Effect of age on in vivo oxidative capacity in two locomotory muscles of the leg

To determine the effects of age and sex on in vivo mitochondrial function of distinct locomotory muscles, the tibialis anterior (TA) and medial gastrocnemius (MG), of young (Y; 24 ± 3 years) and older (O; 69 ± 4) men (M) and women (W) of similar overall physical activity (PA) was compared. In vivo mitochondrial function was measured using phosphorus magnetic resonance spectroscopy, and PA and physical function were measured in all subjects. Overall PA was similar among the groups, although O (n = 17) had fewer daily minutes of moderate-to-vigorous PA (p = 0.001), and slowed physical function (p < 0.05 for all variables), compared with Y (n = 17). In TA, oxidative capacity (V_max; mM s⁻¹) was higher in O than Y (p < 0.001; Y = 0.90 ± 0.12; O = 1.12 ± 0.18). There was no effect of age in MG (p = 0.5; Y = 0.91 ± 0.17; O = 0.96 ± 0.24), but women had higher oxidative capacity than men (p = 0.007; M = 0.84 ± 0.18; W = 1.03 ± 0.18). In vivo mitochondrial function was preserved in healthy O men and women, despite lower intensity PA and physical function in this group. The extent to which compensatory changes in gait may be responsible for this preservation warrants further investigation. Furthermore, women had higher oxidative capacity in the MG, but not the TA.     

Melatonin reverses the decreases in hippocampal protein serine/threonine kinases observed in an animal model of autism

Lower global cognitive function scores are a common symptom of autism spectrum disorders (ASDs). This study investigates the effects of melatonin on hippocampal serine/threonine kinase signaling in an experimental ASD model. We found that chronic melatonin (1.0 or 5.0 mg/kg/day, 28 days) treatment significantly rescued valproic acid (VPA, 600 mg/kg)‐induced decreases in CaMKII (Thr286), NMDAR1 (Ser896), and PKA (Thr197) phosphorylation in the hippocampus without affecting total protein levels. Compared with control rats, the immunostaining of pyramidal neurons in the hippocampus revealed a decrease in immunolabeling intensity for phospho‐CaMKII (Thr286) in the hippocampus of VPA‐treated rats, which was ameliorated by chronic melatonin treatment. Consistent with the elevation of CaMKII/PKA/PKC phosphorylation observed in melatonin‐treated rat, long‐term potentiation (LTP) was enhanced after chronic melatonin (5.0 mg/kg) treatment, as reflected by extracellular field potential slopes that increased from 56 to 60 min (133.4 ± 3.9% of the baseline, P < 0.01 versus VPA‐treated rats) following high‐frequency stimulation (HFS) in hippocampal slices. Accordingly, melatonin treatment also significantly improved social behavioral deficits at postnatal day 50 in VPA‐treated rats. Taken together, the increased phosphorylation of CaMKII/PKA/PKC signaling might contribute to the beneficial effects of melatonin on autism symptoms.     

Collapsin response‐mediator protein 5 (CRMP5) phosphorylation at threonine 516 regulates neurite outgrowth inhibition

The collapsin response‐mediator proteins (CRMPs) are multifunctional proteins highly expressed during brain development but down‐regulated in the adult brain. They are involved in axon guidance and neurite outgrowth signalling. Among these, the intensively studied CRMP2 has been identified as an important actor in axon outgrowth, this activity being correlated with the reorganisation of cytoskeletal proteins via the phosphorylation state of CRMP2. Another member, CRMP5, restricts the growth‐promotional effects of CRMP2 by inhibiting dendrite outgrowth at early developmental stages. This inhibition occurs when CRMP5 binds to tubulin and the microtubule‐associated protein MAP2, but the role of CRMP5 phosphorylation is still unknown. Here, we have studied the role of CRMP5 phosphorylation by mutational analysis. Using non‐phosphorylatable truncated constructs of CRMP5 we have demonstrated that, among the four previously identified CRMP5 phosphorylation sites (T509, T514, T516 and S534), only the phosphorylation at T516 residue was needed for neurite outgrowth inhibition in PC12 cells and in cultured C57BL/6J mouse hippocampal neurons. Indeed, the expression of the CRMP5 non‐phosphorylated form induced a loss of function of CRMP5 and the mutant mimicking the phosphorylated form induced the growth inhibition function seen in wildtype CRMP5. The T516 phosphorylation was achieved by the glycogen synthase kinase‐3β (GSK‐3β), which can phosphorylate the wildtype protein but not the non‐phosphorylatable mutant. Furthermore, we have shown that T516 phosphorylation is essential for the tubulin‐binding property of CRMP5. Therefore, CRMP5‐induced growth inhibition is dependent on T516 phosphorylation through the GSK‐3β pathway. The findings provide new insights into the mechanisms underlying neurite outgrowth.     

