A comprehensive and systematic analysis of Dihydrolipoamide S-acetyltransferase (DLAT) as a novel prognostic biomarker in pan-cancer and glioma

Background:Dihydrolipoamide S-acetyltransferase(DLAT)is a subunit of the pyruvate dehydrogenase complex(PDC),a rate-limiting enzyme complex,that can participate in either glycolysis or the tricarboxylic acid cycle(TCA).However,the pathogenesis is not fully understood.We aimed to perform a more systematic and comprehensive analysis of DLAT in the occurrence and progression of tumors,and to investigate its function in patients’prognosis and immunotherapy.Methods:The differential expression,diagnosis,prognosis,genetic and epigenetic alterations,tumor microenvironment,stemness,immune infiltration cells,function enrichment,single-cell analysis,and drug response across cancers were conducted based on multiple computational tools.Additionally,we validated its carcinogenic effect and possible mechanism in glioma cells.Results:We exhibited that DLAT expression was increased in most tumors,especially in glioma,and affected the survival of tumor patients.DLAT was related to RNA modification genes,DNA methylation,immune infiltration,and immune infiltration cells,including CD4+T cells,CD8+T cells,Tregs,and cancer-associatedfibroblasts.Single-cell analysis displayed that DLAT might regulate cancer by mediating angiogenesis,inflammation,and stemness.Enrichment analysis revealed that DLAT might take part in the cell cycle pathway.Increased expression of DLAT leads tumor cells to be more resistant to many kinds of compounds,including PI3Kβinhibitors,PKC inhibitors,HSP90 inhibitors,and MEK inhibitors.In addition,glioma cells with DLAT silence inhibited proliferation,migration,and invasion ability,and promoted cell apoptosis.Conclusion:We conducted a comprehensive analysis of DLAT in the occurrence and progression of tumors,and its possible functions and mechanisms.DLAT is a potential diagnostic,prognostic,and immunotherapeutic biomarker for cancer patients.

Suppression of a core metabolic enzyme dihydrolipoamide dehydrogenase (dld ) protects against amyloid beta toxicity in C.elegans model of Alzheimer’s disease

A decrease in energy metabolism is associated with Alzheimer’s disease(AD),but it is not known whether the observed decrease exacerbates or protects against the disease.The importance of energy metabolism in AD is reinforced by the observation that variants of dihydrolipoamide dehydrogenase(DLD),is genetically linked to late-onset AD.To determine whether DLD is a suitable therapeutic target,we suppressed the dld-1 gene in Caenorhabditis elegans that express human Ab peptide in either muscles or neurons.Suppression of the dld-1 gene resulted in significant restoration of vitality and function that had been degraded by Ab pathology.This included protection of neurons and muscles cells.The observed decrease in proteotoxicity was associated with a decrease in the formation of toxic oligomers rather than a decrease in the abundance of the Ab peptide.The mitochondrial uncoupler,carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone(FCCP),which like dld-1 gene expression inhibits ATP synthesis,had no significant effect on Ab toxicity.Proteomics data analysis revealed that beneficial effects after dld-1 suppression could be due to change in energy metabolism and activation of the pathways associated with proteasomal degradation,improved cell signaling and longevity.Thus,some features unique to dld-1 gene suppression are responsible for the therapeutic benefit.By direct genetic intervention,we have shown that acute inhibition of dld-1 gene function may be therapeutically beneficial.This result supports the hypothesis that lowering energy metabolism protects against Ab pathogenicity and that DLD warrants further investigation as a therapeutic target.

From identification of fluorescent flavoproteins to mitochondrial redox indicators in intact tissues

Development of the use of favin and nicotinamide-adenine nucleotide fluorescence in monitoringthe redox state of the free mitochondrial NADH/NAD+couple in cels,tissues and organs isreviewed.A break-through was the identification of dihydrolipoamide dehydrogenase(FpL)asthe major NAD-linked fluorescent fla voprotein of mitochondria.This mitochondrial matrix fla-voprotein is in equilibriwn with the fre NADH/NAD+pool and its mid-potential is suficientlynear to that of NADH/NAD+so that its percentage reduction follows that of the latter.Pos.sibilities of monitoring mitochondial and cytosolic NADH depend on the population density ofmitochondria and thus are tissue-dependent.Upon a shift toward reduction,fluorescenceintensitis of NADH and flavins swing to reciprocal directions,so that the NADH/favin fluo-rescence ratio can be used to increase the sensitivity of redox monitoring.This method is attainingwidening use in studies on metabolic regulation under normal and pathological conditions.

N6-methyladenosine-modified DBT alleviates lipid accumulation and inhibits tumor progression in clear cell renal cell carcinoma through the ANXA2/YAP axis-regulated Hippo pathway

Background:The mechanism of metabolism reprogramming is an unsolved problem in clear cell renal cell carcinoma(ccRCC).Recently,it was discovered that the Hippo pathway altered tumor metabolism and promoted tumor progression.Thus,this study aimed at identifying key regulators of metabolism reprogramming and the Hippo pathway in ccRCC and pinpointing potential therapeutic targets for ccRCC patients.Methods:Hippo-related gene sets and metabolic gene sets were used to screen potential regulators of the Hippo pathway in ccRCC.Public databases and samples from patients were applied to investigate the association of dihydrolipoamide branched chain transacylase E2(DBT)with ccRCC and Hippo signaling.The role of DBT was confirmed by gain or loss of function assays in vitro and in vivo.Mechanistic results were yielded by luciferase reporter assay,immunoprecipitation,mass spectroscopy,and mutational studies.Results:DBT was confirmed as a Hippo-related marker with significant prognostic predictive value,and its downregulationwas caused bymethyltransferaselike-3(METTL3)-mediated N6-methyladenosine(m6A)modification in ccRCC.Functional studies specified DBT as a tumor suppressor for inhibiting tumor progression and correcting the lipid metabolism disorder in ccRCC.Mechanistic findings revealed that annexin A2(ANXA2)interacted with the lipoyl-binding domain of DBT to activate Hippo signaling which led to decreased nuclear localization of yes1-associated transcriptional regulator(YAP)and transcriptional repression of lipogenic genes.Conclusions:This study demonstrated a tumor-suppressive role for the DBT/ANXA2/YAP axis-regulated Hippo signaling and suggested DBT as a potential target for pharmaceutical intervention in ccRCC.