Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022716 (Menkes)
 1,057 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recently, mutations in the gene encoding for the bi-functional enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE/MNK), symbol GNE or GLCNE (MIM: 603824) [EC 5.1.3.14], were associated with IBM2 (MIM: 600737). IBM2 is a recessively inherited vacuolar myopathy with a prevalence rate of 1-2/1000 amongst people of Iranian-Jewish descent. Seven missense mutations were previously described by Eisenberg et al. All families tested from Iranian and Middle Eastern Jewish ancestry have the same homozygous mutation (bp2186t>c). Here we review the mutations in GNE associated with IBM2, and we describe additional four mutations found in individuals suffering from clinically similar disorder who are not of Iranian or Jewish descent. These findings further confirm that homozygous or compound heterozygous mutations of GNE/MNK gene associated with IBM2 are not confined to any single specific region of the enzyme outside its negative feedback regulatory domain located at codons 249-275.
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PMID:Four novel mutations associated with autosomal recessive inclusion body myopathy (MIM: 600737). 1240 74

Recently, bi-allelic mutations in the gene coding for the bi-functional enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE/MNK), symbol GNE or GLCNE (MIM: 603824), were associated with the recessively inherited phenotype of IBM2 (MIM: 600737). All patients tested so far have bi-allelic missense mutation(s) of epimerase and/or kinase domains of GNE gene, which clearly explains the recessive inheritance pattern of this phenotype. Single allelic mutations of codons 263-266 of GNE have been implicated as the cause of French type sialuria (MIM: 269921). The dominantly inherited French type sialuria seems to result from defective allosteric feedback inhibitory regulation of GNE/MNK by cytidine monophosphate-N-acetylneuraminic acid (CMP-NANA), resulting in overproduction of cytosolic N-acetylneuraminic acid, and massive urinary excretion of free sialic acid. Because GNE is relatively weakly expressed in skeletal muscle cells, and involvement of other organs are not clinically evident in patients affected with IBM2, it is likely that the missense mutation(s) found in these patients cause a partial reduction of the efficiency of either the epimerase or the kinase activity of this enzyme. Therapeutic dietary modifications are recommended including reduction of ethanol consumption, avoidance of excess selenium, copper, and zinc, and dietary promotion of magnesium (Mg(2+)), which is an essential co-factor for this enzyme.
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PMID:Magnesium may help patients with recessive hereditary inclusion body myopathy, a pathological review. 1245 Jul 72

The Menkes copper-translocating P-type ATPase (ATP7A; MNK) is a ubiquitous protein that regulates the absorption of copper in the gastrointestinal tract. Inside cells the protein has a dual function: it delivers copper to cuproenzymes in the Golgi compartment and effluxes excess copper. The latter property is achieved through copper-dependent vesicular trafficking of the Menkes protein to the plasma membrane of the cell. The trafficking mechanism and catalytic activity combine to facilitate absorption and intercellular transport of copper. The mechanism of catalysis and copper-dependent trafficking of the Menkes protein are the subjects of this review. Menkes disease, a systemic copper deficiency disorder, is caused by mutations in the gene encoding the Menkes protein. The effect of these mutations on the catalytic cycle and the cell biology of the Menkes protein, as well as predictions of the effect of particular mutant MNKs on observed Menkes disease symptoms will also be discussed.
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PMID:Menkes copper-translocating P-type ATPase (ATP7A): biochemical and cell biology properties, and role in Menkes disease. 1253 63

The Menkes protein (ATP7A; MNK) is a ubiquitous human copper-translocating P-type ATPase and it has a key role in regulating copper homeostasis. Previously we characterised fundamental steps in the catalytic cycle of the Menkes protein. In this study we analysed the role of several conserved regions of the Menkes protein, particularly within the putative cytosolic ATP-binding domain. The results of catalytic studies have indicated an important role of 1086His in catalysis. Our findings provide a biochemical explanation for the most common Wilson disease-causing mutation (H1069Q in the homologous Wilson copper-translocating P-type ATPase). Furthermore, we have identified a unique role of 1230Asp, within the DxxK motif, in coupling ATP binding and acylphosphorylation with copper translocation. Finally, we found that the Menkes protein mutants with significantly reduced catalytic activity can still undergo copper-regulated exocytosis, suggesting that only the complete loss of catalytic activity prevents copper-regulated trafficking of the Menkes protein.
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PMID:Mutational analysis of the Menkes copper P-type ATPase (ATP7A). 1256 88

