A Common Ca2+-Driven Interdomain Module Governs Eukaryotic NCX Regulation

Na+/Ca2+ exchanger (NCX) proteins mediate Ca2+-fluxes across the cell membrane to maintain Ca2+ homeostasis in many cell types. Eukaryotic NCX contains Ca2+-binding regulatory domains, CBD1 and CBD2. Ca2+ binding to a primary sensor (Ca3-Ca4 sites) on CBD1 activates mammalian NCXs, whereas CALX, a Drosophila NCX ortholog, displays an inhibitory response to regulatory Ca2+. To further elucidate the underlying regulatory mechanisms, we determined the 2.7 Å crystal structure of mammalian CBD12-E454K, a two-domain construct that retains wild-type properties. In conjunction with stopped-flow kinetics and SAXS (small-angle X-ray scattering) analyses of CBD12 mutants, we show that Ca2+ binding to Ca3-Ca4 sites tethers the domains via a network of interdomain salt-bridges. This Ca2+-driven interdomain switch controls slow dissociation of “occluded” Ca2+ from the primary sensor and thus dictates Ca2+ sensing dynamics. In the Ca2+-bound conformation, the interdomain angle of CBD12 is very similar in NCX and CALX, meaning that the interdomain distances cannot account for regulatory diversity in NCX and CALX. Since the two-domain interface is nearly identical among eukaryotic NCXs, including CALX, we suggest that the Ca2+-driven interdomain switch described here represents a general mechanism for initial conduction of regulatory signals in NCX variants

MicroRNA-30a-5p in the prefrontal cortex controls the transition from moderate to excessive alcohol consumption.

MicroRNAs (miRNAs) induce messenger RNA (mRNA) degradation and repress mRNA translation. Several miRNAs control the expression of the brain-derived neurotrophic factor (BDNF) in the prefrontal cortex (PFC). The BDNF signaling pathway is activated by moderate intake of alcohol to prevent escalation to excessive drinking. Here, we present data to suggest that the transition from moderate to uncontrolled alcohol intake occurs, in part, upon a breakdown of this endogenous protective pathway via a miRNA-dependent mechanism. Specifically, a mouse paradigm that mimics binge alcohol drinking in humans produced a robust reduction in BDNF mRNA levels in the medial PFC (mPFC), which was associated with increased expression of several miRNAs including miR-30a-5p. We show that miR-30a-5p binds the 3′ untranslated region of BDNF, and that overexpression of miR-30a-5p in the mPFC decreased BDNF expression. Importantly, overexpression of miR-30a-5p in the mPFC produced an escalation of alcohol intake and a preference over water. Conversely, inhibition of miR-30a-5p in the mPFC using a Locked Nucleic Acid sequence that targets miR-30a-5p restored BDNF levels and decreased excessive alcohol intake. Together, our results indicate that miR-30a-5p plays a key role in the transition from moderate to excessive alcohol intake

Dose-response relationship for breast cancer induction at radiotherapy dose

<p>Abstract</p> <p>Purpose</p> <p>Cancer induction after radiation therapy is known as a severe side effect. It is therefore of interest to predict the probability of second cancer appearance for the patient to be treated including breast cancer.</p> <p>Materials and methods</p> <p>In this work a dose-response relationship for breast cancer is derived based on</p> <p>(i) the analysis of breast cancer induction after Hodgkin's disease,</p> <p>(ii) a cancer risk model developed for high doses including fractionation based on the linear quadratic model, and</p> <p>(iii) the reconstruction of treatment plans for Hodgkin's patients treated with radiotherapy,</p> <p>(iv) the breast cancer induction of the A-bomb survivor data.</p> <p>Results</p> <p>The fitted model parameters for an <it>α/β = 3 </it>Gy were <it>α = 0.067Gy</it>^{<it>-1 </it>}and <it>R = 0.62</it>. The risk for breast cancer is according to this model for small doses consistent with the finding of the A-bomb survivors, has a maximum at doses of around 20 Gy and drops off only slightly at larger doses. The predicted <it>EAR </it>for breast cancer after radiotherapy of Hodgkin's disease is 11.7/10000PY which can be compared to the findings of several epidemiological studies where EAR for breast cancer varies between 10.5 and 29.4/10000PY. The model was used to predict the impact of the reduction of radiation volume on breast cancer risk. It was estimated that mantle field irradiation is associated with a 3.2-fold increased risk compared with mediastinal irradiation alone, which is in agreement with a published value of 2.7. It was also shown that the modelled age dependency of breast cancer risk is in satisfying agreement with published data.</p> <p>Conclusions</p> <p>The dose-response relationship obtained in this report can be used for the prediction of radiation induced secondary breast cancer of radiotherapy patients.</p