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

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The BRCA1 associated C-terminal helicase (BACH1) associated with breast cancer has been implicated in double strand break (DSB) repair. More recently, BACH1 (FANCJ) has been genetically linked to the chromosomal instability disorder Fanconi Anemia (FA). Understanding the roles of BACH1 in cellular DNA metabolism and how BACH1 dysfunction leads to tumorigenesis requires a comprehensive investigation of its catalytic mechanism and molecular functions in DNA repair. In this study, we have determined that BACH1 helicase contacts with both the translocating and the non-translocating strands of the duplex are critical for its ability to track along the sugar phosphate backbone and unwind dsDNA. An increased motor ATPase of a BACH1 helicase domain variant (M299I) enabled the helicase to unwind the backbone-modified DNA substrate in a more proficient manner. Alternatively, increasing the length of the 5' tail of the DNA substrate allowed BACH1 to overcome the backbone discontinuity, suggesting that BACH1 loading mechanism is critical for its ability to unwind damaged DNA molecules.
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PMID:Inhibition of BACH1 (FANCJ) helicase by backbone discontinuity is overcome by increased motor ATPase or length of loading strand. 1714 8

The Fanconi syndrome is a common side effect of the chemotherapeutic agent ifosfamide. Current evidences suggest that chloroacetaldehyde (CAA), one of the main metabolites of ifosfamide activation, contributes to its nephrotoxicity. However, the pathophysiology of CAA-induced Fanconi syndrome is not fully understood. The present work examined the adverse effects of CAA on precision-cut rat renal cortical slices, which allowed studying the toxic effect of CAA on proximal endocytosis. We demonstrated that clinically relevant concentrations of CAA (< or =200 microM) are able to inhibit the uptake of horseradish peroxidase, a marker of proximal tubular cell endocytosis in renal tubular proximal cells. CAA > or =75 microM has adverse effects, both on viability parameters and on energy metabolism, as shown by the great decrease in total glutathione and ATP levels. In addition, the V-ATPase, which plays a crucial role in intracellular vesicle trafficking, was inhibited by 100 microM of CAA. By contrast, the slight decrease in Na-K-ATPase activity observed for CAA> or = 125 microM (maximum inhibition: 33%) could not totally explain the inhibition of the reabsorption processes. In conclusion, the addition of the two main adverse effects of CAA (decrease in ATP levels and inhibition of the V-ATPase) could explain the inhibition of endocytosis and the Fanconi syndrome observed during ifosfamide treatments.
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PMID:Mechanisms of the ifosfamide-induced inhibition of endocytosis in the rat proximal kidney tubule. 1821 44

Alterations in ATP metabolism have been proposed to be involved in the pathogenesis of cystinosis, the most common form of inherited Fanconi syndrome. A recent study showed normal activity of respiratory chain complexes I-IV with decreased ATP levels in cystinotic fibroblasts. Here, we show normal complex V expression and activity in mitochondria of cystinotic fibroblasts. This indicates that alterations in mitochondrial oxidative phosphorylation enzymes are not responsible for ATP decrease in cystinotic fibroblasts.
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PMID:Mitochondrial complex V expression and activity in cystinotic fibroblasts. 1859 76

Cadmium and lead are divalent cations with a propensity to settle in the proximal tubule of the nephron, leading to nephrotoxicity. The pathophysiological results, however, tend to diverge. Cadmium in sufficient cumulative dosage leads to the production of the Fanconi syndrome, a generalized proximal tubular reabsorptive defect thought to be related to inhibition of both ATP production and Na-K-ATPase activity. On the other hand, lead accumulation in the proximal tubule leads to hyperuricaemia and gout, presumably by inhibiting uric acid secretion, and diminished glomerular filteration rate (GFR). Fanconi syndrome is seen unusually only in children and experimental animals. Cadmium nephrotoxicity is heralded by increased excretion of beta2-microglobulin, retinol binding protein and alpha1-microglobulin, indicative of decreased proximal tubule function. Beta2-microglobulinuria is not found in lead nephropathy. In lead nephropathy albuminuria is absent or minimal whereas in cadmium nephropathy albuminuria is variable. From the standpoint of pathology, both entities are characterized by tubulointerstitial disease and fibrosis, but only early lead nephropathy is characterized by the presence of proximal tubule nuclear inclusion bodies, due to the combination of lead with a lead binding-protein.
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PMID:Nephrotoxicity of cadmium & lead. 1910 33

