Fig. 5: GPR81 induces WAT browning through activation of p38.
From: Activation of GPR81 by lactate drives tumour-induced cachexia
a, Heat map showing the differentially phosphorylated proteins and the enriched pathways in the iWAT from WT tumour-free (WT control), WT TB, GPR81 knockout tumour-free (GPR81−/− control) and GPR81−/− tumour-bearing (GPR81−/− TB) mice. b, Result of Kinase–Substrate Enrichment Analysis (KSEA) showing changes in kinase activity in the iWAT of tumour-bearing mice due to GPR81 ablation. Delta counts indicate the number of substrates of each kinase in the iWAT of GPR81−/− TB minus that in the WT TB mice. c, Representative western blots and statistical data showing the levels of phosphorylated (p-p38) and total p38 in the iWAT (n = 6 for each group). d,e, Representative images (d) and statistical data (e) of immunofluorescence signal intensity of p38 (green) and phosphorylated p38 (p-p38; red) in the adipose tissue from patients with or without cancer cachexia (n = 4 for each group). The nuclei were stained with DAPI (blue). Scale bars, 100 μm. f, Representative western blots and statistical data showing the levels of phosphorylated (p-p38), total p38 and UCP1 in the SVF-derived adipocytes treated with sodium l-lactate for the indicated time points (n = 6 biologically independent samples in each group). g, Representative western blots and statistical data showing the lactate-induced activation of p38-ATF2 was abolished in GPR81−/− SVF-derived adipocytes (n = 5 biologically independent samples in each group). h, Knocking down the expression of p38 by specific siRNA abolished the lactate-induced activation of p38-ATF2 and upregulation of UCP1 (n = 5 biologically independent samples in each group). All data are presented as the mean ± s.e.m. P values were determined by one-way ANOVA with Tukey’s multiple-comparisons test (c and f–h) and two-tailed unpaired Student’s t-test (e). In b, KSEA was used to analyze the possible kinases of the differentially phosphorylated peptides and the statistical significance was calculated by hypergeometric test; *p < 0.05, ** p < 0.01.
