USP30 and infection: As previous interferon stimulation experiments had shown that USP30 did not respond to interferon (Fig 2A–2C) but considering that other secreted molecules during infection might play a role, we extracted conditioned medium, which is a virus-free cell culture medium containing a pool of diverse antiviral and inflammatory molecules secreted by infected cells, to treat A549 cells for determining how USP30 would react to.