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The force-from-lipids hypothesis of cellular mechanosensation posits that membrane channels open and close in response to changes in the physical state of the lipid bilayer, induced for example by lateral tension. Here, we investigate the molecular basis for this transduction mechanism by studying the mechanosensitive ion channel MscS from Escherichia coli and its eukaryotic homolog MSL1 from Arabidopsis thaliana. First, we use single-particle cryo-electron microscopy to determine the structure of a novel open conformation of wild-type MscS, stabilized in a thinned lipid nanodisc. Compared with the closed state, the structure shows a reconfiguration of helices TM1, TM2, and TM3a, and widening of the central pore. Based on these structures, we examined how the morphology of the membrane is altered upon gating, using molecular dynamics simulations. The simulations reveal that closed-state MscS causes drastic protrusions in the inner leaflet of the lipid bilayer, both in the absence and presence of lateral tension, and for different lipid compositions. These deformations arise to provide adequate solvation to hydrophobic crevices under the TM1-TM2 hairpin, and clearly reflect a high-energy conformation for the membrane, particularly under tension. Strikingly, these protrusions are largely eradicated upon channel opening. An analogous computational study of open and closed MSL1 recapitulates these findings. The gating equilibrium of MscS channels thus appears to be dictated by opposing conformational preferences, namely those of the lipid membrane and of the protein structure. We propose a membrane deformation model of mechanosensation, which posits that tension shifts the gating equilibrium towards the conductive state not because it alters the mode in which channel and lipids interact, but because it increases the energetic cost of the morphological perturbations in the membrane required by the closed state.

Prokaryotic mechanosensitive (MS) channels open by sensing the physical state of the membrane. As such, lipid-protein interactions represent the defining molecular process underlying mechanotransduction. Here, we describe cryo-electron microscopy (cryo-EM) structures of the E. coli small-conductance mechanosensitive channel (MscS) in nanodiscs (ND). They reveal a novel membrane-anchoring fold that plays a significant role in channel activation and establish a new location for the lipid bilayer, shifted ~14 Å from previous consensus placements. Two types of lipid densities are explicitly observed. A phospholipid that ‘hooks’ the top of each TM2-TM3 hairpin and likely plays a role in force sensing, and a bundle of acyl chains occluding the permeation path above the L105 cuff. These observations reshape our understanding of force-from-lipids gating in MscS and highlight the key role of allosteric interactions between TM segments and phospholipids bound to key dynamic components of the channel.

Purpose - Since the development of antipsychotic drugs in the 1950s, a variety of studies and case reports have been published that suggest an association between exposure to typical antipsychotics and venous thromboembolisms (VTE). Therefore, when starting treatment with antipsychotics, especially low-potency typical antipsychotics and clozapine, health-care providers must account for the patient's existing VTE risk factors. Design/methodology/approach - In this case report, the authors describe the development of a pulmonary embolism associated with use of chlorpromazine in the treatment of an acute manic episode in a 51-year-old female patient with bipolar disorder type 1. Findings - The patient was brought to the emergency room by the police on a legal hold for bizarre behaviors at a bus stop, which included incessantly yelling at bystanders. The patient was found to have disorganized thoughts, poor sleep, rapid speech, labile mood, distractibility, auditory hallucinations and grandiose delusions. During the course of her stay, the patient received extensive IM chlorpromazine for extreme agitation, in addition to chlorpromazine 200 mg IM Q8H, which was later decreased to chlorpromazine 100 mg chlorpromazine IM/PO Q8H. On day 4 of the treatment, the patient experienced difficulty breathing, hypoxia and tachycardia and was found to have bilateral expiratory wheezes. CT angiography showed sub-segmental pulmonary embolus and the patient was transferred to MICU service. The patient was then intubated and started on heparin by the medical team. Over the course of the next day, her respiratory distress resolved and the patient was extubated. Originality/value - It is possible that chlorpromazine may indeed increase VTEs, and there are various physiological postulations regarding the mechanism of action. However, multiple confounding variables existed in the authors' report, including venous stasis and the use of restraints, tobacco and valproic acid. Each of these variables has been shown to increase VTE occurrence. Further controlled studies are necessary to identify the true relationship between antipsychotics and VTEs. [ABSTRACT FROM AUTHOR]

