Fig. 2.

Transforming growth factor (TGF)-β signaling pathway. TGF-β is a pleiotropic cytokine that mediates fibrosis by inducing fibrogenic target genes. TGF-β is generally secreted as part of a large latent complex bound to latency-associated protein (LAP) and latent-TGF-β-binding protein (LTBP). Latent TGF-β is activated when it dissociates from LAP and LTBP. The active TGF-β binds its receptor to initiate Smad-dependent and independent signaling. Smad-dependent signaling regulates fibrogenic target genes such as α-smooth muscle actin (SMA), collagen, connective tissue growth factor (CTGF), tissue inhibitor of metalloprotease (TIMP-1), and periostin. TGF-β can also induce a number of Smad-independent pathways such as Ras, TGF-β-activated kinase (TAK), RhoA, and phosphatidylinositol-3-kinase (PI3K), thereby adding to its pleiotropic effects. *Protein has been linked to EoE.