Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

p47 is the major protein identified in complex with the cytosolic AAA ATPase p97. It functions as an essential cofactor of p97-regulated membrane fusion, which has been suggested to disassemble t-t-SNARE complexes and prepare them for further rounds of membrane fusion. Here, we report the high-resolution NMR structure of the C-terminal domain from p47. It comprises a UBX domain and a 13 residue long structured N-terminal extension. The UBX domain adopts a characteristic ubiquitin fold with a betabetaalphabetabetaalphabeta secondary structure arrangement. Three hydrophobic residues from the N-terminal extension pack closely against a cleft in the UBX domain. We also identify, for the first time, the p97 interaction surface using NMR chemical shift perturbation studies.
 ...
PMID:Solution structure and interaction surface of the C-terminal domain from p47: a major p97-cofactor involved in SNARE disassembly. 1147 59

In eukaryotic cells, incorrectly folded proteins in the endoplasmic reticulum (ER) are exported into the cytosol and degraded by the proteasome. This pathway is co-opted by some viruses. For example, the US11 protein of the human cytomegalovirus targets the major histocompatibility complex class I heavy chain for cytosolic degradation. How proteins are extracted from the ER membrane is unknown. In bacteria and mitochondria, members of the AAA ATPase family are involved in extracting and degrading membrane proteins. Here we demonstrate that another member of this family, Cdc48 in yeast and p97 in mammals, is required for the export of ER proteins into the cytosol. Whereas Cdc48/p97 was previously known to function in a complex with the cofactor p47 (ref. 5) in membrane fusion, we demonstrate that its role in ER protein export requires the interacting partners Ufd1 and Npl4. The AAA ATPase interacts with substrates at the ER membrane and is needed to release them as polyubiquitinated species into the cytosol. We propose that the Cdc48/p97-Ufd1-Npl4 complex extracts proteins from the ER membrane for cytosolic degradation.
 ...
PMID:The AAA ATPase Cdc48/p97 and its partners transport proteins from the ER into the cytosol. 1174 May 63

Although nuclear envelope (NE) assembly is known to require the GTPase Ran, the membrane fusion machinery involved is uncharacterized. NE assembly involves formation of a reticular network on chromatin, fusion of this network into a closed NE and subsequent expansion. Here we show that p97, an AAA-ATPase previously implicated in fusion of Golgi and transitional endoplasmic reticulum (ER) membranes together with the adaptor p47, has two discrete functions in NE assembly. Formation of a closed NE requires the p97-Ufd1-Npl4 complex, not previously implicated in membrane fusion. Subsequent NE growth involves a p97-p47 complex. This study provides the first insights into the molecular mechanisms and specificity of fusion events involved in NE formation.
 ...
PMID:Distinct AAA-ATPase p97 complexes function in discrete steps of nuclear assembly. 1178 82

Starting with a mutation impacting photoreceptor morphogenesis, we identify here a Drosophila gene, eyes closed (eyc), as a fly homolog of p47, a protein co-factor of the p97 ATPase implicated in membrane fusion. Temporal misexpression of Eyc during rhabdomere extension early in pupal life results in inappropriate retention of normally transient adhesions between developing rhabdomeres. Later Eyc misexpression results in endoplasmic reticulum proliferation and inhibits rhodopsin transport to the developing photosensitive membrane. Loss of Eyc function results in a lethal failure of nuclear envelope assembly in early zygotic divisions. Phenotypes resulting from eyc mutations provide the first in vivo evidence for a role for p47 in membrane biogenesis.
 ...
PMID:Eyes closed, a Drosophila p47 homolog, is essential for photoreceptor morphogenesis. 1178 8

The phagocyte nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH) oxidase was functionally reconstituted in monkey kidney COS-7 cells by transfection of essential subunits, gp91(phox), p22(phox), p47(phox), and p67(phox). COS-7 cells express the essential small guanosine 5'-triphosphatase, Rac1. Transgenic COS-phox cells were capable of arachidonic acid-induced NADPH oxidase activity up to 80% of that of human neutrophils, and of phorbol myristate acetate (PMA)-induced activity up to 20% of that of neutrophils. Expression of all 4 phox components was required for enzyme activity, and enzyme activation was associated with membrane translocation of p47(phox), p67(phox), and Rac1. Expression of p47(phox) Ser303Ala/Ser304Ala or Ser379Ala phosphorylation-deficient mutants resulted in significantly impaired NAPDH oxidase activity, compared with expression of wild-type p47(phox) or the p47(phox) Ser303Glu/Ser304Glu phosphorylation mimic, suggesting that p47(phox) phosphorylation contributes to enzyme activity in the COS system, as is the case in neutrophils. Hence, COS-phox cells should be useful as a new whole-cell model that is both capable of high-level superoxide production and readily amenable to genetic manipulation for investigation of NADPH oxidase function. PMA-elicited superoxide production in COS-phox cells was regulated by activation of protein kinase C (PKC) and Rac. Although COS-7 cells differ from human neutrophils in PKC isoform expression, transient expression of major neutrophil isoforms in COS-phox cells did not increase PMA-induced superoxide production, suggesting that endogenous isoforms were not rate limiting. Val204 in p67(phox), previously shown to be required for NADPH oxidase activity under cell-free conditions, was found to be essential for superoxide production by intact COS-phox cells, on the basis of transfection studies using a p67(phox) (Val204Ala) mutant.
 ...
PMID:Creation of a genetic system for analysis of the phagocyte respiratory burst: high-level reconstitution of the NADPH oxidase in a nonhematopoietic system. 1192 50

