Huntingtin-interacting proteins, HIP14 and HIP14L, mediate dual functions, palmitoyl acyltransferase and Mg2+ transport.
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."
Goytain
Angela
A
Department of Medicine, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
Hines
Rochelle M
RM
Quamme
Gary A
GA
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
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D009419:Nerve Tissue Proteins; D000217:Acyltransferases; C473038:ZDHHC17 protein, human; D008274:Magnesium
Cell Calcium. 2003 May-Jun;33(5-6):519-31
12765697
Nature. 2001 May 31;411(6837):590-5
11385574
J Biol Chem. 1996 Oct 25;271(43):26465-8
8900112
Science. 2001 Feb 9;291(5506):1043-7
11161216
Mol Cell Neurosci. 2004 Jun;26(2):251-7
15207850
Neurosci Lett. 1991 Aug 5;129(1):22-4
1833674
J Cell Biol. 2007 Jan 29;176(3):249-54
17242068
Nature. 1970 Aug 15;227(5259):680-5
5432063
Proc Natl Acad Sci U S A. 2005 Apr 26;102(17):5964-8
15837928
AJNR Am J Neuroradiol. 1993 Mar-Apr;14(2):275-81
8456699
Nat Genet. 1995 May;10(1):104-10
7647777
Nature. 2001 May 31;411(6837):595-9
11385575
Exp Neurol. 1998 Jul;152(1):34-40
9682010
Hum Mol Genet. 2002 Nov 1;11(23):2815-28
12393793
J Biol Chem. 2005 Oct 28;280(43):36464-73
16085648
J Neurochem. 2007 Apr;101(1):241-9
17394466
Proc Natl Acad Sci U S A. 1998 Apr 14;95(8):4690-5
9539800
Nat Rev Mol Cell Biol. 2007 Jan;8(1):74-84
17183362
J Neuropathol Exp Neurol. 2007 Apr;66(4):313-20
17413322
Neuron. 2004 Dec 16;44(6):977-86
15603740
Biochem J. 2003 Jul 1;373(Pt 1):91-9
12670300
J Neurosci. 2004 Jun 30;24(26):5881-91
15229235
J Biol Chem. 2007 Jun 22;282(25):18339-18347
17478424
J Biol Chem. 2007 Mar 16;282(11):8060-8
17166836
Curr Biol. 2003 Oct 14;13(20):R799-801
14561419
Nat Neurosci. 2006 Jun;9(6):824-31
16699508
Neuron. 1995 May;14(5):1075-81
7748555
Science. 2001 Aug 17;293(5533):1327-30
11509734
Biochim Biophys Acta. 2007 Aug;1772(8):813-21
17481860
Proc Natl Acad Sci U S A. 2007 Jun 12;104(24):10045-50
17548833
J Biol Chem. 1987 Oct 5;262(28):13713-23
2443496
Biochem Biophys Res Commun. 2002 Aug 16;296(2):492-6
12163046
Neuron. 2005 Sep 1;47(5):709-23
16129400
J Lipid Res. 2007 Aug;48(8):1873-84
17525474
Physiol Rev. 2001 Jan;81(1):51-84
11152754
J Cell Sci. 2002 Mar 1;115(Pt 5):941-8
11870213
J Cell Biol. 2000 Jan 10;148(1):159-72
10629226
BMC Genomics. 2005 Apr 01;6:48
15804357
J Neurosci. 2006 Dec 6;26(49):12758-68
17151279
Hum Mol Genet. 2000 Feb 12;9(3):387-94
10655548
Hum Mol Genet. 2007 Aug 15;16(16):1905-20
17567778
Biochem Cell Biol. 2006 Dec;84(6):912-7
17215878
Kidney Int. 1997 Nov;52(5):1180-95
9350641
J Cell Biol. 2006 Feb 13;172(4):605-18
16476778
Hum Mol Genet. 2000 Nov 22;9(19):2789-97
11092755
Cell Mol Biol (Noisy-le-grand). 2000 Jun;46(4):821-33
10875443
Oncogene. 2004 Dec 9;23(57):9230-7
15489887
J Gen Physiol. 2006 Apr;127(4):421-34
16533898
Hum Mol Genet. 2007 Feb 15;16(4):391-409
17189290