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1. chinaXiv:201605.01525 [pdf]

Three-dimensional super-resolution protein localization correlated with vitrified cellular context

Liu, Bei; Xue, Yanhong; Zhao, Wei; Chen, Yan; Fan, Chunyan; Gu, Lusheng; Zhang, Yongdeng; Zhang, Xiang; Sun, Lei; Huang, Xiaojun; Ding, Wei; Sun, Fei; Ji, Wei; Xu, Tao; Liu, Bei; Gu, Lusheng; Zhang, Yongdeng; Xu, Tao; Zhao, Wei; Chen, Yan
Subjects: Biology >> Biophysics

We demonstrate the use of cryogenic super-resolution correlative light and electron microscopy (csCLEM) to precisely determine the spatial relationship between proteins and their native cellular structures. Several fluorescent proteins (FPs) were found to be photoswitchable and emitted far more photons under our cryogenic imaging condition, resulting in higher localization precision which is comparable to ambient super-resolution imaging. Vitrified specimens were prepared by high pressure freezing and cryo-sectioning to maintain a near-native state with better fluorescence preservation. A 2-3-fold improvement of resolution over the recent reports was achieved due to the photon budget performance of screening out Dronpa and optimized imaging conditions, even with thin sections which is at a disadvantage when calculate the structure resolution from label density. We extended csCLEM to mammalian cells by introducing cryo-sectioning and observed good correlation of a mitochondrial protein with the mitochondrial outer membrane at nanometer resolution in three dimensions.

submitted time 2016-05-12 Hits2069Downloads1224 Comment 0

2. chinaXiv:201605.01499 [pdf]

YAP Enhances Autophagic Flux to Promote Breast Cancer Cell Survival in Response to Nutrient Deprivation

Song, Qinghe; Mao, Beibei; Cheng, Jinbo; Gao, Yuhao; Yuan, Zengqiang; Song, Qinghe; Gao, Yuhao; Yuan, Zengqiang; Jiang, Ke; Meng, Songshu; Chen, Jun
Subjects: Biology >> Biophysics

The Yes-associated protein (YAP), a transcriptional coactivator inactivated by the Hippo tumor suppressor pathway, functions as an oncoprotein in a variety of cancers. However, its contribution to breast cancer remains controversial. This study investigated the role of YAP in breast cancer cells under nutrient deprivation (ND). Here, we show that YAP knockdown sensitized MCF7 breast cancer cells to nutrient deprivation-induced apoptosis. Furthermore, in response to ND, YAP increased the autolysosome degradation, thereby enhancing the cellular autophagic flux in breast cancer cells. Of note, autophagy is crucial for YAP to protect MCF7 cells from apoptosis under ND conditions. In addition, the TEA domain (TEAD) family of growth-promoting transcription factors was indispensable for YAP-mediated regulation of autophagy. Collectively, our data reveal a role for YAP in promoting breast cancer cell survival upon ND stress and uncover an unappreciated function of YAP/TEAD in the regulation of autophagy.

submitted time 2016-05-12 Hits2019Downloads1206 Comment 0

3. chinaXiv:201605.01491 [pdf]

Mechanical coupling of the multiple structural elements of the large-conductance mechanosensitive channel during expansion

Li, Jie; Guo, Jianli; Ou, Xiaomin; Liu, Zhenfeng; Li, Jie; Zhang, Mingfeng; Li, Yuezhou
Subjects: Biology >> Biophysics

The prokaryotic mechanosensitive channel of large conductance (MscL) is a pressure-relief valve protecting the cell from lysing during acute osmotic downshock. When the membrane is stretched, MscL responds to the increase of membrane tension and opens a nonselective pore to about 30 angstrom wide, exhibiting a large unitary conductance of similar to 3 nS. A fundamental step toward understanding the gating mechanism of MscL is to decipher the molecular details of the conformational changes accompanying channel opening. By applying fusion-protein strategy and controlling detergent composition, we have solved the structures of an archaeal MscL homolog from Methanosarcina acetivorans trapped in the closed and expanded intermediate states. The comparative analysis of these two new structures reveals significant conformational rearrangements in the different domains of MscL. The large changes observed in the tilt angles of the two transmembrane helices (TM1 and TM2) fit well with the helix-pivoting model derived from the earlier geometric analyses based on the previous structures. Meanwhile, the periplasmic loop region transforms from a folded structure, containing an.-shaped loop and a short beta-hairpin, to an extended and partly disordered conformation during channel expansion. Moreover, a significant rotating and sliding of the N-terminal helix (N-helix) is coupled to the tilting movements of TM1 and TM2. The dynamic relationships between the N-helix and TM1/TM2 suggest that the N-helix serves as a membrane-anchored stopper that limits the tilts of TM1 and TM2 in the gating process. These results provide direct mechanistic insights into the highly coordinated movement of the different domains of the MscL channel when it expands.

submitted time 2016-05-12 Hits1753Downloads910 Comment 0

4. chinaXiv:201605.01395 [pdf]

