Role of gap-junctional communication in cell proliferation and adipocyte conversion

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Gap junctional intercellular communication is considered to play an important role in the control of cell proliferation and cell differentiation, and the exact mechanism of its control was investigated. Growth Stimulation by the serum transiently suppressed the gap-junctional communication and then enhanced DNA synthesis in 3t3-L1 cells. Pretreatment of quiescent cells with 12-O-tetradecanoylphorbol-13-acetate (TPA) suppressed the gap-junctional communication and enhanced serum-induced DNA synthesis. Pretreatment with dibutyryl cyclic AMP (cAMP) stimulated the cell communication and suppressed serum-induced DNA synthesis. The addition of the serum induced adipocyte conversion from 3T3-L1 cells. TPA inhibited adipocyte conversion and cAMP enhanced adipocyte conversion. Substances exchanged through gap junctions were investigated by fractionating the cell homoginates. Calcium ions are candidates for small substances permeable through gap junction.s Growth stimulation also induced the increase in the intracellular concentration of calcium ions. Treatment with TPA also enhanced the increase in calcium ions and cAMP suppressed it. In this project, the gap-junctional communication is suggested to be involved in the control of cell proliferation and cell differentiation.