Calcium-, calcium/calmodulin-, and calcium/phospholipid-stimulated protein phosphorylation in the rat anterior pituitary.
Calcium-dependent protein phosphorylation may be a critical step in the stimulated secretion of anterior pituitary hormones. We have noted the existence of a number of calcium-calcium/calmodulin-, and calcium/phospholipid-dependent phosphoproteins in the normal rat anterior pituitary. Cell extracts were prepared from anterior pituitary glands of male rats and phosphorylated with [gamma 32P]ATP in the presence or absence of calcium, calmodulin, and phosphatidylserine. The samples were electrophoresed on SDS-PAGE gels, autoradiographs prepared, and phosphate incorporation into specific proteins quantitated with microdensitometry. Calcium alone significantly stimulated the phosphorylation of proteins with molecular weights of 80.0-, 62.0-, 51.0-, 30.5-, and 25.0-kDa. The phosphorylation of 21.5-, 51.0-, and 80.0-kDa MW phosphoproteins was found to be phospholipid dependent. The phosphorylation of 62.0-, 51.0-, 33.0-, 30.5-, and 25.0-kDa MW phosphoproteins was found to be calcium/calmodulin kinase dependent. Calcium/calmodulin also inhibited phosphorylation of the 80.0-kDa phosphoprotein.
Pryor
J C
JC
Department of Psychiatry, Duke University Medical Center, Durham, North Carolina 27710.
Cain
S T
ST
Nemeroff
C B
CB
D000818:Animals; D001345:Autoradiography; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D003720:Densitometry; D004591:Electrophoresis, Polyacrylamide Gel; D066298:In Vitro Techniques; D010743:Phospholipids / Q000494:pharmacology*; D010750:Phosphoproteins / Q000096:biosynthesis*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D013268:Stimulation, Chemical
D002147:Calmodulin; D010743:Phospholipids; D010750:Phosphoproteins; D011493:Protein Kinase C; D002118:Calcium