Renal tubular acidosis (RTA) is a hyperchloremic metabolic acidosis characterized by a normal anion gap and normal (or near normal) glomerular filtration rate in the absence of diarrhoea. Inherited isolated forms of renal tubular acidosis are not common. However, they can also be a part of a more generalized tubule defect, like in Fanconi syndrome. In recent years more and more gene mutations have been found which are associated with RTA (mutations in the gene SLC4A4, encoding a Na(+)-HCO(3)(-) cotransporter (NBC-1); in the gene SLC4A1, encoding Cl(-)/HCO3(-) exchanger (AE1); in the gene ATP6B1, encoding B1 subunit of H(+)-ATPase; in the gene CA2 encoding carbonic anhydrase II; and others) and allow better understanding of underlying processes of bicarbonate and H(+) transport. Isolated renal tubular acidosis can be frequently acquired due to use of certain drug groups, autoimmune disease or kidney transplantation. As the prevalence of acquired forms of RTA is common, new therapeutic options for the currently used supplementation of oral alkali, are awaited.
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PMID:Renal tubular acidosis--underrated problem? 2269 89

Fanconi-Bickel syndrome is a rare autosomal-recessive disorder caused by mutations in the SLC2A2 gene coding for the glucose transporter protein 2 (GLUT2). Major manifestations include hepatomegaly, glucose intolerance, post-prandial hypoglycaemia and renal disease that usually presents as proximal tubular acidosis associated with proximal tubule dysfunction (renal Fanconi syndrome). We report a patient harbouring a homozygous mutation of SLC2A2 who presented a dramatic exacerbation of metabolic acidosis in the context of a viral infection, owing to both ketosis and major urinary bicarbonate loss. The kidney biopsy revealed nuclear and cytoplasmic accumulation of glycogen in proximal tubule cells, a lack of expression of GLUT2, and major defects of key proteins of the proximal tubule such as megalin, cubilin and the B2 subunit of H(+)-ATPase. These profound alterations of the transport systems most likely contributed to proximal tubule alterations and profound bicarbonate loss.
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PMID:Acute metabolic acidosis in a GLUT2-deficient patient with Fanconi-Bickel syndrome: new pathophysiology insights. 2516 76

Cystinosis is a rare autosomal recessive storage disorder characterized by defective lysosomal efflux of cystine due to mutations in the CTNS gene encoding the lysosomal cystine transporter, cystinosin. Lysosomal cystine accumulation leads to crystal formation and functional impairment of multiple organs. Moreover, cystinosis is the most common inherited cause of renal Fanconi syndrome in children. Oral cysteamine therapy delays disease progression by reducing intracellular cystine levels. However, because cysteamine does not correct all complications of cystinosis, including Fanconi syndrome, we hypothesized that cystinosin could have novel roles in addition to transporting cystine out of the lysosome. By coimmunoprecipitation experiments and mass spectrometry, we found cystinosin interacts with almost all components of vacuolar H(+)-ATPase and the Ragulator complex and with the small GTPases Ras-related GTP-binding protein A (RagA) and RagC. Furthermore, the mammalian target of rapamycin complex 1 (mTORC1) pathway was downregulated in proximal tubular cell lines derived from Ctns(-/-) mice. Decrease of lysosomal cystine levels by cysteamine did not rescue mTORC1 activation in these cells, suggesting that the downregulation of mTORC1 is due to the absence of cystinosin rather than to the accumulation of cystine. Our results show a dual role for cystinosin as a cystine transporter and as a component of the mTORC1 pathway, and provide an explanation for the appearance of Fanconi syndrome in cystinosis. Furthermore, this study highlights the need to develop new treatments not dependent on lysosomal cystine depletion alone for this devastating disease.
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PMID:Cystinosin is a Component of the Vacuolar H+-ATPase-Ragulator-Rag Complex Controlling Mammalian Target of Rapamycin Complex 1 Signaling. 2644 7

