This gene encodes a protein that binds to transforming growth factor-beta (TGF-beta) receptors and plays a role in TGF-beta signaling. The encoded protein acts as a chaprone in signaling downstream of TGF-beta. It is involved in signal-dependent association with SMAD4. The protein is also a component of mammalian CORVET, a multisubunit tethering protein complex that is involved in fusion of early endosomes.