FIG. 3.

Increased SOCS-1 or SOCS-3 inhibits tyrosine phosphorylation of IRS proteins and downstream signaling in liver. (a) Comparable expression of SOCS-1 and SOCS-3 introduced by adenovirus injection to those induced by LPS treatment. The panels show representative results of RT-PCR using RNA from liver with the indicated treatment. (b) Liver contents of SOCS-1 and SOCS-3. The immunoprecipitates (IP) with αSOCS-1, αSOCS-3, or αFLAG from liver lysates were immunoblotted (IB) with the same antibody. (c) Tyrosine phosphorylation of IRS-1, IRS-2, and IR. The immunoprecipitates with αIRS-1, αIRS-2, or αIR antibodies from liver lysates with or without insulin stimulation were immunoblotted with αPY (top) or the same antibody (middle). (d) Insulin-induced PI 3-kinase activity. p85 subunit of PI 3-kinase bound to tyrosine-phosphorylated proteins (top) and PI 3-kinase activity (middle) were estimated by using the immunoprecipitates with αIRS-1, αIRS-2, or αPY from liver lysates with or without insulin stimulation. The top and middle panels show representative results; in the bottom panels each bar represents the means ± standard errors (n = 3). *, P < 0.05 for LacZ versus SOCS-1; **, P < 0.05 for LacZ versus SOCS-3 adenovirus treatment.