Infiltration by IgG-positive plasma cells is a common finding in tubulointerstitial nephritis. Indeed, it has been thought that CD138-positive mature plasma cells secrete mainly IgG, and the occurrence of tubulointerstitial nephritis with CD138-positive plasma cells secreting IgM has rarely been reported. Routine immunofluorescence of fresh frozen sections is considered the gold standard for detection of immune deposits. However, the immunoenzyme method with formalin-fixed, paraffin-embedded sections is superior for detecting IgM- or IgG-positive cells within the renal interstitium, thus histologic variants may often go undetected. We recently discovered a case of tubulointerstitial nephritis showing IgM-positive plasma cell accumulation within the interstitium. To further explore the morphologic and clinical features of such cases, we performed a nationwide search for patients with biopsy-proven tubulointerstitial nephritis and high serum IgM levels. We identified 13 patients with tubulointerstitial nephritis and IgM-positive plasma cell infiltration confirmed with the immunoenzyme method. The clinical findings for these patients included a high prevalence of distal renal tubular acidosis (100%), Fanconi syndrome (92%), and anti-mitochondrial antibodies (82%). The pathologic findings were interstitial nephritis with diffusely distributed CD3-positive T lymphocytes and colocalized IgM-positive plasma cells, as well as tubulitis with CD3-positive T lymphocytes in the proximal tubules and collecting ducts. Additionally, levels of H⁺-ATPase, H⁺, K⁺-ATPase, and the HCO₃^--Cl^- anion exchanger were markedly decreased in the collecting ducts. We propose to designate this group of cases, which have a common histologic and clinical form, as IgM-positive plasma cell-tubulointerstitial nephritis.
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PMID:Tubulointerstitial Nephritis with IgM-Positive Plasma Cells. 2879 48

Cystinosis is a lysosomal storage disorder caused by defects in CTNS, the gene that encodes the lysosomal cystine transporter cystinosin. Patients with nephropathic cystinosis are characterized by endocrine defects, defective proximal tubule cell (PTC) function, the development of Fanconi syndrome and, eventually, end-stage renal disease. Kidney disease is developed despite the use of cysteamine, a drug that decreases lysosomal cystine overload but fails to correct overload-independent defects. Chaperone-mediated autophagy (CMA), a selective form of autophagy, is defective in cystinotic mouse fibroblasts, and treatment with cysteamine is unable to correct CMA defects in vivo, but whether the vesicular trafficking mechanisms that lead to defective CMA in cystinosis are manifested in human PTCs is not currently known and whether PTC-specific mechanisms are corrected upon CMA upregulation remains to be elucidated. Here, using CRISPR-Cas9 technology, we develop a new human PTC line with defective cystinosin expression (CTNS-KO PTCs). We show that the expression and localization of the CMA receptor, LAMP2A, is defective in CTNS-KO PTCs. The expression of the lipidated form of LC3B, a marker for another form of autophagy (macroautophagy), is decreased in CTNS-KO PTCs indicating decreased autophagosome numbers under basal conditions. However, the autophagic flux is functional, as measured by induction by starvation or by blockage using the v-ATPase inhibitor bafilomycin A, and by degradation of the macroautophagy substrate SQSTM1 under starvation and proteasome-inhibited conditions. Previous studies showed that LAMP2A accumulates in Rab11-positive vesicles in cystinotic cells. Here, we show defective Rab11 expression, localization and trafficking in CTNS-KO PTCs as determined by confocal microscopy, immunoblotting and TIRFM. We also show that both Rab11 expression and trafficking in cystinotic PTCs are rescued by the upregulation of CMA using small-molecule CMA activators. Cystinotic PTCs are characterized by PTC de-differentiation accompanied by loss of the endocytic receptor megalin, and megalin recycling is regulated by Rab11. Here we show that megalin plasma membrane localization is defective in CTNS-KO PTCs and its expression is rescued by treatment with CMA activators. Altogether, our data support that CMA upregulation has the potential to improve PTC function in cystinosis.
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PMID:Chaperone-Mediated Autophagy Upregulation Rescues Megalin Expression and Localization in Cystinotic Proximal Tubule Cells. 3077 22

RUVBL1 and RUVBL2 are two highly conserved AAA+ ATPases that form a hetero-hexameric complex that participates in a wide range of unrelated cellular processes, including chromatin remodeling, Fanconi Anemia (FA), nonsense-mediated mRNA decay (NMD), and assembly and maturation of several large macromolecular complexes such as RNA polymerases, the box C/D small nucleolar ribonucleoprotein (snoRNP) and mTOR complexes. How the RUVBL1-RUVBL2 complex works in such a variety of processes, sometimes antagonistic, has been obscure for a long time. Recent cryo-electron microscopy (cryo-EM) studies have started to reveal how RUVBL1-RUVBL2 forms a scaffold for complex protein-protein interactions and how the structure and ATPase activity of RUVBL1-RUVBL2 can be affected and regulated by the interaction with clients.
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PMID:RUVBL1-RUVBL2 AAA-ATPase: a versatile scaffold for multiple complexes and functions. 3312 13


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