
FAU - Kang, Youhou
AU  - Kang Y
FAU - Xie, Huanli
AU  - Xie H
FAU - Huang, Ya-Chi
AU  - Huang YC
FAU - Gaisano, Herbert Y
AU  - Gaisano HY
LA  - eng
GR  - MOP 86544/Canadian Institutes of Health Research/Canada
GR  - MOP 89889/Canadian Institutes of Health Research/Canada
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20150313
PL  - Germany
TA  - Diabetologia
JT  - Diabetologia
JID - 0006777
RN  - 0 (Biphasic Insulins)
RN  - 0 (Insulin)
RN  - 0 (Luminescent Proteins)
RN  - 0 (Munc18 Proteins)
RN  - 0 (Qa-SNARE Proteins)
RN  - 0 (R-SNARE Proteins)
RN  - 0 (RNA, Small Interfering)
RN  - 0 (VAMP2 protein, human)
RN  - 0 (VAMP8 protein, human)
RN  - 0 (Vesicle-Associated Membrane Protein 2)
RN  - 0 (syntaxin 4, human)
RN  - IY9XDZ35W2 (Glucose)
SB  - IM
MH  - Animals
MH  - Biphasic Insulins/*blood
MH  - Cells, Cultured
MH  - *Exocytosis
MH  - Gene Knockdown Techniques
MH  - Glucose/metabolism
MH  - Humans
MH  - Insulin/*metabolism
MH  - Insulin Secretion
MH  - Insulin-Secreting Cells/*cytology
MH  - Luminescent Proteins/metabolism
MH  - Mice
MH  - Mice, Inbred C57BL
MH  - Microscopy, Confocal
MH  - Munc18 Proteins/metabolism
MH  - Patch-Clamp Techniques
MH  - Qa-SNARE Proteins/*metabolism
MH  - R-SNARE Proteins/metabolism
MH  - RNA, Small Interfering/metabolism
MH  - Single-Cell Analysis
MH  - Vesicle-Associated Membrane Protein 2/metabolism
MH  - Red Fluorescent Protein
EDAT- 2015/03/13 06:00
MHDA- 2016/03/11 06:00
CRDT- 2015/03/13 06:00
PHST- 2014/08/12 00:00 [received]
PHST- 2015/02/03 00:00 [accepted]
PHST- 2015/03/13 06:00 [entrez]
PHST- 2015/03/13 06:00 [pubmed]
PHST- 2016/03/11 06:00 [medline]
AID - 10.1007/s00125-015-3545-4 [doi]
PST - ppublish
SO  - Diabetologia. 2015 Jun;58(6):1250-9. doi: 10.1007/s00125-015-3545-4. Epub 2015 
      Mar 13.