ABSTRACT
Vici syndrome is a human inherited multi-system disorder caused by recessive mutations in EPG5, encoding the EPG5 protein that mediates the fusion of autophagosomes with lysosomes. Immunodeficiency characterized by lack of memory B cells and increased susceptibility to infection is an integral part of the condition, but the role of EPG5 in the immune system remains unknown. Here we show that EPG5 is indispensable for the transport of the TLR9 ligand CpG to the late endosomal-lysosomal compartment, and for TLR9-initiated signaling, a step essential for the survival of human memory B cells and their ultimate differentiation into plasma cells. Moreover, the predicted structure of EPG5 includes a membrane remodeling domain and a karyopherin-like domain, thus explaining its function as a carrier between separate vesicular compartments. Our findings indicate that EPG5, by controlling nucleic acids intracellular trafficking, links macroautophagy/autophagy to innate and adaptive immunity.
Subject(s)
Adaptive Immunity , Autophagy/immunology , DNA/metabolism , Endosomes/metabolism , Immunity, Innate , Lysosomes/metabolism , Proteins/metabolism , RNA/metabolism , Agenesis of Corpus Callosum/genetics , Agenesis of Corpus Callosum/immunology , Autophagy-Related Proteins , B-Lymphocytes/immunology , Biological Transport , Cataract/genetics , Cataract/immunology , Cell Line , Humans , Lysosomal Membrane Proteins , Mutation , Proteins/genetics , Toll-Like Receptor 9/metabolism , Vesicular Transport ProteinsABSTRACT
Vici syndrome is a rare congenital multisystem disorder characterized by agenesis of the corpus callosum, hypotonia, developmental delay, hypopigmentation, cataract, cardiomyopathy, and immunological abnormalities. Recurrent infections, mainly affecting the respiratory tract, have been reported in the majority of cases, representing an important risk factor for morbidity and mortality. The immunological phenotype of patients is extremely variable, ranging from a combined immunodeficiency to nearly normal immunity. We report on a new patient with Vici syndrome, in whom we have extensively investigated immunological features. Despite a mild impairment of the cellular compartment, a defect of humoral immunity was found, requiring treatment with intravenous immunoglobulin. A wider knowledge of immune system abnormalities of Vici syndrome will help to plan strategies for treatment and prevention of infections, such as immunoglobulin replacement and antimicrobial prophylaxis, resulting in improved survival rates.
