Single-stranded nucleic acids promote SAMHD1 complex formation

SAM domain and HD domain-containing protein 1 (SAMHD1) is a dGTP-dependent triphosphohydrolase that degrades deoxyribonucleoside triphosphates (dNTPs) thereby limiting the intracellular dNTP pool. Mutations in SAMHD1 cause Aicardi–Goutières syndrome (AGS), an inflammatory encephalopathy that mimics congenital viral infection and that phenotypically overlaps with the autoimmune disease systemic lupus erythematosus. Both disorders are characterized by activation of the antiviral cytokine interferon-α initiated by immune recognition of self nucleic acids. Here we provide first direct evidence that SAMHD1 associates with endogenous nucleic acids in situ. Using fluorescence cross-correlation spectroscopy, we demonstrate that SAMHD1 specifically interacts with ssRNA and ssDNA and establish that nucleic acid-binding and formation of SAMHD1 complexes are mutually dependent. Interaction with nucleic acids and complex formation do not require the SAM domain, but are dependent on the HD domain and the C-terminal region of SAMHD1. We finally demonstrate that mutations associated with AGS exhibit both impaired nucleic acid-binding and complex formation implicating that interaction with nucleic acids is an integral aspect of SAMHD1 function.Fil: Tuengler, Victoria. Technische Universität Dresden; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wolfgang, Staroske. Technische Universität Dresden; AlemaniaFil: Kind, Barbara. Technische Universität Dresden; AlemaniaFil: Dobrick, Manuela. Technische Universität Dresden; AlemaniaFil: Kretschmer, Stefanie. Technische Universität Dresden; AlemaniaFil: Schmidt, Franziska. Technische Universität Dresden; AlemaniaFil: Krug, Claudia. Technische Universität Dresden; AlemaniaFil: Lorenz, Mike. Max Planck Institute of Molecular Cell Biology and Genetics; AlemaniaFil: Chara, Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentina. Technische Universität Dresden; AlemaniaFil: Schwille, Petra. Max Planck Institute Of Biochemistry; AlemaniaFil: Lee-Kirsch, Min Ae. Technische Universität Dresden; Alemani

Naturally Occurring Genetic Variants of Human Caspase-1 Differ Considerably in Structure and the Ability to Activate Interleukin-1β

Caspase-1 (Interleukin-1 Converting Enzyme, ICE) is a proinflammatory enzyme that plays pivotal roles in innate immunity and many inflammatory conditions such as periodic fever syndromes and gout. In- flammation is often mediated by enzymatic activation of interleukin (IL)-1β and IL-18. We detected seven naturally occurring human CASP1 variants with different effects on protein structure, expression, and enzymatic activity. Most mutations destabilized the caspase-1 dimer interface as revealed by crystal structure analysis and homology modeling followed by molecular dynamics simulations. All variants demonstrated decreased or absent enzymatic and IL-1β releasing activity in vitro, in a cell transfection model, and as low as 25% of normal ex vivo in a whole blood assay of samples taken from subjects with variant CASP1, a subset of whom suffered from unclassified autoinflammation. We conclude that decreased enzymatic activity of caspase-1 is compatible with normal life and does not prevent moderate and severe autoinflammation.Fil: Luksch, Hella. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Romanowski, Michael J.. Sunesis Pharmaceuticals. Department of Structural Biology; Estados UnidosFil: Chara, Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentina. Technische Universitat Dresden. Center for Information Services and High-Performance Computing; AlemaniaFil: Tuengler, Victoria. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Caffarena, Ernesto Raúl. Escola Nacional de Saude Publica Sergio Arouca. Fundación Oswaldo Cruz; BrasilFil: Heymann, Michael C.. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Lohse, Peter. Ludwig-Maximilians-Universit; AlemaniaFil: Aksentijevich, Ivona. Inflammatory Disease Section; Estados UnidosFil: Remmers, Elaine F.. Inflammatory Disease Section; Estados UnidosFil: Flecks, Silvana. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Quoos, Nadine. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Gramatté, Johannes. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Petzold, Cathleen. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Hofmann, Sigrun R.. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Winkler, Stefan. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Pessler, Frank. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; Alemania. Helmholtz Centre for Infection Research; AlemaniaFil: Kallinich, Tilmann. Universität zu Berlin; AlemaniaFil: Ganser, Gerd. Sendenhorst. St. Josef-Stift; AlemaniaFil: Nimtz-Talaska, Antje. Kinderrheumatologie; AlemaniaFil: Baumann, Ulrich. Hannover Medical School; AlemaniaFil: Runde, Volker. Wilhelm-Anton-Hospital; AlemaniaFil: Grimbacher, Bodo. University Hospital Freiburg; AlemaniaFil: Birmelin, Jennifer. University Hospital Freiburg; AlemaniaFil: Gahr, Manfred. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Roesler, Joachim. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; AlemaniaFil: Rösen-Wolff, Angela. University Hospital Carl Gustav Carus. Department of Pediatrics. Dresden; Alemani