The Menkes copper-translocating P-type ATPase (ATP7A; MNK) is a key regulator of copper homeostasis in humans. It has a dual role in supplying copper to essential cuproenzymes in the trans-Golgi network (TGN) and effluxing copper from the cell. These functions are achieved through copper-regulated trafficking of MNK between the TGN and the plasma membrane. However, the exact mechanism(s) which regulate the localisation and biochemical functions of MNK are still unknown. Here we investigated copper-dependent phosphorylation of MNK by a putative protein kinase(s). We found that in the presence of elevated copper there was a substantial increase in phosphorylation of the wild-type MNK in vivo. The majority of copper-dependent phosphorylation was on serine residues in two phosphopeptides. In contrast, there was no up-regulation of phosphorylation of a non-trafficking MNK mutant with mutated cytosolic copper-binding sites. Our findings suggest a potentially important role of kinase-dependent phosphorylation in the regulation of function of the MNK protein.
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PMID:Protein kinase-dependent phosphorylation of the Menkes copper P-type ATPase. 1264 8

Excess copper is effluxed from mammalian cells by the Menkes or Wilson P-type ATPases (MNK and WND, respectively). MNK and WND have six metal binding sites (MBSs) containing a CXXC motif within their N-terminal cytoplasmic region. Evidence suggests that copper is delivered to the ATPases by Atox1, one of three cytoplasmic copper chaperones. Attempts to monitor a direct Atox1-MNK interaction and to determine kinetic parameters have not been successful. Here we investigated interactions of Atox1 with wild-type and mutated pairs of the MBSs of MNK using two different methods: yeast two-hybrid analysis and real-time surface plasmon resonance (SPR). A copper-dependent interaction of Atox1 with the MBSs of MNK was observed by both approaches. Cys to Ser mutations of conserved CXXC motifs affected the binding of Atox1 underlining the essentiality of Cys residues for the copper-induced interaction. Although the yeast two-hybrid assay failed to show an interaction of Atox1 with MBS5/6, SPR analysis clearly demonstrated a copper-dependent binding with all six MBSs highlighting the power and sensitivity of SPR as compared with other, more indirect methods like the yeast two-hybrid system. Binding constants for copper-dependent chaperone-MBS interactions were determined to be 10-5-10-6 m for all the MBSs representing relatively low affinity binding events. The interaction of Atox1 with pairs of the MBSs was non-cooperative. Therefore, a functional difference of the MBSs in the MNK N terminus cannot be attributed to cooperativity effects or varying affinities of the copper chaperone Atox1 with the MBSs.
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PMID:Kinetic analysis of the interaction of the copper chaperone Atox1 with the metal binding sites of the Menkes protein. 1267 32

MNK (Menkes copper-translocating P-type ATPase, or the Menkes protein; ATP7A) plays a key role in regulating copper homoeostasis in humans. MNK has been shown to have a dual role in the cell: it delivers copper to cuproenzymes in the Golgi compartment and effluxes excess copper from the cell. These roles can be achieved through copper-regulated trafficking of MNK. It has previously been shown to undergo trafficking from the trans -Golgi network to the plasma membrane in response to elevated copper concentrations, and to be endocytosed from the plasma membrane to the trans -Golgi network upon the removal of elevated copper. However, the fundamental question as to whether copper influences trafficking of MNK to or from the plasma membrane remained unanswered. In this study we utilized various methods of cell-surface biotinylation to attempt to resolve this issue. These studies suggest that copper induces trafficking of MNK to the plasma membrane but does not affect its rate of internalization from the plasma membrane. We also found that only a specific pool of MNK can traffic to the plasma membrane in response to elevated copper. Significantly, copper appeared to divert MNK into a fast-recycling pool and prevented it from recycling to the Golgi compartment, thus maintaining a high level of MNK in the proximity of the plasma membrane. These findings shed new light on the cell biology of MNK and the mechanism of copper homoeostasis in general.
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PMID:Copper stimulates trafficking of a distinct pool of the Menkes copper ATPase (ATP7A) to the plasma membrane and diverts it into a rapid recycling pool. 1464 Sep 79

