Figure 4

Inhibitory effect of SOCS1 and SOCS3 on reporter gene induction by LEPRb point mutants. HepG2 cells were transfected with pGL3α₂M-215Luc and vectors for the indicated LEPRb point mutants along with varying amounts of expression plasmids for SOCS3 or SOCS1. Cells were treated with leptin (100 ng/ml) for 16 h before luciferase activities were determined and normalized to β-galactosidase. A, Reporter gene activities for the different LEPRb constructs in the absence of co-transfected pEF-SOCS expression plasmids (means ± S.D. from 6 experiments). The difference between FYY and FFY is statistically significant (Student's t-test, P < 0.01). B and C, The graphs present the normalized luciferase activities relative to those of cells expressing no exogenous SOCS protein (means ± S.D. from 3 experiments). The differential response of FYY and FFY to the highest expression level of SOCS3 was statistically significant. The difference of the response of WT and FYY to SOCS1 was significant at all expression levels (Welch's t-test, P < 0.05).