Tomaszewski-Flick Monica Jo, Rowe David T
Department of Infectious Diseases and Microbiology, Graduate School of Public Health, University of Pittsburgh, 130 DeSoto St, Pittsburgh, PA 15213, USA.
Virus Genes. 2007 Oct;35(2):225-34. doi: 10.1007/s11262-007-0118-8. Epub 2007 Jun 13.
The EBV Latent Membrane Protein 2 (LMP2) may have a role in the establishment and maintenance of in vivo latency. The gene is transcribed into two mRNAs that produce two LMP2 protein isoforms. The LMP2a protein isoform has 12 transmembrane segments (TMs) and an amino terminal cytoplasmic signaling domain (CSD) while the LMP2b isoform is identical but lacks the CSD. There has not been a consensus on the cellular membrane localization being sometimes ascribed to either a plasma membrane or an intracellular location [M. Rovedo, R. Longnecker, J. Virol. 81:89-94, 2007; D. Lynch, J. Zimmerman, D.T. Rowe, J. Gen. Virol. 83:1025-1035, 2002; C. Dawson, J. George, S. Blake, R. Longnecker, L.S. Young, Virology 289:192-207, 2001]. Fluorescent marker and epitope tagged LMP2b truncation mutants progressively removing TMs from the N and C termini were used to assess the localization and aggregation properties of LMP2b. wtLMP2b had an exclusively intracellular perinuclear localization, while all truncations of the protein resulted in localization to the cell surface. By epitope loop-tagging, all the truncated LMP2b proteins were verified to be in the predicted membrane orientation. In co-transfection experiments, the C-terminal region was implicated in the self-aggregation properties of LMP2b. Thus, an intact 12 TM domain was required for intracellular localization and protein-protein interaction while a C-terminal region was responsible for auto-aggregative properties.
EB病毒潜伏膜蛋白2（LMP2）可能在体内潜伏的建立和维持中发挥作用。该基因转录成两种mRNA，产生两种LMP2蛋白异构体。LMP2a蛋白异构体有12个跨膜区段（TMs）和一个氨基末端胞质信号结构域（CSD），而LMP2b异构体与之相同但缺少CSD。关于细胞膜定位一直没有达成共识，其有时被认为定位于质膜或细胞内位置[M. Rovedo, R. Longnecker, J. Virol. 81:89 - 94, 2007; D. Lynch, J. Zimmerman, D.T. Rowe, J. Gen. Virol. 83:1025 - 1035, 2002; C. Dawson, J. George, S. Blake, R. Longnecker, L.S. Young, Virology 289:192 - 207, 2001]。使用荧光标记和表位标签的LMP2b截短突变体，从N端和C端逐步去除TMs，以评估LMP2b的定位和聚集特性。野生型LMP2b仅定位于细胞核周围的细胞内，而该蛋白的所有截短形式都定位于细胞表面。通过表位环标签法，证实所有截短的LMP2b蛋白都处于预测的膜方向。在共转染实验中，C端区域与LMP2b的自聚集特性有关。因此，完整的12个TM结构域是细胞内定位和蛋白质 - 蛋白质相互作用所必需的，而C端区域负责自聚集特性。
