Molecular determinants of voltage-dependent slow inactivation of the Ca2+ channel.

Ba(2+) current through the L-type Ca(2+) channel inactivates essentially by voltage-dependent mechanisms with fast and slow kinetics. Here we found that slow inactivation is mediated by an annular determinant composed of hydrophobic amino acids located near the cytoplasmic ends of transmembrane segments S6 of each repeat of the alpha(1C) subunit. We have determined the molecular requirements that completely obstruct slow inactivation. Critical interventions include simultaneous substitution of A752T in IIS6, V1165T in IIIS6, and I1475T in IVS6, each preventing in additive manner a considerable fraction of Ba(2+) current from inactivation. In addition, it requires the S405I mutation in segment IS6. The fractional inhibition of slow inactivation in tested mutants caused an acceleration of fast inactivation, suggesting that fast and slow inactivation mechanisms are linked. The channel lacking slow inactivation showed approximately 45% of the sustained Ba(2+) or Ca(2+) current with no indication of decay. The remaining fraction of the current was inactivated with a single-exponential decay (pi(f) approximately 10 ms), completely recovered from inactivation within 100 ms and did not exhibit Ca(2+)-dependent inactivation properties. No voltage-dependent characteristics were significantly changed, consistent with the C-type inactivation model suggesting constriction of the pore as the main mechanism possibly targeted by Ca(2+) sensors of inactivation.     

<Emphasis Type="Italic">In vitro</Emphasis> Enhancement of Lactate Esters on the Percutaneous Penetration of Drugs with Different Lipophilicity

Lactate esters are widely used as food additives, perfume materials, medicine additives, and personal care products. The objective of this work was to investigate the effect of a series of lactate esters as penetration enhancers on the in vitro skin permeation of four drugs with different physicochemical properties, including ibuprofen, salicylic acid, dexamethasone and 5-fluorouracil. The saturated donor solutions of the evaluated drugs in propylene glycol were used in order to keep a constant driving force with maximum thermodynamic activity. The permeability coefficient (K _p), skin concentration of drugs (SC), and lag time (T), as well as the enhancement ratios for K _p and SC were recorded. All results indicated that lactate esters can exert a significant influence on the transdermal delivery of the model drugs and there is a structure-activity relationship between the tested lactate esters and their enhancement effects. The results also suggested that the lactate esters with the chain length of fatty alcohol moieties of 10–12 are more effective enhancers. Furthermore, the enhancement effect of lactate esters increases with a decrease of the drug lipophilicity, which suggests that they may be more efficient at enhancing the penetration of hydrophilic drugs than lipophilic drugs. The influence of the concentration of lactate esters was evaluated and the optimal concentration is in the range of 5∼10 wt.%. In sum, lactate esters as a penetration enhancer for some drugs are of interest for transdermal administration when the safety of penetration enhancers is a prime consideration.     

Enrichment of AT-TA transversion at 5′-CAG-3′ motif is not a unique mutational signature of aristolochic acid

<正>Aristolochic acids, mutational signature, and hepatocellular carcinoma Aristolochic acids (AA) are the etiologic agents of aristolochic acid nephropathy (AAN) and contribute to the global prevalence of chronic kidney disease and urothelial cancer (Grollman et al., 2007). DNA adducts formed by AA generate a unique AT transversions mutation spectrum at     

Solution structure of the N‐terminal domain of DC‐UbP/UBTD2 and its interaction with ubiquitin

DC‐UbP/UBTD2 is a ubiquitin (Ub) domain‐containing protein first identified from dendritic cells, and is implicated in ubiquitination pathway. The solution structure and backbone dynamics of the C‐terminal Ub‐like (UbL) domain were elucidated in our previous work. To further understand the biological function of DC‐UbP, we then solved the solution structure of the N‐terminal domain of DC‐UbP (DC‐UbP_N) and studied its Ub binding properties by NMR techniques. The results show that DC‐UbP_N holds a novel structural fold and acts as a Ub‐binding domain (UBD) but with low affinity. This implies that the DC‐UbP protein, composing of a combination of both UbL and UBD domains, might play an important role in regulating protein ubiquitination and delivery of ubiquitinated substrates in eukaryotic cells.     

Isoliquiritigenin prevents hyperglycemia-induced renal injuries by inhibiting inflammation and oxidative stress via SIRT1-dependent mechanism

