Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.4.25.1 (proteasome)
28,817 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have used RNA interference (RNAi) to examine the functional relationship between valosin-containing protein (VCP/p97/Cdc48p/TER94) ATPase and the ubiquitin-proteasome system (UPS) in Drosophila S2 and human HeLa cells. In both cell types, RNAi of VCP (and, to a lesser extent, of certain VCP-interacting proteins) caused significant accumulation of high-molecular-weight conjugates of ubiquitin, an indication of inhibited UPS function. However, decreased VCP levels did not directly inhibit proteasome activity. In HeLa cells, polyubiquitinated proteins accumulated as dispersed aggregates rather than as single aggresomes, even in the presence of proteasome inhibitors, which normally promote aggresome formation. RNAi of VCP caused extensive vacuolization of the cytoplasm, and proteasome inhibitors exaggerated this feature. RNAi of VCP had little effect on S2 cell proliferation but blocked cell-cycle progression and induced mitotic abnormalities and apoptosis in HeLa cells. These results indicate that VCP plays an important general role in mediating the function of the UPS, probably by interacting with potential proteasome substrates before they are degraded by the proteasome.
...
PMID:RNA interference of valosin-containing protein (VCP/p97) reveals multiple cellular roles linked to ubiquitin/proteasome-dependent proteolysis. 1465 77

Inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD) is a dominant progressive disorder that maps to chromosome 9p21.1-p12. We investigated 13 families with IBMPFD linked to chromosome 9 using a candidate-gene approach. We found six missense mutations in the gene encoding valosin-containing protein (VCP, a member of the AAA-ATPase superfamily) exclusively in all 61 affected individuals. Haplotype analysis indicated that descent from two founders in two separate North American kindreds accounted for IBMPFD in approximately 50% of affected families. VCP is associated with a variety of cellular activities, including cell cycle control, membrane fusion and the ubiquitin-proteasome degradation pathway. Identification of VCP as causing IBMPFD has important implications for other inclusion-body diseases, including myopathies, dementias and Paget disease of bone (PDB), as it may define a new common pathological ubiquitin-based pathway.
...
PMID:Inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia is caused by mutant valosin-containing protein. 1503 82

The 97-kDa valosin-containing protein (p97 or VCP) is a type-II AAA ( ATPases associated with a variety of activities) ATPases, which are characterized by possessing two conserved ATPase domains. VCP forms a stable homo-hexameric structure, and this two-tier ring-shaped complex acts as a molecular chaperone that mediates many seemingly unrelated cellular activities. The involvement of VCP in the ubiquitin-proteasome degradation pathway and the identification of VCP cofactors provided us important clues to the understanding of how this molecular chaperone works. In this review, we summarize the reported biological functions of VCP and explore the molecular mechanisms underlying the diverse cellular functions. We discuss the structural and biochemical studies, and elucidate how this sophisticated enzymatic machine converts chemical energy into the mechanical forces required for the chaperone activity.
...
PMID:Molecular perspectives on p97-VCP: progress in understanding its structure and diverse biological functions. 1503 36

Valosin-containing protein, VCP/p97 or Cdc48, is a eukaryotic ATPase involved in membrane fusion, protein transport, and protein degradation. We describe two proteins, Ubx2 and Ubx3, which interact with Cdc48 in fission yeast. Ubx3 is the ortholog of p47/Shp1, a previously described Cdc48 cofactor involved in membrane fusion, whereas Ubx2 is a novel protein. Cdc48 binds the UBX domains present in both Ubx2 and Ubx3, indicating that this domain is a general Cdc48-interacting module. Ubx2 and Ubx3 also interact with ubiquitin chains. Disruption of the ubx3(+)-gene causes both temperature and canavanine sensitivity and stabilizes some ubiquitin-protein conjugates including the CDK inhibitor Rum1, but not a model substrate of the ER-degradation pathway. Moreover the ubx3 null displays synthetic lethality with a pus1 null mutant, a multiubiquitin binding subunit of the 26S proteasome. In contrast, the ubx2 null mutant did not display any obvious protein-degradation phenotype. In conclusion Ubx3/p47 is not, as previously thought, only important for membrane fusion; it's also important for the specific degradation of a subset of cell proteins. Our genetic analyses revealed that Ubx3/p47 functionally parallels a substrate receptor of the 26S proteasome, Pus1/Rpn10, indicating that the Cdc48-Ubx3 complex is involved in delivering substrates to the 26S proteasome.
...
PMID:The Ubx2 and Ubx3 cofactors direct Cdc48 activity to proteolytic and nonproteolytic ubiquitin-dependent processes. 1512 77

