Vascular types I and II transforming growth factor‐beta receptor expression: differential dependency on tyrosine kinases during induction by TGF‐β

Abstract
Recent evidence indicates that the type II transforming growth factor‐β (TGF‐β) receptor (TβRII) is a serine‐threonine‐tyrosine kinase. However, the significance of its tyrosine kinase is unclear. We investigated in vascular smooth muscle cells the effects of tyrosine kinase inhibition on the expression of TGF‐β receptor types I (ALK‐5) and II (TβRII) mRNA, induced by TGF‐β 1. TGF‐β 1 elevated ALK‐5 mRNA levels 5‐fold; essentially similar TGF‐β 1‐dependent elevations were observed with growth factors, PDGF‐BB and FGF‐2. The tyrosine kinase inhibitor genistein abolished these TGF‐β 1 and growth factor responses. TGF‐β 1 also elevated TβRII mRNA levels which were not inhibited by genistein. We conclude that tyrosine kinases participate in defining how cells respond to TGF‐β.