Protein TMEPAI (PMEPA1)

Functions as a negative regulator of TGF-beta signaling and thereby likely plays a role in cell proliferation, differentiation, apoptosis, motility, extracellular matrix production and immunosuppression. In the canonical TGF-beta pathway, ZFYVE9/SARA recruits the intracellular signal transducer and transcriptional modulators SMAD2 and SMAD3 into the TGF-beta receptor.

Phosphorylated by the receptor, SMAD2 and SMAD3 then form a heteromeric complex with SMAD4 which translocates into the nucleus to regulate transcription. Through discussion with SMAD2 and SMAD3, LDLRAD4 may compete with ZFYVE9 and SMAD4 and prevent propagation of the intracellular signal (PubMed:20129061, PubMed:24627487).