W. Breuer et al., PROTEIN-KINASE-C MEDIATES DOWN-REGULATION OF CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR LEVELS IN EPITHELIAL-CELLS, The Journal of biological chemistry, 268(19), 1993, pp. 13935-13939
Expression of the cystic fibrosis transmembrane conductance regulator
(CFTR) in epithelial cells is known to be down-regulated by the action
of phorbol myristate acetate (PMA). We show here that in addition to
suppressing the rate of transcription of the CFTR gene, PMA treatment
stimulates degradation of the CFTR protein. HT-29 colon epithelial cel
ls and the CFTR-transfected pancreatic cells PLJ-4.7 lost 55-80% of th
eir CFTR protein after 3-6 h of treatment with 100 nm PMA, as analyzed
by quantitative Western blotting. In contrast to PMA, actinomycin D a
nd cycloheximide reduced the CFTR protein content by 19 and 9% in HT-2
9 cells and by 22 and 40% in PLJ-4.7 cells, respectively, while inhibi
ting total cellular RNA and protein synthesis by over 80%. The PMA-ind
uced loss of CFTR was partially reversed by the protein kinase C inhib
itor GF109203X. The PMA-induced degradation of CFTR may represent a re
gulatory pathway for terminating CFTR-mediated chloride and mucin secr
etion.