A MURINE INTESTINAL ENDOCRINE TUMOR-CELL LINE, STC-1, EXPRESSES CCK, PC1 AND PC2 MESSENGER-RNA, PROCESSES PRO-CCK TO CCK-8 AND DISPLAYS CAMP-REGULATED RELEASE

The STC-1 cell line, derived from murine intestinal endocrine tumor ce lls, has been shown previously to produce a number of peptides includi ng CCK. These cells express CCK mRNA detectable by Northern analysis a nd contain approximately 1 ng/mg of immunoreactive CCK as measured by radioimmunoassay. Surprisingly, given the fact that pro CCK processing in the gut usually produces immunoreactive forms larger than CCK 8, t he major CCK immunoreactive product in these cells elutes in the same fraction as CCK 8 as measured on both Sephadex G-50 chromatography and HPLC. This cell line, as well as several others which express CCK mRN A and process pro CCK to CCK 8, also expresses mRNA for the subtilisin -like endoproteases PC1 and PC2. These enzymes have been implicated in the processing of other propeptides and are likely candidates for the dibasic cleavage sites in pro CCK. A significant increase in CCK 8 im munoreactivity was measured in the media of STC-1 after incubation in forskolin and IBMX, supporting a cAMP regulated mechanism of release i n these cells. These cells should be a useful model to study CCK biosy nthesis, processing and regulation of secretion.