Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P42345 (mTOR)
 26,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Diagnosis and treatment of autosomal dominant polycystic kidney disease (ADPKD) is rapidly changing. Cellular pathways that involve the polycystins are being mapped and involve the primary cilium, intracellular calcium and cAMP regulation, and the mammalian target of rapamycin (mTOR) pathway. With the use of new imaging approaches, earlier diagnosis of hepatic cystic disease is possible, and measurement of kidney and cystic growth as well as kidney blood flow is possible over relatively short periods. PKD gene type, gender, proteinuria, and the presence of hypertension relate to the rate of kidney growth in ADPKD. On the basis of risk factors for progression to ESRD and the pathogenic roles that intracellular cAMP and mTOR play in cystogenesis, novel therapies are now being tested, including maximal inhibition of the renin-angiotensin system, inhibition of renal intracellular cAMP using vasopressin V2 receptor antagonists, and somatostatin analogues, as well as inhibitors of mTOR. This review addresses the current understanding of the pathogenesis and the natural history of ADPKD; accuracy and reliability of diagnostic approaches in utero, childhood, and adulthood; the value of reliable magnetic resonance imaging to measure disease progression early in the course of ADPKD; and novel therapeutic approaches that are being evaluated in ADPKD.
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PMID:Autosomal dominant polycystic kidney disease: time for a change? 1742 47

Wasting of lean tissue as a consequence of metabolic acidosis is a serious problem in patients with chronic renal failure. A possible contributor is inhibition by low pH of the System A (SNAT2) transporter, which carries the amino acid L-glutamine (L-Gln) into muscle cells. The aim of this study was to determine the effect of selective SNAT2 inhibition on intracellular amino acid profiles and amino acid-dependent signaling through mammalian target of rapamycin in L6 skeletal muscle cells. Inhibition of SNAT2 with the selective competitive substrate methylaminoisobutyrate, metabolic acidosis (pH 7.1), or silencing SNAT2 expression with small interfering RNA all depleted intracellular L-Gln. SNAT2 inhibition also indirectly depleted other amino acids whose intracellular concentrations are maintained by the L-Gln gradient across the plasma membrane, notably the anabolic amino acid L-leucine. Consequently, SNAT2 inhibition strongly impaired signaling through mammalian target of rapamycin to ribosomal protein S6 kinase, ribosomal protein S6, and 4E-BP1, leading to impairment of protein synthesis comparable with that induced by rapamycin. It is concluded that even though SNAT2 is only one of several L-Gln transporters in muscle, it may determine intracellular anabolic amino acid levels, regulating the amino acid signaling that affects protein mass, nucleotide/nucleic acid metabolism, and cell growth.
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PMID:Acidosis-sensing glutamine pump SNAT2 determines amino acid levels and mammalian target of rapamycin signalling to protein synthesis in L6 muscle cells. 1742 52

Cardiovascular disease is the major cause of death in renal transplant recipients. Renal transplant recipients share the same cardiovascular risk factors as the general population, including hypertension, hyperlipidemia, diabetes mellitus, smoking, and positive family history. However, renal transplant recipients are also exposed to transplant-specific risk factors such as chronic immunosuppression. Most renal transplant recipients receive combinations or permutations of immunosuppressive drugs including a calcineurin inhibitor (cyclosporine or tacrolimus), a mammalian target of rapamycin (mTOR) inhibitor (sirolimus), an antiproliferative drug (mycophenolate mofetil and azathioprine), and corticosteroids. Cyclosporine and tacrolimus can induce glucose intolerance, hypertension, and hyperlipidemia. Sirolimus can induce hyperlipidemia. Corticosteroids can induce glucose intolerance, hypertension, hyperlipidemia, and weight gain. Central to the development of metabolic complications in renal transplant recipients is insulin resistance induced by immunosuppressive drugs. Insulin resistance is considered to be the central pathophysiological feature of metabolic syndrome, which is linked to increased risk of cardiovascular disease and to chronic renal failure. Therefore, metabolic syndrome likely contributes to cardiovascular disease and chronic renal allograft dysfunction in renal transplant recipients. Treatment of metabolic complications in renal transplant recipients is difficult, as conversion to an alternate immunosuppressive drug may lead to introduction of new metabolic complications, and as discontinuation of immunosuppressive therapy may lead to rejection. Future research should focus on designing immunosuppressive regimens that have minimal effects on insulin resistance and metabolic complications but that are effective in preventing acute rejection and in prolonging both allograft and patient survival.
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PMID:Immunosuppression and metabolic syndrome in renal transplant recipients. 1837 Jun 95

