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PIEZO2 is a mechanosensitive cation channel that has a key role in sensing touch, tactile pain, breathing and blood pressure. Here we describe the cryo-electron microscopy structure of mouse PIEZO2, which is a three-bladed, propeller-like trimer that comprises 114 transmembrane helices (38 per protomer). Transmembrane helices 1-36 (TM1-36) are folded into nine tandem units of four transmembrane helices each to form the unusual non-planar blades. The three blades are collectively curved into a nano-dome of 28-nm diameter and 10-nm depth, with an extracellular cap-like structure embedded in the centre and a 9-nm-long intracellular beam connecting to the central pore. TM38 and the C-terminal domain are surrounded by the anchor domain and TM37, and enclose the central pore with both transmembrane and cytoplasmic constriction sites. Structural comparison between PIEZO2 and its homologue PIEZO1 reveals that the transmembrane constriction site might act as a transmembrane gate that is controlled by the cap domain. Together, our studies provide insights into the structure and mechanogating mechanism of Piezo channels. The cryo-electron microscopy structure of mouse PIEZO2 is determined and compared to that of PIEZO1, providing insights into the potential gating mechanisms of these mechanosensitive ion channels., Author(s): Li Wang [sup.1] , Heng Zhou [sup.2] , Mingmin Zhang [sup.1] [sup.3] , Wenhao Liu [sup.1] [sup.3] , Tuan Deng [sup.1] , Qiancheng Zhao [sup.1] , Yiran Li [sup.1] [...]

Estrogen influences myosin phosphorylation and post-tetanic potentiation in murine fast muscle. We tested the hypothesis that this influence is mediated by estrogen effects on skeletal myosin light chain kinase (skMLCK) activity. To this end, extensor digitorum longus muscles from female wildtype and skMLCK-absent ([skMLCK.sup.-/-]) mice were grouped as follows: ovariectomized with estrogen (E+), ovariectomized without estrogen (E-), sham surgery, and intact baseline. At 8 weeks of age, the ovariectomized groups were ovariectomized followed by implantation of either a 0.1 mg 17[beta]-estradiol (E+) or placebo pellet (E-). Two weeks later, muscles were isolated and suspended in vitro (25[degrees]C) for determination of regulatory light chain phosphorylation and post-tetanic potentiation. Regulatory light chain phosphorylation was not different across conditions within either genotype although wildtype values were significantly greater than [skMLCK.sup.-/-] values. Consistent with this, the potentiation of concentric twitch force was similar between E+ and E- groups within each genotype but wildtype values were greater than [skMLCK.sup.-/-] values. However, unaltered estradiol levels following ovariectomy, likely due to previously underappreciated confounds of mouse age, development, and growth during estrogen supplementation, prevented direct testing of the hypothesis. Future studies should note the importance of estrous cycles and continuing physiological developments of young adult mice when working with ovarian hormones. Key words: estrogen, myosin phosphorylation, potentiation, murine, fast twitch. Les restrogenes influencent la phosphorylation et la potentialisation post-tetanique de la myosine dans le muscle rapide de souris. Nous avons tente de verifier l'hypothese selon laquelle cette influence est mediee par les effets des restrogenes sur l'activite de la kinase des chaines legeres de la myosine squelettique (skMLCK pour <>). A cette fin, nous avons reuni des muscles extenseurs communs des orteils de souris femelles de type sauvage et avec absence de skMLCK ([skMLCK.sup.-/-]) dans les groupes suivants: ovariectomie avec restrogenes (E+), ovariectomie sans restrogenes (E-), intervention chirurgicale factice et intact au debut de l'etude. Les souris des groupes avec ovariectomie subissaient une ovariectomie a l'age de 8 semaines, suivie de l'implantation d'une pastille de 0,1 mg de 17[beta]-estradiol (E+) ou de placebo (E-). Deux semaines plus tard, les muscles etaient isoles et suspendus in vitro (25[degrees]C) afin d'etablir la phosphorylation de la chaine legere regulatrice et de la potentialisation post-tetanique. La phosphorylation de la chaine legere regulatrice n'etait pas differente d'un groupe a l'autre pour un meme genotype, mais les valeurs etaient nettement plus elevees pour le type sauvage que chez les [skMLCK.sup.-/-]. En accord avec cela, la potentialisation de la force de contraction concentrique etait semblable dans les groupes E+ et E- pour un meme genotype, mais les valeurs etaient plus elevees pour le type sauvage que chez les [skMLCK.sup.-/-]. Cependant, nous n'avons pas pu verifier l'hypothese directement en raison de l'absence de diminution des taux d'restradiol apres ovariectomie, probablement en raison de facteurs confondants sous-evalues quant a l'age, ainsi qu'au developpement et a la croissance des souris pendant la supplementation en restrogenes. Des etudes futures devraient remarquer l'importance du developpement en continu des cycles restraux et de la physiologie des jeunes souris adultes lors d'etudes portant sur les hormones ovariennes. [Traduit par la Redaction] Mots-cles: restrogenes, phosphorylation de la myosine, potentialisation, murin, contraction rapide., Introduction A muscle contraction is triggered by an influx of intracellular calcium ([Ca.sup.2+]) from the sarcoplasmic reticulum into the sarcoplasm (Ebashi and Endo 1968). In addition to activating the thin [...]

