Inhibitory Effect of the α1-Antitrypsin Pittsburgh Type-Mutant (α1-PIM/R) on Proinsulin Processing in the Regulated Secretory Pathway of the Pancreatic β-Cell Line MIN6

Endocrine Journal

JUNKO ONO²  KUMIKO OHKUBO²  YUKO NAITO²  TOSHIYUKI FUJIWARA¹  JUN-ICHI MIYAZAKI³  YUKIO IKEHARA¹ 

[1] Department of Cell Biology, Fukuoka University School of Medicine;Department of Laboratory Medicine, Fukuoka University School of Medicine;Division of Stem Cell Regulation Research, Course of Advanced Medicine, Osaka University Graduate School of Medicine

关键词: Proinsulin;    Processing;    Regulated pathway;    α1-Antitrypsin Pittsburgh;    MIN6;   

DOI  :  10.1507/endocrj.50.9

学科分类：内分泌与代谢学

来源: Japan Endocrine Society

【 摘 要 】

References(39)Cited-By(2)To elucidate its effect on proinsulin processing, we introduced the expression of a Pittsburgh type-mutant, α1-protease inhibitor M/R (α1-PIM/R) and its chimera protein with growth hormone (GH) (GHα1-PIM/R) into MIN6 cells. In metabolic labeling and chasing experiments with [3H]-Leu and [35S]-Met, proinsulin appeared in the medium during stimulatory secretion only from MIN6 clones expressing GHα1-PIM/R and, surprisingly, α1-PIM/R, but not from the clones of either the control or α1-PI. The major part of α1-PIM/R was secreted through the constitutive pathway and about 10% of total secreted α1-PIM/R in the chase periods entered the regulated pathway. On the other hand, GHα1-PIM/R was mainly transported to the secretory granules and about 80% of the total secreted GHα1-PIM/R in the chase periods was secreted during stimulatory secretion. In the first 3 h chase periods without stimulation, only α1-PIM/R and no GHα1-PIM/R appeared in the medium, thus suggesting that α1-PIM/R might be transported through a constitutive-like pathway for those periods. The α1-PI, which had no inhibitory effect on proinsulin processing, showed similar secretion pathways to those of α1-PIM/R. This implies that some part of α1-PIM/R and α1-PI entered the regulated pathway, not due to any specific interaction between the processing endoproteases and serine protease inhibitors, but due to some type of passive transport in a nonselective manner. The inhibitory effect of α1-PIM/R in the regulated secretory pathway was slightly but clearly evident when it was expressed in MIN6 β-cells.

【 授权许可】

Unknown