Insulin resistance is a major cause of muscle wasting in patients with ESRD. Uremic metabolic acidosis impairs insulin signaling, which normally suppresses proteolysis. The low pH may inhibit the SNAT2 l-Glutamine (L-Gln) transporter, which controls protein synthesis via amino acid-dependent insulin signaling through mammalian target of rapamycin (mTOR). Whether SNAT2 also regulates signaling to pathways that control proteolysis is unknown. In this study, inhibition of SNAT2 with the selective competitive substrate methylaminoisobutyrate or metabolic acidosis (pH 7.1) depleted intracellular L-Gln and stimulated proteolysis in cultured L6 myotubes. At pH 7.1, inhibition of the proteasome led to greater depletion of L-Gln, indicating that amino acids liberated by proteolysis sustain L-Gln levels when SNAT2 is inhibited by acidosis. Acidosis shifted the dose-response curve for suppression of proteolysis by insulin to the right, confirming that acid increases proteolysis by inducing insulin resistance. Blocking mTOR or phosphatidylinositol-3-kinase (PI3K) increased proteolysis, indicating that both signaling pathways are involved in its regulation. When both mTOR and PI3K were inhibited, methylaminoisobutyrate or acidosis did not stimulate proteolysis further. Moreover, partial silencing of SNAT2 expression in myotubes and myoblasts with small interfering RNA stimulated proteolysis and impaired insulin signaling through PI3K. In conclusion, SNAT2 not only regulates mTOR but also regulates proteolysis through PI3K and provides a link among acidosis, insulin resistance, and protein wasting in skeletal muscle cells.
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PMID:Inhibition of SNAT2 by metabolic acidosis enhances proteolysis in skeletal muscle. 1865 Apr 82

Polycystic kidney diseases (PKD) are common genetic disorders characterized by formation and progressive enlargement of cysts kidney, liver and other organs, leading to end stage renal disease. Regardless of the genetic defect underlying PKD, cystic epithelia seem to display common abnormalities: increased proliferation and apoptosis, loss of cellular differentiation and polarity, hypersecretion. The localization of multiples proteins, whose function are disrupted in PKD, in the primary cilium or at basal body at the base of the cilium highlight this neglected organelle as a common trigger of cystic diseases. Significant progresses have been made over the last few years towards a greater understanding of the molecular pathogenesis of cysts formation, particularly in the signaling pathways involved in cytogenesis: cAMP, mTOR, Wnt, Ras/MAPK. These advances have already brought several potential therapies targeting several key pathways of cystogenesis.
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PMID:[Recent advances in molecular pathogenesis and treatment of polycystic kidney disease]. 1867 99

Chronic kidney disease is often complicated by uremic cardiomyopathy that consists of left ventricular hypertrophy and interstitial fibrosis. It is thought that hypertension and volume overload are major causes of this disease, but here we sought to identify additional mechanisms using a mouse model of chronic renal insufficiency. Mice with a remnant kidney developed an elevated blood urea nitrogen by 1 week, as expected, and showed progressive cardiac hypertrophy and fibrosis at 4 and 8 weeks even though their blood pressures were not elevated nor did they show signs of volume overload. Cardiac extracellular signal-regulated kinase (ERK) was activated in the uremic animals at 8 weeks. There was also an increased phosphorylation of S6 kinase, which is often mediated by activation of the mammalian target of rapamycin (mTOR). To test the involvement of this pathway, we treated these uremic mice with rapamycin and found that it reduced cardiac hypertrophy. Reduction of blood pressure, however, by hydralazine had no effect. These studies suggest that uremic cardiomyopathy is mediated by activation of a pathway that involves the mTOR pathway.
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PMID:Uremic cardiac hypertrophy is reversed by rapamycin but not by lowering of blood pressure. 1933 17

Responsible factors in progressive tubular dysfunction in chronic renal failure have not been fully identified. In the present study, we hypothesized that the mammalian target of rapamycin, mTOR, was a key molecule in the degenerative and progressive tubular damage in chronic renal failure. Everolimus, an mTOR inhibitor, was administered for 14 days in 5/6 nephrectomized (Nx) rats at 2 and 8 weeks after renal ablation. Marked activation of the mTOR pathway was found at glomeruli and proximal tubules in remnant kidneys of Nx rats. The reduced expression levels of the phosphorylated S6 indicated the satisfactory pharmacological effects of treatment with everolimus for 14 days. Everolimus suppressed the accumulation of smooth muscle alpha actin, infiltration of macrophages and expression of kidney injury molecule-1 in the proximal tubules. In addition, everolimus-treatment restored the tubular reabsorption of albumin, and had a restorative effect on the expression levels of membrane transporters in the polarized proximal tubular epithelium, when its administration was started at 8 weeks after Nx. These results indicate that the constitutively activated mTOR pathway in proximal tubules has an important role in the progressive tubular dysfunction, and that mTOR inhibitors have renoprotective effects to improve the proximal tubular functions in end-stage renal disease.
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PMID:mTOR inhibitor everolimus ameliorates progressive tubular dysfunction in chronic renal failure rats. 1966 Apr 39

