Subcellular localization of G-proteins in primary-cultured mouse preadipocytes and adipocytes

Abstract

The subcellular localization of G5 alpha, Gi alpha 1&2, Gi alpha 3, and G beta was studied in primary-cultured undifferentiated and differentiated, lipid replete, adipose cells. The results show a distinct distribution for each of these G-proteins and differences between differentiated and undifferentiated cells. All the G-proteins examined had a cytoplasmic localization; only Gi alpha 1 and 2 showed a significant colocalization with the plasma membrane and this only in differentiated cells. Most studies using cells in culture have reported an intracellular localization for G-proteins, whereas in tissue sections the localization has been reported to be largely with the plasma membrane, with some intracellular localization. The results suggest that the cell-cell interactions or the specific geometry imposed by culture conditions favor the intracellular compared to peripheral localization of G-proteins. Alternately, the posttranslational modifications necessary for G-protein insertion in the plasma membrane may be deficient in cultured cells.

Transcriptional regulation by the γ5 subunit of a heterotrimeric G protein during adipogenesis

“…Nuclear localization of several Gα (e.g. Gsα, Giα2 and Giα3) and Giβ subunits has been reported (Crouch, 1991; Bégin‐Heick et al ., 1997; Crouch and Simson, 1997). The physiological significance of the nuclear localization of these G protein subunits is not clearly understood.…”

Nuclear and cytoskeletal translocation and localization of heterotrimeric G‐proteins

“…It is well established that certain G‐proteins, namely G i α and G s α, are intimately involved in adipogenesis 52 , 53 . Furthermore, observations have been made that some of these molecules are present in the nucleus of preadipocytes 54 , 55 , 56 . A functional role for nuclear G‐proteins during adipogenesis has been recently elucidated 57 .…”

RGS4 Inhibits G-Protein Signaling in Cardiomyocytes

“…30 To determine the subcellular localization of native RGS4 protein, untransfected cardiomyocytes were probed with purified polyclonal anti-RGS4 antibody followed by secondary antibody (FITC-coupled anti-rabbit immunoglobulin) or with secondary antibody alone (control). Immunofluorescence microscopy revealed that native RGS4 protein was localized to the cytoplasm and plasma membrane ( Figure 1, A and B).…”