Project description:Charcot-Marie-Tooth disease is the most common inherited peripheral neuropathy. Dominant mutations in the glycyl-tRNA synthetase (GARS) gene cause peripheral nerve degeneration and lead to CMT disease type 2D. The underlying mechanisms of mutations in GARS (GARSCMT2D ) in disease pathogenesis are not fully understood. In this study, we report that wild-type GARS binds the NAD+ -dependent deacetylase SIRT2 and inhibits its deacetylation activity, resulting in the acetylated α-tubulin, the major substrate of SIRT2. The catalytic domain of GARS tightly interacts with SIRT2, which is the most CMT2D mutation localization. However, CMT2D mutations in GARS cannot inhibit SIRT2 deacetylation, which leads to a decrease of acetylated α-tubulin. Genetic reduction of SIRT2 in the Drosophila model rescues the GARS-induced axonal CMT neuropathy and extends the life span. Our findings demonstrate the pathogenic role of SIRT2-dependent α-tubulin deacetylation in mutant GARS-induced neuropathies and provide new perspectives for targeting SIRT2 as a potential therapy against hereditary axonopathies.
Project description:β-Nicotinamide mononucleotide is a biologically active nucleotide compound, and its excellent anti-aging activity is widely used in medicine and has multiple functions, making NMN have broad application prospects in the fields of nutrition, health food, and even medicine. Herein, based on the supply of the co-substrate PRPP, we designed and constructed three in vivo NMN synthesis pathways using glucose, xylose, and arabinose as raw materials and Escherichia coli as the host. The best in vivo pathway through whole-cell catalysis was identified. Then, we optimized the cell culture and catalytic conditions of the optimal path to determine the optimal conditions and ultimately obtained an NMN titer of 1.8 mM.
Project description:Like most other types of cancer cells, leukaemia cells undergo metabolic reprogramming to support rapid proliferation through enhancing biosynthetic processes. Pentose phosphate pathway (PPP) plays a pivotal role in meeting the anabolic demands for cancer cells. However, the molecular mechanism by which PPP contributes to leukaemia remains elusive. Here, we report that leukaemia cell proliferation is dependent on the oxidative branch of PPP, in particular the first and rate-limiting enzyme glucose-6-phosphate dehydrogenase (G6PD). Knockdown of G6PD reduces NADPH level in acute myeloid leukaemia (AML) cell lines. Exogenous lipid supplements partially restore the proliferation of G6PD-depleted cells. Deacetylase SIRT2 promotes NADPH production through deacetylating G6PD at lysine 403 (K403). Activation of G6PD by SIRT2 supports the proliferation and clonogenic activity of leukaemia cells. Chemical inhibitors against SIRT2 suppress G6PD activity, leading to reduced cell proliferation of leukaemia cells, but not normal hematopoietic stem and progenitor cells. Importantly, SIRT2 is overexpressed in clinical AML samples, while K403 acetylation is downregulated and G6PD catalytic activity is increased comparing to that of normal control. Together, our study reveals that acetylation regulation of G6PD is involved in the metabolic reprogramming of AML, and SIRT2 serves as a promising target for further therapeutic investigations.
Project description:Mice overexpressing the mitotic checkpoint kinase gene BubR1 live longer, whereas mice hypomorphic for BubR1 (BubR1(H/H)) live shorter and show signs of accelerated aging. As wild-type mice age, BubR1 levels decline in many tissues, a process that is proposed to underlie normal aging and age-related diseases. Understanding why BubR1 declines with age and how to slow this process is therefore of considerable interest. The sirtuins (SIRT1-7) are a family of NAD(+)-dependent deacetylases that can delay age-related diseases. Here, we show that the loss of BubR1 levels with age is due to a decline in NAD(+) and the ability of SIRT2 to maintain lysine-668 of BubR1 in a deacetylated state, which is counteracted by the acetyltransferase CBP. Overexpression of SIRT2 or treatment of mice with the NAD(+) precursor nicotinamide mononucleotide (NMN) increases BubR1 abundance in vivo. Overexpression of SIRT2 in BubR1(H/H) animals increases median lifespan, with a greater effect in male mice. Together, these data indicate that further exploration of the potential of SIRT2 and NAD(+) to delay diseases of aging in mammals is warranted.
