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Transport by the (Na + , K + ) ATPase: Modulation by differentiation inducers and inhibition of protein synthesis in the MDCK kidney epithelial cell line
Author(s) -
Kennedy Brian G.,
Lever Julia E.
Publication year - 1985
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.1041230317
Subject(s) - cycloheximide , ouabain , inducer , protein biosynthesis , intracellular , stimulation , cell culture , atpase , biology , protein synthesis inhibitor , microbiology and biotechnology , cell , chemistry , biophysics , biochemistry , sodium , enzyme , endocrinology , genetics , organic chemistry , gene
MDCK kidney epithelial cell cultures exposed to the differentiation inducer hexamethylene bisacetamid (HMBA) for 24 hours exhibited a 50% decrease in transport activity per (Na + , K + )‐ATPase molecule (turnover number) but an unchanged number of pump sites (Kennedy and Lever, 1984). Inhibition of protein synthesis by either 10 μM cycloheximide or 2 μM emetine blocked the inhibitory effects of HMBA on Na + /K + pump efficiency assessed by measurements of [ 3 H]‐ouabain binding to intact cells, (Na + , K + ) ATPase activity of detergent‐activated cell extracts, and ouabain‐sensitive Rb + uptake. In the absence of inducer treatment, inhibition of protein synthesis increased Na + /K + pump turnover number by twofold while maintaining Na + /K + pump activity per cell at a constant level. Intracellular Na + levels were decreased after cycloheximide treatment; therefore, pump stimulation was not due to substrate effects. Furthermore, cycloheximide effects of Rb + uptake could be dissociated from effects on tight junctions. These observations suggest that the transport activity of the (Na + , K + ) ATPase is tightly regulated by factors dependent on protein synthesis.