Modulation of the mitochondrial dynamics by clusterin in insulin–secreting beta-cells

초록

Modulation of the mitochondrial dynamics by clusterin in insulin–secreting beta-cells Yoen-ju Kwon, Han-Sol Park, and In-Sun Park Department of Anatomy, School of Medicine, Inha University Mitochondrion is a dynamic cellular organelle showing a diverse morphological change in response to biological processes including energy metabolism and viability of the cells. Clusterin is an intriguing protein with a variety of biological functions, particularly in association with cytoprotection. Pancreatic beta cells produce and secrete insulin, but are susceptible to internal and external challenges, leading to hyperglycemia and diabetes. The present study aimed to elucidate the clusterin action on the profiles of beta cell mitochondria regarding to mitochondrial dynamics including their fusion/fission and autophage formation. Clusterin expression was regulated from by transfection of over-expression vector and siRNA, respectively using MIN-6 and INS-I cell lines which secrete insulin as well as clusterin simultaneously. Mitochondrial proteins which are associated with mitochondrial fusion and fission were monitored after clusterin over-expression and deletion, along with their morphological observation. We found that clusterin overexpression down-regulated the mitochondrial fusion factors including OPA-1, MFN-1, MFN-2. In contrast, the mitochondrial fusion proteins were up-regulated by knock-down of the clusterin genes. Although there was no significant changes in mitochondrial fission preoteins (Drp-1 and-2), LC3B, an autophagy marker, was decreased by clusterin over-expression, while being increased by clusterin deprivation. We have traced the expressions of OPA-1 and LC3B in the mitochondria and lysosomes by confocal microscopy, demonstrating a concurrent modification in the cytoplasm of the bet cells. We also found a significantly reduced autophages upon overexpression of clusterin, and their increased formation by downregulation of the clusterin. Take