Rhinoviruses infect human epithelial cells via ceramide-enriched membrane platforms

The cell membrane contains very small distinct membrane domains enriched of sphingomyelin and cholesterol that are named rafts. We have shown that the formation of ceramide via activation of the acid sphingomyelinase transforms rafts into ceramide-enriched membrane platforms. These platforms are required for infection of mammalian cells with Pseudomonas aeruginosa, Staphylococcus aureus, or Neisseriae gonorrhoeae. In the present study we determined whether the acid sphingomyelinase, ceramide, and ceramide-enriched membrane platforms are also involved in the infection of human cells with pathogenic rhinoviruses. We demonstrate that infection of human epithelial cells with several rhinovirus strains triggers a rapid activation of the acid sphingomyelinase correlating with microtubules- and microfilament-mediated translocation of the enzyme from an intracellular compartment onto the extracellular leaflet of the cell membrane. The activity of the acid sphingomyelinase results in the formation of ceramide in the cell membrane and, finally, large ceramide-enriched membrane platforms. Rhinoviruses colocalize with ceramide-enriched membrane platforms during the infection. The significance of ceramide-enriched membrane platforms for rhinoviral uptake is demonstrated by the finding that genetic deficiency or pharmacological inhibition of the acid sphingomyelinase prevented infection of human epithelial cells by rhinoviruses. The data identify the acid sphingomyelinase and ceramide as key molecules for the infection of human cells with rhinoviruses.