COMPARISON OF THE SUBCELLULAR-DISTRIBUTION OF G-PROTEINS IN HEPATOCYTES IN-SITU AND IN PRIMARY CULTURES

The subcellular localization of the heterotrimeric C-proteins in hepat ocytes in situ was compared to that in hepatocytes in primary culture. The ability of various ligands to activate adenylyl cyclase (AC) in m embrane preparations was also investigated. In hepatocytes in situ the C proteins were mainly localized at the plasma membrane while in hepa tocytes in culture they were predominantly cytoplasmic. The localizati on of the C-proteins in hepatocytes in situ correlates with their role in signal transduction. In homogenates prepared from the cultured cel ls, ligands which stimulate AC via G(s) alpha were without effect, whi ch was consistent with the localization of G(s) alpha in the cytoplasm ic and nuclear compartments. The ''relocalization'' of the G proteins to the cytoplasm when cells are cultured suggests that transmembrane s ignalling may be regulated by cell differentiation and cell-cell and c ell-extracellular matrix interactions. (C) 1996 Wiley-Liss, Inc.