Elevated membrane association of phospholipase C-gamma 1 in MDA-468 mammary tumor cells.
We have examined the distribution of phospholipase C-gamma 1 (PLC-gamma 1) between membrane and cytosolic fractions in several cell lines. In MDA-468 cells, which are derived from a human breast tumor, greater than one-half of the total PLC-gamma 1 is associated with the membrane fraction of the cell. Unlike the situation in A-431 cells [G. Todderud, M. I. Wahl, S. G. Ree, and G. Carpenter, Science, 248: 296-298, 1990], epidermal growth factor (EGF) stimulation of MDA-468 cells does not result in significantly increased PLC-gamma 1 association with membranes. Immunoblot analysis reveals low levels of phosphotyrosine in PLC-gamma 1 and EGF receptors in unstimulated MDA-468 cells and greatly increased phosphotyrosine levels in these proteins as a result of EGF stimulation of the cells. We conclude that autocrine activation of EGF receptors is not responsible for the elevated association of PLC-gamma 1 with membranes in these cells.
Soderquist
A M
AM
Department of Biochemistry, Vanderbilt University of School of Medicine, Nashville 37232-0146.
Todderud
G
G
Carpenter
G
G
D000818:Animals; D002462:Cell Membrane / Q000737:chemistry*; D003600:Cytosol / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D004815:Epidermal Growth Factor / Q000494:pharmacology; D066246:ErbB Receptors / Q000032:analysis* / Q000378:metabolism; D007527:Isoenzymes / Q000032:analysis* / Q000378:metabolism; D008325:Mammary Neoplasms, Experimental / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000032:analysis* / Q000378:metabolism
D007527:Isoenzymes; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D010738:Type C Phospholipases