title: Huntingtin-interacting proteins, HIP14 and HIP14L, mediate dual functions, palmitoyl acyltransferase and Mg2+ transport.
abstract: Polyglutamine expansions of huntingtin protein are responsible for the Huntington neurological disorder. HIP14 protein has been shown to interact with huntingtin. HIP14 and a HIP14-like protein, HIP14L, with a 69% similarity reside in the Golgi and possess palmitoyl acyltransferase activity through innate cysteine-rich domains, DHHC. Here, we used microarray analysis to show that reduced extracellular magnesium concentration increases HIP14L mRNA suggesting a role in cellular magnesium metabolism. Because HIP14 was not on the microarray platform, we used real-time reverse transcriptase-PCR to show that HIP14 and HIP14L transcripts were up-regulated 3-fold with low magnesium. Western analysis with a specific HIP14 antibody also showed that endogenous HIP14 protein increased with diminished magnesium. Furthermore, we demonstrate that when expressed in Xenopus oocytes, HIP14 and HIP14L mediate Mg2+ uptake that is electrogenic, voltage-dependent, and saturable with Michaelis constants of 0.87 +/- 0.02 and 0.74 +/- 0.07 mm, respectively. Diminished magnesium leads to an apparent increase in HIP14-green fluorescent protein and HIP14L-green fluorescent fusion proteins in the Golgi complex and subplasma membrane post-Golgi vesicles of transfected epithelial cells. We also show that inhibition of palmitoylation with 2-bromopalmitate, or deletion of the DHHC motif HIP14DeltaDHHC, diminishes HIP14-mediated Mg2+ transport by about 50%. Coexpression of an independent protein acyltransferase, GODZ, with the deleted HIP14DeltaDHHC mutant restored Mg2+ transport to values observed with wild-type HIP14. Although we did not directly measure palmitoylation of HIP14 in these studies, the data are consistent with a regulatory role of autopalmitoylation in HIP14-mediated Mg2+ transport. We conclude that the huntingtin interacting protein genes, HIP14 and HIP14L, encode Mg2+ transport proteins that are regulated by their innate palmitoyl acyltransferases thus fulfilling the characteristics of "chanzymes."
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Angela
authors.initials: A
authors.lastname: Goytain
authors.forename: Rochelle M
authors.initials: RM
authors.lastname: Hines
authors.forename: Gary A
authors.initials: GA
authors.lastname: Quamme
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002522:Chlorocebus aethiops; D004285:Dogs; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D006056:Golgi Apparatus / Q000201:enzymology*; D006801:Humans; D017136:Ion Transport / Q000502:physiology; D008274:Magnesium / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D017434:Protein Structure, Tertiary / Q000502:physiology; D014981:Xenopus
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D009419:Nerve Tissue Proteins; D000217:Acyltransferases; C473038:ZDHHC17 protein, human; D008274:Magnesium
references.citation: Cell Calcium. 2003 May-Jun;33(5-6):519-31
references.pmid: 12765697
references.citation: Nature. 2001 May 31;411(6837):590-5
references.pmid: 11385574
references.citation: J Biol Chem. 1996 Oct 25;271(43):26465-8
references.pmid: 8900112
references.citation: Science. 2001 Feb 9;291(5506):1043-7
references.pmid: 11161216
references.citation: Mol Cell Neurosci. 2004 Jun;26(2):251-7
references.pmid: 15207850
references.citation: Neurosci Lett. 1991 Aug 5;129(1):22-4
references.pmid: 1833674
references.citation: J Cell Biol. 2007 Jan 29;176(3):249-54
references.pmid: 17242068
references.citation: Nature. 1970 Aug 15;227(5259):680-5
