Abstract
Cellular susceptibility to viral infections is in part determined by the presence of a host cellular receptor. Here we use murine norovirus as a model to uncover an unappreciated connection between an intracellular lipid biosynthetic enzyme and a receptor conformation that is permissive for viral infection. The serine palmitoyltransferase complex is required for de novo sphingolipid biosynthesis and we find that its absence impairs the ability of murine norovirus to bind and enter cells. Although the serine palmitoyltransferase complex is dispensable for the surface expression of the norovirus receptor, CD300lf, serine palmitoyltransferase activity is required for CD300lf to adopt a conformation permissive for viral binding. Addition of extracellular ceramide to serine palmitoyltransferase-deficient cells chemically complements both the conformational changes of CD300lf and the cellular susceptibility to murine norovirus infection. Taken together, these data indicate that intracellular sphingolipid biosynthesis regulates the conformation of the murine norovirus receptor and therefore the tropism of murine norovirus. This indicates that intracellular biosynthetic pathways can regulate viral tropism even when the receptor for a virus is expressed on the target cell surface.