The first 17 amino acids of Huntingtin modulate its sub-cellular localization, aggregation and effects on calcium homeostasis.
A truncated form of the Huntington's disease (HD) protein that contains the polyglutamine repeat, Httex1p, causes HD-like phenotypes in multiple model organisms. Molecular signatures of pathogenesis appear to involve distinct domains within this polypeptide. We studied the contribution of each domain, singly or in combination, to sub-cellular localization, aggregation and intracellular Ca2+ ([Ca2+]i) dynamics in cells. We demonstrate that sub-cellular localization is most strongly influenced by the first 17 amino acids, with this sequence critically controlling Httex1p mitochondrial localization and also promoting association with the endoplasmic reticulum (ER) and Golgi. This domain also enhances the formation of visible aggregates and together with the expanded polyQ repeat acutely disrupts [Ca2+]i levels in glutamate-challenged PC12 cells. Isolated cortical mitochondria incubated with Httex1p resulted in uncoupling and depolarization of these organelles, further supporting the idea that Httex1p-dependent mitochondrial dysfunction could be instrumental in promoting acute Ca2+ dyshomeostasis. Interestingly, neither mitochondrial nor ER associations seem to be required to promote long-term [Ca2+]i dyshomeostasis.
Rockabrand
Erica
E
Department of Psychiatry and Human Behavior, University of California, Gillespie 2121, Irvine, CA 92697, USA.
Slepko
Natalia
N
Pantalone
Antonello
A
Nukala
Vidya N
VN
Kazantsev
Aleksey
A
Marsh
J Lawrence
JL
Sullivan
Patrick G
PG
Steffan
Joan S
JS
Sensi
Stefano L
SL
Thompson
Leslie Michels
LM
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002525:Cerebellar Cortex / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D006706:Homeostasis; D000071058:Huntingtin Protein; D008297:Male; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D016716:PC12 Cells; D010455:Peptides / Q000235:genetics; D011392:Proline / Q000737:chemistry; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D014162:Transfection
D045222:Electron Transport Chain Complex Proteins; C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D017382:Reactive Oxygen Species; C097188:polyglutamine; D011392:Proline; D002118:Calcium