Calcium Regulation of Myosin-I Tension Sensing

AbstractMyo1b is a myosin that is exquisitely sensitive to tension. Its actin-attachment lifetime increases > 50-fold when its working stroke is opposed by 1 pN of force. The long attachment lifetime of myo1b under load raises the question: how are actin attachments that last >50 s in the presence of force regulated? Like most myosins, forces are transmitted to the myo1b motor through a light-chain binding domain that is structurally stabilized by calmodulin, a calcium-binding protein. Thus, we examined the effect of calcium on myo1b motility using ensemble and single-molecule techniques. Calcium accelerates key biochemical transitions on the ATPase pathway, decreases the working-stroke displacement, and greatly reduces the ability of myo1b to sense tension. Thus, calcium provides an effective mechanism for inhibiting motility and terminating long-duration attachments

Brain-Derived Neurotrophic Factor Expression and Respiratory Function Improve after Ampakine Treatment in a Mouse Model of Rett Syndrome

Rett syndrome (RTT) is caused by loss-of-function mutations in the gene encoding methyl-CpG-binding protein 2 (MeCP2). Although MeCP2 is thought to act as a transcriptional repressor of brain-derived neurotrophic factor (BDNF), Mecp2 null mice, which develop an RTT-like phenotype, exhibit progressive deficits in BDNF expression. These deficits are particularly significant in the brainstem and nodose cranial sensory ganglia (NGs), structures critical for cardiorespiratory homeostasis, and may be linked to the severe respiratory abnormalities characteristic of RTT. Therefore, the present study used Mecp2 null mice to further define the role of MeCP2 in regulation of BDNF expression and neural function, focusing on NG neurons and respiratory control. We find that mutant neurons express significantly lower levels of BDNF than wild-type cells in vitro, as in vivo, under both depolarizing and nondepolarizing conditions. However, BDNF levels in mutant NG cells can be increased by chronic depolarization in vitro or by treatment of Mecp2 null mice with CX546, an ampakine drug that facilitates activation of glutamatergic AMPA receptors. Ampakine-treated Mecp2 null mice also exhibit marked functional improvement, characterized by restoration of normal breathing frequency and minute volume. These data demonstrate that BDNF expression remains plastic in Mecp2 null mice and raise the possibility that ampakine compounds could be of therapeutic value in the treatment of RTT

Poster 312 Efficacy of Combined Intra‐articular Facet Joint and Transforaminal Epidural Steroid Injection in the Management of Symptomatic Lumbosacral Lateral Recess Stenosis: A Retrospective Analysis

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/147060/1/pmr2s280a.pd

A chemical genetic approach reveals distinct EphB signaling mechanisms during brain development.

EphB receptor tyrosine kinases control multiple steps in nervous system development. However, it remains unclear whether EphBs regulate these different developmental processes directly or indirectly. In addition, given that EphBs signal through multiple mechanisms, it has been challenging to define which signaling functions of EphBs regulate particular developmental events. To address these issues, we engineered triple knock-in mice in which the kinase activity of three neuronally expressed EphBs can be rapidly, reversibly and specifically blocked. We found that the tyrosine kinase activity of EphBs was required for axon guidance in vivo. In contrast, EphB-mediated synaptogenesis occurred normally when the kinase activity of EphBs was inhibited, suggesting that EphBs mediate synapse development by an EphB tyrosine kinase-independent mechanism. Taken together, our data indicate that EphBs control axon guidance and synaptogenesis by distinct mechanisms and provide a new mouse model for dissecting EphB function in development and disease

Ca2+ Influx Regulates BDNF Transcription by a CREB Family Transcription Factor-Dependent Mechanism

AbstractCREB is a transcription factor implicated in the control of adaptive neuronal responses. Although one function of CREB in neurons is believed to be the regulation of genes whose products control synaptic function, the targets of CREB that mediate synaptic function have not yet been identified. This report describes experiments demonstrating that CREB or a closely related protein mediates Ca2+-dependent regulation of BDNF, a neurotrophin that modulates synaptic activity. In cortical neurons, Ca2+ influx triggers phosphorylation of CREB, which by binding to a critical Ca2+ response element (CRE) within the BDNF gene activates BDNF transcription. Mutation of the BDNF CRE or an adjacent novel regulatory element as well as a blockade of CREB function resulted in a dramatic loss of BDNF transcription. These findings suggest that a CREB family member acts cooperatively with an additional transcription factor(s) to regulate BDNF transcription. We conclude that the BDNF gene is a CREB family target whose protein product functions at synapses to control adaptive neuronal responses

Mechanical dysfunction of the sarcomere induced by a pathogenic mutation in troponin T drives cellular adaptation

Familial hypertrophic cardiomyopathy (HCM), a leading cause of sudden cardiac death, is primarily caused by mutations in sarcomeric proteins. The pathogenesis of HCM is complex, with functional changes that span scales, from molecules to tissues. This makes it challenging to deconvolve the biophysical molecular defect that drives the disease pathogenesis from downstream changes in cellular function. In this study, we examine an HCM mutation in troponin T, R92Q, for which several models explaining its effects in disease have been put forward. We demonstrate that the primary molecular insult driving disease pathogenesis is mutation-induced alterations in tropomyosin positioning, which causes increased molecular and cellular force generation during calcium-based activation. Computational modeling shows that the increased cellular force is consistent with the molecular mechanism. These changes in cellular contractility cause downstream alterations in gene expression, calcium handling, and electrophysiology. Taken together, our results demonstrate that molecularly driven changes in mechanical tension drive the early disease pathogenesis of familial HCM, leading to activation of adaptive mechanobiological signaling pathways

Creating an experimental testbed for information-theoretic analysis of architectures for x-ray anomaly detection

Anomaly detection requires a system that can reliably convert measurements of an object into knowledge about that object. Previously, we have shown that an information-theoretic approach to the design and analysis of such systems provides insight into system performance as it pertains to architectural variations in source fluence, view number/angle, spectral resolution, and spatial resolution.(1) However, this work was based on simulated measurements which, in turn, relied on assumptions made in our simulation models and virtual objects. In this work, we describe our experimental testbed capable of making transmission x-ray measurements. The spatial, spectral, and temporal resolution is sufficient to validate aspects of the simulation-based framework, including the forward models, bag packing techniques, and performance analysis. In our experimental CT system, designed baggage is placed on a rotation stage located between a tungsten-anode source and a spectroscopic detector array. The setup is able to measure a full 360 rotation with 18,000 views, each of which defines a 10 ms exposure of 1,536 detector elements, each with 64 spectral channels. Measurements were made of 1,000 bags that comprise 100 clutter instantiations each with 10 different target materials. Moreover, we develop a systematic way to generate bags representative of our desired clutter and target distributions. This gives the dataset a statistical significance valuable in future investigations.US Department of Homeland Security through the Advanced X-Ray Material Discrimination ProgramThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

67/08/31 Brief for the N.A.A.C.P Legal Defense and Educational Fund, Inc., as Amicus Curiae

The Court should hold that neither stops nor frisks may be made without probable cause. In each of these cases, the judgment of conviction should be reversed -- conclusion, p. 69