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)

N-ethylmaleimide-sensitive fusion protein (NSF) and its co-factor soluble NSF attachment protein (alpha)-SNAP) are essential components of the synaptic vesicle fusion machinery and form part of a structurally-conserved 20S protein complex. However, their precise function, relative to fusion itself, is not clear. Using a UV-activated cross-linking approach, we have measured the rate at which a single round of NSF-driven ATP hydrolysis leads to 20S complex disassembly within synaptic membranes. Although this rate is substantially faster than previous estimates of NSF-dependent ATP hydrolysis, it remains much lower than published rates for fusion of synaptic vesicles. Furthermore, the stability of 20S complexes is unaffected by Ca(2+) at concentrations that elicit rapid membrane fusion. We conclude that the ATPase activity of NSF does not contribute directly to vesicle fusion, but more likely plays an earlier role in the synaptic vesicle cycle.
 ...
PMID:Disassembly of membrane-associated NSF 20S complexes is slow relative to vesicle fusion and is Ca(2+)-independent. 1076 9

N-Ethylmaleimide-sensitive factor (NSF) is an ATPase involved in many membrane fusion events within the exocytic and endocytotic pathways. In the present study we showed that NSF is associated with the nuclear envelope. Golgi-associated NSF was released from membranes upon incubation with Mg(2+)-ATP, reflecting the disassembly of a complex consisting of NSF, soluble NSF attachment proteins (SNAPs), and SNAP receptors (SNAREs). In contrast nuclear envelope-associated NSF in interphase cells was not released by the same treatment. During mitosis, however, it was released from nuclear membranes by Mg(2+)-ATP. These results suggest that the binding mode of nuclear membrane-associated NSF changes during the cell cycle.
 ...
PMID:N-ethylmaleimide-sensitive factor is associated with the nuclear envelope. 1091 77

In this study we show the interaction of N-ethylmaleimide-sensitive fusion protein (NSF) with a small GTP-binding protein, Rab6. NSF is an ATPase involved in the vesicular transport within eukaryotic cells. Using the yeast two-hybrid system, we have isolated new NSF-binding proteins from the rat lung cDNA library. One of them was Rab6, which is involved in the vesicular transport within the Golgi and trans-Golgi network as a Ras-like GTPase. We demonstrated that the N-terminal domain of NSF interacted with the C-terminal domain of Rab6, and these proteins were co-immunoprecipitated from the rat brain extract. This interaction was maintained preferentially in the presence of hydrolysable ATP. Recombinant NSF-His(6) can also bind to C-terminal Rab6-glutathione S-transferase under the conditions to allow the ATP hydrolysis. Surprisingly, Rab6 stimulates the ATPase activity of NSF by approx. 2-fold as does alpha-soluble NSF attachment protein receptor. Anti-Rab6 polyclonal antibodies significantly inhibited the Rab6-stimulated ATPase activity of NSF. Furthermore, we found that Rab3 and Rab4 can also associate with NSF and stimulate its ATPase activity. Taken together, we propose a model in which Rab can form an ATP hydrolysis-regulated complex with NSF, and function as a signalling molecule to deliver the signal of vesicle fusion through the interaction with NSF.
 ...
PMID:Identification of Rab6 as an N-ethylmaleimide-sensitive fusion protein-binding protein. 1106 69

The N-ethylmaleimide sensitive factor (NSF) plays a critical role in intracellular trafficking by disassembling soluble NSF attachment protein receptor (SNARE ) complexes. The NSF protomer consists of three domains (NSF-N, NSF-D1, and NSF-D2). Two domains (NSF-D1 and NSF-D2) contain a conserved approximately 230 amino acid cassette, which includes a distinctive motif termed the second region of homology (SRH) common to all ATPases associated with various cellular activities (AAA). In hexameric NSF, several SRH residues become trans elements of the ATP binding pocket. Mutation of two conserved arginine residues in the NSF-D1 SRH (R385A and R388A) did not effect basal or soluble NSF attachment protein (SNAP)-stimulated ATPase activity; however, neither mutant underwent ATP-dependent release from SNAP-SNARE complexes. A trans element of the NSF-D2 ATP binding site (K631) has been proposed to limit the ATPase activity of NSF-D2, but a K631D mutant retained wild-type activity. A mutation of the equivalent residue in NSF-D1 (D359K) also did not affect nucleotide hydrolysis activity but did limit NSF release from SNAP-SNARE complexes. These trans elements of the NSF-D1 ATP binding site (R385, R388, and D359) are not required for nucleotide hydrolysis but are important as nucleotide-state sensors. NSF-N mediates binding to the SNAP-SNARE complex. To identify the structural features required for binding, three conserved residues (R67, S73, and Q76) on the surface of NSF-N were mutated. R67E completely eliminated binding, while S73R and Q76E showed limited effect. This suggests that the surface important for SNAP binding site lies in the cleft between the NSF-N subdomains adjacent to a conserved, positively charged surface.
 ...
PMID:Uncoupling the ATPase activity of the N-ethylmaleimide sensitive factor (NSF) from 20S complex disassembly. 1178 Oct 91

