Untersuchungen zur Rolle des VP24 im Vermehrungszyklus des Marburgvirus

The highly pathogenic enveloped Marburgvirus (MARV) is composed of seven structural proteins and the nonsegmented negative-sensed viral RNA genome. Four proteins (NP, VP35, VP30, and L) make up the helical nucleocapsid complex which is surrounded by a matrix that is composed of VP40 and VP24. VP40 is functionally homologous to the matrix proteins of other nonsegmented negative strand RNA viruses. As of yet, the function of VP24 remains elusive. In the present study we found that VP24 colocalized with inclusions in MARV infected cells that contain preformed nucleocapsids and with nucleocapsids outside the inclusions. Coexpression studies revealed that VP24 is recruited into the inclusions by the presence of NP. VP24 displayed membrane-binding properties and was colocalized with VP40 at the plasma membrane of MARV infected cells and in cells that coexpressed the two proteins. Moreover, VP24 and VP40 were shown to functionally interact resulting in the recruitment of VP24 into filamentous virus-like particles (VLP) which are formed in the presence of VP40. The presence of VP24 neither altered the morphology of VLPs nor the efficiency of VLP release. When VP24 was silenced in MARV infected cells by siRNA technology, the release of viral particles was significantly reduced. This effect was not due to an influence of VP24 on viral transcription and replication. Our data support the idea that VP24 affects the formation of transport-competent nucleocapsids and/or the interaction between the nucleocapsids and the budding sites at the plasma membrane.