Prohormone convertase 1 is necessary for the formation of cholecystokinin 8 in Rin5F and STC-1 cells.
Several immortalized cell lines serve as models for procholecystokinin (pro-CCK) processing. Rin5F cells, derived from a rat insulinoma, and STC-1 cells, derived from a murine intestinal tumor, process pro-CCK mainly to amidated CCK 8. Both also make significant quantities of amidated CCK 22, a slightly larger form found in the gut. Many modifications are necessary during pro-CCK processing including cleavages performed by endoproteases, the identities of which are unknown. A candidate endoprotease is prohormone convertase 1 (PC1) also known as PC3, a Ca2+-dependent serine endoprotease of the subtilisin family. Constitutive expression of antisense PC1 message in stably transfected Rin5F cells resulted in a significant reduction of the cellular content of CCK 8 as measured by radioimmunoassay. Several affected cell lines displayed about 80% reduction in CCK content in early passages after transfection. Expression of antisense PC1 message in these cell lines resulted in a selective depletion of CCK 8 and a comparative sparing of CCK 22. The induction of antisense PC1 message within a single subclone of Rin5F cells using the Lac Switch system also resulted in a significant inhibition of CCK content. Expression of antisense PC1 message in a stably transfected STC-1 cell line also resulted in a decrease in CCK content and in PC1 protein expression, and the specific depletion of CCK 8 with comparative sparing of CCK 22. These observations support the hypothesis that PC1 is necessary for pro-CCK processing in Rin5F and STC-1 cells and suggests a role for PC1 endoprotease in the biosynthesis of CCK 8 in vivo.
Yoon
J
J
Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA.
Beinfeld
M C
MC
D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D002766:Cholecystokinin / Q000378:metabolism; D002850:Chromatography, Gel; D007340:Insulinoma / Q000378:metabolism; D007414:Intestinal Neoplasms / Q000378:metabolism; D008956:Models, Chemical; D016376:Oligonucleotides, Antisense / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D043484:Proprotein Convertases; D051381:Rats; D012844:Sincalide / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured
D016376:Oligonucleotides, Antisense; D010446:Peptide Fragments; D002766:Cholecystokinin; C044926:cholecystokinin 22 C-terminal fragment; D043484:Proprotein Convertases; D016282:Aspartic Acid Endopeptidases; D012844:Sincalide