Observing Dynamic Conformational Changes within the Coiled-Coil Domain of Different Laminin Isoforms Using High-Speed Atomic Force Microscopy.

Laminins are trimeric glycoproteins with important roles in cell-matrix adhesion and tissue organization. The laminin α, ß, and γ-chains have short N-terminal arms, while their C-termini are connected via a triple coiled-coil domain, giving the laminin molecule a well-characterized cross-shaped morphology as a result. The C-terminus of laminin alpha chains contains additional globular laminin G-like (LG) domains with important roles in mediating cell adhesion. Dynamic conformational changes of different laminin domains have been implicated in regulating laminin function, but so far have not been analyzed at the single-molecule level. High-speed atomic force microscopy (HS-AFM) is a unique tool for visualizing such dynamic conformational changes under physiological conditions at sub-second temporal resolution. After optimizing surface immobilization and imaging conditions, we characterized the ultrastructure of laminin-111 and laminin-332 using HS-AFM timelapse imaging. While laminin-111 features a stable S-shaped coiled-coil domain displaying little conformational rearrangement, laminin-332 coiled-coil domains undergo rapid switching between straight and bent conformations around a defined central molecular hinge. Complementing the experimental AFM data with AlphaFold-based coiled-coil structure prediction enabled us to pinpoint the position of the hinge region, as well as to identify potential molecular rearrangement processes permitting hinge flexibility. Coarse-grained molecular dynamics simulations provide further support for a spatially defined kinking mechanism in the laminin-332 coiled-coil domain. Finally, we observed the dynamic rearrangement of the C-terminal LG domains of laminin-111 and laminin-332, switching them between compact and open conformations. Thus, HS-AFM can directly visualize molecular rearrangement processes within different laminin isoforms and provide dynamic structural insight not available from other microscopy techniques.

S100A11 promotes focal adhesion disassembly via myosin II-driven contractility and Piezo1-mediated Ca2+ entry.

S100A11 is a small Ca2+-activatable protein known to localize along stress fibers (SFs). Analyzing S100A11 localization in HeLa and U2OS cells further revealed S100A11 enrichment at focal adhesions (FAs). Strikingly, S100A11 levels at FAs increased sharply, yet transiently, just before FA disassembly. Elevating intracellular Ca2+ levels with ionomycin stimulated both S100A11 recruitment and subsequent FA disassembly. However, pre-incubation with the non-muscle myosin II (NMII) inhibitor blebbistatin or with an inhibitor of the stretch-activatable Ca2+ channel Piezo1 suppressed S100A11 recruitment, implicating S100A11 in an actomyosin-driven FA recruitment mechanism involving Piezo1-dependent Ca2+ influx. Applying external forces on peripheral FAs likewise recruited S100A11 to FAs even if NMII activity was inhibited, corroborating the mechanosensitive recruitment mechanism of S100A11. However, extracellular Ca2+ and Piezo1 function were indispensable, indicating that NMII contraction forces act upstream of Piezo1-mediated Ca2+ influx, in turn leading to S100A11 activation and FA recruitment. S100A11-knockout cells display enlarged FAs and had delayed FA disassembly during cell membrane retraction, consistent with impaired FA turnover in these cells. Our results thus demonstrate a novel function for S100A11 in promoting actomyosin contractility-driven FA disassembly.

Exploring new pharmacology and toxicological screening and safety evaluation of one widely used formulation of Nidrakar Bati from South Asia region.

