Adapter protein for several members of the tyrosine kinase receptor family. Involved in multiple signaling pathways mediated by Janus kinase (JAK) and receptor tyrosine kinases, including the receptors of insulin (INS), insulin-like growth factor I (IGF1), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), platelet-derived growth factor (PDGF) and fibroblast growth factors (FGFs). In growth hormone (GH) signaling, autophosphorylated ('Tyr-813') JAK2 recruits SH2B1, which in turn is phosphorylated by JAK2 on tyrosine residues. These phosphotyrosines form potential binding sites for other signaling proteins. GH also promotes serine/threonine phosphorylation of SH2B1 and these phosphorylated residues may serve to recruit other proteins to the GHR-JAK2-SH2B1 complexes, such as RAC1. In leptin (LEP) signaling, binds to and potentiates the activation of JAK2 by globally enhancing downstream pathways. In response to leptin, binds simultaneously to both, JAK2 and IRS1 or IRS2, thus mediating formation of a complex of JAK2, SH2B1 and IRS1 or IRS2. Mediates tyrosine phosphorylation of IRS1 and IRS2, resulting in activation of the PI 3-kinase pathway. Acts as positive regulator of NGF-mediated activation of the Akt/Forkhead pathway; prolongs NGF-induced phosphorylation of AKT1 on 'Ser-473' and AKT1 enzymatic activity. Enhances the kinase activity of the cytokine receptor-associated tyrosine kinase JAK2 and of other receptor tyrosine kinases, such as FGFR3 and NTRK1. For JAK2, the mechanism seems to involve dimerization of both, SH2B1 and JAK2. Enhances RET phosphorylation and kinase activity. Isoforms seem to be differentially involved in IGF-I and PDGF-induced mitogenesis (By similarity). Self-associates. Homopentamer. Forms a heteromultimeric complex with SH2B2. Interacts with SH2B2. Isoform 1 interacts via its SH2 domain with JAK2. Isoform 2 interacts via its SH2 domain and its N-terminus with JAK2; the SH2 domain is required for the major interaction with JAK2 phosphorylated on tyrosine residues; the N-terminus provides a low-affinity binding to JAK2 independent of JAK2 phosphorylation. Isoform 1 interacts via its SH2 domain with INSR; the interaction requires receptor activation. Isoform 1 interacts with IGF1R; the interaction requires receptor activation. Isoform 2 interacts via its SH2 domain with FGFR3. Isoform 2 interacts with RET; the interaction requires RET kinase activity. Isoform 2 interacts with RAC1. Isoform 2 interacts with PDGFRA and/or PDGFRB; the interaction requires receptor activation. Interacts with ISR1 and ISR2. Probably part of a complex consisting of INSR, ISR1 and SH2B1. Probably part of a ternary complex consisting of SH2B1, JAK2 and ISR1 or ISR2 (By similarity). May interact with FCER1G. Interacts (via SH2 domain) with NTRK1 (phosphorylated). Shuttles between the nucleus and the cytoplasm. Isoform 1 is ubiquitously expressed. Expressed in epididymal adipose tissue, liver and skeletal muscle. Phosphorylated on tyrosine residues in response to treatment with growth hormone (GH), IFN-gamma (IFNG), BDNF, PDGF and FGF. Phosphorylated on tyrosine residues by JAK2 and JAK1. Phosphorylated on multiple serine and threonine residues in response to treatment with NGF. Phosphorylated on serine residues. Belongs to the SH2B adapter family.