The Cu-ATPase ATP7A (MNK) is localized in the trans-Golgi network (TGN) and relocalizes in the plasma membrane via vesicle-mediated traffic following exposure of the cells to high concentrations of copper. Rab proteins are organelle-specific GTPases, markers of different endosomal compartments; their role has been recently reviewed (Trends Cell Biol. 11(2001) 487). In this article we analyze the endosomal pathway of trafficking of the MNK protein in stably transfected clones of CHO cells, expressing chimeric Rab5-myc or Rab7-myc proteins, markers of early or late endosome compartments, respectively. We demonstrate by immunofluorescence and confocal and electron microscopy techniques that the increase in the concentration of copper in the medium (189 microM) rapidly induces a redistribution of the MNK protein from early sorting endosomes, positive for Rab5-myc protein, to late endosomes, containing the Rab7-myc protein. Cell fractionation experiments confirm these results; i.e., the MNK protein is recruited to the endosomal fraction on copper stimulation and colocalizes with Rab5 and Rab7 proteins. These findings allow the first characterization of the vesicles involved in the intracellular routing of the MNK protein from the TGN to the plasma membrane, a key mechanism allowing appropriate efflux of copper in cells grown in high concentrations of the metal.
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PMID:Endosomal trafficking of the Menkes copper ATPase ATP7A is mediated by vesicles containing the Rab7 and Rab5 GTPase proteins. 1464 59

We have used genetic and microarray analysis to determine how ionizing radiation (IR) induces p53-dependent transcription and apoptosis in Drosophila melanogaster. IR induces MNK/Chk2-dependent phosphorylation of p53 without changing p53 protein levels, indicating that p53 activity can be regulated without an Mdm2-like activity. In a genome-wide analysis of IR-induced transcription in wild-type and mutant embryos, all IR-induced increases in transcript levels required both p53 and the Drosophila Chk2 homolog MNK. Proapoptotic targets of p53 include hid, reaper, sickle, and the tumor necrosis factor family member EIGER: Overexpression of Eiger is sufficient to induce apoptosis, but mutations in Eiger do not block IR-induced apoptosis. Animals heterozygous for deletions that span the reaper, sickle, and hid genes exhibited reduced IR-dependent apoptosis, indicating that this gene complex is haploinsufficient for induction of apoptosis. Among the genes in this region, hid plays a central, dosage-sensitive role in IR-induced apoptosis. p53 and MNK/Chk2 also regulate DNA repair genes, including two components of the nonhomologous end-joining repair pathway, Ku70 and Ku80. Our results indicate that MNK/Chk2-dependent modification of Drosophila p53 activates a global transcriptional response to DNA damage that induces error-prone DNA repair as well as intrinsic and extrinsic apoptosis pathways.
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PMID:Drosophila melanogaster MNK/Chk2 and p53 regulate multiple DNA repair and apoptotic pathways following DNA damage. 1472 67

The human X-linked recessive copper deficiency disorder, Menkes disease, is caused by mutations in the ATP7A (MNK) gene, which encodes a transmembrane copper-transporting P-type ATPase (MNK). The MNK protein is localised to the Golgi apparatus and relocalises to the plasma membrane when copper levels are elevated. Previous studies have identified a C-terminal di-leucine endocytic motif (L1487L1488) in MNK, thought to direct it into the clathrin-mediated endocytic pathway. To determine whether MNK is internalised via clathrin-dependent endocytosis, this pathway was blocked in MNK-overexpressing HeLa cells by the transient expression of dominant negative dynamin and Eps15 mutants. MNK internalisation was not inhibited in such cells. MNK internalisation was inhibited in cells treated with hypertonic sucrose that not only blocked clathrin-mediated endocytosis but also fluid-phase endocytosis. These studies, together with earlier studies on the requirement for L1487L1488, suggest that MNK can utilise both clathrin-dependent and clathrin-independent endocytosis in HeLa cells.
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PMID:Studies on endocytic mechanisms of the Menkes copper-translocating P-type ATPase (ATP7A; MNK). Endocytosis of the Menkes protein. 1497 65


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