Project description:Hutchinson-Gilford syndrome (HGPS, OMIM 176670, a rare premature aging disorder that leads to death at an average age of 14.7 years due to myocardial infarction or stroke, is caused by mutations in the LMNA gene. Lamins help maintain the shape and stability of the nuclear envelope in addition to regulating DNA replication, DNA transcription, proliferation and differentiation. The LMNA mutation results in the deletion of 50 amino acids from the carboxy-terminal region of prelamin A, producing the truncated, farnesylated protein progerin. The accumulation of progerin in HGPS nuclei causes numerous morphological and functional changes that lead to premature cellular senescence. Attempts to reverse this HGPS phenotype have identified rapamycin, an inhibitor of mammalian target of rapamycin (mTOR), as a drug that is able to rescue the HGPS cellular phenotype by promoting autophagy and reducing progerin accumulation. Rapamycin is an obvious candidate for the treatment of HGPS disease but is difficult to utilize clinically. To further assess rapamycin's efficacy with regard to proteostasis, mitochondrial function and the degree of DNA damage, we tested temsirolimus, a rapamycin analog with a more favorable pharmacokinetic profile than rapamycin. We report that temsirolimus decreases progerin levels, increases proliferation, reduces misshapen nuclei, and partially ameliorates DNA damage, but does not improve proteasome activity or mitochondrial dysfunction. Our findings suggest that future therapeutic strategies should identify new drug combinations and treatment regimens that target all the dysfunctional hallmarks that characterize HGPS cells.
Project description:Wild-type p53-induced phosphatase 1 (WIP1) is a serine/threonine phosphatase that dephosphorylates proteins in the ataxia telangiectasia mutated (ATM)-initiated DNA damage response pathway. WIP1 may have a homeostatic role in ATM signaling by returning the cell to a normal pre-stress state following completion of DNA repair. To better understand the effects of WIP1 on ATM signaling, we crossed Atm-deficient mice to Wip1-deficient mice and characterized phenotypes of the double knockout progeny. We hypothesized that the absence of Wip1 might rescue Atm deficiency phenotypes. Atm null mice, like ATM-deficient humans with the inherited syndrome ataxia telangiectasia, exhibit radiation sensitivity, fertility defects, and are T-cell lymphoma prone. Most double knockout mice were largely protected from lymphoma development and had a greatly extended lifespan compared with Atm null mice. Double knockout mice had increased p53 and H2AX phosphorylation and p21 expression compared with their Atm null counterparts, indicating enhanced p53 and DNA damage responses. Additionally, double knockout splenocytes displayed reduced chromosomal instability compared with Atm null mice. Finally, doubly null mice were partially rescued from gametogenesis defects observed in Atm null mice. These results indicate that inhibition of WIP1 may represent a useful strategy for cancer treatment in general and A-T patients in particular.
Project description:Excessive alcohol users have increased risk of developing respiratory infections in part due to oxidative stress-induced alveolar macrophage (AM) phagocytic dysfunction. Chronic ethanol exposure increases cellular oxidative stress in AMs via upregulation of NADPH oxidase (Nox) 4, and treatment with the peroxisome proliferator-activated receptor gamma (PPARγ) ligand, rosiglitazone, decreases ethanol-induced Nox4. However, the mechanism by which ethanol induces Nox4 expression and the PPARγ ligand reverses this defect has not been elucidated. Since microRNA (miR)-92a has been predicted to target Nox4 for destabilization, we hypothesized that ethanol exposure decreases miR-92a expression and leads to Nox4 upregulation. Previous studies have implicated mitochondrial-derived oxidative stress in AM dysfunction. We further hypothesized that ethanol increases mitochondrial-derived AM oxidative stress and dysfunction via miR-92a, and that treatment with the PPARγ ligand, pioglitazone, could reverse these derangements. To test these hypotheses, a mouse AM cell line, MH-S cells, was exposed to ethanol in vitro, and primary AMs were isolated from a mouse model of chronic ethanol consumption to measure Nox4, mitochondrial target mRNA (qRT-PCR) and protein levels (confocal microscopy), mitochondria-derived reactive oxygen species (confocal immunofluorescence), mitochondrial fission (electron microscopy), and mitochondrial bioenergetics (extracellular flux analyzer). Ethanol exposure increased Nox4, enhanced mitochondria-derived oxidative stress, augmented mitochondrial fission, and impaired mitochondrial bioenergetics. Transfection with a miR-92a mimic in vitro or pioglitazone treatment in vivo diminished Nox4 levels, resulting in improvements in these ethanol-mediated derangements. These findings demonstrate that pioglitazone may provide a novel therapeutic approach to mitigate ethanol-induced AM mitochondrial derangements.