In the vertebrate visual system, all output of the retina is carried by retinal ganglion cells. Each type encodes distinct visual features in parallel for transmission to the brain. How many such 'output channels' exist and what each encodes are areas of intense debate. In the mouse, anatomical estimates range from 15 to 20 channels, and only a handful are functionally understood. By combining two-photon calcium imaging to obtain dense retinal recordings and unsupervised clustering of the resulting sample of more than 11,000 cells, here we show that the mouse retina harbours substantially more than 30 functional output channels. These include all known and several new ganglion cell types, as verified by genetic and anatomical criteria. Therefore, information channels from the mouse eye to the mouse brain are considerably more diverse than shown thus far by anatomical studies, suggesting an encoding strategy resembling that used in stateof-the-art artificial vision systems., Visual processing begins in the retina (reviewed in ref. 1). Here, photoreceptors feed into bipolar cells (2), which provide input to a diverse set of retinal ganglion cells (RGCs). Each [...]

A large population of neurons can, in principle, produce an astronomical number of distinct firing patterns. In cortex, however, these patterns lie in a space of lower dimension (1-4), as if individual neurons were 'obedient members of a huge orchestra' (5). Here we use recordings from the visual cortex of mouse (Mus musculus) and monkey (Macaca mulatta) to investigate the relationship between individual neurons and the population, and to establish the underlying circuit mechanisms. We show that neighbouring neurons can differ in their coupling to the overall firing of the population, ranging from strongly coupled 'choristers' to weakly coupled 'soloists'. Population coupling is largely independent of sensory preferences, and it is a fixed cellular attribute, invariant to stimulus conditions. Neurons with high population coupling are more strongly affected by non-sensory behavioural variables such as motor intention. Population coupling reflects a causal relationship, predicting the response of a neuron to optogenetically driven increases in local activity. Moreover, population coupling indicates synaptic connectivity; the population coupling of a neuron, measured in vivo, predicted subsequent in vitro estimates of the number of synapses received from its neighbours. Finally, population coupling provides a compact summary of population activity; knowledge of the population couplings of n neurons predicts a substantial portion of their [n.sup.2] pairwise correlations. Population coupling therefore represents a novel, simple measure that characterizes the relationship of each neuron to a larger population, explaining seemingly complex network firing patterns in terms of basic circuit variables., The cortex represents its computations through the joint activity of multiple neurons. This activity can be remarkably diverse even among neighbouring neurons, belonging to the same morphological and laminar cell [...]

