SLC35A2 gene product modulates paramyxovirus fusion events during infection

Area of Science:

• Virology
• Molecular Biology
• Cell Biology

Background:

• Paramyxoviruses, including mumps virus (MuV), Newcastle disease virus (NDV), and Sendai virus (SeV), are significant human and animal pathogens.
• Knowledge of host factors governing paramyxovirus infection remains limited.

Purpose of the Study:

• To identify novel host factors essential for paramyxovirus infection using a loss-of-function CRISPR screen.
• To elucidate the specific roles of identified host factors in paramyxovirus entry and cell-to-cell spread.

Main Methods:

• A recombinant Sendai virus (SeV) expressing destabilized enhanced green fluorescent protein (rSeVCdseGFP) was used in a loss-of-function CRISPR screen.
• Knockout (KO) cell lines for SLC35A1 (CMP-sialic acid transporter - CST) and SLC35A2 (UDP-galactose transporter - UGT) were generated and infected with SeV, NDV, and MuV.
• Virus-cell and cell-to-cell fusion events were analyzed in KO cells.

Main Results:

• SLC35A1 KO cells exhibited significantly reduced infection by SeV, NDV, and MuV, consistent with the absence of sialic acid receptors.
• SLC35A2 KO cells demonstrated critical roles for UGT in virus-cell and cell-to-cell fusion for various paramyxoviruses.
• UGT was essential for SeV entry but not for NDV or MuV entry, yet it promoted syncytia formation in MuV infections, indicating a role in cell-to-cell spread.
• Paramyxoviruses can infect cells lacking canonical sialic acid decorations, and UGT facilitates fusion processes for paramyxovirus entry and spread.

Conclusions:

• The UDP-galactose transporter (UGT) plays a critical, previously unrecognized role in paramyxovirus fusion.
• UGT's function in fusion is virus-specific, affecting entry and/or cell-to-cell spread.
• These findings expand our understanding of host-pathogen interactions in paramyxovirus infections, identifying UGT as a key facilitator of fusion events.