The Anti-Inflammatory and Skin Barrier Function Recovery Effects of Schisandra chinensis in Mice with Atopic Dermatitis.

Background and Objectives: The fruit of Schisandra chinensis (Turcz.) Baill. is widely used medicinally to treat coughs, asthma, exhaustion, eczema, and pruritus in Northeast Asian countries, including Korea, China, and Japan. This study was designed to investigate the effects of S. chinensis on dermatitis in mice with calcipotriol (MC-903)-induced atopic dermatitis (AD), and its effects on skin barrier dysfunction was also investigated. Materials and Methods: The inhibitory effects of an ethanolic extract of S. chinensis (EESC) on skin lesions, water content, water-holding capacity (WHC), histopathological abnormalities, and inflammatory cytokine and chemokine levels were evaluated in mice with AD induced by MC903. Results: Topical EESC ameliorated skin lesions, reduced skin water content, and increased MC903-induced WHC. EESC also prevented MC-903-induced histopathological abnormalities such as epidermal disruption, hyperkeratosis, spongiotic changes, and immune cell infiltration in inflamed tissue. Moreover, topical EESC reduced MC-903-induced levels of pro-inflammatory cytokines and chemokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-4, IL-6, IL-8, monocyte chemotactic protein (MCP)-1, and thymic stromal lymphopoietin (TSLP). Furthermore, unlike dexamethasone, EESC did not reduce the spleen/body weight ratio. Conclusions: These results suggest that S. chinensis can be used as an alternative to external corticosteroids and that its anti-inflammatory and skin barrier dysfunction-restoring effects are related to the downregulation of pro-inflammatory cytokines and chemokines, such as TNF-α, IL-4, IL-6, IL-8, and TSLP.

Structural mechanism for regulation of Rab7 by site-specific monoubiquitination.

Site-specific ubiquitination can regulate the functions of Rab proteins in membrane trafficking. Previously we showed that site-specific monoubiquitination on Rab5 downregulates its function. Rab7 acts in the downstream of Rab5. Although site-specific ubiquitination of Rab7 can affect its function, it remains elusive how the ubiquitination is involved in modulation of the function of Rab7 at molecular level. Here, we report molecular basis for the regulation of Rab7 by site-specific monoubiquitination. Rab7 was predominantly monoubiquitinated at multiple sites in the membrane fraction of cultured cells. Two major ubiquitination sites (K191 and K194), identified by mutational analysis with single K mutants, were responsible for membrane localization of monoubiquitinated Rab7. Using small-angle X-ray scattering, we derived structural models of site-specifically monoubiquitinated Rab7 in solution. Structural analysis combined with molecular dynamics simulation corroborated that the ubiquitin moieties on K191 and K194 are key determinants for exclusion of Rab7 from the endosomal membrane. Ubiquitination on the two major sites apparently mitigated colocalization of Rab7 with ORF3a of SARS-CoV-2, potentially deterring the egression of SARS-CoV-2. Our results establish that the regulatory effects of a Rab protein through site-specific monoubiquitination are commonly observed among Rab GTPases while the ubiquitination sites differ in each Rab protein.

Understanding the role of the CB1 toggle switch in interaction networks using molecular dynamics simulation.

The cannabinoid receptor 1 (CB1) is a class A G-protein coupled receptor (GPCR) that can exert various effects on the human body through the endocannabinoid system. Understanding CB1 activation has many benefits for the medical use of cannabinoids. A previous study reported that CB1 has two notable residues referred to as the toggle switch, F3.36 and W6.48, which are important for its activation mechanism. We performed a molecular dynamics simulation with a mutation in the toggle switch to examine its role in active and inactive states. We also examined structural changes, the residue-residue interaction network, and the interaction network among helices and loops of wildtype and mutant CB1 for both activation states. As a result, we found that the energetic changes in the hydrogen-bond network of the Na+ pocket, extracellular N-terminus-TM2-ECL1-TM3 interface including D2.63-K3.28 salt-bridge, and extracellular ECL2-TM5-ECL3-TM6 interface directly linked to the toggle switch contribute to the stability of CB1 by the broken aromatic interaction of the toggle switch. It makes the conformation of inactive CB1 receptor to be unstable. Our study explained the role of the toggle switch regarding the energetic interactions related to the Na+ pocket and extracellular loop interfaces, which could contribute to a better understanding of the activation mechanism of CB1.

Aggregation-Prone Structural Ensembles of Transthyretin Collected With Regression Analysis for NMR Chemical Shift.

Monomer dissociation and subsequent misfolding of the transthyretin (TTR) is one of the most critical causative factors of TTR amyloidosis. TTR amyloidosis causes several human diseases, such as senile systemic amyloidosis and familial amyloid cardiomyopathy/polyneuropathy; therefore, it is important to understand the molecular details of the structural deformation and aggregation mechanisms of TTR. However, such molecular characteristics are still elusive because of the complicated structural heterogeneity of TTR and its highly sensitive nature to various environmental factors. Several nuclear magnetic resonance (NMR) spectroscopy and molecular dynamics (MD) studies of TTR variants have recently reported evidence of transient aggregation-prone structural states of TTR. According to these studies, the stability of the DAGH ß-sheet, one of the two main ß-sheets in TTR, is a crucial determinant of the TTR amyloidosis mechanism. In addition, its conformational perturbation and possible involvement of nearby structural motifs facilitates TTR aggregation. This study proposes aggregation-prone structural ensembles of TTR obtained by MD simulation with enhanced sampling and a multiple linear regression approach. This method provides plausible structural models that are composed of ensemble structures consistent with NMR chemical shift data. This study validated the ensemble models with experimental data obtained from circular dichroism (CD) spectroscopy and NMR order parameter analysis. In addition, our results suggest that the structural deformation of the DAGH ß-sheet and the AB loop regions may correlate with the manifestation of the aggregation-prone conformational states of TTR. In summary, our method employing MD techniques to extend the structural ensembles from NMR experimental data analysis may provide new opportunities to investigate various transient yet important structural states of amyloidogenic proteins.

Mitochondrial DNA sequence-based population genetic structure of the firefly, Pyrocoelia rufa (Coleoptera: Lampyridae).

The genetic divergence, population genetic structure, and possible speciation of the Korean firefly, Pyrocoelia rufa, were investigated on the midsouthern Korean mainland, coastal islets, a remote offshore island, Jedu-do, and Tsushima Island in Japan. Analysis of DNA sequences from the mitochondrial COI protein-coding gene revealed 20 mtDNA-sequence-based haplotypes with a maximum divergence of 5.5%. Phylogenetic analyses using PAUP, PHYLIP, and networks subdivided the P. rufa into two clades (termed clade A and B) and the minimum nucleotide divergence between them was 3.7%. Clade A occurred throughout the Korean mainland and the coastal islets and Tsushima Island in Japan, whereas clade B was exclusively found on Jeju-do Island. In the analysis of the population genetic structure, clade B formed an independent phylogeographic group, but clade A was further subdivided into three groups: two covering western and eastern parts of the Korean peninsula, respectively, and the other occupying one eastern coastal islet and Japanese Tsushima Island. Considering both phylogeny and population structure of P. rufa, the Jeju-do Island population is obviously differentiated from other P. rufa populations, but the Tsushima Island population was a subset of the Korean coastal islet, Geoje. We interpreted the isolation of the Jeju-do population and the grouping of Tsushima Island with Korean coastal islets in terms of Late Pleistocene-Holocene events. The eastern-western subdivision on the Korean mainland was interpreted partially by the presence of a large major mountain range, which bisects the midpart of the Korean peninsula into western and eastern parts.