Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2011
Publication Date: 9/1/2011
Citation: Deng, Q., Weng, Y., Lu, W., Demers, A., Song, M., Wang, D., Yu, Q., and Li, F. 2011. Topology and cellular localization of the small hydrophobic protein of avian metapneumovirus. Virus Research. 160:102-107. Interpretive Summary: A number of human and animal infectious diseases are caused by infection of paramyxoviruses, such as measles, mumps, human respiratory syncytial virus, Newcastle disease virus, and human and avian metapneumoviruses. The small hydrophobic protein (SH) is a structural component of certain paramyxoviruses including metapneumovirus. Sequence analyses have shown that SH proteins among the different viruses vary significantly in size as well as the primary sequence. However, little is known about the biological properties or function of the SH protein. In the present study, we characterized metapneumovirus SH protein with respect to topology, subcellular localization, transport, and oligomerization using avian metapneumovirus subgroup C (aMPV-C) as a model system. We showed that aMPV-C SH is an integral membrane protein with NinCout orientation located in both the plasma membrane as well as within intracellular compartments, which is similar to what has been described previously for SH proteins of other paramyxoviruses. Furthermore, we demonstrated that aMPV-C SH protein localizes in the endoplasmic reticulum (ER) and Golgi region, and is efficiently released to the extracellular environment through the conventional ER-Golgi secretory pathway. Finally, we provide direct evidence that SH protein of aMPV-C can form a homo-oligomeric complex inside the cell as well as a hetero-oligomeric complex with viral fusion (F) protein, not matrix protein (M). These findings provide valuable information for anti-viral drug design and vaccine development against metapneumovirus diseases.
Technical Abstract: The small hydrophobic protein (SH) is a type II integral membrane protein that is packaged into virions and is only present in certain paramyxoviruses including metapneumovirus. In addition to a highly divergent primary sequence, SH proteins vary significantly in size among the different viruses. Human respiratory syncytial virus (HRSV) encodes the smallest SH protein consisting of only 64 amino acids, while metapneumoviruses have the longest SH protein ranging from 174 to 179 amino acids in length. Little is currently known about the cellular localization and topology of the metapneumovirus SH protein. Here we characterize for the first time metapneumovirus SH protein with respect to topology, subcellular localization, and transport using avian metapneumovirus subgroup C (AMPV-C) as a model system. We show that AMPV-C SH is an integral membrane protein with NinCout orientation located in both the plasma membrane as well as within intracellular compartments, which is similar to what has been described previously for SH proteins of other paramyxoviruses. Furthermore, we demonstrate that AMPV-C SH protein localizes in the endoplasmic reticulum (ER), Golgi, and cell surface, and is transported through ER-Golgi secretory pathway.