Cyclic AMP-dependent protein kinase in mammary epithelial cells; activity and subcellular distribution are acutely modulated by isoprenaline.
Brief incubation of a mammary epithelial cellular preparation from lactating rats with isoprenaline is shown to result in major re-distribution of the activity of cyclic AMP-dependent protein kinase (measured in the presence of saturating cyclic AMP) within the cell. Activity in the soluble fraction was halved and a corresponding increase in the sedimentable activity occurred. Similar effects were observed when cell-free extracts were treated with cyclic AMP in the presence of inhibitors of phosphodiesterase and subsequently fractionated by a simple one-step centrifugation procedure. The concentration of the catalytic subunit of cyclic AMP-dependent protein kinase, assessed by quantitative Western blot analysis, did not reflect these activity changes. Quantitation of the regulatory subunits (R-I plus R-II) of A-kinase enabled independent assessment of the possible total A-kinase holoenzyme in mammary epithelial cells and was in reasonable agreement with the measured total A-kinase activity. Isoprenaline selectively increased the apparent mean specific catalytic activity of the C-subunit in the particulate fraction.
Clegg
R A
RA
Hannah Research Institute, Ayr, U.K.
Connor
K
K
D000818:Animals; D015153:Blotting, Western; D000242:Cyclic AMP / Q000502:physiology; D003600:Cytosol / Q000201:enzymology; D004848:Epithelium / Q000201:enzymology; D005260:Female; D007545:Isoproterenol / Q000494:pharmacology*; D008321:Mammary Glands, Animal / Q000187:drug effects / Q000201:enzymology*; D009928:Organ Specificity; D011494:Protein Kinases / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012995:Solubility
D000242:Cyclic AMP; D011494:Protein Kinases; D007545:Isoproterenol