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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1994 Apr 12;91(8):3242–3246. doi: 10.1073/pnas.91.8.3242

Proglucagon is processed to glucagon by prohormone convertase PC2 in alpha TC1-6 cells.

Y Rouillé 1, G Westermark 1, S K Martin 1, D F Steiner 1
PMCID: PMC43552  PMID: 8159732

Abstract

Proglucagon is processed differentially in the pancreatic alpha cells and the intestinal L cells to yield either glucagon or glucagon-like peptide 1, respectively, structurally related hormones with opposing metabolic actions. Here, we have studied the processing of proglucagon in alpha TC1-6 cells, an islet-cell line transformed by simian virus 40 large tumor (T) antigen, a model of the pancreatic alpha cell. We found that these cells process proglucagon at certain dibasic cleavage sites to release glucagon and only small amounts of glucagon-like peptide 1, as demonstrated by both continuous and pulse-chase labeling experiments. Both normal islet alpha cells and alpha TC1-6 cells were shown to express the prohormone convertase PC2 at high levels, but not the related protease PC3. Expression of PC2 antisense RNA in alpha TC1-6 cells inhibited both PC2 production and proglucagon processing concomitantly. We conclude that PC2 is the key endoprotease responsible for proglucagon processing in cells with the alpha-cell phenotype.

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