Cell-shape regulation and matrix protein p52 content in phenotypic variants of ras-transformed rat kidney fibroblasts. Functional analysis and biochemical comparison of p52 with proteins implicated in cell-shape determination.
The 52 kDa transformation-sensitive protein p52 was previously identified as a major substrate-associated component of normal rat kidney (NRK) fibroblasts [Higgins & Ryan (1989) Biochem. J. 257, 173-182]. p52 selectively localized to cellular fractions enriched in substrate focal-contact sites and associated ventral undersurface elements. Rapid attachment/spreading of NRK cells on to prepared p52 matrices and inhibition of fibroblast spreading by antibodies to p52 indicated that this protein participates in shape determination or cell-to-substrate adhesion. NRK cells transformed with Kirsten murine sarcoma virus (KiMSV), with a temperature-sensitive mutant (ts-371 KiMSV) and maintained at the permissive temperature, or with the cloned EJrasval.12 oncogene, exhibited down-regulated accumulation of p52 in the ventral undersurface region. Immunochemical, lectin-affinity and electrophoretic analyses indicated that p52 shares considerable sequence similarity with plasminogen-activator inhibitor type-1, which is consistent with its subcellular localization and likely morphoregulatory activity. The marked down-regulation of p52 expression seen in four different ras-mediated transformation systems, its induction prior to butyrate-induced morphological reorganization in KiMSV-transformed cells, and the morphological consequences of exogenously added p52 or p52 antibodies on NRK fibroblasts suggest that this protein probably functions in cell-shape regulation. Abrogation of p52 matrix accumulation typically seen in ras transformants may contribute, therefore, to the aberrant cytoarchitecture characteristic of malignant fibroblasts.
Higgins
P J
PJ
Laboratory of Cell and Molecular Biology, Veterans Administration Medical Center, Albany, NY 12208, U.S.A.
Chaudhari
P
P
Ryan
M P
MP
D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D005347:Fibroblasts / Q000166:cytology; D011905:Genes, ras; D006023:Glycoproteins / Q000032:analysis* / Q000096:biosynthesis; D006801:Humans; D007668:Kidney; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D051381:Rats; D014162:Transfection
D006023:Glycoproteins; D008715:Methionine