Protein phosphorylation constitutes the major mechanism by which extracellular hormones and growth factors modulate intracellular events.
The aims of this application comprise studies to pursue the regulation and function of a newly recognized phospholipid-, diolein-dependent protein phosphorylation activity which is independent of Ca2+ and is prominent in a number of estrogen-responsive tissues including rabbit and rat corpora lutea (CL), rabbit endometrium, and human breast cancer MCF-7 cells. In rabbit CL, a Mr=76,000 protein (p76) is phosphorylated by this kinase, and phosphorylation of p76 is increased by estradiol. Phosphorylation of p76 represents autophosphorylation by this kinase. We have named the phospholipid-, diolein-dependent, Ca2+-independent kinase which is autophosphorylated and exhibits a Mr=76,000 in rabbit CL p76 C-kinase. We propose to evaluate p76 C-kinase, determining its biochemical properties, its subcellular localization, its hormonal regulation, and its amino acid sequence.
Specific aims are: (1) To purify and characterize biochemically p76 C-kinase; (2) To determine the amino acid sequence of p76 C-kinase by isolating the cDNA encoding this protein from a rabbit luteal cDNA library and sequencing it and to produce antibodies to a unique peptide fragment of p76 C-kinase; (3) To identify structural features of p76 C-kinase, based on its amino acid sequence, that are important for its regulation; (4) To evaluate the subcellular distribution of p76 C-kinase and to determine if in vivo hormone administration promotes redistribution of p76 C-kinase; and (5) To evaluate the hormonal/growth factor regulation of p76 C-kinase activity, protein and mRNA in vivo and in vitro.
