Serine/threonine protein kinase which forms a receptor complex on ligand binding. The receptor complex consists of 2 type II and 2 type I transmembrane serine/threonine kinases. Type II receptors phosphorylate and activate type I receptors which autophosphorylate, then bind and activate SMAD transcriptional regulators, SMAD2 and SMAD3. Receptor for activin AB, activin B, activin E and NODAL. Upon NODAL binding, activation results in increased apoptosis and reduced proliferation through suppression of AKT signaling and the activation of Smad2-dependent signaling pathway in pancreatic beta-cells, trophoblasts, epithelial or neuronal cells (PubMed:15531507, PubMed:15150278). Acts as a positive regulator for macrophage activation partially through down-regulation of PPARG expression (By similarity). {ECO:0000250|UniProtKB:P70539, ECO:0000250|UniProtKB:Q8K348, ECO:0000269|PubMed:12063393, ECO:0000269|PubMed:15150278, ECO:0000269|PubMed:15531507}. This is the function of ACVR1C (activin A receptor type 1C, ENSG00000123612).