A highly phosphorylated subpopulation of insulin-like growth factor II/mannose 6-phosphate receptors is concentrated in a clathrin-enriched plasma membrane fraction.
AUTOR(ES)
Corvera, S
RESUMO
Insulin-like growth factor II (IGF-II)/mannose 6-phosphate (Man-6-P) receptors immunoprecipitated from purified plasma membranes of 32P-labeled rat adipocytes are markedly heterogenous in their phosphorylation state. Approximately 80% of the plasma membrane receptors are solubilized in 1% (vol/vol) Triton X-100 and are phosphorylated on serine residues at a stoichiometry of approximately 0.1-0.2 mol of phosphate per mol of receptor. In contrast, 15-20% of the receptors are Triton X-100-insoluble and are phosphorylated on serine and threonine residues at approximately 4 or 5 mol of phosphate per mol of receptor. This Triton X-100-insoluble membrane subfraction contains only 5% of the total plasma membrane protein and yet contains all of the clathrin heavy chain associated with plasma membrane, as detected by immunoblotting with a monoclonal antibody. Based on the relative yields of protein in the detergent-insoluble material, IGF-II/Man-6-P receptors are concentrated approximately equal to 3-fold in this clathrin-enriched subfraction. Insulin treatment of intact cells increased the total IGF-II/Man-6-P receptors in the Triton X-100-soluble fraction of the plasma membrane, whereas no change in receptor number in the detergent-insoluble fraction was seen. However, insulin markedly decreased the phosphorylation stoichiometry of the Triton X-100-insoluble receptors. Taken together, these results indicate that insulin decreases the phosphorylation state of a highly phosphorylated subpopulation of IGF-II/Man-6-P receptors on the plasma membrane. In addition, insulin action may prevent the concentration of these receptors in a clathrin-enriched membrane subfraction.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=282233Documentos Relacionados
- Conversion of G-protein specificity of insulin-like growth factor II/mannose 6-phosphate receptor by exchanging of a short region with beta-adrenergic receptor.
- Insulin-like growth factor II signaling through the insulin-like growth factor II/mannose-6-phosphate receptor promotes exocytosis in insulin-secreting cells
- Binding of insulin-like growth factor II (IGF-II) by human cation-independent mannose 6-phosphate receptor/IGF-II receptor expressed in receptor-deficient mouse L cells.
- The receptor for insulin-like growth factor II mediates an insulin-like response.
- Translocation between chromosomes 6 and 15 (45,XX,t(6;15)(q25;q11.2)) with further evidence for lack of imprinting of the insulin-like growth factor II/mannose-6-phosphate receptor in humans.