Project description:Postoperative acute renal failure in patients with obstructive jaundice is still a serious clinically complication, yet the mechanisms remain unclear. Renin-angiotensin-aldosterone system (RAAS) plays a central role in renal disease progression. Several lines of evidence shows that angiotensin-converting-enzyme-2 (ACE2), a main effector of RAAS acts as a local regulator for renal protection. This study aims to investigate the role of ACE2 and the effect of spironolactone treatment in obstructive jaundice(OJ) rats with renal injury. The rats with obstructive jaundice were established by bile duct ligation. Total bilirubin (TBil), serum creatinine (Scr) and the expression of ACE2 in kidney tissue of obstructive jaundice rats were detected. Comparatively, the expression of ACE2, renin, angiotensin II (AngII), angiotensin-(1-7)[Ang-(1-7)], aldosterone and intercellular adhesion molecule 1 (ICAM-1) in kidney tissues after spironolactone administration were measured by ELISA. Renal necrosis, inflammation and fibrosis induced by OJ were also measured by HE staining and Masson staining. The correlation between the expression of ACE2 and TBil, also the Scr level were investigated. With the time of common bile duct ligation prolonged, the TBil and Scr concentration increased while the expression of ACE2 in OJ rats' kidney tissues decreased. However, after spironolactone intervention, the expressions of ACE2, renin, AngII, Ang-(1-7), aldosterone and ICAM-1 in kidney tissue were changed, moreover, necrotic, inflammatory and fibrotic condition was also decreased. The relationship between the mRNA expression of ACE2 and TBil/Scr was observed to be moderately negatively correlated (r = -0.516, R2 = 0.292, P < 0.01), (r = -0.576, R2 = 0.332, P < 0.01), respectively. RAAS exerted an important effect in the renal damage caused by OJ. Spironolactone intervention not only improved the degree of renal fibrosis induced by OJ, but also upregulated the ACE2 expression in the kidney of OJ rats and rescued the renal function.
Project description:Glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme in the pentose phosphate pathway (PPP) and plays an essential role in the oxidative stress response by producing NADPH, the main intracellular reductant. G6PD deficiency is the most common human enzyme defect, affecting more than 400 million people worldwide. Here, we show that G6PD is negatively regulated by acetylation on lysine 403 (K403), an evolutionarily conserved residue. The K403 acetylated G6PD is incapable of forming active dimers and displays a complete loss of activity. Knockdown of G6PD sensitizes cells to oxidative stress, and re-expression of wild-type G6PD, but not the K403 acetylation mimetic mutant, rescues cells from oxidative injury. Moreover, we show that cells sense extracellular oxidative stimuli to decrease G6PD acetylation in a SIRT2-dependent manner. The SIRT2-mediated deacetylation and activation of G6PD stimulates PPP to supply cytosolic NADPH to counteract oxidative damage and protect mouse erythrocytes. We also identified KAT9/ELP3 as a potential acetyltransferase of G6PD. Our study uncovers a previously unknown mechanism by which acetylation negatively regulates G6PD activity to maintain cellular NADPH homeostasis during oxidative stress.