Insulin-like growth factor I receptor beta-subunit heterogeneity. Evidence for hybrid tetramers composed of insulin-like growth factor I and insulin receptor heterodimers.

摘要: Abstract In both NIH3T3 cells and HepG2 cells, insulin-like growth factor I (IGF-I) receptors possess two beta-subunits that display different electrophoretic mobilities. Increasing concentrations of IGF-I stimulated the phosphorylation to a similar extent, whereas insulin subunits only at elevated concentrations. Both were immunoprecipitated with p5, an receptor-specific anti-peptide antibody, or A410, polyclonal anti-insulin receptor antisera. However, if tetrameric was first dissociated into alpha-beta heterodimers 1 mM dithiothreitol, lower molecular weight beta-subunit immunoprecipitated. These results suggested p5 A410 specifically recognized but higher because it present in same disulfide linked tetramer. Similarly, alpha-IR-3, antibody specific for alpha-subunit receptor, types from intact tetramer heterodimers, suggesting there are alpha-subunits by alpha-IR-3 is associated beta-subunit. Tryptic phosphopeptide maps beta-subunit, those Thus, immunochemical cross-reactivity structural criteria, receptor. data suggest exists species hybrid composed heterodimer heterodimer. The existence such could have important functional consequences.