IFITM1 enhances nonenveloped viral RNA replication by facilitating cholesterol transport to the Golgi

Abstract

Aichi virus (AiV), a small non-enveloped RNA virus, hijacks the endoplasmic reticulum (ER)–Golgi cholesterol transport machinery to form cholesterol-rich replication sites originating from Golgi membranes. Interferon-induced transmembrane proteins (IFITMs) are antiviral restriction factors, whose involvement in intracellular cholesterol transport is suggested. Here, we describe the roles of IFITM1 in cholesterol transport that affect AiV RNA replication. IFITM1 stimulated AiV RNA replication and its knockdown significantly reduced the replication. In replicon RNA-transfected or infected cells, endogenous IFITM1 localized to the viral RNA replication sites. Further, IFITM1 interacted with viral proteins and host Golgi proteins, ACBD3, PI4KB, OSBP, which constitute the replication sites. When overexpressed, IFITM1 localized to the Golgi as well as endosomes, and this phenotype was also observed for endogenous IFITM1 early in AiV RNA replication, leading to the distribution of cholesterol at the Golgi-derived replication sites. The pharmacological inhibition of ER–Golgi cholesterol transport or endosomal cholesterol export impaired AiV RNA replication and cholesterol accumulation at the replication sites. Such defects were corrected by expression of IFITM1. Overexpressed IFITM1 facilitated late endosome–Golgi cholesterol transport without any viral proteins. In summary, we propose a model in which IFITM1 enhances cholesterol transport to the Golgi to accumulate cholesterol at Golgi-derived replication sites, providing a novel mechanism by which IFITM1 enables efficient genome replication of non-enveloped RNA virus.

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“…Viruses 2023, 15, 1993 2 of 16 IFITMs in their lipid composition, as evidence in support of both possibilities is present in the literature [6][7][8][9][10].…”

IFITM1 and IFITM3 Proteins Inhibit the Infectivity of Progeny HIV-1 without Disrupting Envelope Glycoprotein Clusters

“…However, intriguingly, IFITMs have little or no effect on the Murine Leukemia Virus and arenaviruses such as the Lassa virus and lymphocytic choriomeningitis virus [23][24][25]. Furthermore, several studies have reported that IFITMs can promote infection by the human papillomavirus 16 [25], Aichi picornavirus [26], and human coronavirus OC43 [27,28].…”