Contents of Volume 53

Plant Molecular Biology -     

严重急性呼吸综合征冠状病毒2膜蛋白对宿主细胞pre-mRNA 3"UTR加工的影响

目的 研究严重急性呼吸综合征冠状病毒2（SARS-CoV-2）膜蛋白对宿主细胞mRNA前体（pre-mRNA）3"非翻译区（UTR）加工的影响。方法 本研究以人肺上皮细胞系A549为模型，利用瞬时转染在细胞内过表达SARS-CoV-2膜蛋白；利用RNA-Seq测序技术及生物信息学分析方法，系统性描绘宿主细胞选择性多聚腺苷酸化（alternative polyadenylation，APA）事件；Metascape数据库对发生显著APA变化的基因进行功能富集分析；RT-qPCR验证靶基因3"UTR长度变化；蛋白质免疫印迹（Western blot）检测目的蛋白表达水平。结果 SARS-CoV-2膜蛋白外源表达后宿主细胞内共813个基因发生显著APA变化。GO和KEGG分析显示，差异APA基因广泛参与有丝分裂细胞周期、调节细胞应激等生物过程，涉及病毒感染和蛋白质加工等。从中进一步筛选出AKT1基因，在IGV软件中显示3"UTR延长；RT-qPCR验证AKT1基因的3"UTR长度变化趋势；Western blot结果显示AKT1蛋白磷酸化水平增加。结论 SARS-CoV-2膜蛋白潜在影响宿主pre-mRNA的3"UTR加工，其中参与多种病毒性生物过程的AKT1基因 3"UTR延长，且其编码的蛋白质功能在细胞内被激活。     

Reactivation and Dedifferentiation of Differentiated Murine Erythroleukemic Cell Nuclei

A murine erythroleukemic cell line, 745 A4-TG, deficient in hypoxanthine-guanine-phosphoribosyl transferase, can be induced with 3 mM hexamethylene bisacetamide to yield at least 50% of cells undergoing irreversible erythroid differentiation and finally losing capacity for cell divisions. The effects of such induced differentiation of 745 A4-TG on its ability to form viable and proliferating hybrids when fused with 3T3 1T22 fibroblasts were investigated. We found that when the induced 745 A4-TG cells were used, more continuously proliferating hybrids were obtained than could be accounted for by the residual uninduced cells which remained in these induced preparations. This suggests that some of the induced 745 A4-TG cells, when fused with 3T3 1T22 reverted from the induced phenotype of a limited capacity for cell proliferation to an uninduced state of continuous proliferation. This observation was further confirmed with the use of fully differentiated 745 A4-TG cells, which were obtained after selection with a bromodeoxyuridine suicide treatment to eliminate the uninduced and the partially differentiated cells in the preparations. When these selected, fully differentiated cells, as characterized by their lack of proliferation capacity and thymidine kinase activity, were fused with 3T3 1T22 (also deficient in thymidine kinase), it was found that not only were viable hybrid colonies obtained in a selection medium, which precluded the proliferation of either parental cells, but these hybrids continued to proliferate for more than two months in selection medium. These data thus confirmed that some fully differentiated erythroleukemic nucleus components in the hybrids were reactivated to regain capacity for cell proliferation and to dedifferentiate to synthesize thymidine kinase for survival in the selection medium. The lack of hemoglobin synthesis by these hybrids also indicates dedifferention of these murine erythroleukemic components in the hybrids.     

The Stress Hormone Corticosterone Increases Synaptic ��-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors via Serum- and Glucocorticoid-inducible Kinase (SGK) Regulation of the GDI-Rab4 Complex

Corticosterone, the major stress hormone, plays an important role in regulating neuronal functions of the limbic system, although the cellular targets and molecular mechanisms of corticosteroid signaling are largely unknown. Here we show that a short treatment of corticosterone significantly increases α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated synaptic transmission and AMPAR membrane trafficking in pyramidal neurons of prefrontal cortex, a key region involved in cognition and emotion. This enhancing effect of corticosterone is through a mechanism dependent on Rab4, the small GTPase-controlling receptor recycling between early endosome and plasma membrane. Guanosine nucleotide dissociation inhibitor (GDI), which regulates the cycle of Rab proteins between membrane and cytosol, forms an increased complex with Rab4 after corticosterone treatment. Corticosterone also triggers an increased GDI phosphorylation at Ser-213 by the serum- and glucocorticoid-inducible kinase (SGK). Moreover, AMPAR synaptic currents and surface expression and their regulation by corticosterone are altered by mutating Ser-213 on GDI. These results suggest that corticosterone, via SGK phosphorylation of GDI at Ser-213, increases the formation of GDI-Rab4 complex, facilitating the functional cycle of Rab4 and Rab4-mediated recycling of AMPARs to the synaptic membrane. It provides a potential mechanism underlying the role of corticosteroid stress hormone in up-regulating excitatory synaptic efficacy in cortical neurons.     

斑纹小贻贝(Mytella strigata)基础生物学与生物入侵

生物入侵是继栖息地破坏之后，全球生物多样性丧失的第二大驱动因素。近年来，原产于南美洲地区的斑纹小贻贝（Mytella strigata）在印度-西太平洋海区被陆续报道，而我国台湾、广东、海南、福建、广西等省份同样发现斑纹小贻贝，且其已经建立可自我维持的种群。但是，作为一种新型入侵生物，斑纹小贻贝尚未引起国内海洋管理部门和科研人员足够重视，亟待查明其在我国沿海的分布现状、扩散趋势和生态影响等，为斑纹小贻贝的检测、监测、防控和管理提供科学依据。综述了斑纹小贻贝的基础生物学特征和全球生物入侵现状，发现国内的斑纹小贻贝源于南美洲加勒比海地区，于2014年左右通过船舶压舱水或船体生物污损的形式侵入我国南方沿海并迅速扩散。此外，斑纹小贻贝在我国的生物入侵处于"引进-传播"阶段，即将大规模扩繁，因此亟需开展应急清除行动。     

大鼠脑室注射P物质引起的血压升高与脑啡肽和β-内啡肽有关

给乌拉坦麻醉大鼠侧脑室注射P物质(SP)10μg 引起的升压效应,可被脑室注射纳洺酮15μg 部分阻断。将抗β-内啡肽抗血清、抗甲啡肽抗血清及抗亮啡肽抗血清各10μl 分别注入侧脑室预处理60min 后,再注入 SP,其升压效应明显减弱;而抗强啡肽抗血清则对其无影响。上述结果提示:大鼠脑室注射 SP 引起的升压效应,可能是通过释放β-内啡肽和脑啡肽实现的。     

肌苷对缺氧心肌跨膜电位和收缩强度的影响

本工作在正常和缺氧情况下,观察肌苷对豚鼠心室乳头肌跨膜电位和收缩强度的影响。结果表明肌苷使正常心肌细胞动作电位时间(APD_(10)、APD_(50)延长。在缺氧心肌,肌苷使细胞静息电位增大,动作电位去极化幅度增高,零期最大去极化速度加快和动作电位时间延长。肌苷增加正常心肌收缩力,使缺氧心肌收缩的衰减显著缓和,亦即使收缩功能改善,且表现剂量-依从性。肌苷对心肌细胞跨膜电位的影响提示它很可能有抗心律失常作用,特别是在缺氧心脏。肌苷对离休乳头肌收缩的影响,证明其对心肌有直接的强心作用。