HCLS1-associated protein X-1 (HAX1)

HCLS1-associated protein X-1 (HAX1) is a ubiquitously expressed, multifunctional intracellular protein originally identified as a binding partner of HS1, and is known primarily for its anti-apoptotic function. HAX1 regulates apoptosis by inhibiting caspase activation and stabilizing mitochondrial membrane potential, playing a critical protective role in hematopoietic, neural, and cardiac tissues. It also regulates calcium homeostasis (notably in cardiomyocytes via modulation of phospholamban and SERCA2), participates in cytoskeletal reorganization, cell migration, endocytosis, and post-transcriptional mRNA processing. Congenital loss-of-function mutations in HAX1 cause severe congenital neutropenia, sometimes with neurological symptoms, owing to impaired neutrophil survival and possibly neuronal dysfunction. HAX1 overexpression is linked to tumorigenesis and metastasis in several cancers, and its multitasking role involves cell survival, metabolism, migration, and immune responses, as well as protein and RNA binding partners in multiple cellular compartments.

Other names

HS1BP1HAX-1HSP1BP-1HCLSBP1HS1-associating protein X-1HS1-binding protein 1SCN3HCLS1 (and PKD2) associated proteinHS1 binding protein

Anti-apoptotic (inhibits caspase activation, e.g. caspase-9); Modulation of calcium cycling proteins (interaction with phospholamban and SERCA2); Protein-protein interactions affecting mitochondrial and cytoskeletal functions.