references.pmid: 5432063
references.citation: Proc Natl Acad Sci U S A. 2005 Apr 26;102(17):5964-8
references.pmid: 15837928
references.citation: AJNR Am J Neuroradiol. 1993 Mar-Apr;14(2):275-81
references.pmid: 8456699
references.citation: Nat Genet. 1995 May;10(1):104-10
references.pmid: 7647777
references.citation: Nature. 2001 May 31;411(6837):595-9
references.pmid: 11385575
references.citation: Exp Neurol. 1998 Jul;152(1):34-40
references.pmid: 9682010
references.citation: Hum Mol Genet. 2002 Nov 1;11(23):2815-28
references.pmid: 12393793
references.citation: J Biol Chem. 2005 Oct 28;280(43):36464-73
references.pmid: 16085648
references.citation: J Neurochem. 2007 Apr;101(1):241-9
references.pmid: 17394466
references.citation: Proc Natl Acad Sci U S A. 1998 Apr 14;95(8):4690-5
references.pmid: 9539800
references.citation: Nat Rev Mol Cell Biol. 2007 Jan;8(1):74-84
references.pmid: 17183362
references.citation: J Neuropathol Exp Neurol. 2007 Apr;66(4):313-20
references.pmid: 17413322
references.citation: Neuron. 2004 Dec 16;44(6):977-86
references.pmid: 15603740
references.citation: Biochem J. 2003 Jul 1;373(Pt 1):91-9
references.pmid: 12670300
references.citation: J Neurosci. 2004 Jun 30;24(26):5881-91
references.pmid: 15229235
references.citation: J Biol Chem. 2007 Jun 22;282(25):18339-18347
references.pmid: 17478424
references.citation: J Biol Chem. 2007 Mar 16;282(11):8060-8
references.pmid: 17166836
references.citation: Curr Biol. 2003 Oct 14;13(20):R799-801
references.pmid: 14561419
references.citation: Nat Neurosci. 2006 Jun;9(6):824-31
references.pmid: 16699508
references.citation: Neuron. 1995 May;14(5):1075-81
references.pmid: 7748555
references.citation: Science. 2001 Aug 17;293(5533):1327-30
references.pmid: 11509734
references.citation: Biochim Biophys Acta. 2007 Aug;1772(8):813-21
references.pmid: 17481860
references.citation: Proc Natl Acad Sci U S A. 2007 Jun 12;104(24):10045-50
references.pmid: 17548833
references.citation: J Biol Chem. 1987 Oct 5;262(28):13713-23
references.pmid: 2443496
references.citation: Biochem Biophys Res Commun. 2002 Aug 16;296(2):492-6
references.pmid: 12163046
references.citation: Neuron. 2005 Sep 1;47(5):709-23
references.pmid: 16129400
references.citation: J Lipid Res. 2007 Aug;48(8):1873-84
references.pmid: 17525474
references.citation: Physiol Rev. 2001 Jan;81(1):51-84
references.pmid: 11152754
references.citation: J Cell Sci. 2002 Mar 1;115(Pt 5):941-8
references.pmid: 11870213
references.citation: J Cell Biol. 2000 Jan 10;148(1):159-72
references.pmid: 10629226
references.citation: BMC Genomics. 2005 Apr 01;6:48
references.pmid: 15804357
references.citation: J Neurosci. 2006 Dec 6;26(49):12758-68
references.pmid: 17151279
references.citation: Hum Mol Genet. 2000 Feb 12;9(3):387-94
references.pmid: 10655548
references.citation: Hum Mol Genet. 2007 Aug 15;16(16):1905-20
references.pmid: 17567778
references.citation: Biochem Cell Biol. 2006 Dec;84(6):912-7
references.pmid: 17215878
references.citation: Kidney Int. 1997 Nov;52(5):1180-95
references.pmid: 9350641
references.citation: J Cell Biol. 2006 Feb 13;172(4):605-18
references.pmid: 16476778
references.citation: Hum Mol Genet. 2000 Nov 22;9(19):2789-97
references.pmid: 11092755
references.citation: Cell Mol Biol (Noisy-le-grand). 2000 Jun;46(4):821-33
references.pmid: 10875443
references.citation: Oncogene. 2004 Dec 9;23(57):9230-7
references.pmid: 15489887
references.citation: J Gen Physiol. 2006 Apr;127(4):421-34
references.pmid: 16533898
references.citation: Hum Mol Genet. 2007 Feb 15;16(4):391-409
references.pmid: 17189290