Structure of Drosophila Oskar reveals a novel RNA binding protein

Yang, Na; Yu, Zhenyu; Hu, Menglong; Wang, Mingzhu; Xu, Rui-Ming; Yang, Na; Xu, Rui-Ming; Lehmann, Ruth; Lehmann, Ruth
Subjects: Biology >> Biophysics

Oskar (Osk) protein plays critical roles during Drosophila germ cell development, yet its functions in germ-line formation and body patterning remain poorly understood. This situation contrasts sharply with the vast knowledge about the function and mechanism of osk mRNA localization. Osk is predicted to have an N-terminal LOTUS domain (Osk-N), which has been suggested to bind RNA, and a C-terminal hydrolase-like domain (Osk-C) of unknown function. Here, we report the crystal structures of Osk-N and Osk-C. Osk-N shows a homodimer of winged-helix-fold modules, but without detectable RNA-binding activity. Osk-C has a lipase-fold structure but lacks critical catalytic residues at the putative active site. Surprisingly, we found that Osk-C binds the 3'UTRs of osk and nanos mRNA in vitro. Mutational studies identified a region of Osk-C important for mRNA binding. These results suggest possible functions of Osk in the regulation of stability, regulation of translation, and localization of relevant mRNAs through direct interaction with their 3'UTRs, and provide structural insights into a novel protein-RNA interaction motif involving a hydrolase-related domain.

submitted time 2016-05-12 Hits1685Downloads950 Comment 0

5. chinaXiv:201605.01332 [pdf]

Hypomagnetic Field Alters Circadian Rhythm and Increases Algesia in Adult Male Mice

Liu Ying; Mo Wei-Chuan; Fu Jing-Peng; Liu Ying; He Rong-Qiao; Fu Jing-Peng; Liu Ying; He Rong-Qiao; Ding Hai-Min; Hua Qian
Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology

It has been established that exposure in the hypomagnetic field (HMF), which is one of the environmental factor of outer space, has adverse effects on animal and human behavior and brain function. Thus, it is necessary to develop appropriate counteract strategy to avoid the HMF-induced risks to the health of the astronauts during long-term and long-distance manned space mission. However, the physical and mental effects of the HMF in details still await systematic evaluation and the underlying mechanism remains elusive, so far. In this study, we constructed an HMF animal rearing system (<500 nT) and examined the effects of one-month HMF exposure on the circadian behavior, pain response and emotions in adult male C57BL/6 mice (4 similar to 6 weeks old, (20 +/- 2) g). The control animals were reared in the geomagnetic field (GMF). The HMF-exposed animals exhibited a prolonged alteration of the circadian drinking rhythm and a decrease in general activity, accompanied with an increase in thermal hyperalgesia. But the HMF did not induce obvious depression-like and anxiety-related behaviors. The serum noradrenalin concentration in HMF-exposed mice significantly decreased. These findings indicate that the HMF disturbs the behavior rhythm and the function of endocrine system, which probably leads to the subsequently weakened activities of the animal.

submitted time 2016-05-11 Hits1710Downloads859 Comment 0

6. chinaXiv:201605.01297 [pdf]

Asymmetric dimethylarginine exacerbates A beta-induced toxicity and oxidative stress in human cell and Caenorhabditis elegans models of Alzheimer disease

Luo, Yunfeng; Yue, Wenhui; Quan, Xin; Wang, Yue; Lu, Zhongbing; Zhao, Baolu
Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology

Growing evidence suggests a strong association between cardiovascular risk factors and incidence of Alzheimer disease (AD). Asymmetric dimethylarginine (ADMA), the endogenous nitric oxide synthase inhibitor, has been identified as an independent cardiovascular risk factor and is also increased in plasma of patients with AD. However, whether ADMA is involved in the pathogenesis of AD is unknown. In this study, we found that ADMA content was increased in a transgenic Caenorhabditis elegans beta-amyloid (A beta) overexpression model, strain CL2006, and in human SH-SY5Y cells overexpressing the Swedish mutant form of human A beta precursor protein (APPsw). Moreover, ADMA treatment exacerbated A beta-induced paralysis and oxidative stress in CL2006 worms and further elevated oxidative stress and A beta secretion in APPsw cells. Knockdown of type 1 protein arginine N-methyltransferase to reduce ADMA production failed to show a protective effect against A beta toxicity, but resulted in more paralysis in CL2006 worms as well as increased oxidative stress and A beta secretion in APPsw cells. However, overexpression of dimethylarginine dimethylaminohydrolase 1 (DDAH1) to promote ADMA degradation significantly attenuated oxidative stress and A beta secretion in APPsw cells. Collectively, our data support the hypothesis that elevated ADMA contributes to the pathogenesis of AD. Our findings suggest that strategies to increase DDAH1 activity in neuronal cells may be a novel approach to attenuating AD development. (C) 2014 Elsevier Inc. All rights reserved.

