Mutant Huntingtin: Nuclear translocation and cytotoxicity mediated by GAPDH

doi:10.1073/pnas.0511316103

Mutant Huntingtin: Nuclear translocation and cytotoxicity mediated by GAPDH

Departments of *Neuroscience,
^¶Psychiatry,
^∥Neurology, and
^‡‡Pharmacology, and
^†Program in Cellular Molecular Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205;
^‡Departments of Pathology and Laboratory Medicine and
^§Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC, Canada V5Z 4H4;
**Department of Biochemistry and Molecular Biology, Georgetown University Medical Center, Washington, DC 20057; and
^††Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322

Contributed by Solomon H. Snyder, December 30, 2005

Abstract

The pathophysiology of Huntington’s disease reflects actions of mutant Huntingtin (Htt) (mHtt) protein with polyglutamine repeats, whose N-terminal fragment translocates to the nucleus to elicit neurotoxicity. We establish that the nuclear translocation and associated cytotoxicity of mHtt reflect a ternary complex of mHtt with GAPDH and Siah1, a ubiquitin-E3-ligase. Overexpression of GAPDH or Siah1 enhances nuclear translocation of mHtt and cytotoxicity, whereas GAPDH mutants that cannot bind Siah1 prevent translocation. Depletion of GAPDH or Siah1 by RNA interference diminishes nuclear translocation of mHtt.

Footnotes

^§§To whom correspondence may be addressed. E-mail: ssnyder{at}jhmi.edu or asawa1{at}jhmi.edu
Author contributions: B.-I.B., S.H.S., and A.S. designed research; B.-I.B., C.L.W., and H.C.H. performed research; M. R. Hara, M.B.C., M. R. Hayden, and X.-J.L. contributed new reagents/analytic tools; B.-I.B., C.A.R., S.H.S., and A.S. analyzed data; and B.-I.B., S.H.S., and A.S. wrote the paper.
Conflict of interest statement: No conflicts declared.
Abbreviations:

Abbreviations:

HD,

Huntington’s disease;

polyQ,

polyglutamine;

Htt,

Huntingtin;

mHtt,

mutant Htt;

wtHtt,

wild-type Htt;

RNAi,

RNA interference;

Siah1ΔRING,

Siah1 lacking the RING finger domain;

GAPDH-K225A,

mutant GAPDH in which lysine-225 is replaced with alanine;

NLS,

nuclear localization signal;

Siah1ΔNLS,

Siah1 lacking NLS;

HA,

hemagglutinin.