Fig. 6

Irisin antagonizes TGF-β1 via interfering TGFBR 1 activation in primary tubule cell cultures. a TGF-β1 Signaling Phosphoproteome array in tubule cells (TGF-β1 vs. TGF-β1 plus irisin). Data showing the fold change of enhanced phosphoproteins (red) and suppressed phosphoproteins (blue). b Irisin enhanced ERK/p38 signaling but suppressed Smads signaling upon TGF-β1 stimulation. c Representative western blots (from three independent experiments) confirmed that irisin suppressed Smad2/3 phosphorylation (left panel) while stimulated ERK and p38 phosphorylation. d Representative western blots revealing irisin-induced ERK1/2 phosphorylation was eliminated in DR 26 (TGFBR2 mutant) but not in R1B cell (TGFBR1 mutant). Results were repeated in three independent experiments. e In primary cultured tubule cell, fluorescein labeled irisin (green) bound to cell membrane that was co-localized with TGFBR2 (red). f Representative western blot showing irisin dose-dependently suppressing TGF-β1-induced Smad2/3 phosphorylation. Results were repeated in 3 independent experiments. g In tubule cells, overexpression of TGFBR2 blunted the inhibitory effect of irisin on Smad2/3 phosphorylation (representative western blot from three independent experiments). h A possible working model exhibiting how irisin compete TGF-β1 binding with TGFBR2