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Loss of the PGE 1 requirement for MDCK cell growth associated with a defect in cyclic AMP phosphodiesterase
Author(s) -
Taub Mary,
Saier Milton H.,
Chuman Lorraine,
Hiller Sue
Publication year - 1983
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041140203
Subject(s) - phosphodiesterase , microbiology and biotechnology , cyclic nucleotide phosphodiesterase , cell growth , chemistry , cell , biophysics , biology , biochemistry , enzyme
Prostaglandin E 1 (PGE 1 ), one of the components in the hormone‐supplemented, serum‐free medium for Madin Darby Canine Kidney (MDCK) cells (Medium K‐1), is required for both long‐term growth and for dome formation. Variant cells have been isolated from MDCK populations, which lack the PGE 1 , requirement for long‐term growth in Medium K‐1. These variants will be useful in identifying the molecular events initiated by PGE 1 which are necessary for the growth response to be observed. The growth and functional properties of five independently isolated PGE 1 independent clones have been examined. Normal MDCK cells grew at an equivalent rate in Medium K‐1 and in serum‐supplemented medium; the growth rate was lower in Medium K‐1 lacking PGE 1 . In contrast, PGE 1 independent clone 1 grew at an equivalent rate in Medium K‐1 minus PGE 1 , and in serum‐supplemented medium. When PGE 1 was added to K‐1 minus PGE 1 , less growth of PGE 1 independent clone 1 was observed. A similar observation was made with one other PGE 1 independent clone which was studied. A hormone deletion study indicated that PGE 1 independent clone 1 still retained growth responses to the other four supplements in Medium K‐1 (insulin, transferrin, T 3 , and hydrocortisone). The molecular alterations associated with loss of the PGE 1 requirement for long‐term growth were examined. At confluency, all of the PGE 1 independent clones studied had higher intracellular cyclic AMP levels following PGE 1 treatment, as compared with normal MDCK cells. The increased cyclic AMP levels in the variant cells could result from a number of different types of defects, including reduced cyclic adenylic acid (cyclic AMP) efflux, an increased affinity of PGE 2 for the PGE 1 receptor, or a defect in cyclic AMP metabolism. However, in all of the variant clones studied a decreased rate of cyclic AMP degradation by cyclic AMP phosphodiesterase was observed. Thus, the increased cyclic AMP levels in the PGE 1 independent variants may result from alterations which affect cyclic AMP metabolism. The effect of PGE 1 on dome formation by the variant cells was also examined. The frequency of dome formation by PGE 1 independent clone 1 was enhanced in a dosage‐dependent manner, like normal MDCK cells. This observation suggests that PGE 1 affects MDCK cell growth and dome formation by different mechanisms.