Altered proglucagon processing in an alpha-cell line derived from prohormone convertase 2 null mouse islets.
The endoproteolytic processing of proproteins in the secretory pathway depends on the expression of selected members of a family of subtilisin-like endoproteases known as the prohormone convertases (PCs). The main PC family members expressed in mammalian neuroendocrine cells are PC2 and PC1/3. The differential processing of proglucagon in pancreatic alpha-cells and intestinal L cells leads to production of distinct hormonal products with opposing physiological effects from the same precursor. Here we describe the establishment and characterization of a novel alpha-cell line (alphaTC-DeltaPC2) derived from PC2 homozygous null animals. The alphaTC-DeltaPC2 cells are shown to be similar to the well characterized alphaTC1-6 cell line in both morphology and overall gene expression. However, the absence of PC2 activity in alphaTC-DeltaPC2 leads to a complete block in the production of mature glucagon. Surprisingly, alphaTC-DeltaPC2 cells are able to efficiently cleave the interdomain site in proglucagon (KR 70-71). Further analysis reveals that alphaTC-DeltaPC2 cells, unlike alphaTC1-6 cells, express low levels of PC1/3 that lead to the generation of glicentin as well as low amounts of oxyntomodulin, GLP-1, truncated GLP-1, and N-terminally extended GLP-2. We conclude that alphaTC-DeltaPC2 cells provide additional evidence for PC2 as the major convertase in alpha-cells leading to mature glucagon production and provide a robust model for further analysis of the mechanisms of proprotein processing by the prohormone convertases.
Webb
Gene C
GC
Department of Medicine, Committee on Genetics, University of Chicago, Illinois 60637, USA.
Dey
Arunangsu
A
Wang
Jie
J
Stein
Jeffrey
J
Milewski
Margaret
M
Steiner
Donald F
DF
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D020869:Gene Expression Profiling; D005934:Glucagon / Q000378:metabolism*; D007515:Islets of Langerhans / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D016253:Microscopy, Immunoelectron; D008954:Models, Biological; D020411:Oligonucleotide Array Sequence Analysis; D052336:Proglucagon; D045706:Proprotein Convertase 2 / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational
D017931:DNA Primers; D011498:Protein Precursors; D052336:Proglucagon; D005934:Glucagon; D045706:Proprotein Convertase 2