Abstract
Viral protein 24 (VP24) from Ebola virus (EBOV) was first recognized as a minor matrix protein that associates with cellular membranes. However, more recent studies shed light on its roles in inhibiting viral genome transcription and replication, facilitating nucleocapsid assembly and transport, and interfering with immune responses in host cells through downregulation of interferon (IFN)-activated genes. Thus, whether VP24 is a peripheral protein with lipid-binding ability for matrix layer recruitment has not been explored. Here, we examined the lipid-binding ability of VP24 with a number of lipid-binding assays. The results indicated that VP24 lacked the ability to associate with lipids tested regardless of VP24 posttranslational modifications. We further demonstrate that the presence of the EBOV major matrix protein VP40 did not promote VP24 membrane association in vitro or in cells. Further, no protein–protein interactions between VP24 and VP40 were detected by co-immunoprecipitation. Confocal imaging and cellular membrane fractionation analyses in human cells suggested VP24 did not specifically localize at the plasma membrane inner leaflet. Overall, we provide evidence that EBOV VP24 is not a lipid-binding protein and its presence in the viral matrix layer is likely not dependent on direct lipid interactions.
Highlights
IntroductionEbola virus (EBOV) is a lipid-enveloped filovirus with a non-segmented negative single-strand
Ebola virus (EBOV) is a lipid-enveloped filovirus with a non-segmented negative single-strandRNA genome that belongs to the order Mononegavirales
The results showed that Viral protein 24 (VP24) was not present in the pellet under medium (0.15 M) and high (1 M) salt concentrations whereas the nucleocapsid marker NP was in the pellet only, which lead to the assumption that VP24 (7.5% of virion protein) may behave as a secondary membrane associated protein like the matrix protein VP40
Summary
Ebola virus (EBOV) is a lipid-enveloped filovirus with a non-segmented negative single-strand. The results showed that VP24 was not present in the pellet under medium (0.15 M) and high (1 M) salt concentrations whereas the nucleocapsid marker NP was in the pellet only, which lead to the assumption that VP24 (7.5% of virion protein) may behave as a secondary membrane associated protein like the matrix protein VP40 The typical matrix proteins in filovirus such as EBOV VP40 (eVP40) and Marburg virus (MARV) VP40 (mVP40) are membrane associated peripheral proteins that bind to membrane lipids directly with high affinity. The results we present here demonstrate that Ebola VP24 is not a direct lipid-binding protein and may not serve as a minor matrix protein with respect to lipid–protein interactions
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