Protein affects key life-history traits, and deficiencies in this nutrient may have selected for the ability to invoke physiological or morphological mechanisms to aid nutrient assimilation. I examined the effect of dietary protein on gut characters in lactating mice (Mus musculus L., 1758) and predicted that mice, to improve assimilation efficiency, would increase the mass of the stomach and small intestine and (or) increase food retention in these organs. Mice were maintained on isocaloric diets differing in protein and carbohydrate content (P:C) during the reproductive period. The hypothesis that food would be preferentially retained was not supported. However, both the stomach and the small intestine responded to low P:C with increased mass, and the small intestine exhibited increased diameter. This study demonstrates that mammalian gut morphology of lactating mice can respond to nutrient availability under conditions of constant energy intake. Further study is needed to determine if gut flexibility in response to decreasing P:C levels results in improved nitrogen assimilation efficiency and if this response is a general strategy of mammals or is limited to those with particular breeding strategies. Key words: intestinal plasticity, life history, protein deficiency, laboratory mouse, Mus musculus. Les proteines ont une incidence sur des caracteres cles du cycle de vie, et des carences proteiques pourraient avoir mene a la selection d'une capacite de faire appel a des mecanismes physiologiques ou morphologiques pour faciliter l'assimilation d'elements nutritifs. J'ai examine l'effet des proteines alimentaires sur les caracteres du tube digestif de souris (Mus musculus L., 1758) en lactation et predit que, pour ameliorer l'efficacite de l'assimilation, les souris accroitraient la masse de leur estomac et de leur intestin grele ou la retention de nourriture dans ces organes. Les souris etaient assujetties a des regimes isoenergetiques de differentes teneurs en proteines et en glucides (P:C) durant la periode de reproduction. Les resultats n'ont pas appuye l'hypothese voulant que la nourriture soit preferentiellement retenue. Toutefois, l'estomac et l'intestin grele ont tous deux reagi a de faibles P:C par un accroissement de leur masse, l'intestin grele presentant egalement un diametre accru. L'etude demontre que la morphologie du tube digestif mammalien de souris en lactation peut reagir a la disponibilite d'elements nutritifs dans des conditions d'apport energetique constant. D'autres etudes sont necessaires pour determiner si la souplesse du tube digestif en reponse a des P:C reduits se traduit par une assimilation plus efficace de l'azote et si cette reponse constitue une strategie generalisee chez les mammiferes ou se limite aux mammiferes presentant des strategies de reproduction particulieres. [Traduit par la Redaction] Mots-cles: plasticite intestinale, cycle de vie, carence proteique, souris de laboratoire, Mus musculus., Introduction The ability of the digestive system to efficiently process the nutritional components of food is inherently linked to an organism's life history though its impact on growth, survival, and [...]

The rate of nutrient incorporation into most organisms is an unknown but important factor in temporally variable systems. We investigate within-species variation in tissue turnover and metabolic rate among house mice (Mus musculus L., 1758). By establishing a predictive relationship between tissue turnover rate and metabolic rate, field-based studies could more easily estimate tissue turnover rates using metabolic rate as a surrogate. Here, a diet change was administered using male and female mice of two strains (BALB/c and CBA/J) to test whether a predictive relationship was detectable within a species. Resting metabolic rate (mean values of 1.50-3.64 mL [0.sub.2]-[h.sub.-1]x[g.sub.-1]) and metabolic tissue turnover m (0.02-0.07), were significantly different between sexes, but not between strains. Females of both strains exhibited a nitrogen turnover rate significantly faster than males. Females had less mass than males, which could account for the differences in tissue replacement rates between sexes. The difference in metabolic rate within a species (between strains) may not be large enough to affect the rate of tissue turnover, suggesting that field researchers may be able to assume similar turnover rates among same-sex individuals of the same species. However, it may be important to account for sexual dimorphism when studying tissue turnover and metabolism. Key words: isotope turnover, metabolic rate, stable isotopes, Mus musculus. Le taux d'incorporation de nutriments dans la plupart des organismes n'est pas connu, bien qu'il joue un role important dans les systemes variables dans le temps. Nous avons examine les variations intraspecifiques du taux de renouvellement tissulaire et du taux metabolique chez la souris commune (Mus musculus L., 1758). En etablissant une relation predictive entre le taux de renouvellement tissulaire et le taux metabolique, il serait plus facile d' estimer les taux de renouvellement tissulaire en utilisant le taux metabolique comme valeur substitutive dans le cadre d'etudes de terrain. Nous avons assujetti des souris males et femelles de deux souches (BALB/c et CBA/J) a un changement de regime alimentaire afin de verifier si une relation predictive existait au sein d'une espece donnee. Le taux metabolique au repos (valeurs moyennes de 1,50 a 3,64 [0.sub.2]-[h.sub.-1]-[g.sub.-1]) et le renouvellement tissulaire metabolique m (0,02-0,07) variaient de maniere significative d'un sexeal'autre, mais non d'une souche a l'autre. Les femelles des deux souches presentaient un taux de renouvellement de l' azote significativement plus eleve que celui des males. La masse des femelles etait plus faible que celle des males, ce qui pourrait expliquer la difference entre les taux de remplacement tissulaire des males et des femelles. Les variations intraspecifiques (entre differentes souches) du taux metabolique pourraient etre trop faibles pour avoir une incidence sur le taux de renouvellement tissulaire. Ainsi, il pourrait etre raisonnable de presumer, dans le cadre d'etudes de terrain, que les taux de renouvellement sont semblables pour les individus du meme sexe d'une espece donnee. Il pourrait par ailleurs etre important de tenir compte du dimorphisme sexuel dans l'etude du renouvellement tissulaire et du metabolisme. Mots-cles : renouvellement isotopique, taux metabolique, isotopes stables, Mus musculus. [Traduit par la Redaction], Introduction An increasing number of studies have recognized the importance of more fully understanding the time required for an organism to achieve isotope equilibrium with their environment (Gannes et al. [...]

