Transforming growth factor beta receptor type I (ALK5) (TGF-betaRI (ALK5))

Transforming growth factor beta receptor type I (TGF-betaRI/ALK5) is a serine/threonine kinase cell surface receptor that mediates signaling by TGF-beta cytokines, particularly TGF-beta1, which is the most studied isoform in fibrosis. Upon ligand binding, TGF-betaRI, in complex with TGF-betaRII, phosphorylates intracellular SMAD proteins (SMAD2 and SMAD3), triggering their nuclear translocation and regulation of pro-fibrotic gene expression, including collagen and extracellular matrix proteins. Overactivation of TGF-betaRI signaling drives myofibroblast differentiation, matrix deposition, and organ fibrosis. As such, small-molecule kinase inhibitors and antibodies targeting TGF-betaRI are under development as anti-fibrotic therapies, although the pleiotropic nature of the pathway raises concerns regarding side effects, including effects on immunity, cell growth, and tumor suppression.

Other names

TGF-beta type I receptorActivin receptor-like kinase 5ALK5TGFBR1

Inhibition of TGF-betaRI kinase activity (prevents phosphorylation of SMAD2/3); Blockade of ligand binding (prevents receptor activation); Interference with the TGF-betaRI/II complex assembly or activity; Inhibition of downstream SMAD-dependent and SMAD-independent pro-fibrotic signaling