The sesame crop is highly susceptible to infection by phytoplasmas, a class of cell wall-less plant pathogenic bacteria (Mollicutes), which is responsible for widespread loss of sesame crops in both North and South India in recent years. Therefore, characterizing the pathogen population is required before the control measures can be devised and implemented. With molecular tools based on nested polymerase chain reaction (PCR) assays, sequencing, restriction profiling, and phylogenetic analysis, phyllody-affected sesame plants collected from nine different states of India were found to be infected by phytoplasmas belonging to two 16Sr groups, namely 16SrI and II. Two subgroups of phytoplasma −16SrI-B and 16SrII-D— were prevalent in symptomatic sesame samples collected from North India, whereas phytoplasma of only the 16SrII group was found in South India. However, the latter samples were diverse, belonging to three different subgroups (16SrII-A, II-C, and II-D). In addition, yearly phyllody-affected sesame samples from Delhi for 4 consecutive years (2007–2010) showed variation in the infecting phytoplasma: the subgroup 16SrII-D was detected in samples collected in 2007, and 16SrI-B was predominantly found in the samples collected in the subsequent years. The study also provides molecular evidence for the association between 16SrI-B phytoplasma and different symptoms in sesame crops such as fasciation, little leaf, and stunting. This is the first study to report the association of the phytoplasma subgroups 16SrII-A and II-D with sesame crops in India. This study provides a baseline for designing specific detection and molecular analysis strategies for quarantine purposes. It also highlights the need for examining the dynamics of seasonal or location-specific variation in vector populations to determine the pattern of infection outbreaks. [ABSTRACT FROM AUTHOR]

Limited information is available on the role of MAPK phosphatase 1 (MKP1) signaling in osteoblasts. We have recently reported distinct roles for MKP1 during osteoblast proliferation, differentiation, and skeletal responsiveness to parathyroid hormone (PTH). As MKP1 regulates the phosphorylation status of MAPKs, we investigated the involvement of P-ERK and P-p38 MAPKs in MKP1 knockout (KO) early and mature osteoblasts with respect to mineralization and PTH response. Calvarial osteoblasts from 9-14-week-old WT and MKP1 KO male and female mice were examined. Western blot analysis revealed downregulation and sustained expressions of P-ERK and P-p38 with PTH treatment in differentiated osteoblasts derived from KO males and females respectively. Exposure of early osteoblasts to p38 inhibitor, SB203580 (S), markedly inhibited mineralization in WT and KO osteoblasts from both genders as determined by von Kossa assay. In osteoblasts from males, ERK inhibitor U0126 (U), not p38 inhibitor (S), prevented the inhibitory effects of PTH on mineralization in early or mature osteoblasts. In osteoblasts from KO females, PTH sustained mineralization in early osteoblasts and decreased mineralization in mature cells. This effect of PTH was attenuated by S in early osteoblasts and by U in mature KO cells. Changes in matrix Gla protein expression with PTH in KO osteoblasts did not correlate with mineralization, indicative of MKP1-dependent additional mechanisms essential for PTH action on osteoblast mineralization. We conclude that PTH regulation of osteoblast mineralization in female mice is maturation stage specific and involves MKP1 modulation of P-ERK and P-p38 MAPKs. [ABSTRACT FROM AUTHOR]

Abstract In this work, a comparative failure analysis of aluminum (AA8011/AA8011) and glass fiber reinforced polyester (GFRP/GFRP) based similar and dissimilar joints is presented. The GFRP is prepared using pultrusion technique. Single lap joints are prepared by using Araldite R2011 epoxy as an adhesive. The lap joints are then tested under tension to estimate the average shear strength of the assembly. It is observed that the average bond strength of AA8011/AA8011 is lesser than that of the GFRP/GFRP joint. The failure of similar joints occurred by fracture within the adhesive. The dissimilar joint is failed predominantly by interface debonding. Further, a detailed three dimensional stress analysis of the joints is carried out using finite element method (FEM). The damage analysis of adhesive layer is carried out by coupling FEM with cohesive zone model (CZM). The stress, damage distributions and failure mechanisms are compared for similar joints in detail. A failure mechanism is proposed for AA8011/AA8011 type joint that favours a rapid crack growth in the adhesive after crack initiation, which is responsible for lesser bond strength. The increase in overlap length has positive effect that the peak load increases proportionally with overlap length. [ABSTRACT FROM AUTHOR]