Important note: Information in this article was accurate in 1995. The state of the art may have changed since the publication date.
Signal transduction complex from 13762 ascites rat mammary tumor cells: molecular cloning of a major protein and phosphorylation studies.
Diss Abstr Int [B]; 54(11):5529 1994. Unique Identifier : AIDSLINE ICDB/95606787 Juang S; Univ. of Miami
Abstract:
MAT-B1 and MAT-C1 sublines of the 13762 rat mammary ascites adenocarcinoma differ in their cell surface morphology, receptor mobility and xenotransplatability. These differences have been ascribed to differences in the structure and stability of the microvilli present on the surfaces of these sublines. The MAT-C1 subline has stable, branched microvilli; the MAT-B1 subline has dynamic, unbranched microvilli. These microvilli differ at the molecular level by the presence of a 58-kD protein (58K) in the MAT-C1 subline, which is absent in the MAT-B1 subline. It has been suggested that the 58K is involved in the membrane-microfilament interaction that provides the stability for the microvilli of MAT-C1 cells. 58K binds phospholipid and microfilaments in a Ca+2-independent manner and is associated with a high M(r) glycoprotein complex containing the (proto)oncogene p185neu and other signal transduction components. By screening a MAT-C1 cDNA library with a degenerate oligonucleotide and 5' RACE method permitted the isolation of overlapping cDNAs encoding the 427 amino acid sequence of the 58K. The predicted amino acid sequence showed a surprising similarity to mammalian retroviral gag proteins and included regions corresponding to p15, p12 and the N-terminal 80% of p30. Interestingly, the 58K also contained two sequence (PPPYPVPTAPP and PPPWAEPFVDP) similar to those found in Src and Abl SH3 domain-binding peptides. The microvilli are greatly enriched in kinase and phosphatase activities as well as their protein substrates. Several in vitro phosphorylated proteins can be identified in the TMC-containing microvillar fraction. Anti-phosphotyrosine immunoblots showed that several proteins were phosphorylated on the tyrosine residues. Phalloidin shift velocity sedimentation analysis of extracted microvilli showed that kinase(s), phosphatase(s) and their substrates are associated with the microfilament core. Microvillar microfilament cores, and various TMC containing preparations showed, by renaturation blot analysis, five prominent autophosphorylating kinases. These results demonstrate that specific kinases are stably associated with the membrane-microfilament interaction sites in the microvilli and suggest a role for the kinases in morphology and/or signal transduction in the tumor cells. (Full text available from University Microfilms International, Ann Arbor, MI, as Order No. AAD94-12940)
Keywords: Animal Cloning, Molecular Gene Products, gag/GENETICS Mammary Neoplasms, Experimental/*GENETICS/METABOLISM Microvilli/METABOLISM Neoplasm Proteins/*GENETICS/METABOLISM Phosphorylation Protein Kinases/METABOLISM Protein-Tyrosine Kinase/METABOLISM Rats *Signal Transduction Tumor Cells, Cultured THESIS 950430
M9541141
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Important note: Information in this article was accurate in 1995. The state of the art may have changed since the publication date.
