AAA ATPase p97/VCP: cellular functions, disease and therapeutic potential

Vij, Neeraj

doi:10.1111/j.1582-4934.2008.00462.x

Cited by 70 publications

(96 citation statements)

References 51 publications

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“…Therefore, the processing of MMTV and betaretrovirus SPs appears to be fundamentally different from other positive-stranded RNA viruses. Because defects in protein folding and ERAD are associated with many human diseases (26), further studies of betaretrovirus SP trafficking will continue to illuminate many important aspects of cell biology and pathogenic processes.…”

Section: Discussionmentioning

confidence: 99%

Retroviral Rem protein requires processing by signal peptidase and retrotranslocation for nuclear function

Byun

Halani²,

Mertz³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

114

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Mouse mammary tumor virus (MMTV) is a complex murine retrovirus that encodes an HIV Rev-like export protein, Rem, from a doubly spliced version of envelope (Env) mRNA. Previously, the Nterminal 98-amino acid sequence of Rem, which is identical to Env signal peptide (SP), and full-length Rem were shown to be functional in a reporter assay that measures a postexport function. Here we show that MMTV-infected cells or cells transfected with rem or env cDNAs express SP, which is the active component in the reporter assay. Uncleaved Rem was partially glycosylated, but mutations in both glycosylation sites within the C terminus prevented Rem function. Mutations that reduced Rem or Env cleavage by signal peptidase greatly reduced SP levels and functional activity in the reporter assay and allowed accumulation of the uncleaved protein. Fluorescence microscopy revealed that GFP-tagged cleavagesite mutants are unstable and lack fluorescence compared with wild-type Rem, suggesting improper folding. Proteasome inhibitors allowed accumulation of uncleaved Rem relative to SP and increased reporter activity, consistent with SP retrotranslocation and proteasome escape before nuclear entry. Expression of a dominant-negative p97 ATPase did not alter levels of unprocessed Rem and SP but decreased reporter activity, suggesting p97-facilitated retrotranslocation of SP. Our results provide an example of a SP that is processed by signal peptidase and retrotranslocated to allow nuclear localization and function. mouse mammary tumor virus | retrotranslocation | retrovirus | signal peptide | ERAD M ouse mammary tumor virus (MMTV) has provided many insights into cell and cancer biology. MMTV is a complex mouse retrovirus with regulatory features similar to those found in human complex retroviruses, such as HIV and human T-cell leukemia virus (HTLV) (1). These features include the ability to manipulate the immune system and to produce a doubly spliced mRNA encoding a protein (Rem) functionally similar to HIV Rev (1, 2). Rem mRNA is translated in the same reading frame as the MMTV envelope (env) gene but has a deletion of internal sequences encoding the surface (SU) and transmembrane (TM) proteins (1, 2) (Fig. 1A).MMTV Rem is a 301-amino acid protein that regulates expression and export of full-length viral RNA from the nucleus to the cytoplasm using the Crm1 export pathway (1, 2). The Rem protein contains several Rev-like motifs, including a nuclear localization signal (NLS), a nucleolar localization sequence, an arginine-rich RNA-binding motif, and a leucine-rich nuclear export sequence (Fig. 1A). These motifs map to the N-terminal 98 amino acids, which are identical in sequence to the signal peptide (SP) of the MMTV Env protein (1, 2). Similar to HIV Rev or HTLV-1 Rex (3, 4), GFP fusions to Rem or the SP are localized to nucleoli. Both GFPRem and GFP-SP fusions are functional in a reporter assay that measures a postexport function (e.g., translation) (5). Rem-dependent reporter activity requires the NLS as well as the presence of a Rem-re...

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Section: Discussionmentioning

confidence: 99%

Retroviral Rem protein requires processing by signal peptidase and retrotranslocation for nuclear function

Byun

Halani²,

Mertz³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

114

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“…Importantly, it has been implicated in protein degradation via both the ubiquitin-proteasome and autophagy pathways, and in membrane fusion, transcriptional activation, apoptosis, and molecular chaperoning. [25][26][27][28] The 6 VCP mutations detected in this series are predominantly in the CDC48 substrate binding domain or the associated L1 linker between the CDC48 and D1 domains (figure 2). These residues are highly conserved across species; these mutations were predicted to be pathogenic by Pmut (http://mmb2.pcb.ub.es:8080/PMut/), with the exception of I114V, which was predicted to be neutral.…”

