Redistribution of Endosomal Membranes to the African Swine Fever Virus Replication Site.

Miguel Cuesta-Geijo,Raquel Muñoz-Moreno,Lucía Barrado-Gil,Inmaculada Galindo,Covadonga Alonso

doi:10.3390/v9060133

Abstract

African swine fever virus (ASFV) infection causes endosomal reorganization. Here, we show that the virus causes endosomal congregation close to the nucleus as the infection progresses, which is necessary to build a compact viral replication organelle. ASFV enters the cell by the endosomal pathway and reaches multivesicular late endosomes. Upon uncoating and fusion, the virus should exit to the cytosol to start replication. ASFV remodels endosomal traffic and redistributes endosomal membranes to the viral replication site. Virus replication also depends on endosomal membrane phosphoinositides (PtdIns) synthesized by PIKfyve. Endosomes could act as platforms providing membranes and PtdIns, necessary for ASFV replication. Our study has revealed that ASFV reorganizes endosome dynamics, in order to ensure a productive infection.

Highlights

Endocytosis is a common entry pathway for nutrients, receptors and pathogens to get into cells that converges on early endosomes (EE)
We used the early endosome marker EEA1, the multivesicular bodies (MVB) marker CD63, the late endosomes (LE) marker Rab7 and lysosomal marker Lamp1 (Figure 1A), and Vero cells were infected with recombinant African swine fever virus (ASFV) engineered to express green fluorescent protein (GFP) or cherry fluorescent protein (ChFP) as fusion proteins of p54, as previously described [27], or non-infected
Between 8 and 16 hpi, the virus establishes its site of replication or viral factory (VF), which is recognized by confocal fluorescent microscopy as recombinant fluorescent virus accumulated in the perinuclear region

Summary

Introduction

Endocytosis is a common entry pathway for nutrients, receptors and pathogens to get into cells that converges on early endosomes (EE). From EE, cargo can be sorted back to the plasma membrane (PM) through the recycling pathway. Lysosomes are the end-point of the degradative pathway. Starting on the cytosolic face of the EE, invaginations of the limiting membrane into the lumen of the endosome give rise to the intraluminal vesicles (ILV). EE matures into multivesicular bodies (MVB), and as the pH decreases more ILV are generated [2]. The systematic maturation of this pathway depends on endosomal membrane signaling that is tightly regulated by both proteins and lipids [3]. Sequential transport from EE to LE involves the switch of GTPase Rab to Rab. Sequential transport from EE to LE involves the switch of GTPase Rab to Rab7 Rab proteins and their effectors are recruited by phosphoinositides by specific lipid-binding domains. Short-lived phosphatidylinositol-3-phosphate (PtdIns3P) synthesized by PI3K controls EE functions and is a substrate for the generation of PtdIns(3,5)P2 at the LE membrane by the Viruses 2017, 9, 133; doi:10.3390/v9060133 www.mdpi.com/journal/viruses

Methods

Results

Conclusion