title: The Arg98Trp mutation in human VKORC1 causing VKCFD2 disrupts a di-arginine-based ER retention motif.
abstract: Vitamin K 2,3-epoxide reductase complex subunit 1 (VKORC1) is an enzyme localized to the endoplasmic reticulum (ER) membrane. VKORC1 catalyzes the reduction of vitamin K 2,3-epoxide to vitamin K and to vitamin K hydroquinone, the latter required by the enzyme γ-carboxylase for γ-carboxylation of all vitamin K-dependent (VKD) proteins. Until now, only 1 human VKORC1 mutation, p.Arg98Trp, is known to cause combined deficiency of VKD clotting factors type 2 (VKCFD2), a disease phenotype reported in 3 unrelated families. VKCFD2 patients suffer from spontaneous bleeding episodes because of decreased levels of γ-carboxylated VKD clotting factors. Daily supraphysiological vitamin K supplementation restores clotting for VKCFD2 patients and results in high serum levels of vitamin K 2,3-epoxide, suggesting that supplemented vitamin K is reduced in vivo. Although the p.Arg98Trp mutation results in reduced vitamin K 2,3-epoxide reductase activity, the molecular mechanism underlying this pathophysiology is unknown. Using a combination of in silico analysis and confocal microscopy, we demonstrate for the first time that VKORC1:p.Arg98Trp disrupts a di-arginine ER retention motif resulting in 20% ER colocalization only. As a consequence, VKORC1 exits the ER membrane by cellular quality control systems and results in the observed VKCFD2 phenotype.
authors: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany; and.
authors: Katrin J
authors: KJ
authors: Czogalla
authors: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany; and.
authors: Arijit
authors: A
authors: Biswas
authors: Institute of Human Genetics, University of Würzburg, Würzburg, Germany.
authors: Simone
authors: S
authors: Rost
authors: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany; and.
authors: Matthias
authors: M
authors: Watzka
authors: Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany; and.
authors: Johannes
authors: J
authors: Oldenburg
mesh_terms: D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D001779:Blood Coagulation Factors / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000201:enzymology* / Q000235:genetics; D006801:Humans; D020125:Mutation, Missense; D021381:Protein Transport / Q000502:physiology; D014812:Vitamin K / Q000235:genetics / Q000378:metabolism*; D064417:Vitamin K Epoxide Reductases / Q000235:genetics / Q000378:metabolism*
chemical_list: D001779:Blood Coagulation Factors; D014812:Vitamin K; C578523:VKORC1 protein, human; D064417:Vitamin K Epoxide Reductases