HSH2 is a 352 amino acid nuclear and cytoplasmic protein that is predominantly expressed in spleen and hematopoietic cells, such as peripheral blood leukocytes, and weakly expressed in prostate, thymus, heart, small intestine and placenta. Containing an SH2 domain, four PXXP polyproline sequences and two possible tyrosine phosphorylation sites, HSH2 interacts with tyrosine kinases Fes and ACK. Considered an adaptor protein, HSH2 participates in tyrosine kinase signaling and may be involved in the regulation of cytokine signaling and cytoskeletal reorganization in hematopoietic cells. HSH2 may also act to attenuate apoptosis through modulating the apoptotic response by promoting mitochondrial stability. HSH2 exists as two alternatively spliced isoforms and is encoded by a gene located on human chromosome 19p13.11.