Calcium-, calcium/calmodulin-, and calcium/phospholipid-stimulated protein phosphorylation in the rat anterior pituitary

✍ Scribed by Dr. James C. Pryor; Scott T. Cain; Charles B. Nemeroff

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 705 KB
• Volume: 11
• Category: Article
• ISSN: 0887-4476
• DOI: 10.1002/syn.890110207

✦ Synopsis

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-calciudcalmodulin-, and calciudphospholipid-dependent phosphoproteins in the normal rat anterior pituitary. Cell extracts were prepared from anterior pituitary glands of male rats and phosphorylated with [y3'P]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 calciudcalmodulin kinase dependent. Calciudcalmodulin also inhibited phosphorylation of the 80.0-kDa phosphoprotein. 61 1992 Wiley-Liss, Inc.