Accelerated induction of apoptosis in insect cells by baculovirus‐expressed SARS‐CoV membrane protein

It has been shown that severe acute respiratory syndrome‐associated coronavirus (SARS‐CoV) 3a and 7a proteins, but not membrane (M) protein, induce apoptosis in mammalian cells. Upon expression of SARS‐CoV M protein using the baculovirus/insect cell expression system, however, we found that the expressed M protein triggered accelerated apoptosis in insect cells, as characterized by rapid cell death, elevated cytotoxicity, cell shrinkage, nuclear condensation and DNA fragmentation. Conversely, the M protein expressed in mammalian cells did not induce apoptosis. This is the first report describing the induction of apoptosis by SARS‐CoV M protein in animal cells and possible implications are discussed.