Member of the G protein alpha subunit family that plays a crucial role in intracellular signaling. Functions as a molecular switch, transducing signals from G protein-coupled receptors (GPCRs) to downstream effectors. In collaboration with the adapter protein TTC1, promotes HRAS activation and ERK1/2 phosphorylation independently of phospholipase Cbeta signaling (PubMed:12748287, PubMed:20639119). Also initiates EMR2-mediated signaling, leading to activation of Akt, MAPK, and NF-kappa-B, which in turn drives macrophage differentiation and inflammatory responses (PubMed:28421075). {ECO:0000269|PubMed:12748287, ECO:0000269|PubMed:20639119, ECO:0000269|PubMed:28421075}. This is the function of ENSG00000060558 (GNA15, G protein subunit alpha 15).