Recruitment of Alix/AIP1 to the plasma membrane by Sendai virus C protein facilitates budding of virus-like particles.

Sendai virus (SeV) is unique in that one of the viral accessory proteins, C, enhances budding of virus-like particles (VLPs) formed by SeV matrix protein M by physically interacting with Alix/AIP1. C protein itself does not have the ability to form VLPs, while M protein provides viral budding force, like other enveloped viruses. Here we show that SeV C protein recruits Alix/AIP1 to the plasma membrane (PM) to facilitate VLP budding. SeV M-VLP budding is sensitive to overexpression of a dominant-negative (DN) form of VPS4A only in the presence of the C proteins, which is able to recruit Alix/AIP1 to the PM. Our results indicate that SeV M and C proteins play separate roles in the budding process: M protein drives budding and C protein enhances the efficiency of the utilization of cellular MVB sorting machinery for efficient VLP budding.