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Phosphorylation of chloroform soluble compounds in plasma membranes of human epidermoid carcinoma A431 cells
Author(s) -
Brautigan David L.,
Randazzo Paul,
Shriner Carol,
Fain John N.
Publication year - 1985
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02534242
Subject(s) - a431 cells , phosphoserine , phosphatidic acid , epidermoid carcinoma , phosphatidylinositol , epidermal growth factor , phosphorylation , biochemistry , chemistry , membrane , biology , phospholipid , receptor , serine , carcinoma , genetics , molecular medicine , cell cycle , cell
This study investigated a possible role for the epidermal growth factor (EGF) receptor protein tyrosine kinase in phosphoinositide metabolism with plasma membrane vesicles from human epidermoid carcinoma (A431) cells. We found a novel chloroform‐soluble product radiolabeled with [gamma‐ 32 P] ATP that did not migrate from the origin in the thin layer system designed to separate the phosphoinositides, appeared as a single band of M r =3500 on polyacrylamide gels in the presence of dodecyl sulfate, had an ultraviolet absorbance spectrum with a maximum at 275 nm and stained with Coomassie dye. Based on these properties this phosphorylation product is referred to as a proteolipid. The 32 P label was not detected in phosphotyrosine [Tyr(P)], phosphoserine [Ser(P)] or phosphothreonine [Thr(P)] and was lost during acid or base hydrolysis. Phosphorylation of proteolipid was increased significantly by EGF, whereas phosphorylation of phosphatidic acid was decreased and labeling of phosphoinositides was unaffected. Thus, it appears that in A431 membranes the EGF receptor/ kinase does not utilize phosphatidylinositol as a substrate, but does phosphorylate a membrane proteolipid.