Analysis Of Cell Surface Proteins Research Articles

Electrophoretic analysis of cell surface proteins of preimplantation mouse embryos

Cell surface proteins expressed during mouse preimplantation development have been labeled by lactoperoxidase-catalyzed iodination and analyzed by SDS-polyacrylamide gel electrophoresis. Results reveal that embryonic surface proteins are labeled at all stages tested and that the major qualitative changes in surface protein composition occur following fertilization and coincident with blastocyst formation.

Immunoselection of mutants deficient in cell surface glycoproteins encoded by murine erythroleukemia viruses.

We have described a heterogeneously processed glycoprotein with an apparent molecular weight of 55,000 (gp55) that is encoded by the Friend spleen focus-forming virus, an acute erythroleukemia virus [Dresler, S., Ruta, M., Murray, M.J. & Kabat, D. (1976) J. Virol. 30, 564-573]. Several lines of evidence suggest that a small proportion of the gp55 in infected cells is located on the surface membranes. First, different nonproducer cell lines infected with cloned Friend spleen focus-forming virus were efficiently killed in the presence of complement by cytotoxic antisera that react with gp55. Furthermore, a clone of cells selected for resistance to the cytotoxic antibody synthesized an altered intracellular form of gp55. This immunoselection procedure appears to also be useful for isolating glycoprotein mutants of other RNA tumor viruses. Analysis of cell surface proteins labeled with [125I]iodine supported the idea that gp55 occurs on the plasma membranes. However, the cell surface gp55 had more highly processed oligosaccharides than the majority of the gp55, which occurs within the infected cells. In addition, we have found that leukemia cells from mice infected with the erythroleukemic Rauscher virus complex contain a membrane glycoprotein that appears similar to the gp55 encoded by Friend spleen focus-forming virus. The encoding of similar glycoproteins by independently isolated acute erythroleukemia viruses suggests that these glycoproteins may be important in leukemogenesis.

Characterization of the action of retinoids on mouse fibroblast cell lines

Retinoic acid affects 3T6 and 3T3 cells by inhibiting growth, causing a morphological change and increasing cell-to-substratum adhesiveness. Retinoic acid does not exert such effects on virus-transformed 3T3SV cells. Retinoic acid treatment of 3T6 cells causes a concentration-dependent increase in generation time and a reduction in saturation density. Analysis of cell surface proteins shows that a high molecular weight band of 230 000 D, corresponding to the position of the LETS glycoprotein, is more intensely labeled by iodination of cells treated with retinoic acid compared to control cells. Retinoic acid substantially stimulates the incorporation of 35SO 4 into cell-associated glycosaminoglycans and causes a less dramatic increase in glycosaminoglycans excreted into the medium. The relationship between the increase in these cell surface components and the enhanced adhesiveness is discussed. A retinoic acid binding protein is detectable in the cytosol of 3T6 and 3T3 cells but not in 3T3SV cells, suggesting that the action of retinoids on these cells is mediated via this protein.