Manganese modulates protein phosphorylation in the rat pancreas: in vitro evidence for cation selective regulation.
The effects of manganese (Mn2+) on phosphorylation activity in the rat pancreas were examined in an in vitro phosphorylation assay and by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of endogenous proteins. Several histones were phosphorylated in the presence of pancreatic supernatant obtained following a 10-min centrifugation at 15,000 g. The histone preference for this reaction was VII-S greater than V-S or II-S greater than III-S greater than other histones. The Mn2+ (10 mM) enhanced the phosphorylation of some histones (II-A, III-S, VI-S, and VIII-S) but inhibited the phosphorylation of other histones (II-S, V-S, and VII-S). The same concentration of Mn2+ also enhanced the incorporation of 32P into cytosolic proteins in the absence of exogenous histones. This effect was not mimicked by Ca2+, Mg2+, Ba2+, or Zn2+. Analysis of endogenous proteins by SDS-PAGE revealed Mn2(+)-dependent and time-dependent phosphorylation of high (98-200-kDa), intermediate (59-,52-,35-, and 30-kDa), and low-molecular weight proteins. The Mn2+ exerted similar effects in the presence of pancreatic cytosol obtained following a 60-min centrifugation at 100,000 g. However, the 35- and 30-kDa phosphoproteins and the low-molecular weight proteins were not readily visible. In both the 15,000- and the 100,000-g preparations, there was a dose-dependent increase in the phosphorylation of the Mr 98-kDa protein (p98) at concentrations ranging from 0.03 to 1.0 mM Mn2+ but a lesser stimulatory effect at 10.0 mM Mn2+.(ABSTRACT TRUNCATED AT 250 WORDS)
Brockenbrough
J S
JS
Department of Medicine, University of California, Irvine 92717.
Korc
M
M
D000818:Animals; D002413:Cations, Divalent; D003600:Cytosol / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D006657:Histones / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008345:Manganese / Q000494:pharmacology*; D008970:Molecular Weight; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D002413:Cations, Divalent; D006657:Histones; D010750:Phosphoproteins; D008345:Manganese; D011494:Protein Kinases