Evolution of the sodium pump

Rainbow Trout (Oncorhynchus mykiss) Pre-Smolts Treated with 11-Deoxycorticosterone Regulate Liver Carbohydrate Metabolism and Gill Osmoregulation

Smoltification is stressful for salmonids, and cortisol is one of the central endocrine regulators for seawater adaptation. It has been established that cortisol plays both mineralocorticoid and glucocorticoid functions by MR and GR, respectively, since the aldosterone hormone is absent. Recently, investigations have proposed that the 11-deoxycorticosterone (DOC) mineralocorticoid precursor might support cortisol effects, but this mechanism remains unclear. Hence, we assessed the early effects of DOC on rainbow trout pre-smolts, the key smoltification stage, via metabolic and transcriptomic approaches. Thirty-six juveniles (~120 g) were treated for 3 h with DOC (1 mg/kg) and/or mineralocorticoid (eplerenone) or glucocorticoid (mifepristone) receptor antagonists (n = 6 for each group). DOC decreased plasma glucose and pyruvate and increased phosphate and liver glycogen. DOC also downregulated carbohydrate metabolism-related genes in the liver. Finally, gill RNA-seq analysis presented 1660 differentially expressed transcripts in DOC versus vehicle, 1022 for eplerenone + DOC versus DOC and 3324 for mifepristone + DOC versus DOC. The enrichment analysis mainly revealed the upregulation of ion transmembrane transport and carbohydrate metabolism and the downregulation of stress and innate immune responses. This suggests a significant role of DOC in liver carbohydrate metabolism and gill osmoregulation of pre-smolts through both receptors. Hence, this could contribute to improving animal welfare monitoring during smoltification by featuring novel and potential biomarkers.

Metabolite profiling and adaptation mechanisms of Aspergillus cristatus under pH stress

Introduction

pH is an important environmental factor affecting the survival of fungi, and Aspergillus cristatus, which can grow and reproduce over a wide range of pH, is suitable for studying their adaptation mechanism to pH stress.

Methods

In this study, A. cristatus was cultured on plates of different initial pH (pH 3.8-8.0), with the results revealing distinct morphologies at pH 3.0-5.0, pH 6.0-7.0 and pH 8.0. Liquid chromatography-mass spectrometry (LC-MS) and multivariate analysis subsequently were used to analyze the changes of substance metabolism of A. cristatus at different pH.

Results and discussion

LC-MS and multivariate analyses showed that A. cristatus's growth at different pH involved significantly different metabolites. In particular, comparing pH 4.0 vs pH 6.0, pH 6.0 vs pH 8.0 and pH 4.0 vs pH 8.0 revealed a total of 317, 171 and 404 significantly different substances, respectively. Finally, as the pH changed from 4.0 to 6.0 to 8.0, eight changes in the patterns of differential substances were identified. At low pH, A. cristatus accumulated large amounts of energy substances (e.g., adenosine), active antioxidants (e.g., glutathione) and osmo-protective substances (e.g., raffinose). In contrast, at high pH, large amounts of phosphatidylcholine (PC), lysophosphatidyl ethanolamine (LPE), lysophosphatidyl choline (LPC), lysophosphatidyl serine (LPS) related to biofilms were synthesized, alongside antioxidants (e.g., formononetin) and acidic substances. The aforementioned results indicate that A. cristatus adapts to changes in pH by adjusting their metabolite synthesis. Therefore, under unsuitable pH environments, A. cristatus synthesizes specific sets of metabolites that play key roles to cope with the stress.

Primary amino acid sequences of decapod (Na+, K+)-ATPase provide evolutionary insights into osmoregulatory mechanisms

Decapod Crustacea exhibit a marine origin, but many taxa have occupied environments ranging from brackish to fresh water and terrestrial habitats, overcoming their inherent osmotic challenges. Osmotic and ionic regulation is achieved by the gill epithelia, driven by two active ATP-hydrolyzing ion transporters, the basal (Na+, K+)-ATPase and the apical V(H+)-ATPase. The kinetic characteristic of gill (Na+, K+)-ATPase and the mRNA expression of its α subunit have been widely studied in various decapod species under different salinity challenges. However, the evolution of the primary structure has not been explored, especially considering the functional modifications associated with decapod phylogeny. Here, we proposed a model for the topology of the decapod α subunit, identifying the sites and motifs involved in its function and regulation, as well as the patterns of its evolution assuming a decapod phylogeny. We also examined both the amino acid substitutions and their functional implications within the context of biochemical and physiological adaptation. The α-subunit of decapod crustaceans shows greater conservation (∼94% identity) compared to the β-subunit (∼40%). While the binding sites for ATP and modulators are conserved in the decapod enzyme, the residues involved in the α-β interaction are only partially conserved. In the phylogenetic context of the complete sequence of (Na+, K+)-ATPase α-subunit, most substitutions appear to be characteristic of the entire group, with specific changes for different subgroups, especially among brachyuran crabs. Interestingly, there was no consistent separation of α-subunit partial sequences related to habitat, suggesting that the convergent evolution for freshwater or terrestrial modes of life is not correlated with similar changes in the enzyme's primary amino acid sequence.

Effect of Cations on ATP Binding to the N-domain of Na+, K+-ATPase

The nucleotide-binding domain (N-domain) of the Na+, K+-ATPase (NKA) is physicochemically characterized by a high content of Glu and Asp residues, resulting in a low isoelectric point (pI = 5.0). Acidic proteins are known to interact with cations. The analysis in silico revealed potential cation interaction sites in the NKA N-domain structure. The interaction with cations was tested in vitro by using a recombinant NKA N-domain. The N-domain contains two Trp residues at the protein surface, as determined by acrylamide-mediated fluorescence quenching, that are useful for structural studies through fluorescence changes. Intrinsic fluorescence of the N-domain was decreased by the presence of cations (Na+, K+, Ca2+) indicating an effect on the protein structure. ATP binding also decreased the N-domain intrinsic fluorescence, which allowed nucleotide affinity determination. In the presence of cations, the N-domain affinity for ATP was increased. Molecular docking of fluorescein isothiocyanate (FITC) with the N-domain showed two binding modes with the isothiocyanate group located 5-6 Å close to Lys485 and Lys506 in the nucleotide-binding site. The presence of ATP prevented the FITC covalent labeling of the N-domain demonstrating the competitive behavior for the binding site. It is proposed that cations interact with the N-domain structure and thereby modulate nucleotide (ATP) affinity and possibly affecting NKA catalysis.

14-3-3ε: a protein with complex physiology function but promising therapeutic potential in cancer

Over the past decade, the role of the 14-3-3 protein has received increasing interest. Seven subtypes of 14-3-3 proteins exhibit high homology; however, each subtype maintains its specificity. The 14-3-3ε protein is involved in various physiological processes, including signal transduction, cell proliferation, apoptosis, autophagy, cell cycle regulation, repolarization of cardiac action, cardiac development, intracellular electrolyte homeostasis, neurodevelopment, and innate immunity. It also plays a significant role in the development and progression of various diseases, such as cardiovascular diseases, inflammatory diseases, neurodegenerative disorders, and cancer. These immense and various involvements of 14-3-3ε in diverse processes makes it a promising target for drug development. Although extensive research has been conducted on 14-3-3 dimers, studies on 14-3-3 monomers are limited. This review aimed to provide an overview of recent reports on the molecular mechanisms involved in the regulation of binding partners by 14-3-3ε, focusing on issues that could help advance the frontiers of this field. Video Abstract.