M. Jose et al., CHARACTERIZATION OF THE HEPATIC INSULIN-RECEPTOR UNDERGOING INTERNALIZATION THROUGH CLATHRIN-COATED VESICLES AND ENDOSOMES, FEBS letters, 334(3), 1993, pp. 286-288
Administration of insulin to rats caused a transient increase in the a
mount of hepatic insulin receptor present in clathrin-coated vesicles
and endosomes. However, the total 'in vitro' insulin stimulated tyrosi
ne kinase activity of the receptor present in endosomes did not vary w
hen expressed per mg of protein and decreased when expressed per beta-
subunit content. A decrease in the endogenous phospho tyrosine content
of the receptor beta-subunit was observed in endosomes in response to
insulin. This indicates that a fraction of the internalized receptor
is dephosphorylated in endosomes, which renders it unable to become st
imulated by insulin 'in vitro'.