title: Effects of Different Variants in the ENPP1 Gene on the Functional Properties of Ectonucleotide Pyrophosphatase/Phosphodiesterase Family Member 1.
abstract: Ectonucleotide pyrophosphatase/phosphodiesterase family member 1 (E-NPP1), encoded by ENPP1, is a plasma membrane protein that generates inorganic pyrophosphate (PPi), a physiologic inhibitor of hydroxyapatite formation. In humans, variants in ENPP1 are associated with generalized arterial calcification of infancy, an autosomal-recessive condition causing premature onset of arterial calcification and intimal proliferation resulting in stenoses. ENPP1 variants also cause pseudoxanthoma elasticum characterized by ectopic calcification of soft connective tissues. To determine the functional impact of ENPP1 missense variants, we analyzed 13 putative pathogenic variants in vitro regarding their functional properties, that is, activity, localization, and PPigeneration. Transfection of eight of the 13 variants led to complete loss of NPP activity, whereas four mutants (c.1412A > G, p.Tyr471Cys; c.1510A > C, p.Ser504Arg; c.1976A > G, p.Tyr659Cys; c.2330A > G, p.His777Arg) showed residual activity compared with wild-type E-NPP1. One putative pathologic variant (c.2462 G > A, p.Arg821His) showed normal activity. The five mutants with normal or residual E-NPP1 enzyme activity were still able to generate PPiand localized in the plasma membrane. In this study, we identified a functional ENPP1 polymorphism, which was expected to be pathogenic till now. Furthermore, we identified four mutants (p.Tyr471Cys, p.Ser504Arg, p.Tyr659Cys, p.His777Arg) with residual E-NPP1 function, which would be potential therapeutical targets for conformational-stabilizing agents.
authors.affiliation: Department of General Pediatrics, Muenster University Children's Hospital, Albert-Schweitzer-Campus 1, Muenster, 48149, Germany.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Stella
authors.affiliation: Department of General Pediatrics, Muenster University Children's Hospital, Albert-Schweitzer-Campus 1, Muenster, 48149, Germany.
authors.forename: Insa
authors.initials: I
authors.lastname: Buers
authors.affiliation: Division of Molecular Oncology, Netherlands Cancer Institute, Amsterdam, 1066 CX, The Netherlands.
authors.forename: Koen
authors.initials: K
authors.lastname: van de Wetering
authors.affiliation: Cologne Center of Genomics, Koeln University, Zuelpicher Strasse 47, Koeln, 50674, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Höhne
authors.affiliation: Department of General Pediatrics, Muenster University Children's Hospital, Albert-Schweitzer-Campus 1, Muenster, 48149, Germany. rutschf@ukmuenster.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Rutsch
authors.affiliation: Department of General Pediatrics, Muenster University Children's Hospital, Albert-Schweitzer-Campus 1, Muenster, 48149, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Nitschke
mesh_terms: D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D011756:Diphosphates / Q000378:metabolism; D015536:Down-Regulation; D057809:HEK293 Cells; D006801:Humans; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D010727:Phosphoric Diester Hydrolases / Q000235:genetics* / Q000378:metabolism*; D011755:Pyrophosphatases / Q000235:genetics* / Q000378:metabolism*; D061205:Vascular Calcification / Q000235:genetics*
chemical_list: D011756:Diphosphates; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases
keywords: E-NPP1; GACI; enzyme activity; pyrophosphate