RESUMO
The innate antiviral response is mediated, at least in part, by Toll-like receptors (TLRs). TLR3 signaling is activated in response to viral infection, and the absence of TLR3 in mice significantly increases mortality after infection with enteroviruses that cause myocarditis and/or dilated cardiomyopathy. We screened TLR3 in patients diagnosed with enteroviral myocarditis/cardiomyopathy and identified a rare variant in one patient as well as a significantly increased occurrence of a common polymorphism compared with controls. Expression of either variant resulted in significantly reduced TLR3-mediated signaling after stimulation with synthetic double-stranded RNA. Furthermore, Coxsackievirus B3 infection of cell lines expressing mutated TLR3 abrogated activation of the type I interferon pathway, leading to increased viral replication. TLR3-mediated type I interferon signaling required cellular autophagy and was suppressed by 3-methyladenine and bafilomycin A1, by inhibitors of lysosomal proteolysis, and by reduced expression of Beclin 1, Atg5, or microtubule-associated protein 1 light chain 3beta (MAP1LC3beta). However, TLR3-mediated signaling was restored upon exogenous expression of Beclin 1 or a variant MAP1LC3beta fusion protein refractory to RNA interference. These data suggest that individuals harboring these variants may have a blunted innate immune response to enteroviral infection, leading to reduced viral clearance and an increased risk of cardiac pathology.
Assuntos
Cardiomiopatia Dilatada/genética , Cardiomiopatia Dilatada/virologia , Enterovirus/fisiologia , Mutação , Miocardite/genética , Miocardite/virologia , Receptor 3 Toll-Like/genética , Adulto , Idoso , Sequência de Aminoácidos , Animais , Autofagia/efeitos dos fármacos , Autofagia/genética , Sequência de Bases , Cardiomiopatia Dilatada/metabolismo , Cardiomiopatia Dilatada/patologia , Linhagem Celular , Cloroquina/farmacologia , Infecções por Coxsackievirus/genética , Infecções por Coxsackievirus/metabolismo , Infecções por Coxsackievirus/patologia , Análise Mutacional de DNA , Endossomos/metabolismo , Feminino , Humanos , Interferons/metabolismo , Masculino , Pessoa de Meia-Idade , Dados de Sequência Molecular , Miocardite/metabolismo , Miocardite/patologia , Fenótipo , Transporte Proteico , Receptor 3 Toll-Like/química , Receptor 3 Toll-Like/metabolismo , Replicação ViralRESUMO
Isolated left ventricular noncompaction (LVNC) is a form of cardiomyopathy that most commonly presents in infancy with a hypertrophic and dilated left ventricle characterized by deep trabeculations and intertrabecular recesses. Our goal was to determine the frequency of mutations in G4.5, alpha-dystrobrevin, and FK Binding protein-12 in isolated LVNC patients. No mutations were identified in 47 of the 48 patients studied, while a splice site acceptor site mutation of intron 10 of G4.5 was identified in one patient, resulting in the deletion of exon 10 from the mRNA.
Assuntos
Proteínas Associadas à Distrofina/genética , Hipertrofia Ventricular Esquerda/genética , Mutação/genética , Proteínas/genética , Proteína 1A de Ligação a Tacrolimo/genética , Fatores de Transcrição/genética , Aciltransferases , Sequência de Bases , Humanos , Sítios de Splice de RNA/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismoRESUMO
Myocarditis and dilated cardiomyopathy (DCM) are common causes of morbidity and mortality in children and adults, most commonly due to infection with coxsackievirus B or adenovirus. Increased expression of the common human coxsackievirus B-adenovirus receptor (CAR) has been reported in patients with DCM. We investigated the CAR gene in patients with acquired or familial myocarditis/DCM for mutations/polymorphisms. Several polymorphisms or intronic substitutions, distant from the intron-exon boundaries, were identified but no mutations. Based upon these data it appears that CAR gene mutations are not a major host determinant in the development of myocarditis and DCM.