BACKGROUND: Nidrakar Bati (NKB) is an herbal remedy consisted with seven medicinal herbs widely used to cure Somnifacient (sleeping aid) in South Asia as Ayurvedic medicinal system. In the present study, pharmacological and toxicological effects of this medicine was investigated in mice to validate the safety and efficacy of the herb. METHODS: Organic solvent extracts NKB were prepared using maceration method. Effect of extracts on the central nervous system was evaluated using hypnotic activity assay. Effect of the extracts on metabolic activity, assessing involvement of thyroid was conducted using hypoxia test. analgesic and anti-inflammatory activities were assessed in mice using acetic acid induced writhing, formalin induced paw edema, xylene induced ear edema assays. Anxiolytic activity was performed using plus maze, climbing out and forced swimming tests. Effect of the extracts on psychopharmacological effect was carried out using locomotor activity tests (open field, Hole-board and Hole-cross tests). Neuropharmacological effect of the extracts was performed using motor coordination (rotarod test). Toxicological potential of the extract was evaluated using gastro-intestinal activity (gastric emptying and gastrointestinal motility tests). RESULTS: The studied formulation reduced the CNS stimulant effects dose independently. In the hypoxia test, only a dose of 100 mg/kg of NKB decreased the survival time. Orally administration of the NKB (200 and 400 mg/kg) produced significant inhibition (P < 0.01) of the acetic acid-induced writhing in mice and suppressed xylene induced ear edema and formalin-induced licking response of animals in both phases of the test. NKB showed locomotor activity (p < 0.05) both in higher and lower doses (100 and 400 mg/kg). NKB increased the total ambulation dose dependently (p < 0.05). NKB, at all tested doses (100, 200 and 400 mg/kg) increased some locomotion activity parameters (ambulation, head dipping and emotional defecation) in hole board test. At higher doses (200 and 400 mg/kg), NKB showed a significant increase in hole cross test. NKB showed an increase in the time on the open arms of the maze at low to medium doses (100 and 200 mg/kg). When using the Rotarod method, NKB showed a considerable increase on motor coordination of the mice. NKB produced marked gastric emptying effect and decreased gastrointestinal motility in mice at low dose. CONCLUSIONS: NKB demonstrated various pharmacological effects and toxicological effects due to presence of several herbs in the formulation those are not closely fit for the effect of CNS depressants.

Evaluation of antinociceptive, in-vivo & in-vitro anti-inflammatory activity of ethanolic extract of Curcuma zedoaria rhizome.

BACKGROUND: The present study was aimed to investigate the antinociceptive and anti-inflammatory activity of the Curcuma zedoaria (family Zingiberaceae) ethanolic rhizome extract in laboratory using both in vitro and in vivo methods so as to justify its traditional use in the above mentioned pathological conditions. METHODS: Phytochemical screening was done to find the presence of various secondary metabolites of the plant. In vivo antinociceptive activity was performed employing the hot plate method, acidic acid induced writhing test and formalin induced writhing test on Swiss albino mice at doses of 250 and 500 mg/kg body weight. Anti-inflammatory activity test was done on Long Evans rats at two different doses (250 and 500 mg/kg body weight) by using carrageenan induced paw edema test. Finally in vitro anti-inflammatory test by protein-denaturation method was followed. Data were analyzed by one-way analysis of variance (ANOVA) and Dunnett's t-test was used as the test of significance. P value <0.05 was considered as the minimum level of significance. RESULTS: Phytochemical screening revealed presence of tannins, saponins, flavonoids, gums & carbohydrates, steroids, alkaloids, reducing sugars and terpenoids in the extract. In the hot plate method, the extract increased the reaction time of heat sensation significantly to 61.99% and 78.22% at the doses of 250 and 500 mg/kg BW respectively. In acetic acid induced writhing test, the percent inhibition of writhing response by the extract was 48.28% and 54.02% at 250 and 500 mg/kg doses respectively (p < 0.001). The extract also significantly inhibited the licking response in both the early phase (64.49%, p < 0.01) and the late phase (62.37%, p < 0.01) in formalin induced writhing test. The extract significantly (p < 0.05, p < 0.01 and p < 0.001) inhibited carrageenan induced inflammatory response in rats in a dose related manner. In in-vitro anti-inflammatory test, the extract significantly inhibited protein denaturation of 77.15, 64.43, 53.04, 36.78 and 23.70% for doses of 500, 400, 300, 200 and 100 µg/mL respectively. CONCLUSIONS: The results obtained from the tests indicate that the plant might have one or more secondary metabolite(s) having central and peripheral analgesic and anti-inflammatory activity.