Polyglutamine expansion in huntingtin alters its interaction with phospholipids.
Huntingtin has an expanded polyglutamine tract in patients with Huntington's disease. Huntingtin localizes to intracellular and plasma membranes but the function of huntingtin at membranes is unknown. Previously we reported that exogenously expressed huntingtin bound pure phospholipids using protein-lipid overlays. Here we show that endogenous huntingtin from normal (Hdh(7Q/7Q)) mouse brain and mutant huntingtin from Huntington's disease (Hdh(140Q/140Q)) mouse brain bound to large unilamellar vesicles containing phosphoinositol (PI) PI 3,4-bisphosphate, PI 3,5-bisphosphate, and PI 3,4,5-triphosphate [PI(3,4,5)P3]. Huntingtin interactions with multivalent phospholipids were similar to those of dynamin. Mutant huntingtin associated more with phosphatidylethanolamine and PI(3,4,5)P3 than did wild-type huntingtin, and associated with other phospholipids not recognized by wild-type huntingtin. Wild-type and mutant huntingtin also bound to large unilamellar vesicles containing cardiolipin, a phospholipid specific to mitochondrial membranes. Maximal huntingtin-phospholipid association required inclusion of huntingtin amino acids 171-287. Endogenous huntingtin recruited to the plasma membrane in cells that incorporated exogenous PI 3,4-bisphosphate and PI(3,4,5)P3 or were stimulated by platelet-derived growth factor or insulin growth factor 1, which both activate PI 3-kinase. These data suggest that huntingtin interacts with membranes through specific phospholipid associations and that mutant huntingtin may disrupt membrane trafficking and signaling at membranes.
Kegel
Kimberly B
KB
Laboratory of Cellular Neurobiology, Department of Neurology, Massachusetts General Hospital, 11416th Street, Room 2150, Charlestown, MA 02129, USA. kkegel@partners.org
Sapp
Ellen
E
Alexander
Jonathan
J
Valencia
Antonio
A
Reeves
Patrick
P
Li
Xueyi
X
Masso
Nicholas
N
Sobin
Lindsay
L
Aronin
Neil
N
DiFiglia
Marian
M
D000818:Animals; D002308:Cardiolipins / Q000378:metabolism; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D006801:Humans; D000071058:Huntingtin Protein; D006816:Huntington Disease / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D010743:Phospholipids / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology
D002308:Cardiolipins; C086055:HTT protein, human; D000071058:Huntingtin Protein; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D010455:Peptides; D010743:Phospholipids; C097188:polyglutamine; D019869:Phosphatidylinositol 3-Kinases