Acts as an adapter protein of the FYN and LCP2 signaling cascades in T-cells (By similarity). May play a role in linking T-cell signaling to remodeling of the actin cytoskeleton (PubMed:10747096, PubMed:16980616). Modulates the expression of IL2 (By similarity). Involved in platelet activation (By similarity). Prevents the degradation of SKAP1 and SKAP2 (PubMed:15849195). May be involved in high affinity immunoglobulin epsilon receptor signaling in mast cells (By similarity). {ECO:0000250|UniProtKB:D3ZIE4, ECO:0000250|UniProtKB:O35601, ECO:0000269|PubMed:10747096, ECO:0000269|PubMed:15849195, ECO:0000269|PubMed:16980616}. This is the function of FYB1 (FYN binding protein 1, ENSG00000082074).