| Structural highlights
Function
[POLG_POL1M] Capsid proteins VP1, VP2, VP3 and VP4 form a closed capsid enclosing the viral positive strand RNA genome. VP4 lies on the inner surface of the protein shell formed by VP1, VP2 and VP3. All the three latter proteins contain a beta-sheet structure called beta-barrel jelly roll. Together they form an icosahedral capsid (T=3) composed of 60 copies of each VP1, VP2, and VP3, with a diameter of approximately 300 Angstroms. VP1 is situated at the 12 fivefold axes, whereas VP2 and VP3 are located at the quasi-sixfold axes. The interaction of five VP1 proteins in the fivefold axes results in a prominent protusion extending to about 25 Angstroms from the capsid shell. The resulting structure appears as a steep plateau encircled by a valley or cleft. This depression also termed canyon is the receptor binding site. The capsid interacts with human PVR at this site to provide virion attachment to target cell. This attachment induces virion internalization predominantly through clathrin- and caveolin-independent endocytosis in Hela cells and through caveolin-mediated endocytosis in brain microvascular endothelial cells. VP4 and VP1 subsequently undergo conformational changes leading to the formation of a pore in the endosomal membrane, thereby delivering the viral genome into the cytoplasm.[1] [2] [3] VP0 precursor is a component of immature procapsids (By similarity).[4] [5] [6] Protein 2A is a cysteine protease that is responsible for the cleavage between the P1 and P2 regions. It cleaves the host translation initiation factor EIF4G1, in order to shut down the capped cellular mRNA transcription.[7] [8] [9] Protein 2B affects membrane integrity and cause an increase in membrane permeability (By similarity).[10] [11] [12] Protein 2C associates with and induces structural rearrangements of intracellular membranes. It displays RNA-binding, nucleotide binding and NTPase activities.[13] [14] [15] Protein 3A, via its hydrophobic domain, serves as membrane anchor. It also inhibits endoplasmic reticulum-to-Golgi transport (By similarity).[16] [17] [18] Protein 3C is a cysteine protease that generates mature viral proteins from the precursor polyprotein. In addition to its proteolytic activity, it binds to viral RNA, and thus influences viral genome replication. RNA and substrate bind co-operatively to the protease (By similarity).[19] [20] [21] RNA-directed RNA polymerase 3D-POL replicates genomic and antigenomic RNA by recognizing replications specific signals (By similarity).[22] [23] [24]
Publication Abstract from PubMed
Previously, we reported on the in vitro antiviral activity of single domain antibody fragments (VHHs) directed against poliovirus type 1. Five VHHs were found to neutralize poliovirus type 1 in an in vitro setting, and showed EC50 values in the nanomolar range. In the present study, we further investigated the mechanism of action of these VHHs. All five VHHs interfere at multiple levels of the viral replication cycle, as they interfere both with attachment of the virus to cells and with viral uncoating. The latter effect is consistent with their ability to stabilize the poliovirus capsid, as observed in a thermofluor thermal shift assay, where the virus is gradually heated and the temperature causing 50% of the RNA to be released from the capsid was defined, either in the presence or absence of the VHHs. The VHH-capsid interactions were also seen to induce aggregation of the virus-VHH complexes. However, this observation cannot yet be linked to their mechanism of action. Cryo-electron microscopy (EM) reconstructions of two VHHs in complex with poliovirus type 1 show no conformational changes of the capsid to explain this aggregation. On the other hand, these reconstructions do show that the binding sites of VHHs PVSP6A and PVSP29F overlap with the binding site for the poliovirus receptor (CD155/PVR) and span interfaces that are altered during receptor-induced conformational changes associated with cell entry. This may explain the interference at the level of cell attachment of the virus as well as their effect on uncoating.Importance paragraph: The study describes the mechanism of neutralization and the capsid stabilizing activity of five single domain antibody fragments (VHHs) that have an in vitro neutralizing activity against poliovirus type 1. The results show that the VHHs interfere at multiple levels of the viral replication cycle (cell-attachment and viral uncoating). These mechanisms are possibly shared by some conventional antibodies and may therefore provide some insight in the natural immune responses. Since the binding sites of two VHHs studied by cryo-EM are very similar to that of the receptor, the VHHs can be used as probes to study the authentic virus-cell interaction. The structures and conclusions in this study are original, and raise interesting findings regarding virus-receptor interactions and the order of key events early in infection.
