title: Analysis of Huntingtin-associated protein 1 in mouse brain and immortalized striatal neurons.
abstract: Huntingtin, the protein product of the Huntington's disease (HD) gene, is expressed with an expanded polyglutamine domain in the brain and in nonneuronal tissues in patients with HD. Huntingtin-associated protein 1 (HAP-1), a brain-enriched protein, interacts preferentially with mutant huntingtin and thus may be important in HD pathogenesis. The function of HAP-1 is unknown, but recent evidence supports a role in microtubule-dependent organelle transport. We examined the subcellular localization of HAP-1 with an antibody made against the NH2-terminus of the protein. In immunoblot assays of mouse brain and immortalized striatal neurons, HAP-1 subtypes A and B migrated together at about 68 kD and separately at 95 kD and 110 kD, respectively. In dividing clonal striatal cells, HAP-1 localized to the mitotic spindle apparatus, especially at spindle poles and on vesicles and microtubules of the spindle body. Postmitotic striatal neurons had punctate HAP-1 labeling throughout the cytoplasm. Western blot analysis of protein extracts obtained after subcellular fractionation and differential centrifugation of the clonal striatal cells showed that HAP-1B was preferentially enriched in membrane fractions. Electron microscopic study of adult mouse basal forebrain and striatum showed HAP-1 localized to membrane-bound organelles including large endosomes, tubulovesicular structures, and budding vesicles in neurons. HAP-1 was also strongly associated with an unusual large "dense" organelle. Microtubules were labeled in dendrites and axonal fibers. Results support a role for HAP-1 in vesicle trafficking and organelle movement in mitotic cells and differentiated neurons and implicate HAP-1B as the predominant molecular subtype associated with vesicle membranes in striatal neurons.
authors.affiliation: Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston 02114, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Martin
authors.forename: M
authors.initials: M
authors.lastname: Kim
authors.forename: J
authors.initials: J
authors.lastname: Velier
authors.forename: E
authors.initials: E
authors.lastname: Sapp
authors.forename: H S
authors.initials: HS
authors.lastname: Lee
authors.forename: G
authors.initials: G
authors.lastname: Laforet
authors.forename: L
authors.initials: L
authors.lastname: Won
authors.forename: K
authors.initials: K
authors.lastname: Chase
authors.forename: P G
authors.initials: PG
authors.lastname: Bhide
authors.forename: A
authors.initials: A
authors.lastname: Heller
authors.forename: N
authors.initials: N
authors.lastname: Aronin
authors.forename: M
authors.initials: M
authors.lastname: Difiglia
mesh_terms: D000818:Animals; D001921:Brain / Q000166:cytology*; D001923:Brain Chemistry; D002453:Cell Cycle; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000166:cytology*; D003712:Dendrites / Q000737:chemistry / Q000648:ultrastructure; D006816:Huntington Disease / Q000378:metabolism; D007150:Immunohistochemistry; D051379:Mice; D008870:Microtubules / Q000737:chemistry / Q000648:ultrastructure; D008938:Mitosis; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000032:analysis; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology*; D013347:Subcellular Fractions / Q000737:chemistry; D013572:Synaptic Vesicles / Q000737:chemistry / Q000648:ultrastructure; D014407:Tumor Cells, Cultured
chemical_list: C490758:Hap1 protein, mouse; D009419:Nerve Tissue Proteins