Differentiation of cultured brown adipocytes is associated with a selective increase in the short variant of Gsα protein.: Evidence for higher functional activity of GsαS

In order to examine whether the differentiation process in brown adipocytes cultivated in primary culture is associated with substantial alterations in the complement of G proteins, the levels of these proteins were investigated with immuno-electrophoretic techniques in membrane preparations from proliferating and differentiated cultured mouse brown adipocytes. We observed that differentiation was associated with a dramatic (more than threefold) increase in the short variant of G(s)alpha protein (G(s)alpha S). The long variant of G(s alpha) (G(s)alpha L), as well as G(i)1 alpha, G(i)2 alpha, G(9)alpha, G(11)alpha and C beta subunit proteins remained unchanged whereas G(i)3 alpha protein was decreased. These changes were accompanied by marked increase in isoprenaline-, forskolin- as well as manganese-stimulated adenylyl cyclase. Thus, the marked increase in beta-adrenergic responsiveness of fully differentiated confluent brown adipocytes (day -9), as compared with that of proliferating undifferentiated cells of 'fibroblast phenotype' (day 3-4), is associated with a significant increase in the relative proportion between the short and long variants of G(s)alpha (the G(s)alpha S/G(s)alpha L ratio) along with a decrease in G(i)3 alpha protein. These data also suggest that the short variant of G(s)alpha exhibits higher functional activity than the long variant of this G protein. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.