Herein we have reported the use of rapamycin in immunosuppressive treatment after renal transplantation as a therapy of choice in a patient with diagnosis of tuberous sclerosis complex (TSC). TSC is a genetic disorder, caused by mutations of TSC1 or TSC2 genes. Products of these genes, hamartin and tuberin, create a complex that inhibits mammalian target of rapamycin (mTOR), a key protein engaged in regulation of the cell cycle. Mutations of TSC genes lead to constitutive activation of mTOR resulting in uncontrolled proliferation, differentiation, and migration of cells. As a consequence malformations of many organs arise. We have presented a case of a 47-year-old female TSC patient with multisystem involvement (skin, brain, lungs, and kidneys), who developed end-stage renal disease ESRD due to angiomyolipomas with subsequent bilateral nephrectomy. At the age of 44 years, she started hemodialysis treatments and 10 months later underwent kidney transplantation. Immunosuppressive treatment included the mTOR inhibitor rapamycin. Since the patient was discharged from hospital, she has remained in good clinical condition with stable graft function. Clinical evaluation after 2 years treatment with rapamycin revealed significant regression of skin lesions. Brain, chest, and abdominal cavity computed tomography images remained stable. No complications of immunosuppressive treatment or TSC were observed. Experimental and clinical studies have confirmed that rapamycin exerts beneficial effects in TSC, providing a new therapeutic option. Therefore an immunosuppressive regimen with rapamycin should be considered as the treatment of choice after kidney transplantation among patients with TSC seeking to avoid development or progression of disease complications.
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PMID:Rapamycin as a therapy of choice after renal transplantation in a patient with tuberous sclerosis complex. 1991 66

To clarify the specific molecular events of progressive tubular damage in chronic renal failure (CRF), we conducted microarray analyses using isolated proximal tubules from subtotally nephrectomized (Nx) rats as a model of CRF. Our results clearly demonstrated time-dependent changes in gene expression profiles localized to proximal tubules. The expression of mitosis-specific genes Cyclin B2 and Cell division cycle 2 (Cdc2) was significantly and selectively increased in the proximal tubules during the compensated period but decreased to basal level in the end-stage period. Administration of everolimus, a potent inhibitor of mammalian target of rapamycin, markedly reduced compensatory hypertrophy and hyperplasia of epithelial cells, which was accompanied by complete abolishment of the expression of Cyclin B2 and Cdc2 enhancement; renal function was then severely decreased. Treatment with the Cdc2 inhibitor 2-cyanoethyl alsterpaullone clearly decreased epithelial cell hyperplasia, based on staining of phosphorylated histone H3 and Ki-67, while hypertrophy was not inhibited. In conclusion, we have demonstrated roles of Cyclin B2 and Cdc2 in the epithelial hyperplasia in response to Nx. These results advance the knowledge of the contribution of cell cycle regulators, especially M phase, in pathophysiology of tubular restoration and/or degeneration, and these two molecules are suggested to be a marker for the proliferation of proximal tubular cells in CRF.
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PMID:Impact of Cyclin B2 and Cell division cycle 2 on tubular hyperplasia in progressive chronic renal failure rats. 2007 61

Hemolytic Uremic Syndrome after kidney transplantation affects an increasing number of patients. It is characterized as recurrent and de novo. Older age at onset of HUS, shorter mean interval between HUS and transplantation or ESRD, living related donor and treatment with CNI have been associated with an increased risk of recurrence. Patients who lost the first transplant because of HUS recurrence should not receive a second transplant. The outcome of recurring HUS after transplantation is worse in familial forms leading invariably to graft loss and for this reason doctors should discourage the use of living related donors in this setting. De novo HUS is not a rare complication after kidney transplantation and may be associated with infection, CNI or mTOR inhibitor toxicity, antibody use (OKT3), or acute vascular rejection. The clinical picture is obscure and treatment rests on removal of inciting factor with or without plasma exchange/FFP infusion.
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PMID:Hemolytic uremic syndrome after renal transplantation. 2035 3


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