SH2 Homology Protein B (SHB) is a cytoplasmic adaptor protein that serves as a link between phosphotyrosine residues on multiple receptor tyrosine kinases and downstream signaling pathways. It is 509 amino acids (aa) in length with a predicted molecular mass of 55 kDa. A second, alternatively spliced human isoform has been identified that is 297 aa in length with a predicted molecular mass of 30 kDa. The mouse SHB ortholog shares 94% aa sequence identity with the human protein. SHB is ubiquitously expressed and binds tyrosine kinase receptors such as FGF R1, VEGF R2, and PDGF R following their activation. SHB also mediates T cell receptor signaling, as well as IRS1 and IRS2 signaling. It has been shown to contribute to the development and maintenance of hematopoietic stem cells by regulating cell cycle progression.