Vesicular release of ebola virus matrix protein VP40

We have analysed the expression and cellular localisation of the matrix protein VP40 from Ebola virus. Full-length VP40 and an N-terminal truncated construct missing the first 31 residues [VP40(31-326)] both locate to the plasma membrane of 293T cells when expressed transiently, while a C-terminal truncation of residues 213 to 326 [VP40(31-212)] shows only expression in the cytoplasm, when analysed by indirect immunofluorescence and plasma membrane preparations. In addition, we find that full-length VP40 [VP40(1-326)] and VP40(31-326) are both released into the cell culture supernatant and float up in sucrose gradients. The efficiency of their release, however, is dependent on the presence of the N-terminal 31 residues. VP40 that is released into the supernatant is resistant to trypsin digestion, a finding that is consistent with the formation of viruslike particles detected by electron microscopy. Together, these results provide strong evidence that Ebola virus VP40 is sufficient for virus assembly and budding from the plasma membrane.