Mutant huntingtin impairs vesicle formation from recycling endosomes by interfering with Rab11 activity.
Huntingtin (Htt) localizes to endosomes, but its role in the endocytic pathway is not established. Recently, we found that Htt is important for the activation of Rab11, a GTPase involved in endosomal recycling. Here we studied fibroblasts of healthy individuals and patients with Huntington's disease (HD), which is a movement disorder caused by polyglutamine expansion in Htt. The formation of endocytic vesicles containing transferrin at plasma membranes was the same in control and HD patient fibroblasts. However, HD fibroblasts were delayed in recycling biotin-transferrin back to the plasma membrane. Membranes of HD fibroblasts supported less nucleotide exchange on Rab11 than did control membranes. Rab11-positive vesicular and tubular structures in HD fibroblasts were abnormally large, suggesting that they were impaired in forming vesicles. We used total internal reflection fluorescence imaging of living fibroblasts to monitor fluorescence-labeled transferrin-carrying transport intermediates that emerged from recycling endosomes. HD fibroblasts had fewer small vesicles and more large vesicles and long tubules than did control fibroblasts. Dominant active Rab11 expressed in HD fibroblasts normalized the recycling of biotin-transferrin. We propose a novel mechanism for cellular dysfunction by the HD mutation arising from the inhibition of Rab11 activity and a deficit in vesicle formation at recycling endosomes.
Li
Xueyi
X
Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
Standley
Clive
C
Sapp
Ellen
E
Valencia
Antonio
A
Qin
Zheng-Hong
ZH
Kegel
Kimberly B
KB
Yoder
Jennifer
J
Comer-Tierney
Laryssa A
LA
Esteves
Miguel
M
Chase
Kathryn
K
Alexander
Jonathan
J
Masso
Nicholas
N
Sobin
Lindsay
L
Bellve
Karl
K
Tuft
Richard
R
Lifshitz
Lawrence
L
Fogarty
Kevin
K
Aronin
Neil
N
DiFiglia
Marian
M
D000293:Adolescent; D000328:Adult; D001710:Biotin / Q000378:metabolism; D002478:Cells, Cultured; D002648:Child; D022163:Clathrin-Coated Vesicles / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D004789:Enzyme Activation; D005347:Fibroblasts / Q000201:enzymology / Q000473:pathology; D005799:Genes, Dominant; D006801:Humans; D000071058:Huntingtin Protein; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D050505:Mutant Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D021381:Protein Transport; D011990:Receptors, Transferrin / Q000378:metabolism; D013194:Staining and Labeling; D014168:Transferrin / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000378:metabolism*; D000099193:rab11 GTP-Binding Proteins
D001710:Biotin; D000071058:Huntingtin Protein; D050505:Mutant Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; D011990:Receptors, Transferrin; D014168:Transferrin; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins; C086055:HTT protein, human