REGULATION OF MEMBRANE FUSION

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 本项目的长期目标是详细了解包膜病毒进入细胞的过程和病毒诱导细胞融合的机制。我们继续对小鼠白血病病毒（一种致癌逆转录病毒模型）和副流感病毒（一种呼吸道疾病的重要病因）进行研究。在本报告所述期间，该项目的重点是发现两种不同病毒家族的病毒糖蛋白的胞质结构域能够调节融合活性。我们继续研究了细胞质结构域和结构域的作用， 特征，这对于它们调节融合活性的能力是重要的。我们确定了小鼠逆转录病毒Env蛋白质胞质尾部的特定氨基酸序列作为病毒诱导的膜融合的有效抑制剂的机制。为了进一步确定R肽在融合活性调节中的作用，我们研究了其对Env蛋白的寡聚状态的稳定化的影响。 我们还继续测试R肽增加触发Env从亚稳态到融合活性状态的转化所需的活化能的假设。为了研究R肽是否可以影响外部结构域中的构象变化，我们使用具有野生型或突变型MuLV Env胞质结构域的流感HA嵌合蛋白。我们还确定了是否观察到与细胞因子相互作用的差异与具有差异影响融合活性的胞质结构域的Env蛋白。我们也开始调查一个新的 副粘病毒（SER病毒）与SV 5病毒在核苷酸和氨基酸序列上有很近的同源性。 我们发现SER病毒的F蛋白没有细胞融合活性，这是由于F胞质结构域延长的结果。我们继续确定SER胞质结构域中调节融合活性的序列，以及F胞质结构域抑制融合活性的可能机制。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The long-term objective of this project has been to develop a detailed understanding of the process of cell entry of enveloped viruses, and mechanism of virus-induced cell fusion. We continued our studies with murine leukemia virus, a model oncogenic retrovirus, and parainfluenza virus, an important cause of respiratory disease. For the current reporting period the project focused on findings that the cytoplasmic domains of viral glycoproteins of two distinct virus families are able to regulate fusion activity. We continued our investigation of the role of cytoplasmic domains and structural features, which are important for their ability to modulate fusion activity. We determined the mechanism by which specific amino acid sequences in cytoplasmic tails of murine retrovirus Env proteins serve as potent inhibitors of virus-induced membrane fusion. To further define role of R peptide in regulation of fusion activity, we investigated its effects on stabilization of the oligomeric state of the Env protein. We have also continued to test the hypothesis that R peptide increases activation energy required for triggering conversion of Env from a metastable to a fusion-competent state. To investigate whether R peptide can affect a conformational change in external domain, we used influenza HA chimeric proteins having wild type or mutant MuLV Env cytoplasmic domains. We also determined if differences in interactions with cellular factors are observed with Env proteins having cytoplasmic domains that differentially affect fusion activity. We also have begun to investigate a newly characterized paramyxovirus, SER virus, which is closely related to SV5 in nucleotide and amino acid sequences. We have found that F protein of SER virus exhibits no cell fusion activity and that this is the result of an extended F cytoplasmic domain. We continued to define sequences in the SER cytoplasmic domain which modulate fusion activity, and possible mechanism involved in suppression of fusion activity by F cytoplasmic domain.