The decrease in the short variant of Gsα protein is associated with an increase in [3H]CGP12177 binding, [3H]ouabain binding and Na,K-ATPase activity in brown adipose tissue plasma membranes of cold-acclimated hamsters

Sucrose density gradient purified plasma membranes isolated from brown adipose tissue of cold-acclimated hamsters (4-10 weeks at 0-4 degrees C) were analysed for the content of the short (G(s)alpha S) and long (G(s)alpha L) variants of G(s)alpha protein (the a subunit of the stimulatory G protein) and compared with the membranes isolated from control animals. The relative ratio between the two variants (G(s)alpha S/G(s)alpha L) decreased from 0.48 to 0.24 (P<0.01). This result, obtained by electrophoretic resolution of membrane proteins by standard SDS-PAGE and an immunoblot analysis with an antiserum oriented against an internal sequence of G(s)alpha, was verified by resolution on urea-containing gels and an antiserum oriented against the C-terminus decapeptide of G(s)alpha. Under these conditions, the G(s)alpha S/G(s)alpha L ratio was decreased from 0.41 to 0.31 (P<0.05). The total amount of both isoforms (G(s)alpha S plus G(s)alpha L) decreased to 83% (P<0.05) or 68% (P<0.01) by standard or urea SDS-PAGE respectively. These data demonstrate that cold-acclimation of hamster brown adipose tissue is associated with preferential decrease in the plasma membrane density of the short variant of the G(s)alpha protein. This decrease was paralleled by an increase in the other plasma membrane constituents, [H-3]CGP12177 binding sites, [H-3]ouabain binding sites and Na,K-ATPase activity to 147%, 212% and 191% respectively.