submitted time 2016-05-11 Hits1809Downloads1021 Comment 0

7. chinaXiv:201605.01197 [pdf]

HDAC2 Selectively Regulates FOXO3a-Mediated Gene Transcription during Oxidative Stress-Induced Neuronal Cell Death

Peng, Shengyi; Zhao, Siqi; Cheng, Jinbo; Huang, Li; Chen, Hong; Yuan, Zengqiang; Yan, Feng; Liu, Qingsong; Peng, Shengyi; Yuan, Zengqiang; Peng, Shengyi
Subjects: Biology >> Biophysics >> Neurosciences

All neurodegenerative diseases are associated with oxidative stress-induced neuronal death. Forkhead box O3a (FOXO3a) is a key transcription factor involved in neuronal apoptosis. However, how FOXO3a forms complexes and functions in oxidative stress processing remains largely unknown. In the present study, we show that histone deacetylase 2 (HDAC2) forms a physical complex with FOXO3a, which plays an important role in FOXO3a-dependent gene transcription and oxidative stress-induced mouse cerebellar granule neuron (CGN) apoptosis. Interestingly, we also found that HDAC2 became selectively enriched in the promoter region of the p21 gene, but not those of other target genes, and inhibited FOXO3a-mediated p21 transcription. Furthermore, we found that oxidative stress reduced the interaction between FOXO3a and HDAC2, leading to an increased histone H4K16 acetylation level in the p21 promoter region and upregulated p21 expression in a manner independent of p53 or E2F1. Phosphorylation of HDAC2 at Ser 394 is important for the HDAC2-FOXO3a interaction, and we found that cerebral ischemia/reperfusion reduced phosphorylation of HDAC2 at Ser 394 and mitigated the HDAC2-FOXO3a interaction in mouse brain tissue. Our study reveals the novel regulation of FOXO3a-mediated selective gene transcription via epigenetic modification in the process of oxidative stress-induced cell death, which could be exploited therapeutically.

submitted time 2016-05-11 Hits2051Downloads1166 Comment 0

8. chinaXiv:201605.00768 [pdf]

Amplified RLR signaling activation through an interferon-stimulated gene-endoplasmic reticulum stress-mitochondrial calcium uniporter protein loop

Cheng, Jinbo; Liao, Yajin; Zhou, Lujun; Peng, Shengyi; Chen, Hong; Yuan, Zengqiang; Liao, Yajin; Zhou, Lujun;
Subjects: Biology >> Biophysics

Type I interferon (IFN-I) is critical for a host against viral and bacterial infections via induction of hundreds of interferon-stimulated genes (ISGs), but the mechanism underlying the regulation of IFN-I remains largely unknown. In this study, we first demonstrate that ISG expression is required for optimal IFN-beta levels, an effect that is further enhanced by endoplasmic reticulum (ER) stress. Furthermore, we identify mitochondrial calcium uniporter protein (MCU) as a mitochondrial antiviral signaling protein (MAVS)-interacting protein that is important for ER stress induction and amplified MAVS signaling activation. In addition, by performing an ectopic expression assay to screen a library of 117 human ISGs for effects on IFN-beta levels, we found that tumor necrosis factor receptor 1 (TNFR1) significantly increases IFN-beta levels independent of ER stress. Altogether, our findings suggest that MCU and TNFR1 are involved in the regulation of RIG-I-like receptors (RLR) signaling.

submitted time 2016-05-05 Hits1988Downloads966 Comment 0

9. chinaXiv:201605.00748 [pdf]

c-Abl-p38 alpha signaling plays an important role in MPTP-induced neuronal death

Wu, R.; Chen, H.; Ma, J.; He, Q.; Yuan, Z.; Wu, R.; Ma, J.; He, Q.; Yuan, Z.; Chen, H.; Yuan, Z.; Huang, Q.; Li, M.; Huang, Q.; Li, M.; Liu, Q.;
Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology

Oxidative stress is a major cause of sporadic Parkinson's disease (PD). Here, we demonstrated that c-Abl plays an important role in oxidative stress-induced neuronal cell death. C-Abl, a nonreceptor tyrosine kinase, was activated in an 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP)-induced acute PD model. Conditional knockout of c-Abl in neurons or treatment of mice with STI571, a c-Abl family kinase inhibitor, reduced the loss of dopaminergic neurons and ameliorated the locomotive defects induced by short-term MPTP treatment. By combining the SILAC (stable isotope labeling with amino acids in cell culture) technique with other biochemical methods, we identified p38 alpha as a major substrate of c-Abl both in vitro and in vivo and c-Abl-mediated phosphorylation is critical for the dimerization of p38 alpha. Furthermore, p38 alpha inhibition mitigated the MPTP-induced loss of dopaminergic neurons. Taken together, these data suggested that c-Abl-p38 alpha signaling may represent a therapeutic target for PD.

submitted time 2016-05-05 Hits1670Downloads954 Comment 0

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