Figure 5.

TGF-β1 potentiates Cdk5-mediated phosphorylation of TRPV1, resulting in increased intracellular Ca²⁺ influx in MDPC-23 cells. MDPC-23 cells stably transfected with rat TRPV1 were treated with ascending concentrations of TGF-β1 (0.1, 0.3, 1, and 3 ng/ml), with or without SB431542 (10 μM) or roscovitine (25 μM) over 24 h. We then examined both proton- and capsaicin-induced calcium influx in these cells. Ca²⁺ influx was stimulated with a pH 5.6 buffer (A) or with 100 nM capsaicin (B). The total influx of calcium under both conditions increased significantly following TGF-β1 treatment. In contrast, co-treatment with SB431542 or roscovitine produced a significant decrease in calcium influx caused by the low pH buffer or by capsaicin. All data are presented as the mean and SEM (n = 3). a: p < 0.05 TGF-β1 vs. TGF-β1 plus SB431542 treatment; and b: p < 0.05 TGF-β1 vs. TGF-β1 plus roscovitine treatment (t-Test). ns: not significant.