This gene encodes a member of the GRB2/Sem5/Drk family and functions as a cytoplasmic signaling protein which contains an SH2 domain flanked by two SH3 domains. The SH2 domain interacts with ligand-activated receptors for stem cell factor and erythropoietin, and facilitates the formation of a stable complex with the BCR-ABL oncoprotein. This protein also associates with the Ras guanine nucleotide exchange factor SOS1 (son of sevenless homolog 1) through its N-terminal SH3 domain. In general, it couples signals from receptor and cytoplasmic tyrosine kinases to the Ras signaling pathway.