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

Depending on their membrane locations, lipid rafts are mainly involved in viral entry and release. This study investigated the relationship between lipid rafts and IBV infection. Vero cells were infected with IBV Beaudette strain, and membrane flotation was performed by sucrose density gradient centrifugation after depleting plasma membrane cholesterol with MβCD. As shown in Fig 1, a significant proportion of the IBV structural proteins E, N, and S co-fractionated with caveolin-1 in fractions 3-5 without drug treatment. However, MβCD treatment considerably reduced the amounts of IBV structural proteins, including E, N, and S, in fractions 3-5. By contrast, the IBV NSP5 and NSP12 did not co-fractionate with the lipid rafts (Fig 1) . The depletion of cholesterol via MβCD treatment did not affect the distribution of NSP5 and NSP12 in cellular fractions (Fig 1) . In addition, N, E, S, and caveolin-1 shifted to fractions 10 and 11 after MβCD treatment. These results demonstrated that the structural proteins, and not NSPs of IBV, are partially associated with cholesterol-enriched raft domains in Vero cells during IBV infection.