The first 17 amino acids of Huntingtin modulate its sub-cellular localization, aggregation and effects on calcium homeostasis

• Published in: Human molecular genetics Vol. 16; no. 1; pp. 61 - 77
• Main Authors: Rockabrand, Erica, Slepko, Natalia, Pantalone, Antonello, Nukala, Vidya N., Kazantsev, Aleksey, Marsh, J. Lawrence, Sullivan, Patrick G., Steffan, Joan S., Sensi, Stefano L., Thompson, Leslie Michels
• Format: Journal Article
• Language: English
• Published: Oxford Oxford University Press 01.01.2007; Oxford Publishing Limited (England)
• Subjects: Animals; Biological and medical sciences; Calcium - metabolism; Cell Membrane - metabolism; Cerebellar Cortex - metabolism; Cytoplasm - metabolism; Electron Transport Chain Complex Proteins - metabolism; Endoplasmic Reticulum - metabolism; Fundamental and applied biological sciences. Psychology; Genetics of eukaryotes. Biological and molecular evolution; Golgi Apparatus - metabolism; Homeostasis; Huntingtin Protein; Male; Membrane Potential, Mitochondrial; Mitochondria - metabolism; Mitochondria - physiology; Molecular and cellular biology; Nerve Tissue Proteins - chemistry; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Nerve Tissue Proteins - physiology; Nuclear Proteins - chemistry; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Nuclear Proteins - physiology; PC12 Cells; Peptides - genetics; Proline - chemistry; Protein Structure, Tertiary; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species - metabolism; Transfection; Aggregation; Calcium ion; Huntingtin; Aminoacid; Homeostasis; Genetics; Localization
• ISSN: 0964-6906; 1460-2083
• DOI: 10.1093/hmg/ddl440

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.