Extracellular signal-regulated kinase 1 and 2 (ERK1/2) have been implicated as important regulators of metabolic homeostasis. Here we generated a new mouse model with genetic deletion of two ERK1/2 ...phosphatases, dual specificity phosphatase (DUSP) 6 and 8, to further define the role of ERK1/2 in obesity development. Dusp6/8 double-null mice demonstrated elevated ERK1/2 phosphorylation in multiple tissues, without any change of phosphorylation of p38 and c-Jun N-terminal kinases (JNKs). Elevated ERK1/2 activity in Dusp6/8 double-null mice was associated with larger hearts and other organs, consistent with greater rate of cell proliferation in these mice. However, ERK1/2 activation was not sufficient to protect the mouse hearts from pathological hypertrophy and interstitial fibrosis following angiotensin II and phenylephrine stimulation. Interestingly, mice lacking DUSP6/8 were resistant to high-fat diet-induced obesity. Serum triglyceride, lipid content in the liver and visceral adipose tissues was also dramatically reduced in Dusp6/8 double-null mice. Furthermore, Dusp6/8 double-null mice had improved glucose tolerance. Mechanistically, we found out that elevated ERK1/2 activity increased the expression levels of genes involved in lipid metabolism and glucose homeostasis. Together, our data suggest that ERK1/2 play an essential role for the management of metabolic homeostasis.
Dual‐specificity protein phosphatases (DUSPs), which dephosphorylate both phosphoserine/threonine and phosphotyrosine, play vital roles in immune activation, brain function and cell‐growth ...signalling. A family‐wide structural library of human DUSPs was constructed based on experimental structure determination supplemented with homology modelling. The catalytic domain of each individual DUSP has characteristic features in the active site and in surface‐charge distribution, indicating substrate‐interaction specificity. The active‐site loop‐to‐strand switch occurs in a subtype‐specific manner, indicating that the switch process is necessary for characteristic substrate interactions in the corresponding DUSPs. A comprehensive analysis of the activity–inhibition profile and active‐site geometry of DUSPs revealed a novel role of the active‐pocket structure in the substrate specificity of DUSPs. A structure‐based analysis of redox responses indicated that the additional cysteine residues are important for the protection of enzyme activity. The family‐wide structures of DUSPs form a basis for the understanding of phosphorylation‐mediated signal transduction and the development of therapeutics.
Since the discovery that rapamycin, a small molecule inhibitor of the protein kinase mTOR (mechanistic target of rapamycin), can extend the lifespan of model organisms including mice, interest in ...understanding the physiological role and molecular targets of this pathway has surged. While mTOR was already well known as a regulator of growth and protein translation, it is now clear that mTOR functions as a central coordinator of organismal metabolism in response to both environmental and hormonal signals. This review discusses recent developments in our understanding of how mTOR signaling is regulated by nutrients and the role of the mTOR signaling pathway in key metabolic tissues. Finally, we discuss the molecular basis for the negative metabolic side effects associated with rapamycin treatment, which may serve as barriers to the adoption of rapamycin or similar compounds for the treatment of diseases of aging and metabolism.
In this Review Article, Kennedy and Lamming highlight recent findings regarding the central role of the mechanistic target of rapamycin (mTOR), a protein kinase regulated by many growth factors and environmental cues, in the regulation of organismal metabolism and aging.
•An antibody against clenbuterol could recognize 23 β-agonists and their analogues.•Two critical binding epitopes on β-agonist haptens can affect antibody specificity.•Hydrophobic tert-butyl group on ...C-2′ binding epitope played a decisive role.•Different substituents on benzene ring binding epitope played a regulatory role.
A growing number of β-agonists are illegally using for reducing animal fat deposition in animals, but the development of analytical methods always lags behind the emergence of new illegal compounds. Therefore, class specificity antibody-based immunoassays that can detect a great many β-agonists are important for timely supervision. In this study, a competitive inhibition enzyme-linked immunosorbent assay (ciELISA) based on a clenbuterol monoclonal antibody was developed to recognize 23 β-agonists and analogues. Holographic and three-dimensional quantitative structure–activity relationship (HQSAR and 3D QSAR) revealed that there are two critical binding epitopes on β-agonist hapten affecting antibody specificity, and these epitopes have been further validated using a ractopamine antibody with narrow specificity. Tert-butyl at C-2′ epitope is needed to generate class specific antibodies, and different characteristics of substituents at benzene ring epitope would adjust antibody specificity. This investigation could provide reference for future design of β-agonist haptens.
Benzoxaboroles are effective against bacterial, fungal and protozoan pathogens. We report potent activity of the benzoxaborole AN3661 against Plasmodium falciparum laboratory-adapted strains (mean IC
...32 nM), Ugandan field isolates (mean ex vivo IC
64 nM), and murine P. berghei and P. falciparum infections (day 4 ED
0.34 and 0.57 mg kg
, respectively). Multiple P. falciparum lines selected in vitro for resistance to AN3661 harboured point mutations in pfcpsf3, which encodes a homologue of mammalian cleavage and polyadenylation specificity factor subunit 3 (CPSF-73 or CPSF3). CRISPR-Cas9-mediated introduction of pfcpsf3 mutations into parental lines recapitulated AN3661 resistance. PfCPSF3 homology models placed these mutations in the active site, where AN3661 is predicted to bind. Transcripts for three trophozoite-expressed genes were lost in AN3661-treated trophozoites, which was not observed in parasites selected or engineered for AN3661 resistance. Our results identify the pre-mRNA processing factor PfCPSF3 as a promising antimalarial drug target.
Recent studies have demonstrated improved diagnostic accuracy for detecting coronary artery disease (CAD) when myocardial blood flow (MBF) is quantified in absolute terms, but there are no uniformly ...accepted cutoff values for hemodynamically significant CAD.
The goal of this study was to determine cutoff values for absolute MBF and to evaluate the diagnostic accuracy of quantitative (15)OH2O positron emission tomography (PET).
A total of 330 patients underwent both quantitative (15)OH2O PET imaging and invasive coronary angiography in conjunction with fractional flow reserve measurements. A stenosis >90% and/or fractional flow reserve ≤0.80 was considered obstructive; a stenosis <30% and/or fractional flow reserve >0.80 was nonobstructive.
Hemodynamically significant CAD was diagnosed in 116 (41%) of 281 patients who fulfilled study criteria for CAD. Resting perfusion was 1.00 ± 0.25 and 0.92 ± 0.23 ml/min/g in regions supplied by nonstenotic and significantly stenosed vessels, respectively (p < 0.001). During stress, perfusion increased to 3.26 ± 1.04 ml/min/g and 1.73 ± 0.67 ml/min/g, respectively (p < 0.001). The optimal cutoff values were 2.3 and 2.5 for hyperemic MBF and myocardial flow reserve, respectively. For MBF, these cutoff values showed a sensitivity, specificity, and accuracy for detecting significant CAD of 89%, 84%, and 86%, respectively, at a per-patient level and 87%, 85%, and 85% at a per-vessel level. The corresponding myocardial flow reserve values were 86%, 72%, and 78% (per patient) and 80%, 82%, and 81% (per vessel). Age and sex significantly affected diagnostic accuracy of quantitative PET.
Quantitative MBF measurements with the use of (15)OH2O PET provided high diagnostic performance, but both sex and age should be taken into account.
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