ACVR1B
[5][6] ACVR1B or ALK-4 acts as a transducer of activin or activin-like ligands (e.g., inhibin) signals.[7] ACVR1B also transduces signals of nodal, GDF-1, and Vg1; however, unlike activin, they require other coreceptor molecules such as the protein Cripto.Activins signal through a heteromeric complex of receptor serine kinases which include at least two type I (I and IB) and two type II (II and IIB) receptors.This gene encodes activin A type IB receptor, composed of 11 exons.The mRNA expression of variants 1, 2, and 3 is confirmed, and a potential fourth variant contains an alternative exon 8 and lacks exons 9 through 11, but its mRNA expression has not been confirmed.