Role of the GTPase Rab1b in ebolavirus particle formation.

The Ebolavirus matrix protein VP40 is essential for virion assembly and egress. Recently, we reported that the coat protein complex II (COPII) transport system plays an important role in the transport of VP40 to the plasma membrane. Here, we show that dominant-negative mutants of the GTPase Rab1b interfere with VP40-mediated particle formation. Rab1b activates GBF1 (Golgi-specific BFA [brefeldin A] resistance factor 1), a critical factor in the assembly of COPI vesicles. Activated GBF1 stimulates ARF1 (ADP ribosylation factor 1), which recruits coat protein to cellular membranes for the assembly of COPI vesicles. Here, we demonstrate that GBF1 and ARF1 are involved in Ebolavirus virion formation, suggesting that both the COPII and COPI transport systems play a role in Ebolavirus VP40-mediated particle formation. These findings provide new insights into the cellular pathways employed for Ebolavirus virion formation.