Enables SH3 domain binding activity. Involved in Ras protein signal transduction; neurotrophin TRK receptor signaling pathway; and positive regulation of signal transduction. Located in neuronal cell body; plasma membrane; and postsynaptic density. Human ortholog(s) of this gene implicated in Noonan syndrome; Noonan syndrome 4; and gingival fibromatosis. Orthologous to human SOS1 (SOS Ras/Rac guanine nucleotide exchange factor 1). [provided by Alliance of Genome Resources, Apr 2022]