Intracellular membrane fusion is conserved from yeast to man as well as among different intracellular trafficking pathways. This process can be generally divided into several well-defined biochemical reactions. First, an early recognition (or tethering) takes place between donor and acceptor membranes, mediated by ypt/rab GTPases and complexes of tethering factors. Subsequently, a closer association between the two membranes is achieved by a docking process, which involves tight association between membrane proteins termed SNAREs. The formation of such a trans-SNARE complex leads to the final membrane fusion, resulting in an accumulation of cis-SNARE complexes on the acceptor membrane. Thus, multiple rounds of transport and delivery of the donor SNARE back to its original membrane require dissociation of the SNARE complexes. SNARE dissociation, termed priming, is mediated by the AAA ATPase, N-ethylmaleimide-sensitive factor (NSF) and its partner, soluble NSF attachment protein (SNAP), in a reaction that requires ATP hydrolysis. In the present review we focus on LMA1 and GATE-16, two low-molecular-weight proteins, which assist in priming SNARE molecules in the vacuole in yeast and the Golgi complex in mammals, respectively. LMA1 and GATE-16 are suggested to keep the dissociated cis-SNAREs apart from each other, allowing multiple fusion processes to take place. GATE-16 belongs to a novel family of ubiquitin-like proteins conserved from yeast to man. We discuss here the involvement of this family in multiple intracellular trafficking pathways.
 ...
PMID:Involvement of LMA1 and GATE-16 family members in intracellular membrane dynamics. 1291 55

The hexameric ATPase, N-ethylmaleimide sensitive factor (NSF), is essential to vesicular transport and membrane fusion because it affects the conformations and associations of the soluble NSF attachment protein receptor (SNARE) proteins. NSF binds SNAREs through adaptors called soluble NSF attachment proteins (alpha- or beta-SNAP) and disassembles SNARE complexes to recycle the monomers. NSF contains three domains, two nucleotide-binding domains (NSF-D1 and -D2) and an amino terminal domain (NSF-N) that is required for SNAP-SNARE complex binding. Mutagenesis studies indicate that a cleft between the two sub-domains of NSF-N is critical for binding. The structural conservation of N domains in NSF, p97/VCP, and VAT suggests that a similar type of binding site could mediate substrate recognition by other AAA proteins. In addition to SNAP-SNARE complexes, NSF also binds other proteins and protein complexes such as AMPA receptor subunits (GluR2), beta2-adrenergic receptor, beta-Arrestin1, GATE-16, LMA1, rabs, and rab-containing complexes. The potential for these interactions indicates a broader role for NSF in the assembly/disassembly cycles of several cellular complexes and suggests that NSF may have specific regulatory effects on the functions of the proteins involved in these complexes. The structural requirements for these interactions and their physiological significance will be discussed.
 ...
PMID:Multiple binding proteins suggest diverse functions for the N-ethylmaleimide sensitive factor. 1503 35