The ATPase p97 in complex with p47 participates in Golgi cisternae rebuilding after mitosis. In a Golgi-liposome assay, the complex triggered a phosphatidylethanolamine (PE)-promoted fusion. Here we show for the first time that fusion between mitotic Golgi membranes induced by adding cytosol or purified p97/p47 is modulated by PE present in Golgi membranes. Using model membranes, we demonstrate a PE-dependent recruitment of p97/p47 to membranes, causing dramatic conformational rearrangements and favoring protein-lipid interactions. Previously buried hydrophobic sites become exposed in a controlled manner, which leads to the penetration of (a) domain(s) of the complex into lipid bilayers, facilitated by a PE-dependent increase in headgroup spacing. In contrast, when facing phosphatidylcholine (PC) the complex clusters extensively. This implies that in the presence of PC protein-protein interactions rather than fusion-promoting protein-lipid interactions occur. Importantly, PE-mediated changes in secondary and tertiary structures are exclusively observed when p97 is complexed with p47, which is a prerequisite for membrane fusion. We therefore propose that at physiological conditions PE-induced conformational changes in p97/p47 are relevant in triggering this activity.
 ...
PMID:Phospholipid species act as modulators in p97/p47-mediated fusion of Golgi membranes. 1214 47

The multiple functions of the p97/Cdc48p ATPase can be explained largely by adaptors that link its activity to different cellular pathways, but how these adaptors recognize different substrates is unclear. Here we present evidence that the mammalian adaptors, p47 and Ufd1-Npl4, both bind ubiquitin conjugates directly and so link p97 to ubiquitylated substrates. In the case of Ufd1-Npl4, which is involved in endoplasmic reticulum (ER)-associated degradation and nuclear envelope reassembly, binding to ubiquitin is mediated through a putative zinc finger in Npl4. This novel domain (NZF) is conserved in metazoa and is both present and functional in other proteins. In the case of p47, which is involved in the reassembly of the ER, the nuclear envelope and the Golgi apparatus, binding is mediated by a UBA domain. Unlike Ufd1-Npl4, it binds ubiquitin only when complexed with p97, and binds mono- rather than polyubiquitin conjugates. The UBA domain is required for the function of p47 in mitotic Golgi reassembly. Together, these data suggest that ubiquitin recognition is a common feature of p97-mediated reactions.
 ...
PMID:Direct binding of ubiquitin conjugates by the mammalian p97 adaptor complexes, p47 and Ufd1-Npl4. 1241 82

A topic that is keeping cell biologists across several fields occupied is how the AAA ATPase p97 can have so many apparently unrelated functions. A recent model that proposed sets of adaptors for p97 selected according to the type of p97 activity seemed to afford a simple solution. For example, one known adaptor, the Ufd1-Npl4 complex, has been implicated in ubiquitin-dependent proteolysis whereas another, p47, is an essential co-factor for membrane fusion. However, further investigation has revealed that the situation is more complicated. Both Ufd1-Npl4 and p47 adaptors bind ubiquitin, and so their activities may be more closely related than first thought. A role for ubiquitin in p97-dependent membrane fusion is a particularly surprising development with no obvious explanation. However, some clues may be found from looking at the role of ubiquitin and the AAA ATPase Vps4 during sorting on the endocytic pathway.
 ...
PMID:p97, a protein coping with multiple identities. 1451 84

Interferon-gamma (IFN-gamma) provides an essential component of immunity to tuberculosis by activating infected host macrophages to directly inhibit the replication of Mycobacterium tuberculosis (Mtb). IFN-gamma-inducible nitric oxide synthase 2 (NOS2) is considered a principal effector mechanism, although other pathways may also exist. Here, we identify one member of a newly emerging 47-kilodalton (p47) guanosine triphosphatase family, LRG-47, that acts independently of NOS2 to protect against disease. Mice lacking LRG-47 failed to control Mtb replication, unlike those missing the related p47 guanosine triphosphatases IRG-47 or IGTP. Defective bacterial killing in IFN-gamma-activated LRG-47-/- macrophages was associated with impaired maturation of Mtb-containing phagosomes, vesicles that otherwise recruited LRG-47 in wild-type cells. Thus, LRG-47 may serve as a critical vacuolar trafficking component used to dispose of intracellular pathogens like Mtb.
 ...
PMID:Immune control of tuberculosis by IFN-gamma-inducible LRG-47. 1457 37

Human neutrophil adherence to ECMs induces an initial inhibition of stimulated reactive oxygen species (ROS) formation, followed by an enhanced phase of oxidant production. The initial integrin-mediated suppression of ROS constitutes a mechanism to prevent inappropriate tissue damage as leukocytes migrate to inflammatory sites. The Rac2 guanosine 5'-triphosphatase (GTPase) is a critical regulatory component of the phagocyte NADPH oxidase. We show that activation of Rac2 is inhibited in adherent neutrophils, correlating with inhibition of ROS formation. Conversely, NADPH oxidase components p47 and p67 assemble normally, suggesting a specific action of adhesion on the Rac2 molecular switch. Reconstitution with activated Rac2 restored rapid NADPH oxidase activation kinetics to adherent neutrophils, establishing that inhibition was due to defective Rac2 activity. We provide evidence that integrins inhibit Rac2 activation via a membrane-associated guanine nucleotide exchange factor, likely to be Vav1. Activation of Vav1, but not its upstream activator, Syk, is suppressed by cell adhesion. Vav1 activity is inhibited due to dephosphorylation of the regulatory Tyr174 via enhanced tyrosine phosphatase activity in adherent cells. These studies identify an integrin-mediated pathway in which Vav1 is as a strong candidate for the critical regulatory point in suppression of Rac2 activation and ROS generation during inflammatory responses.
 ...
PMID:The molecular basis for adhesion-mediated suppression of reactive oxygen species generation by human neutrophils. 1466 Jul 49


<< Previous 1 2 3 4 5 6 7 Next >>