Inclusion body myopathy-associated mutations in p97/VCP impair endoplasmic reticulum-associated degradation.
Mutations in the AAA+ protein (ATPase associated with a variety of cellular activities) p97/VCP (valosin-containing protein) cause a dominantly inherited syndrome of inclusion body myopathy with Paget's disease of the bone and fronto-temporal dementia (IBMPFD). p97/VCP is a ubiquitously expressed protein that participates in a number of cellular processes including endoplasmic reticulum-associated degradation (ERAD). p97/VCP aids in the extraction of ubiquitinated proteins from the endoplasmic reticulum (ER) and facilitates their delivery to the proteasome. This study focuses on the effects of disease-associated p97/VCP mutations on this pathway. We show that p97/VCP containing the most prevalent IBMPFD-associated mutation, R155H, has normal ATPase activity and hexameric structure. However, when expressed in cultured cells, both this and a second IBMPFD-associated p97/VCP mutant increase the overall level of ubiquitin-conjugated proteins and specifically impair degradation of mutant DeltaF508-CFTR handled by the ERAD pathway. These effects are similar to those previously described for an ATPase deficient p97/VCP mutant and suggest that IBMPFD mutations impair p97/VCP cellular function. In a subset of cells, IBMPFD mutations also promote formation of aggregates that contain p97/VCP, ubiquitin conjugates and ER-resident proteins. Undegraded mutant DeltaF508-CFTR also accumulates in these aggregates. We conclude that IBMPFD mutations in p97/VCP disrupt ERAD and that this may contribute to the pathogenesis of IBMPFD.
Weihl
Conrad C
CC
Department of Neurology, Washington University School of Medicine, 660 South Euclid Avenue, St Louis, MO 63110, USA. weihlc@neuro.wustl.edu
Dalal
Seema
S
Pestronk
Alan
A
Hanson
Phyllis I
PI
D000251:Adenosine Triphosphatases; D000818:Animals; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D003704:Dementia / Q000150:complications / Q000235:genetics*; D003720:Densitometry; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D051379:Mice; D020125:Mutation, Missense / Q000235:genetics*; D018979:Myositis, Inclusion Body / Q000150:complications / Q000235:genetics*; D010001:Osteitis Deformans / Q000150:complications / Q000235:genetics*; D011506:Proteins / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism; D000074405:Valosin Containing Protein
D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D011506:Proteins; D025801:Ubiquitin; D000251:Adenosine Triphosphatases; D000074405:Valosin Containing Protein; C000614179:Vcp protein, mouse