Biological membrane fusion employs divalent cations as protein cofactors or as signaling ligands. For example, Mg2+ is a cofactor for the N-ethylmaleimide-sensitive factor (NSF) ATPase, and the Ca2+ signal from neuronal membrane depolarization is required for synaptotagmin activation. Divalent cations also regulate liposome fusion, but the role of such ion interactions with lipid bilayers in Rab- and soluble NSF attachment protein receptor (SNARE)-dependent biological membrane fusion is less clear. Yeast vacuole fusion requires Mg2+ for Sec18p ATPase activity, and vacuole docking triggers an efflux of luminal Ca2+. We now report distinct reaction conditions where divalent or monovalent ions interchangeably regulate Rab- and SNARE-dependent vacuole fusion. In reactions with 5 mm Mg2+, other free divalent ions are not needed. Reactions containing low Mg2+ concentrations are strongly inhibited by the rapid Ca2+ chelator BAPTA. However, addition of the soluble SNARE Vam7p relieves BAPTA inhibition as effectively as Ca2+ or Mg2+, suggesting that Ca2+ does not perform a unique signaling function. When the need for Mg2+, ATP, and Sec18p for fusion is bypassed through the addition of Vam7p, vacuole fusion does not require any appreciable free divalent cations and can even be stimulated by their chelators. The similarity of these findings to those with liposomes, and the higher ion specificity of the regulation of proteins, suggests a working model in which ion interactions with bilayer lipids permit Rab- and SNARE-dependent membrane fusion.
 ...
PMID:Ion regulation of homotypic vacuole fusion in Saccharomyces cerevisiae. 1573 91

Nitric oxide (NO) regulates platelet activation by cGMP-dependent mechanisms and by mechanisms that are not completely defined. Platelet activation includes exocytosis of platelet granules, releasing mediators that regulate interactions between platelets, leukocytes, and endothelial cells. Exocytosis is mediated in part by N-ethylmaleimide-sensitive factor (NSF), an ATPase that disassembles complexes of soluble NSF attachment protein receptors. We now demonstrate that NO inhibits exocytosis of dense granules, lysosomal granules, and alpha-granules from human platelets by S-nitrosylation of NSF. Platelets lacking endothelial NO synthase show increased rolling on venules, increased thrombosis in arterioles, and increased exocytosis in vivo. Regulation of exocytosis is thus a mechanism by which NO regulates thrombosis.
 ...
PMID:Regulation of platelet granule exocytosis by S-nitrosylation. 1573 22

Rab5, a small guanosine triphosphatase, is known to regulate the tethering and docking reaction leading to SNARE (soluble NSF attachment protein receptors)-mediated fusion between endosomes. However, it is uncertain how the signal of the activated Rab5 protein is transduced by its downstream effectors during endosome fusion. Here, we show that the Sec1/Munc18 gene vps-45 is essential for not only viability and development but also receptor-mediated and fluid-phase endocytosis pathways in Caenorhabditis elegans. We found that VPS-45 interacts with a Rab5 effector, Rabenosyn-5 (RABS-5), and the mutants of both vps-45 and rabs-5 show similar endocytic phenotypes. In the macrophage-like cells of vps-45 and rabs-5 mutants, aberrantly small endosomes were accumulated, and the endosome fusion stimulated by the mutant RAB-5 (Q78L) is suppressed by these mutations. Our results indicate that VPS-45 is a key molecule that functions downstream from RAB-5, cooperating with RABS-5, to regulate the dynamics of the endocytic system in multicellular organisms.
 ...
PMID:The SM protein VPS-45 is required for RAB-5-dependent endocytic transport in Caenorhabditis elegans. 1723 59

Mannose 6-phosphate receptors (MPRs) are transported from endosomes to the Golgi after delivering lysosomal enzymes to the endocytic pathway. This process requires Rab9 guanosine triphosphatase (GTPase) and the putative tether GCC185. We show in human cells that a soluble NSF attachment protein receptor (SNARE) complex comprised of syntaxin 10 (STX10), STX16, Vti1a, and VAMP3 is required for this MPR transport but not for the STX6-dependent transport of TGN46 or cholera toxin from early endosomes to the Golgi. Depletion of STX10 leads to MPR missorting and hypersecretion of hexosaminidase. Mouse and rat cells lack STX10 and, thus, must use a different target membrane SNARE for this process. GCC185 binds directly to STX16 and is competed by Rab6. These data support a model in which the GCC185 tether helps Rab9-bearing transport vesicles deliver their cargo to the trans-Golgi and suggest that Rab GTPases can regulate SNARE-tether interactions. Importantly, our data provide a clear molecular distinction between the transport of MPRs and TGN46 to the trans-Golgi.
 ...
PMID:A syntaxin 10-SNARE complex distinguishes two distinct transport routes from endosomes to the trans-Golgi in human cells. 1819 6


<< Previous 1 2 3 Next >>