STAT3 serine 727 phosphorylation influences clinical outcome in glioblastoma

Besides STAT3 tyrosine 705 phosphorylation (pTyr705-STAT3), phosphorylation of STAT3 at serine 727 (pSer727-STAT3) is shown to contribute to tumorigenesis and be closely related with resistance to radiotherapy and chemotherapy in glioma, but there is currently no study regarding its relevance to prognosis in glioblastoma (GBM). Here, the expression of phosphorylated STAT3 was detected in tumor specimens from 88 patients with newly diagnosed GBM by immunohistochemistry, the Kaplan-Meier survival curve and COX proportional hazards regression model were applied to estimate its influences on progression-free survival (PFS) and overall survival (OS). Immunohistochemical assay showed elevated expression of pSer727-STAT3 in GBM compared with normal brain tissue. Univariate analysis indicated significant correlations of high percentage of pSer727-STAT3 positive tumor cells with shorter PFS (P = 0.006) and OS (P = 0.002). In multivariate analysis, high pSer727-STAT3 expression was demonstrated as an independent unfavorable prognostic indicator for PFS (HR 1.830, P = 0.022) and OS (HR 1.797, P = 0.040). And patients with high expression of both pTyr705-STAT3 and pSer727-STAT3 had a poorer prognosis compared with the remainder (P < 0.005). In conclusion, the high proportion of pSer727-STAT3 positive neoplastic cells in GBM is an independent unfavorable prognostic factor, and increased expression of both pTyr705-STAT3 and pSer727-STAT3 is predictive of poorer clinical outcome, thereby adding to the growing evidence that STAT3 inhibition may be a potential therapeutic strategy in glioblastoma.     

亨廷顿蛋白的翻译后修饰在亨廷顿病发病机制中的作用(英文)

翻译后修饰能快速、有效且可逆地调节蛋白的稳定性、分布位置、功能及其与其它分子之间的相互作用。翻译后修饰主要包括氨基酸残基的SUMO化、磷酸化、棕榈化以及乙酰化等。这些复杂的生化修饰能严格、规范地调节各种细胞过程。亨廷顿蛋白(Htt)的几种翻译后修饰方式已见报道。这些翻译后修饰会影响Htt的代谢、Htt与其它蛋白质的相互作用以及Htt的细胞毒性。突变Htt的剪切、清除以及与其它细胞蛋白质的相互作用是导致亨廷顿病的重要生化事件。因此,了解Htt修饰的信号转导及其意义,可以帮助我们更好地理解野生型Htt的正常功能和突变Htt的致病机制。     

The interaction between F3 immunoglobulin domains and protein tyrosine phosphatases zeta/beta triggers bidirectional signalling between neurons and glial cells

F3, a mouse glycosyl-phosphatidylinositol anchored molecule of the immunoglobulin superfamily, is known to influence axonal growth and fasciculation via multiple interactions of its modular immunoglobulin-like domains. We prepared an Fc chimeric molecule (F3IgFc) to identify molecules interacting with these domains and characterize the functional impact of the interactions. We affinity-isolated tenascin-C and isoforms of the proteoglycan-type protein tyrosine phosphatases zeta/beta (PTPzeta/RPTPbeta) from extracts of developing mouse brain. We showed that both PTPzeta/RPTPbeta and tenascin-C can bind directly to F3, possibly in an exclusive manner, with the highest affinity for the F3-PTPzeta/RPTPbeta interaction. We observed a strong binding of F3IgFc-coated fluorospheres to astrocytes in neural primary cultures and to C6 astrocytoma cells, and demonstrated, in antibody perturbation experiments, that F3-Ig binding on astrocytes depends on its interaction with PTPzeta/RPTPbeta. We also found by confocal analysis that tenascin-C and PTPzeta/RPTPbeta were colocalized on astrocytes which suggests a complex interplay of interactions between PTPzeta/RPTPbeta, tenascin-C and F3. We showed that the interaction between PTPzeta/RPTPbeta and F3-Ig-like domains can trigger bidirectional signalling. C6 glia-expressed PTPzeta/RPTPbeta stimulated neurite outgrowth by cortical and cerebellar neurons, whereas preclustered F3IgFc specifically modified the distribution of phosphotyrosine labelling in these glial cells. Both effects could be prevented and/or mimicked by anti-F3 and anti-6B4PG antibodies. These results identify F3 and PTPzeta/RPTPbeta as potential mediators of a reciprocal exchange of information between glia and neurons.     

Bisphenol a regulates the estrogen receptor alpha signaling in developing hippocampus of male rats through estrogen receptor

Bisphenol A (BPA), one of the most common environmental endocrine disruptors, has been recognized to have wide adverse effects on the brain development and behavior. These adversities are related to its ability to bind estrogen receptor (ER) with subsequent alteration of its expression in the target areas. However, very little is known about whether BPA exposure also affects ER phosphorylation and its translocation to nucleus during postnatal development, two critical steps for its function. Here, we found that during development from postnatal day 7 (P7) to P21, the alpha subtype of ER (ERα) in the hippocampus of male rats experienced remarkable alterations in terms of its expression, phosphorylation and translocation to nucleus. Exposure to low level of BPA had bidirectional, development‐dependent effects on the expression of ERα mRNA and protein, but decreased ERα phosphorylation and impaired its translocation to nucleus throughout the period investigated. Treatment with low dose of ICI 182,780 (ICI), an ER antagonist to block the binding of ER with BPA, reversed the altered ERα following BPA exposure, highlighting critical involvement of ER. Moreover, ICI treatment rescued the hippocampus‐dependent behavioral deficits in the adult rats experiencing early‐life BPA exposure. Overall, our results indicate that BPA interferes with the ERα signaling in the developing hippocampus in an ER‐dependent manner, which may underlie its adverse behavioral and cognitive outcomes in adult animals. © 2014 Wiley Periodicals, Inc.