Secretagogin affects insulin secretion in pancreatic β-cells by regulating actin dynamics and focal adhesion.
Secretagogin (SCGN), a Ca(2+)-binding protein having six EF-hands, is selectively expressed in pancreatic β-cells and neuroendocrine cells. Previous studies suggested that SCGN enhances insulin secretion by functioning as a Ca(2+)-sensor protein, but the underlying mechanism has not been elucidated. The present study explored the mechanism by which SCGN enhances glucose-induced insulin secretion in NIT-1 insulinoma cells. To determine whether SCGN influences the first or second phase of insulin secretion, we examined how SCGN affects the kinetics of insulin secretion in NIT-1 cells. We found that silencing SCGN suppressed the second phase of insulin secretion induced by glucose and H2O2, but not the first phase induced by KCl stimulation. Recruitment of insulin granules in the second phase of insulin secretion was significantly impaired by knocking down SCGN in NIT-1 cells. In addition, we found that SCGN interacts with the actin cytoskeleton in the plasma membrane and regulates actin remodelling in a glucose-dependent manner. Since actin dynamics are known to regulate focal adhesion, a critical step in the second phase of insulin secretion, we examined the effect of silencing SCGN on focal adhesion molecules, including FAK (focal adhesion kinase) and paxillin, and the cell survival molecules ERK1/2 (extracellular-signal-regulated kinase 1/2) and Akt. We found that glucose- and H2O2-induced activation of FAK, paxillin, ERK1/2 and Akt was significantly blocked by silencing SCGN. We conclude that SCGN controls glucose-stimulated insulin secretion and thus may be useful in the therapy of Type 2 diabetes.
Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul 03760, South Korea.
Seo-Yun
SY
Yang
Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul 03760, South Korea.
Jae-Jin
JJ
Lee
Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul 03760, South Korea.
Jin-Hee
JH
Lee
Advance Analysis Center, Korea Institute of Science and Technology, Hwarang-ro 14-gil, Seongbuk-gu, Seoul 02792, South Korea.
Kyungeun
K
Lee
Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 06351, South Korea.
Seung Hoon
SH
Oh
Severans Biomedical Research Institute, Yonsei University College of Medicine, Seoul 03722, South Korea.
Yu-Mi
YM
Lim
Severans Biomedical Research Institute, Yonsei University College of Medicine, Seoul 03722, South Korea Department of Internal Medicine, Yonsei University College of Medicine, Seoul 03722, South Korea.
Myung-Shik
MS
Lee
Graduate School of Pharmaceutical Sciences, College of Pharmacy, Ewha Womans University, Seoul 03760, South Korea kjl@ewha.ac.kr.
Kong-Joo
KJ
Lee
D000199:Actins / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D022001:Focal Adhesions / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005947:Glucose / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D047468:Immunoprecipitation; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D051419:Paxillin / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011485:Protein Binding; D064046:Secretagogins / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D007328:Insulin; D051419:Paxillin; D064046:Secretagogins; D011189:Potassium Chloride; D006861:Hydrogen Peroxide; D051416:Focal Adhesion Protein-Tyrosine Kinases; D005947:Glucose
actin; calcium-binding protein; focal adhesion; insulin secretion; secretagogin