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confidence: 99%

Novel mutation in VCP gene causes atypical amyotrophic lateral sclerosis

González-Pérez

Cirulli²,

Drory³

et al. 2012

Neurology

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Objective: To identify the genetic variant that causes autosomal dominantly inherited motor neuron disease in a 4-generation Israeli-Arab family using genetic linkage and whole exome sequencing.Methods: Genetic linkage analysis was performed in this family using Illumina single nucleotide polymorphism chips. Whole exome sequencing was then undertaken on DNA samples from 2 affected family members using an Illumina 2000 HiSeq platform in pursuit of potentially pathogenic genetic variants that comigrate with the disease in this pedigree. Variants meeting these criteria were then screened in all affected individuals.Results: A novel mutation (p.R191G) in the valosin-containing protein (VCP) gene was identified in the index family. Direct sequencing of the VCP gene in a panel of DNA from 274 unrelated individuals with familial amyotrophic lateral sclerosis (FALS) revealed 5 additional mutations. Among them, 2 were previously identified in pedigrees with a constellation of inclusion body myopathy with Paget disease of the bone and frontotemporal dementia (IBMPFD) and in FALS, and 2 other mutations (p.R159C and p.R155C) in IBMPFD alone. We did not detect VCP gene mutations in DNA from 178 cases of sporadic amyotrophic lateral sclerosis. Conclusions:We report a novel VCP mutation identified in an amyotrophic lateral sclerosis family (p.R191G) with atypical clinical features. In our experience, VCP mutations arise in approximately 1.5% of FALS cases. Our study supports the view that motor neuron disease is part of the clinical spectrum of VCP-associated disease.

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“…Biochemical studies have shown that VAT unfolds globular proteins and interacts directly with the 20S core particle (CP) of the proteasome, leading to enhanced proteolytic activity for both folded and unfolded protein substrates (18)(19)(20)(21). In eukaryotes, the enzymes Cdc48 and p97/VCP, which are homologous to VAT, play essential roles in a large number of cellular functions, including transcriptional and metabolic regulation, cell cycle progression, membrane fusion, apoptosis, and protein degradation (22). Interestingly, eukaryotic analogs of VAT, such as Cdc48 and p97, lack critical Tyr residues in the pore loops of the D1 domain that are important for unfolding protein substrates and passing them into the lumen of the enzyme.…”

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confidence: 99%

Unfolding the mechanism of the AAA+ unfoldase VAT by a combined cryo-EM, solution NMR study

Huang

Ripstein

Augustyniak

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The AAA+ (ATPases associated with a variety of cellular activities) enzymes play critical roles in a variety of homeostatic processes in all kingdoms of life. Valosin-containing protein-like ATPase of Thermoplasma acidophilum (VAT), the archaeal homolog of the ubiquitous AAA+ protein Cdc48/p97, functions in concert with the 20S proteasome by unfolding substrates and passing them on for degradation. Here, we present electron cryomicroscopy (cryo-EM) maps showing that VAT undergoes large conformational rearrangements during its ATP hydrolysis cycle that differ dramatically from the conformational states observed for Cdc48/p97. We validate key features of the model with biochemical and solution methyl-transverse relaxation optimized spectroscopY (TROSY) NMR experiments and suggest a mechanism for coupling the energy of nucleotide hydrolysis to substrate unfolding. These findings illustrate the unique complementarity between cryo-EM and solution NMR for studies of molecular machines, showing that the structural properties of VAT, as well as the population distributions of conformers, are similar in the frozen specimens used for cryo-EM and in the solution phase where NMR spectra are recorded.T he AAA+ enzymes (ATPases associated with a variety of cellular activities) use the energy of ATP hydrolysis to carry out a myriad of different biological functions that are critical to cellular homeostasis. These molecular machines are typically barrel-shaped, containing a narrow channel that serves to traffic substrates through the enzyme (1-4). In the case of the heat shock protein 104 (Hsp104) AAA+ class of chaperone, for example, substrates are dissociated from aggregates via a pulling motion that forces individual polypeptide chains through the central pore of the enzyme (1, 5). The unfolded proteins that emerge subsequently refold spontaneously or are acted on by additional chaperones that aid in their refolding (6). Other AAA+ enzymes act synergistically with proteases, unfolding targeted substrates and passing them directly to the proteases, where they are subsequently degraded (7). In this way, proteins that have become damaged or that are no longer required can be removed before their accumulation disrupts cellular function (8). A variety of different AAA+ unfoldases have been characterized, including Rpt1-6 in the 19S proteasome regulatory particle in eukaryotes (9-11), PAN in archaea (12-14), Mpa/ARC in Actinobacteria (15), ClpA/X (2) and HslU (3) in bacteria, and VAT in the Thermoplasma acidophilum archaebacterium (16)(17)(18)(19)(20).VAT is an ∼500-kDa homohexamer, with each monomer containing two tandem AAA+ domains, referred to as D1 and D2, and an N-terminal domain (NTD) distinct from the NTD of other AAA+ enzymes (16) (Fig. 1A). Both D1 and D2 are homologous to the single AAA+ modules of PAN and Rpt1-6 (1, 16). Biochemical studies have shown that VAT unfolds globular proteins and interacts directly with the 20S core particle (CP) of the proteasome, leading to enhanced proteolytic activity for both folded and ...

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AAA ATPase p97/VCP: cellular functions, disease and therapeutic potential

Cited by 70 publications

References 51 publications

Retroviral Rem protein requires processing by signal peptidase and retrotranslocation for nuclear function

Retroviral Rem protein requires processing by signal peptidase and retrotranslocation for nuclear function

Novel mutation in VCP gene causes atypical amyotrophic lateral sclerosis

Unfolding the mechanism of the AAA+ unfoldase VAT by a combined cryo-EM, solution NMR study

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