Machado-Joseph disease (MJD)/Spinocerebellar ataxia type 3 (SCA3) is neurodegenerative disease which is caused by polyglutamine expansion in a responsible gene product, MJD1/Ataxin3. MJD1 has now been shown to undergo ubiquitylation and degradation by proteasome-dependent pathway. MJD1 with expanded polyglutamine tract was more resistant to degradation than normal MJD1. We established an in vitro system of ubiquitylation of MJD1, thereby biochemically purified activity to mediate polyubiquitylation of MJD1 from rabbit reticulocyte lysate. An AAA-family ATPase VCP was isolated from the active fraction, and found to binds to MJD1. Furthermore, UFD2a, a mammalian ubiquitin-chain assembly factor (E4), associated with VCP and induced polyubiquitylation of MJD1. UFD2a markedly promoted ubiquitylation and degradation of MJD1 with expanded polyglutamine tract, resulting in the clearance of MJD1 protein. In contrast, dominant-negative mutant UFD2a reduced the degradation rate of MJD1, leading to the formation of intracellular aggregation. In Drosophila model, overexpression of UFD2a significantly suppressed the neurodegeneration induced by expression of MJD1 with expanded polyglutamine tract. These findings suggest that E4 is a rate-limiting factor of degradation of pathologic polyglutamine-containing proteins, and may give a potential tool for gene therapy to control the clinical conditions of MJD.
...
PMID:[Mechanisms to control degradation of polyglutamine-containing protein]. 1515

The stability of the endoplasmic reticulum (ER) glycoprotein 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), the key enzyme in cholesterol biosynthesis, is negatively regulated by sterols. HMGR is anchored in the ER via its N-terminal region, which spans the membrane eight times and contains a sterol-sensing domain. We have previously established that degradation of mammalian HMGR is mediated by the ubiquitin-proteasome system (Ravid, T., Doolman, R., Avner, R., Harats, D., and Roitelman, J. (2000) J. Biol. Chem. 275, 35840-35847). Here we expressed in HEK-293 cells an HA-tagged-truncated version of HMGR that encompasses all eight transmembrane spans (350 N-terminal residues). Similar to endogenous HMGR, degradation of this HMG(350)-3HA protein was accelerated by sterols, validating it as a model to study HMGR turnover. The degradation of HMG(240)-3HA, which lacks the last two transmembrane spans yet retains an intact sterol-sensing domain, was no longer accelerated by sterols. Using HMG(350)-3HA, we demonstrate that transmembrane region of HMGR is ubiquitinated in a sterol-regulated fashion. Through site-directed Lys --> Arg mutagenesis, we pinpoint Lys(248) and Lys(89) as the internal lysines for ubiquitin attachment, with Lys(248) serving as the major acceptor site for polyubiquitination. Moreover, the data indicate that the N terminus is also ubiquitinated. The degradation rates of the Lys --> Arg mutants correlates with their level of ubiquitination. Notably, lysine-less HMG(350)-3HA is degraded faster than wild-type protein, suggesting that lysines other than Lys(89) and Lys(248) attenuate ubiquitination at the latter residues. The ATP-dependent ubiquitination of HMGR in isolated microsomes requires E1 as the sole cytosolic protein, indicating that ER-bound E2 and E3 enzymes catalyze this modification. Polyubiquitination of HMGR is correlated with its extraction from the ER membrane, a process likely to be assisted by cytosolic p97/VCP/Cdc48p-Ufd1-Npl4 complex, as only ubiquitinated HMGR pulls down p97.
...
PMID:Ubiquitin is conjugated by membrane ubiquitin ligase to three sites, including the N terminus, in transmembrane region of mammalian 3-hydroxy-3-methylglutaryl coenzyme A reductase: implications for sterol-regulated enzyme degradation. 1524 8

