The alphavirus Sindbis virus (SINV) causes encephalomyelitis in mice.Lipid-containing membranes, particularly cholesterol and sphingomyelin (SM), play important roles in virus entry, RNA replication, glycoprotein transport, and budding. Levels of SM are regulated by sphingomyelinases (SMases). Acid SMase (ASMase) deficiency results in the lipid storage disease type A Niemann-Pick disease (NPD-A), mimicked in mice by interruption of the ASMase gene. We previously demonstrated that ASMase-deficient mice are more susceptible to fatal SINV encephalomyelitis, with increased viral replication, spread, and neuronal death. To determine the mechanisms by which ASMase deficiency enhances SINV replication, we compared NPD-A fibroblasts (NPAF) to normal human fibroblasts (NHF). NPAF accumulated cholesterol-and sphingolipid-rich late endosomes/lysosomes in the perinuclear region. SINV replication was faster and reached higher titer in NPAF than in NHF, and NPAF died more quickly. SINV RNA and protein synthesis was greater in NHF than in NPAF, but virions budding from NPAF were 26 times more infectious and were regular dense particles whereas virions from NHF were larger particles containing substantial amounts of CD63. Cellular regulation of alphavirus morphogenesis is a previously unrecognized mechanism for control of virus replication and spread.acidic sphingomyelinase deficiency ͉ CD63 ͉ Sindbis virus replication ͉ cholesterol ͉ sphingomyelin
Sindbis virus (SV), an enveloped virus with a single-stranded, plus-sense RNA genome, is the prototype alphavirus in the Togaviridae family. In mice, SV infects neurons and can cause apoptosis of immature neurons. Sphingomyelin (SM) is the most prevalent cellular sphingolipid, is particularly abundant in the nervous systems of mammals, and is required for alphavirus fusion and entry. The level of SM is tightly regulated by sphingomyelinases. A defect in acid sphingomyelinase (ASMase) results in SM storage and subsequent intracellular accumulation of SM. To better understand the role of the SM pathway in SV pathogenesis, we have characterized SV infection of transgenic mice deficient in the ASMase gene. ASMase knockout (ASM-KO) mice were more susceptible to SV infection than wild-type (WT) or heterozygous (Het) animals. Titers of SV were higher in the brains of ASM-KO mice than in the brains of WT mice. More SV RNA was detected by in situ hybridization, more SV protein was detected by immunohistochemistry, and more terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling-positive cells were present in the cortex and hippocampus of ASM-KO mice than in those of WT or Het mice. Interleukin-6 (IL-6), but not IL-1 or tumor necrosis factor alpha, was elevated in infected ASM-KO mice compared to levels in WT or Het mice, but studies with IL-6-KO mice and recombinant SV expressing IL-6 showed no role for IL-6 in fatal disease. Together these data indicate that the increase in susceptibility of ASM-KO mice to SV infection was the result of more-rapid replication and spread of SV in the nervous system and increased neuronal death.Sindbis virus (SV), an enveloped virus with a singlestranded, plus-sense RNA genome, is the prototype alphavirus in the Togaviridae family (60). In nature, SV cycles between mosquito and avian vertebrate hosts, producing a lifelong infection in mosquitoes and transient infection in vertebrates. In humans, SV infection can cause fever, rash, and arthritis. In mice, SV causes encephalomyelitis, and neurons in the brain and spinal cord are the primary target cells. The severity of infection in mammals depends on both virus and host factors (20, 32) and makes SV an excellent model to study the pathogenesis of virus-induced encephalomyelitis.Cellular lipids play an important role in several aspects of alphavirus replication, but the roles of specific lipids and their interactions with cellular proteins are not clear (22,53,56). The plasma membranes of eukaryotic cells consist primarily of sphingolipids, glycerophospholipids, and cholesterol (16). Sphingomyelin (SM), comprised of a highly hydrophobic ceramide moiety and a hydrophilic phosphorylcholine head group, is the most prevalent cellular sphingolipid, is particularly abundant in the nervous system, and is often associated with cholesterol (16, 50). Hydrogen bonds and hydrophobic interactions mediate tight interactions between the cholesterol sterol ring system and the ceramide moiety of SM (16,50,54). The lateral association of...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.