Enhanced ATPase activities as a primary defect of mutant valosin-containing proteins that cause inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia.
Valosin-containing protein (VCP) has been shown to colocalize with abnormal protein aggregates, such as nuclear inclusions of Huntington disease and Machado-Joseph disease, Lewy bodies in Parkinson disease. Several mis-sense mutations in the human VCP gene have been identified in patients suffering inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD). Recently, we have shown that VCP possesses both aggregate-forming and aggregate-clearing activities. Here, we showed that in cells treated with proteasome inhibitors VCP first appeared as several small aggregates throughout the cells; and then, these small aggregates gathered together into a single big aggregate. Subcellular localization and ATPase activity of VCP clearly influenced the localization of the aggregates. Furthermore, all tested IBMPFD-causing mutant VCPs, possessed elevated ATPase activities and enhanced aggregate-forming activities in cultured cells. In Drosophila, these mutants and VCP(T761E), a super active VCP, did not appear to spontaneously induce eye degeneration, but worsened the phenotype when co-expressed with polyglutamines. Unexpectedly, these VCPs did not apparently change sizes and the amounts of polyglutamine aggregates in Drosophila eyes. Elevated ATPase activities, thus, may be a hidden primary defect causing IBMPFD pathological phenotypes, which would be revealed when abnormal proteins are accumulated, as typically observed in aging.
Manno
Atsushi
A
Laboratory of Functional Biology, Kyoto University Graduate School of Biostudies, Kyoto 606-8501, Japan.
Noguchi
Masakatsu
M
Fukushi
Junpei
J
Motohashi
Yasuhiro
Y
Kakizuka
Akira
A
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D004330:Drosophila; D057180:Frontotemporal Dementia / Q000150:complications* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D002479:Inclusion Bodies / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D009135:Muscular Diseases / Q000150:complications* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D010001:Osteitis Deformans / Q000150:complications* / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D000074405:Valosin Containing Protein
D018797:Cell Cycle Proteins; D000251:Adenosine Triphosphatases; C000614178:VCP protein, human; D000074405:Valosin Containing Protein