Cholecystokinin 22 (CCK22)

Two endocrine tumor cell lines from pancreas (RIN5F) and intestine (STC-1) express cholecystokinin (CCK) messenger RNA and are able to posttranslationally process pro-CCK to CCK-22 and CCK-8 amide. Both of these forms are also secreted by these cells. Because they make and secrete forms of amidated CCK larger than CCK-8, they represent a model of pro-CCK processing in the gut and allow investigation of possible mechanisms for tissue differences in prohormone processing. Inhibition of PC1 expression in these cells using stable expression of antisense messenger RNA caused a significant reduction in cellular content of amidated CCK and caused a selective depletion of CCK-8 with a comparative sparing of CCK-22. Inhibition of PC2 expression in these cells also caused a large initial decrease in CCK content and produced a selective depletion of CCK-22 and a comparative sparing of CCK-8.