Bracovirus-Mediated Innexin-Hemichannel Closure in Cell Disassembly

​Cell-cell communication is required for the cellular immune response. Immunosuppression occurs when polydnavirus virions are injected by parasitic wasps into caterpillar hosts. However, the effects of hemichannel closure on cellular immune response are not fully understood. Here, we examined apoptotic body formation triggered by hemichannel closure in haemocytes of the host, Spodoptera litura, infected with bracovirus from the parasitic wasp, Microplitis bicoloratus. We show that Microplitis bicoloratus bracovirus (MbBV) induced apoptotic cell disassembly and apoptotic body formation, accompanied by hemichannel closure. Haemocyte apoptotic body formation was caused by dysregulation of innexins (Inxs) 1‒4 during MbBV-mediated inhibition of pI3K/AKT signalling and activation of protein tyrosine phosphatase 109. Mechanistically, MbBV activated caspase 3, which cleaved gap junction Inx proteins. Our results show that hemichannel opening and closure by various stimuli causing modulation of the levels of the gap junction proteins, Inxs, could inhibit or activate apoptotic body formation, respectively.