Differential sensitivity to guanine nucleotides of basal and insulin-stimulated glucose transporter activity reconstituted from adipocyte membrane fractions

Abstract

The effects of GTP gamma S on glucose transport activity reconstituted from adipocyte membrane fractions were studied in order to test the hypothesis that intrinsic activity changes of the insulin-sensitive glucose transporter may be mediated by guanine nucleotide-dependent mechanisms. GTP gamma S and GTP inhibited reconstituted glucose transport activity by 50% in membrane fractions from insulin-treated cells in a concentration-dependent manner; no inhibitory effect was observed in membrane fractions obtained from basal cells. GDP, GMP and guanosine were less effective than GTP, whereas the adenine nucleotides ATP gamma S and AMP failed to reduce the reconstituted transport activity. The data indicate that guanine nucleotides may modulate the activity of the adipocyte glucose transporter. Since the effect is dependent on treatment of cells with insulin, the hormone appears to induce a specific functional alteration of the glucose transporter.