HCLS1 (Hematopoietic cell-specific Lyn substrate 1) is an actin-binding substrate of the antigen receptor-coupled tyrosine kinase expressed in leukocytes that functions in antigen receptor signaling for both clonal expansion and deletion in lymphoid cells. It regulates ARP2/ARP3-dependent migration of leukocytes and is a direct actin modulator. It also regulates a number of downstream receptors including TCR, CXCR4 and BCR. HCLS1 is also an effective prognostic marker for ovarian carcinoma, where it is involved in cytoskeleton remodeling, cell migration and invasion and where positivity is associated with worse survival. In immunohistochemistry of normal tissue, it has cytoplasmic and membranous positivity in cells of hematopoietic origin and in immune tissues. References: The UniProt Consortium. Nucleic Acids Res. 47: D506-515 (2019); Nucleic Acids Res. 2016 Jan 4;44(D1):D733-45, PMID:26553804; J Leukoc Biol. 2019 May;105(5):881-890, PMID: 30537294; Oncotarget. 2018 Aug 24; 9(66): 32609–32623, PMID: 30220969