Cell surface receptor for IL3 expressed on hematopoietic progenitor cells, monocytes and B-lymphocytes that controls the production and differentiation of hematopoietic progenitor cells into lineage-restricted cells (PubMed:10527461). Ligand stimulation rapidly induces hetrodimerization with IL3RB, phosphorylation and enzyme activity of effector proteins such as JAK2 and PI3K that play a role in signaling cell proliferation and differentiation. Activation of JAK2 leads to STAT5-mediated transcriptional program (By similarity). {ECO:0000250|UniProtKB:P26952, ECO:0000269|PubMed:10527461, ECO:0000269|PubMed:29374162}. This is the function of ENSG00000185291 (IL3RA, interleukin 3 receptor subunit alpha).