A widely expressed protein containing UBA (ubiquitin-associated) and UBX (ubiquitin-like) domains was identified as a substrate of SAPKs (stress-activated protein kinases). Termed SAKS1 (SAPK substrate-1), it was phosphorylated efficiently at Ser200 in vitro by SAPK3/p38gamma, SAPK4/p38delta and JNK (c-Jun N-terminal kinase), but weakly by SAPK2a/p38alpha, SAPK2b/p38beta2 or ERK (extracellular-signal-regulated kinase) 2. Ser200, situated immediately N-terminal to the UBX domain, became phosphorylated in HEK-293 (human embryonic kidney) cells in response to stressors. Phosphorylation was not prevented by SB 203580 (an inhibitor of SAPK2a/p38alpha and SAPK2b/p38beta2) and/or PD 184352 (which inhibits the activation of ERK1 and ERK2), and was similar in fibroblasts lacking both SAPK3/p38gamma and SAPK4/p38delta or JNK1 and JNK2. SAKS1 bound ubiquitin tetramers and VCP (valosin-containing protein) in vitro via the UBA and UBX domains respectively. The amount of VCP in cell extracts that bound to immobilized GST (glutathione S-transferase)-SAKS1 was enhanced by elevating the level of polyubiquitinated proteins, while SAKS1 and VCP in extracts were coimmunoprecipitated with an antibody raised against S5a, a component of the 19 S proteasomal subunit that binds polyubiquitinated proteins. PNGase (peptide N-glycanase) formed a 1:1 complex with VCP and, for this reason, also bound to immobilized GST-SAKS1. We suggest that SAKS1 may be an adaptor that directs VCP to polyubiquitinated proteins, and PNGase to misfolded glycoproteins, facilitating their destruction by the proteasome.
...
PMID:A novel UBA and UBX domain protein that binds polyubiquitin and VCP and is a substrate for SAPKs. 1536 74

In the present report, valosin-containing protein (VCP) was present in Mallory bodies (MBs). To determine if VCP plays a role in MB formation, primary cultured hepatocytes from drug-primed mice that spontaneously form MBs in vitro were studied. The results were compared with control normal hepatocytes. Gene-specific FITC-labeled gripNA (gVCP) was added to the medium of the primary cultures to inhibit the expression of VCP. gVCP increased MB formation by 230% in drug-primed mouse hepatocytes compared with primed liver cells where no VCP oligos were added. Blocking VCP expression induced both multiple small ubiquitin (Ub) and cytokeratin (CK) aggregates to form within the cytoplasm in normal mouse hepatocytes. Inhibition of VCP expression in both drug-primed and control hepatocytes caused a decrease in proteasome chymotrypsin-like (ChT-L) activity. Overexpression of VCP was achieved by transfecting the hepatocytes with a plasmid containing green fluorescent protein (GFP)-fused VCP (pVCP-GFP). Overexpressed VCP was located in both the cytoplasm and nucleus of pVCP-GFP overexpressing drug-primed hepatocytes. VCP was also concentrated within MBs. MB formation was not decreased by the overexpression of VCP in the cells. These results indicate that VCP plays an important role in inducing MB formation, probably through its molecular chaperone function in the ubiquitin-proteasome system (UPS).
...
PMID:RNA interference of VCP/p97 increases Mallory body formation. 1559 54

Misfolded or unassembled polypeptides in the endoplasmic reticulum (ER) are retro-translocated into the cytosol and degraded by the ubiquitin-proteasome system. We reported previously that the SCF(Fbs1,2) ubiquitin-ligase complexes that contribute to ubiquitination of glycoproteins are involved in the ER-associated degradation pathway. Here we investigated how the SCF(Fbs1,2) complexes interact with unfolded glycoproteins. The SCF(Fbs1) complex was associated with p97/VCP AAA ATPase and bound to integrin-beta1, one of the SCF(Fbs1) substrates, in the cytosol in a manner dependent on p97 ATPase activity. Both Fbs1 and Fbs2 proteins interacted with denatured glycoproteins, which were modified with not only high-mannose but also complex-type oligosaccharides, more efficiently than native proteins. Given that Fbs proteins interact with innermost chitobiose in N-glycans, we propose that Fbs proteins distinguish native from unfolded glycoproteins by sensing the exposed chitobiose structure.
...
PMID:Glycoprotein-specific ubiquitin ligases recognize N-glycans in unfolded substrates. 1572 43

Human Fas-associated factor 1 (hFAF1) is a novel protein having multiubiquitin-related domains. We investigated the cellular functions of hFAF1 and found that valosin-containing protein (VCP), the multiubiquitin chain-targeting factor in the degradation of the ubiquitin-proteasome pathway, is a binding partner of hFAF1. hFAF1 is associated with the ubiquitinated proteins via the newly identified N-terminal UBA domain and with VCP via the C-terminal UBX domain. The overexpression of hFAF1 and a truncated UBA domain inhibited the degradation of ubiquitinated proteins and increased cell death. These results suggest that hFAF1 binding to ubiquitinated protein and VCP is involved in the ubiquitin-proteasome pathway. We hypothesize that hFAF1 may serve as a scaffolding protein that regulates protein degradation in the ubiquitin-proteasome pathway.
...
PMID:Human Fas-associated factor 1, interacting with ubiquitinated proteins and valosin-containing protein, is involved in the ubiquitin-proteasome pathway. 1574 42


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---