Mechanism of action and capsid stabilizing properties of VHHs with an in vitro anti-polioviral activity.,Schotte L, Strauss M, Thys B, Halewyck H, Filman DJ, Bostina M, Hogle JM, Rombaut B J Virol. 2014 Feb 5. PMID:24501405[25]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Ventoso I, MacMillan SE, Hershey JW, Carrasco L. Poliovirus 2A proteinase cleaves directly the eIF-4G subunit of eIF-4F complex. FEBS Lett. 1998 Sep 11;435(1):79-83. PMID:9755863
- ↑ Bubeck D, Filman DJ, Cheng N, Steven AC, Hogle JM, Belnap DM. The structure of the poliovirus 135S cell entry intermediate at 10-angstrom resolution reveals the location of an externalized polypeptide that binds to membranes. J Virol. 2005 Jun;79(12):7745-55. PMID:15919927 doi:79/12/7745
- ↑ Bergelson JM. New (fluorescent) light on poliovirus entry. Trends Microbiol. 2008 Feb;16(2):44-7. doi: 10.1016/j.tim.2007.12.004. Epub 2008 , Jan 10. PMID:18191571 doi:10.1016/j.tim.2007.12.004
- ↑ Ventoso I, MacMillan SE, Hershey JW, Carrasco L. Poliovirus 2A proteinase cleaves directly the eIF-4G subunit of eIF-4F complex. FEBS Lett. 1998 Sep 11;435(1):79-83. PMID:9755863
- ↑ Bubeck D, Filman DJ, Cheng N, Steven AC, Hogle JM, Belnap DM. The structure of the poliovirus 135S cell entry intermediate at 10-angstrom resolution reveals the location of an externalized polypeptide that binds to membranes. J Virol. 2005 Jun;79(12):7745-55. PMID:15919927 doi:79/12/7745
- ↑ Bergelson JM. New (fluorescent) light on poliovirus entry. Trends Microbiol. 2008 Feb;16(2):44-7. doi: 10.1016/j.tim.2007.12.004. Epub 2008 , Jan 10. PMID:18191571 doi:10.1016/j.tim.2007.12.004
- ↑ Ventoso I, MacMillan SE, Hershey JW, Carrasco L. Poliovirus 2A proteinase cleaves directly the eIF-4G subunit of eIF-4F complex. FEBS Lett. 1998 Sep 11;435(1):79-83. PMID:9755863
- ↑ Bubeck D, Filman DJ, Cheng N, Steven AC, Hogle JM, Belnap DM. The structure of the poliovirus 135S cell entry intermediate at 10-angstrom resolution reveals the location of an externalized polypeptide that binds to membranes. J Virol. 2005 Jun;79(12):7745-55. PMID:15919927 doi:79/12/7745
- ↑ Bergelson JM. New (fluorescent) light on poliovirus entry. Trends Microbiol. 2008 Feb;16(2):44-7. doi: 10.1016/j.tim.2007.12.004. Epub 2008 , Jan 10. PMID:18191571 doi:10.1016/j.tim.2007.12.004
- ↑ Ventoso I, MacMillan SE, Hershey JW, Carrasco L. Poliovirus 2A proteinase cleaves directly the eIF-4G subunit of eIF-4F complex. FEBS Lett. 1998 Sep 11;435(1):79-83. PMID:9755863
- ↑ Bubeck D, Filman DJ, Cheng N, Steven AC, Hogle JM, Belnap DM. The structure of the poliovirus 135S cell entry intermediate at 10-angstrom resolution reveals the location of an externalized polypeptide that binds to membranes. J Virol. 2005 Jun;79(12):7745-55. PMID:15919927 doi:79/12/7745
- ↑ Bergelson JM. New (fluorescent) light on poliovirus entry. Trends Microbiol. 2008 Feb;16(2):44-7. doi: 10.1016/j.tim.2007.12.004. Epub 2008 , Jan 10. PMID:18191571 doi:10.1016/j.tim.2007.12.004
