The Important Role of Lipid Raft-Mediated Attachment in the Infection of Cultured Cells by Coronavirus Infectious Bronchitis Virus Beaudette Strain

Guo, Huichen; Huang, Mei; Yuan, Quan; Wei, Yanquan; Gao, Yuan; Mao, Lejiao; Gu, Lingjun; Tan, Yong Wah; Zhong, Yanxin; Liu, Dingxiang; Sun, Shiqi

Although IBV receptor(s) remain unidentified [40] , the association of IBV structural proteins with lipid rafts may increase the local concentration of viral structural proteins, particularly that of IBV S protein (Fig 1) , which may facilitate the engagement of IBV S protein with its receptors and enhance IBV infection. Lipid rafts, as attachment factors, may promote viral entry into cells. Although our study confirmed the role of lipid raft in IBV infection, the fate of endocytosed IBV remains unclear. Previous studies found that IBV internalization is mediated via macropinocytosis, in which lipid rafts transit through early endosomes to the recycling endosomes and then back to the cell surface to form new adhesions [41, 42] . Meanwhile, in micropinocytosis, pathogen-host interactions change the downstream signaling network to modify membrane traffic and cytoskeletal dynamics to meet each other's requirements. It is likely that pathogen-host interactions promote lipid raft clustering and focal adhesion formation during endocytosis. The internalized IBV will also be transferred from early endosomes to later endosomes. Although the present study primarily focused on lipid rafts and its role in the early stages of viral infection, the significance of the involvement of lipid rafts in IBV entry goes beyond this molecule. Moreover, further studies should investigate whether protein molecules in lipid rafts serve as a signaling platform to activate downstream kinases and cellular adhesive formation.