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Nat Commun ; 10(1): 3106, 2019 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-31308374


Immune responses need to be controlled tightly to prevent autoimmune diseases, yet underlying molecular mechanisms remain partially understood. Here, we identify biallelic mutations in three patients from two unrelated families in differentially expressed in FDCP6 homolog (DEF6) as the molecular cause of an inborn error of immunity with systemic autoimmunity. Patient T cells exhibit impaired regulation of CTLA-4 surface trafficking associated with reduced functional CTLA-4 availability, which is replicated in DEF6-knockout Jurkat cells. Mechanistically, we identify the small GTPase RAB11 as an interactor of the guanine nucleotide exchange factor DEF6, and find disrupted binding of mutant DEF6 to RAB11 as well as reduced RAB11+CTLA-4+ vesicles in DEF6-mutated cells. One of the patients has been treated with CTLA-4-Ig and achieved sustained remission. Collectively, we uncover DEF6 as player in immune homeostasis ensuring availability of the checkpoint protein CTLA-4 at T-cell surface, identifying a potential target for autoimmune and/or cancer therapy.

N Engl J Med ; 377(1): 52-61, 2017 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-28657829


BACKGROUND: Studies of monogenic gastrointestinal diseases have revealed molecular pathways critical to gut homeostasis and enabled the development of targeted therapies. METHODS: We studied 11 patients with abdominal pain and diarrhea caused by early-onset protein-losing enteropathy with primary intestinal lymphangiectasia, edema due to hypoproteinemia, malabsorption, and less frequently, bowel inflammation, recurrent infections, and angiopathic thromboembolic disease; the disorder followed an autosomal recessive pattern of inheritance. Whole-exome sequencing was performed to identify gene variants. We evaluated the function of CD55 in patients' cells, which we confirmed by means of exogenous induction of expression of CD55. RESULTS: We identified homozygous loss-of-function mutations in the gene encoding CD55 (decay-accelerating factor), which lead to loss of protein expression. Patients' T lymphocytes showed increased complement activation causing surface deposition of complement and the generation of soluble C5a. Costimulatory function and cytokine modulation by CD55 were defective. Genetic reconstitution of CD55 or treatment with a complement-inhibitory therapeutic antibody reversed abnormal complement activation. CONCLUSIONS: CD55 deficiency with hyperactivation of complement, angiopathic thrombosis, and protein-losing enteropathy (the CHAPLE syndrome) is caused by abnormal complement activation due to biallelic loss-of-function mutations in CD55. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

Antígenos CD55/genética , Ativação do Complemento/genética , Proteínas do Sistema Complemento/metabolismo , Mutação , Enteropatias Perdedoras de Proteínas/genética , Trombose/genética , Antígenos CD55/sangue , Criança , Pré-Escolar , Ativação do Complemento/efeitos dos fármacos , Inativadores do Complemento/farmacologia , Feminino , Homozigoto , Humanos , Imunoglobulina A/sangue , Lactente , Intestino Delgado/patologia , Masculino , Linhagem , Enteropatias Perdedoras de Proteínas/complicações , Estatísticas não Paramétricas , Síndrome , Linfócitos T/metabolismo