The adipocyte-derived hormone adiponectin signals from the fat storage depot to regulate metabolism in peripheral tissues. Inversely correlated with body fat levels, adiponectin reduction in obese individuals may play a [...]

Skeletal muscle wasting is a major human morbidity, and contributes to mortality in a variety of clinical settings, including denervation and cancer cachexia. In this study, we demonstrate that the expression level and autoubiquitination of tumor necrosis factor ([alpha]) receptor adaptor protein 6 (TRAF6), a protein involved in receptor-mediated activation of several signaling pathways, is enhanced in skeletal muscle during atrophy. Skeletal muscle-restricted depletion of TRAF6 rescues myofibril degradation and preserves muscle fiber size and strength upon denervation. TRAF6 mediates the activation of JNK1/2, p38 mitogen-activated protein kinase, adenosine monophosphate--activated protein kinase, and nuclear factor [kappa]B, and induces the expression of muscle-specific E3 ubiquitin ligases and autophagy-related molecules in skeletal muscle upon denervation. Inhibition of TRAF6 also preserves the orderly pattern of intermyofibrillar and subsarcolemmal mitochondria in denervated muscle. Moreover, depletion of TRAF6 prevents cancer cachexia in an experimental mouse model. This study unveils a novel mechanism of skeletal muscle atrophy and suggests that TRAF6 is an important therapeutic target to prevent skeletal muscle wasting. doi/ 10.1083/jcb.201006098

Hyperphosphorylated tau plays an important role in the formation of neurofibrillary tangles in brains of patients with Alzheimer's disease (AD) and related tauopathies and is a crucial factor in the pathogenesis of these disorders. Though diverse kinases have been implicated in tau phosphorylation, protein phosphatase 2A (PP2A) seems to be the major tau phosphatase. Using murine primary neurons from wild-type and human tau transgenic mice, we show that the antidiabetic drug metformin induces PP2A activity and reduces tau phosphorylation at PP2A-dependent epitopes in vitro and in vivo. This tau dephosphorylating potency can be blocked entirely by the PP2A inhibitors okadaic acid and fostriecin, confirming that PP2A is an important mediator of the observed effects. Surprisingly, metformin effects on PP2A activity and tau phosphorylation seem to be independent of AMPK activation, because in our experiments (i) metformin induces PP2A activity before and at lower levels than AMPK activity and (ii) the AMPK activator AICAR does not influence the phosphorylation of tau at the sites analyzed. Affinity chromatography and immunoprecipitation experiments together with PP2A activity assays indicate that metformin interferes with the association of the catalytic subunit of PP2A (PP2Ac) to the so-called MID1-[alpha]4 protein complex, which regulates the degradation of PP2Ac and thereby influences PP2A activity. In summary, our data suggest a potential beneficial role of biguanides such as metformin in the prophylaxis and/or therapy of AD. doi: 10.10731pnas.0912793107

Cellular metabolism alters patterns of gene expression through a variety of mechanisms, including alterations in histone modifications and transcription factor activity. Nicotinamide adenine dinucleotide (NAD)-dependent proteins such as poly(ADP ribose) polymerases (PARPs) and sirtuin deacetylases play important roles in this regulation, thus NAD provides a crucial link between metabolism and these cellular signaling processes. Here, we found that lowering NAD levels in mouse primary cortical neurons led to decreased activity-dependent BDNF expression. The altered BDNF transcription occurred independently of Sirt or Parp activities; instead, low NAD levels promoted increased DNA methylation of the activity-dependent BDNF promoter. Increased methylation at this promoter triggered the dissociation of the insulator protein CTCF as well as the accompanying cohesin from the BDNF locus. The loss of these proteins resulted in histone acetylation and methylation changes at this locus consistent with chromatin compaction and gene silencing. Because BDNF is critical for neuronal function, these results suggest that age- or nutrition-associated declines in NAD levels as well as deficits in cohesin function associated with disease modulate BDNF expression and could contribute to cognitive impairment. doi: 10.1073/pnas.1002130107