title: HAP1 facilitates effects of mutant huntingtin on inositol 1,4,5-trisphosphate-induced Ca release in primary culture of striatal medium spiny neurons.
abstract: Huntington's disease is caused by polyglutamine expansion (exp) in huntingtin (Htt). Htt-associated protein-1 (HAP1) was the first identified Htt-binding partner. The type 1 inositol (1,4,5)-trisphosphate receptor (InsP3R1) is an intracellular Ca2+ release channel that plays an important role in neuronal function. Recently, we identified a InsP3R1-HAP1A-Htt ternary complex in the brain and demonstrated that Httexp, but not normal Htt, activates InsP3R1 in bilayers and facilitates InsP3R1-mediated intracellular Ca2+ release in medium spiny striatal neurons [MSN; T.-S. Tang et al. (2003) Neuron, 39, 227-239]. Here we took advantage of mice with targeted disruption of both HAP1 alleles (HAP1 -/-) to investigate the role of HAP1 in functional interactions between Htt and InsP3R1. We determined that: (i) HAP1 is expressed in the MSN; (ii) HAP1A facilitates functional effects of Htt and Htt(exp) on InsP3R1 in planar lipid bilayers; (iii) HAP1 is required for changes in MSN basal Ca2+ levels resulting from Htt or Htt(exp) overexpression; (iv) HAP1 facilitates potentiation of InsP3R1-mediated Ca2+ release by Htt(exp) in mouse MSN. Our present results indicate that HAP1 plays an important role in functional interactions between Htt and InsP3R1.
authors.affiliation: Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA.
authors.forename: Tie-Shan
authors.initials: TS
authors.lastname: Tang
authors.forename: Huiping
authors.initials: H
authors.lastname: Tu
authors.forename: Paul C
authors.initials: PC
authors.lastname: Orban
authors.forename: Edmond Y W
authors.initials: EY
authors.lastname: Chan
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hayden
authors.forename: Ilya
authors.initials: I
authors.lastname: Bezprozvanny
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000502:physiology*; D006816:Huntington Disease / Q000235:genetics; D015544:Inositol 1,4,5-Trisphosphate / Q000502:physiology*; D007700:Kinetics; D008051:Lipid Bilayers; D008562:Membrane Glycoproteins / Q000502:physiology; D026901:Membrane Transport Proteins / Q000502:physiology; D008734:Methoxyhydroxyphenylglycol / Q000031:analogs & derivatives* / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D050486:Serotonin Plasma Membrane Transport Proteins
chemical_list: C490758:Hap1 protein, mouse; D008051:Lipid Bilayers; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050486:Serotonin Plasma Membrane Transport Proteins; C493231:Slc6a4 protein, mouse; D008734:Methoxyhydroxyphenylglycol; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium; C010117:3,4-dihydroxyphenylglycol