Rhinoviruses Infect Human Epithelial Cells via Ceramide-enriched Membrane Platforms

Abstract

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 classic fluid mosaic model of the cell membrane suggests a random distribution of lipids and proteins in the cell membrane (1). This view was challenged by many recent studies indicating that sphingolipids and cholesterol spontaneously separate from other glycophospholipids in the cell membrane to form distinct microdomains (2, 3). (Glyco)sphingolipids bind to each other via hydrophilic and hydrophobic interactions between their headgroups and the saturated fatty acid side chains, respectively. Void spaces between the bulky glycosphingolipids seem to be filled with cholesterol via tight interactions of the sterol-ring system with the sphingosine moiety of the sphingolipids and hydrogen bonds between the C3-hydroxyl groups with the hydrophilic headgroups of sphingomyelin. These interactions result in a lateral stabilization and facilitate the formation of distinct membrane domains that were named "rafts" (3), because they float in the "ocean" of the other phospholipids. We have identified a novel membrane domain, i.e. ceramide-enriched membrane platforms (4, 5). Ceramideenriched membrane platforms are initiated by activation of the acid sphingomyelinase, which has been shown to be stimulated by several receptors, including CD95 (4 -9), tumor necrosis factor receptor (10), CD40 (11), or Fc␥RII (12), pathogenic bacteria, including Neisseria gonorrhoeae, Pseudomonas aeruginosa, and Staphylococcus aureus (13-16), Sindbis virus (17), and many stress stimuli, e.g. radiation, UV light, or cytostatic drugs (18 -22). These stimuli do not only activate the enzyme but also induce the translocation of the acid sphingomyelinase from an intracellular compartment onto the extracellular leaflet of the cell membrane (4, 23). The hydrolysis of sphingomyelin that is predominantly located in the outer leaflet of the cell membrane by the acid sphingomyelinase results in the generation of ceramide. The biophysical properties of ceramide predict that ceramide molecules self-associate to small ceramide-enriched domains (4), which spontaneously fuse to one or a few large ceramide-enriched membrane platforms (24). Ce...

The Role of Sphingolipids and Ceramide in Pulmonary Inflammation in Cystic Fibrosis

“…Ceramide molecules self-associate to small ceramide-enriched membrane microdomains, which have the tendency to spontaneously fuse to large ceramide-enriched membrane domains [36-38]. The formation of ceramide-enriched membrane domains was shown to occur in cells after stimulation via a variety of stimuli including CD95 [39-41], CD40 [42], DR5 [43], FcγRII [44], the PAF-receptor [45], but also after infection with P. aeruginosa [19], Neisseriae gonorrhoeae [46] , Rhinovirus [47], application of stress stimuli such as UV-light [48], cisplatin [49] or Cu 2+ -treatment [50]. The great variety of stimuli that trigger the formation of ceramide-enriched membrane platforms suggests that these membrane domains facilitate signal transduction, but are very likely not part of the specific signal transduction pathway elicited by the these stimuli.…”

Recent advances in the immunobiology of ceramide

“…Ceramide-rich membrane rafts have been shown to mediate CD40 clustering, which appears a critical event in CD40-initiated cell signaling (Grassme et al, 2002). Pseudomonas aeruginosa, Rhinovirus, UV light, Cisplatin, CD20 and limitation of neutrophil life span by reactive oxygen species-mediated activation of death receptor signaling have been implicated in the induction of ceramide-enriched membrane platforms Charruyer et al, 2005;Lacour et al, 2004;Grassme et al, 2005;Scheel-Toellner et al, 2004;Abdel Shakor et al, 2004).…”

Ceramide and sphingosine in pulmonary infections

“…Ceramide in particular has been shown to be involved in the infection of mammalian cells with a variety of bacterial and viral pathogens, including Neisseria gonorrhoeae, Neisseria meningitidis, Staphylococcus aureus, Pseudomonas aeruginosa, Listeria monocytogenes, Salmonella typhimurium, Escherichia coli, mycobacteria, measles virus, rhinovirus, and sindbis virus (Grassmé et al, 1997(Grassmé et al, , 2003a(Grassmé et al, , 2005Hauck et al, 2000;Jan et al, 2000;Esen et al, 2001;Pfeiffer et al, 2001;Utermöhlen et al, 2003;Falcone et al, 2004;McCollister et al, 2007;Utermöhlen et al, 2008;Gassert et al, 2009;Avota et al, 2011;Simonis et al, 2014). The important role of ceramide in the structure of such a variety of infections is explained by its biophysics: sphingolipids, cholesterol, and glycerolipids are the main components of mammalian cell membranes.…”