Small molecules are believed to move directly between the cytoplasms of adjacent cells by means of gap junctions, cell-cell specializations that are distributed widely in multicellular organisms. A model for intercellular communication has been developed as a result of these observations. The model stresses the importance of junctional communication in matters of cell growth and differentiation. However, specific probes have not been available for experimentally evaluating this model and addressing other questions of junctional organization, formation, and function. This project focuses on the production of antibodies specific for the proteins of lens gap junctions. It attempts to take advantage of monoclonal antibodies and chick embryo lens cultures developed in this laboratory. One aspect is designed to provide information on the protein composition of the junctions, rates of synthesis and turnover, and the nature and extent of junctional precursors. Our electron microscope studies have now localized MP26 within lens junctions, using a monoclonal antibody. Functional studies address a correlation of permeability with levels of junctional antigens and structures, as well as a possible regulation of junctional permeability. We are just beginning to inject junctional antibodies into cells. These studies will be important in examining the role of lens gap junctions as communicating junctions. Because we can study lens junction formation in culture, we have been able to investigate the formation of junctions between lens cells and either chick embryo heart cells or Novikoff hepatoma cells. These data are helpful as we evaluate the hypothesis that a family of junctional proteins exists. Other important experiments relate to blocking the development of gap junctions between cells. We are selecting antibodies directed against antigenic sites on the outer or external surface of the membrane, with good candidates now being studied in detail. Our studies include the impact of altered junction formation on dye movement between cells and the differentiation of lens cells in vitro. (A)
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