Effect of protein kinase C on the plasma membrane calcium pump in purified beta cells.
The effect of protein kinase C activation on (Ca(2+)-Mg2+)-ATPase and 45Ca2+ uptake in purified plasma membranes and membrane vesicles from beta cells was examined. PKC activation was achieved by incubating cells for 10 or 30 min in 100 nM or 1 microM of the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) and evident by translocation of the alpha-isoform from the cytosolic to the membrane fraction. (Ca(2+)-Mg2+)-ATPase had a Km for Ca2+ of 0.56 +/- 0.17 microM and the Vmax was 120 +/- 12 nmol/min*mg protein in membranes from cells treated with TPA, while it was 0.66 +/- 0.14 microM and 135 +/- 19 nmol/min*mg protein, respectively, in its absence. In inside-out vesicles 45Ca2+ uptake had a Km for Ca2+ of 79 +/- 19 nM and a Vmax of 1.68 +/- 0.43 nmol/min*mg protein in the presence of TPA. In the absence of TPA, the Km was 71 +/- 17 nM, and the Vmax was 1.59 +/- 0.39 nmol/min*mg protein, respectively. It is concluded that in beta cells PKC activation does not regulate (Ca(2+)-Mg2+)-ATPase activity or Ca2+ transport directly.
Hoenig
M
M
Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens 30602.
Knutson
K L
KL
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002132:Calcium Radioisotopes; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats
D002132:Calcium Radioisotopes; D011493:Protein Kinase C; D000252:Calcium-Transporting ATPases