Pkc Epsilon is the likely mediator of mucin exocytosis in human colonic cell lines. Hong, D. H., J. F. Forstner, G. G. Forstner. Division of Gastroenterology, Research Institute, The Hospital for Sick Children, Departments of Paediatrics and Biochemistry, University of Toronto, Toronto, Ontario, M5G 1X8 Canada
APStracts 3:0146G, 1996.
The phorbol ester PMA induces mucin secretion in the colonic tumor cell line T84 in a Ca2+ -independent manner (14). To determine whether a specific PKC isoform is involved in colonic cells we compared PMA-dependent mucin secretion by three human colonic tumor cell lines (T84, HT29/A1 and LS180) with the expression of PKC isoforms a, b, d, e and z, previously identified in human colon (9). In each cell line PMA (10-7 M) caused mucin secretion within 30 min. PMA-dependent mucin secretion was 3 to 4-fold greater from HT29/A1 and T84 cells than from LS180 cells. All three cell lines contained mRNAs for PKCa, PKC and PKCz, but not PKCb or d. Each cell line also expressed PKCa, e and z protein. PKC expression (mRNA and protein) was 3-4 x greater in HT29/A1 and T84 cells than in LS180 cells, correlating with PMA-responsive mucin secretion, whereas all cell lines contained similar levels of PKC mRNA and protein. When cells were stimulated by PMA only PKCe was translocated from cytosol to membrane fractions early enough to stimulate mucin secretion. Since PKCe is also a Ca2+-independent isoform, it is likely to mediate mucin exocytosis in colonic cells. 

Received 15 May 1996; accepted in final form 24 July 1996.
APS Manuscript Number G196-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 21 August 1996