Fig. 3.

Phospholemman and the Na pump in cardiomyocyte caveolae. A, The sodium pump catalytic subunit was immunoprecipitated from ventricular homogenates from PLM WT and KO hearts, and copurifying proteins immunoblotted as shown. In the absence of PLM, substantially less caveolin 3 copurifies with the pump (n = 5 hearts per group, mean ± S.E. shown). B, Copurification of transfected caveolin 3 with endogenous pump α1 subunit in FT-293 cells is enhanced when PLM-YFP expression is induced. PLM and caveolin 3 are marked with an arrow, resolved from the immunoprecipitating antibody that cross-reacts with the secondary antibody. C, Position of the Na pump α subunit CBM (red) relative to the associated PLM (green) in the Na pump crystal structure (α subunit shown in blue, β subunit in magenta). D, Sucrose density gradient fractionation of PLM WT and KO ventricular homogenates reveals no difference in the distribution of sodium pump α1 or α2 subunit to buoyant (4, 5) or dense (8–12) membranes in the absence of PLM.