Figure 4: A cell non-autonomous action of KSR2 is required for GH signaling in the liver.

(a) Hepatic STAT5b and JAK2 phosphorylation in PN17 WT and ksr2^−/− mice 15 min after IP injection of PBS or 125 μg/kg recombinant human GH. Liver tissue was lysed and analyzed via western blot with the indicated antibodies. The ratio of phosphorylation to total STAT5 and JAK2 was analyzed by LI-COR Odyssey system (n = 4–5 per group). Quantification is shown to the right of the western blot. (b) STAT5 target genes ALS, MUP3, and MUP1/2/6/8 were measured in livers from PN17 WT and ksr2^−/− mice (n = 4–6 per group). WT levels were set to 1. *p < 0.05, **p < 0.01. (c) qPCR of SOCS1-3 and CIS mRNAs from WT and ksr2^−/− liver (n = 6–8 per group). For comparison, levels of WT were set to 1 and rps18 was used as an internal control. (d) Muscle STAT5b phosphorylation in PN17 WT and ksr2^−/− mice treated as in panel a. (e) IGF-1 mRNA levels from kidney, heart, and muscle of PN17 WT and ksr2^−/− mice (n = 3–4 per group). IGF-1 levels of WT were set to 1, and 18srRNA was used as an internal control. (f) STAT5 phosphorylation in primary hepatocytes from PN17 WT and ksr2^−/− liver treated for 5 min with 100 ng/ml GH. Results are representative of three independent experiments. Data are shown as mean ± SEM. *p < 0.05, **p < 0.01.