Transformed 3T3 cells have reduced levels and altered subcellular distribution of the major PKC substrate protein MARCKS.
The MARCKS (myristylated alanine-rich C-kinase substrate) protein is an abundant calmodulin-binding protein that is a major and specific endogenous substrate of protein kinase C (PKC). Stimulation of cells with phorbol esters or other activators of PKC has been shown previously to result in rapid phosphorylation of MARCKS proteins and redistribution of these myristylated C-kinase substrates from membrane to cytosol. Here we show that NIH3T3 murine fibroblasts transformed by p21-HA-C-RAS or pp60-V-SRC oncoproteins have markedly reduced levels of p68-MARCKS and that most of the remaining MARCKS protein is found in the cytosol. 3T3 cells containing a nontransforming oncoprotein p26-BCL2, in contrast, exhibited normal levels and distribution of p68-MARCKS. When taken together with recent evidence that MARCKS proteins are involved in regulating organization of the membrane cytoskeleton, our findings suggest that oncoprotein-mediated alterations in MARCKS protein levels and subcellular distribution may contribute to the development or maintenance of the transformed phenotype.
Reed
J C
JC
University of Pennsylvania School of Medicine, Department of Pathology and Laboratory Medicine, Philadelphia 19104.
Rapp
U
U
Cuddy
M P
MP
D016475:3T3 Cells; D000818:Animals; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051379:Mice; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D015689:Oncogene Protein p21(ras) / Q000378:metabolism; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism; D015513:Oncogene Proteins / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D014162:Transfection
D047908:Intracellular Signaling Peptides and Proteins; C000619711:Marcks protein, mouse; C000619712:Marcks protein, rat; D008565:Membrane Proteins; D015513:Oncogene Proteins; D011506:Proteins; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D015688:Oncogene Protein pp60(v-src); D011493:Protein Kinase C; D015689:Oncogene Protein p21(ras)