Role of prohormone convertases in the tissue-specific processing of proglucagon.
Proglucagon (proG) is processed in a tissue-specific manner to glucagon in the pancreas and to gilcentin, oxyntomodulin, glucagon-like peptide (GLP)-1, and GLP-2 in the intestine. Recombinant vaccinia virus (vv) vectors were used to infect prohormone convertase 1 (PC1) or PC2 into nonendocrine (BHK-proG) cells, which stably express proG. Similarly, endocrine (GH3, AtT-20) cells were coinfected with proG along with PC1 or PC2 alone, or in combination with furin, PACE4, PC5a, or PC5b. Cell extracts were analyzed for various proG-derived peptides by RIA of fractions obtained from HPLC. Upon infection of BHK-proG cells with either vv: furin or vv:PC1, glicentin was produced, while vv: PC2 did not process proG. In GH3 and AtT-20 cells, vv:PC1 produced glicentin, oxyntomodulin, GLP-1(1-37), GLP-1(7-37), and GLP-2. All other enzymes tested produced only glicentin. Interestingly, no enzyme or combination produced glucagon. Coinfection of GH3 cells with vv:PC2 and members of the chromogranin family of peptides, including chromogranin A and B and secretogranin II, as well as the PC2-binding protein 7B2, did not result in processing to glucagon. It is concluded that: 1) PC1 is responsible for the processing of proG to produce the intestinal peptides glicentin, oxyntomodulin, GLP-1(1-37), GLP-1(7-37), and GLP-2, and 2) PC2 processes proG to glicentin but does not produce glucagon, alone or in combination with other enzymes or with known molecular chaperones.
Dhanvantari
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S
Department of Physiology, University of Toronto, Ontario, Canada.
Seidah
N G
NG
Brubaker
P L
PL
D000818:Animals; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D045683:Furin; D053771:Glicentin; D005934:Glucagon / Q000096:biosynthesis* / Q000378:metabolism*; D004763:Glucagon-Like Peptides; D007668:Kidney; D008668:Metallothionein / Q000235:genetics; D051379:Mice; D010446:Peptide Fragments / Q000096:biosynthesis; D052336:Proglucagon; D011401:Promoter Regions, Genetic; D011498:Protein Precursors / Q000096:biosynthesis / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D013381:Subtilisins / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured
D010446:Peptide Fragments; D011498:Protein Precursors; D011994:Recombinant Proteins; D052336:Proglucagon; D004763:Glucagon-Like Peptides; D053771:Glicentin; D005934:Glucagon; D008668:Metallothionein; D013381:Subtilisins; D045683:Furin