- ↑ Ventoso I, MacMillan SE, Hershey JW, Carrasco L. Poliovirus 2A proteinase cleaves directly the eIF-4G subunit of eIF-4F complex. FEBS Lett. 1998 Sep 11;435(1):79-83. PMID:9755863
- ↑ Bubeck D, Filman DJ, Cheng N, Steven AC, Hogle JM, Belnap DM. The structure of the poliovirus 135S cell entry intermediate at 10-angstrom resolution reveals the location of an externalized polypeptide that binds to membranes. J Virol. 2005 Jun;79(12):7745-55. PMID:15919927 doi:79/12/7745
- ↑ Bergelson JM. New (fluorescent) light on poliovirus entry. Trends Microbiol. 2008 Feb;16(2):44-7. doi: 10.1016/j.tim.2007.12.004. Epub 2008 , Jan 10. PMID:18191571 doi:10.1016/j.tim.2007.12.004
- ↑ Ventoso I, MacMillan SE, Hershey JW, Carrasco L. Poliovirus 2A proteinase cleaves directly the eIF-4G subunit of eIF-4F complex. FEBS Lett. 1998 Sep 11;435(1):79-83. PMID:9755863
- ↑ Bubeck D, Filman DJ, Cheng N, Steven AC, Hogle JM, Belnap DM. The structure of the poliovirus 135S cell entry intermediate at 10-angstrom resolution reveals the location of an externalized polypeptide that binds to membranes. J Virol. 2005 Jun;79(12):7745-55. PMID:15919927 doi:79/12/7745
- ↑ Bergelson JM. New (fluorescent) light on poliovirus entry. Trends Microbiol. 2008 Feb;16(2):44-7. doi: 10.1016/j.tim.2007.12.004. Epub 2008 , Jan 10. PMID:18191571 doi:10.1016/j.tim.2007.12.004
- ↑ Ventoso I, MacMillan SE, Hershey JW, Carrasco L. Poliovirus 2A proteinase cleaves directly the eIF-4G subunit of eIF-4F complex. FEBS Lett. 1998 Sep 11;435(1):79-83. PMID:9755863
- ↑ Bubeck D, Filman DJ, Cheng N, Steven AC, Hogle JM, Belnap DM. The structure of the poliovirus 135S cell entry intermediate at 10-angstrom resolution reveals the location of an externalized polypeptide that binds to membranes. J Virol. 2005 Jun;79(12):7745-55. PMID:15919927 doi:79/12/7745
- ↑ Bergelson JM. New (fluorescent) light on poliovirus entry. Trends Microbiol. 2008 Feb;16(2):44-7. doi: 10.1016/j.tim.2007.12.004. Epub 2008 , Jan 10. PMID:18191571 doi:10.1016/j.tim.2007.12.004
- ↑ Ventoso I, MacMillan SE, Hershey JW, Carrasco L. Poliovirus 2A proteinase cleaves directly the eIF-4G subunit of eIF-4F complex. FEBS Lett. 1998 Sep 11;435(1):79-83. PMID:9755863
- ↑ Bubeck D, Filman DJ, Cheng N, Steven AC, Hogle JM, Belnap DM. The structure of the poliovirus 135S cell entry intermediate at 10-angstrom resolution reveals the location of an externalized polypeptide that binds to membranes. J Virol. 2005 Jun;79(12):7745-55. PMID:15919927 doi:79/12/7745
- ↑ Bergelson JM. New (fluorescent) light on poliovirus entry. Trends Microbiol. 2008 Feb;16(2):44-7. doi: 10.1016/j.tim.2007.12.004. Epub 2008 , Jan 10. PMID:18191571 doi:10.1016/j.tim.2007.12.004
- ↑ Schotte L, Strauss M, Thys B, Halewyck H, Filman DJ, Bostina M, Hogle JM, Rombaut B. Mechanism of action and capsid stabilizing properties of VHHs with an in vitro anti-polioviral activity. J Virol. 2014 Feb 5. PMID:24501405 doi:http://dx.doi.org/10.1128/JVI.03402-13
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