Regulation of L-type Ca2+ Channel Activity and Insulin Secretion by Huntingtin-associated Protein 1.
Huntingtin-associated protein 1 (Hap1) was originally identified as a protein that binds to the Huntington disease protein, huntingtin. Growing evidence has shown that Hap1 participates in intracellular trafficking via its association with various microtubule-dependent transporters and organelles. Recent studies also revealed that Hap1 is involved in exocytosis such as insulin release from pancreatic β-cells. However, the mechanism underlying the action of Hap1 on insulin release remains to be investigated. We found that Hap1 knock-out mice had a lower plasma basal insulin level than control mice. Using cultured pancreatic β-cell lines, INS-1 cells, we confirmed that decreasing Hap1 reduces the number of secreted vesicles and inhibits vesicle exocytosis. Electrophysiology and imaging of intracellular Ca2+measurements demonstrated that Hap1 depletion significantly reduces the influx of Ca2+mediated by L-type Ca2+channels (Cav). This decrease is not due to reduced expression of Cav1.2 channel mRNA but results from the decreased distribution of Cav1.2 on the plasma membrane of INS-1 cells. Fluorescence recovery after photobleaching showed a defective movement of Cav1.2 in Hap1 silencing INS-1 cells. Our findings suggest that Hap1 is important for insulin secretion of pancreatic β-cells via regulating the intracellular trafficking and plasma membrane localization of Cav1.2, providing new insight into the mechanisms that regulate insulin release from pancreatic β-cells.
From the Department of Histology and Embryology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030 and.
Jing-Ying
JY
Pan
From the Department of Histology and Embryology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030 and.
Shijin
S
Yuan
the Clinic Laboratory, Wuhan Children's Hospital, Wuhan 430016, China.
Tao
T
Yu
From the Department of Histology and Embryology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030 and.
Cong-Lin
CL
Su
From the Department of Histology and Embryology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030 and.
Xiao-Long
XL
Liu
From the Department of Histology and Embryology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030 and junhe@mails.tjmu.edu.cn.
Jun
J
He
From the Department of Histology and Embryology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030 and heli@mails.tjmu.edu.cn.
He
H
Li
D000818:Animals; D020746:Calcium Channels, L-Type / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000235:genetics / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*
C514350:CACNA1C protein, mouse; D020746:Calcium Channels, L-Type; C490758:Hap1 protein, mouse; D007328:Insulin; D009419:Nerve Tissue Proteins
Huntington disease; calcium channel; insulin secretion; pancreas; transport