Prohormone convertases (PC1/3 and PC2) in rat and human pancreas and islet cell tumors: Subcellular immunohistochemical analysis

摘要

Prohormons convertase 1/3 (PC1/3; also termed PC1 or PC3) and PC2 are enzymes that activate prohormones by cleaving the pairs of basic amlno acids. This mechanlsm was inltlally Interred lrom the series of several endocrine and neuroendocrine precursor protoh, inciudlng proinsulin and prolusion. To determine the cellular and sub cellular distribution of PC1/3 and PC2 in the rat snd human pancreas, Immunohlstochemistry was performed using polyclonal antlers against mouse PC1/3 (ST‐28) and mouse PC2 (ST‐29). These studles showed light and dsctron mlcroacoplc co‐locailzation of Insulln, PC1/3 and PC2, and the coexistence of glucagons and PC2 In the pancreatic islets. This tendency of colocalizstion was also depicted In one case of human insulin and three cam of human glucagonomas, as well as In rat Insullnomas. in two cases of human Insullnomas, Incomplete processing of proinsulin was suggested by the absence of PC2. At the sub cellular level in the rat pancreatic lslet, the colocalizstion of PC1/3 and insulin, and that of PC2 and glucagons, were observed in the same secretor granules by immunoelectron, microscopy and Image analysis. These studles suggest that PC1/3 and PC2 can functlon with the specifictties In the processing of proinsulin and proglucagon Into their active forms, respectively, in the normal and neoplastic pancreatic i