Diabetic nephropathy (DN) as a global health concern is closely related to inflammation and oxidation. Isoliquiritigenin (ISL), a natural flavonoid compound, has been demonstrated to inhibit inflammation in macrophages. Herein, we investigated the effect of ISL in protecting against the injury in STZ-induced type 1 DN and in high glucose-induced NRK-52E cells. In this study, it was revealed that the administration of ISL not only ameliorated renal fibrosis and apoptosis, but also induced the deterioration of renal function in diabetic mice. Mediated by MAPKs and Nrf-2 signaling pathways, respectively, upstream inflammatory response and oxidative stress were neutralized by ISL in vitro and in vivo. Moreover, as further revealed by the results of molecular docking, sirtuin 1 (SIRT1) binds to ISL directly, and the involvement of SIRT1 in ISL-mediated renoprotective effects was confirmed by studies using in vitro models of SIRT1 overexpression and knockdown. In summary, by reducing inflammation and oxidative stress, ISL has a significant pharmacological effect on the deterioration of DN. The benefits of ISL are associated with the direct binding to SIRT1, the inhibition of MAPK activation, and the induction of Nrf-2 signaling, suggesting the potential of ISL for DN treatment.Subject terms: Pharmacology, Molecular biology     

Diet of the Indochinese silvered langur (Trachypithecus germaini) in Kien Luong Karst area,Kien Giang Province

The Indochinese silvered langur (Trachypithecus germaini) is distributed to the west of Mekong River in Cambodia, Lao PDR, Thailand and Vietnam. During a two‐year study, from May 2014 to May 2016, we collected 320.44 hr of behavior, with 17,040 feeding bouts recorded (142 hr) for T. germaini on Chua Hang Karst Mountain, Kien Luong District, Kien Giang Province, Vietnam. Feeding accounted for 45% of the Indochinese silvered langurs’ activity budget. The plant diet of the Indochinese silvered langurs was principally composed of young leaves (58%), followed by mature leaves (9.5%), fruits (22.7%), flowers (4.7%), buds (3.3%), petioles (1.2%), and other (0.5%). A total of 58 plant species were fed on by the silvered langurs, and leaves of eight species (Phyllathus reticulatus, Ficus rumphii, Ficus tinctoria, Ficus microcarpa, Cayratia trifolia, Streblus ilicifolia, Combretum latifolium, and Streblus asper) were fed on throughout the year. P. reticulatus was most frequently eaten (13.9% feeding time, n = 1,733). Food selection differed significantly between months and seasons. The Indochinese silvered langurs ate 27 plant species in the wet season compared with 23 plant species in the dry season. Leaf chemical composition of two food categories, 16 eaten species (with 10 most frequently consumed species and six least consumed species), and four noneaten species, were analyzed. Feeding samples from eaten species in the Indochinese silvered langurs's diet contained lower amounts of condensed tannin, lignin, protein, ash, and lipids, but a higher amount of total sugar compared with samples from noneaten species. Furthermore, the most frequently consumed species contained lower amounts of lignin compared with the less frequently consumed species. Using a generalized linear model with five variables, including neutral detergent fiber (NDF), total sugar, lignin, lipid, and calcium (Ca) indicated that NDF positively correlated and lignin content negatively correlated with feeding records in the diet of these langur.     

Preparation of capacitor’s electrode from sunflower seed shell

Series of nanoporous carbons are prepared from sunflower seed shell (SSS) by two different strategies and used as electrode material for electrochemical double-layer capacitor (EDLC). The surface area and pore-structure of the nanoporous carbons are characterized intensively using N₂ adsorption technique. The results show that the pore-structure of the carbons is closely related to activation temperature and dosage of KOH. Electrochemical measurements show that the carbons made by impregnation-activation process have better capacitive behavior and higher capacitance retention ratio at high drain current than the carbons made by carbonization-activation process, which is due to that there are abundant macroscopic pores and less interior micropore surface in the texture of the former. More importantly, the capacitive performances of these carbons are much better than ordered mesoporous carbons and commercial wood-based active carbon, thus highlighting the success of preparing high performance electrode material for EDLC from SSS.     

A cross-talk between epithelium and endothelium mediates human alveolar–capillary injury during SARS-CoV-2 infection

COVID-19, caused by SARS-CoV-2, is an acute and rapidly developing pandemic, which leads to a global health crisis. SARS-CoV-2 primarily attacks human alveoli and causes severe lung infection and damage. To better understand the molecular basis of this disease, we sought to characterize the responses of alveolar epithelium and its adjacent microvascular endothelium to viral infection under a co-culture system. SARS-CoV-2 infection caused massive virus replication and dramatic organelles remodeling in alveolar epithelial cells, alone. While, viral infection affected endothelial cells in an indirect manner, which was mediated by infected alveolar epithelium. Proteomics analysis and TEM examinations showed viral infection caused global proteomic modulations and marked ultrastructural changes in both epithelial cells and endothelial cells under the co-culture system. In particular, viral infection elicited global protein changes and structural reorganizations across many sub-cellular compartments in epithelial cells. Among the affected organelles, mitochondrion seems to be a primary target organelle. Besides, according to EM and proteomic results, we identified Daurisoline, a potent autophagy inhibitor, could inhibit virus replication effectively in host cells. Collectively, our study revealed an unrecognized cross-talk between epithelium and endothelium, which contributed to alveolar–capillary injury during SARS-CoV-2 infection. These new findings will expand our understanding of COVID-19 and may also be helpful for targeted drug development.Subject terms: Mechanisms of disease, Viral infection