ABSTRACT
OBJECTIVE: To study the longitudinal dynamics of anti-myelin oligodendrocyte glycoprotein (MOG) autoantibodies in childhood demyelinating diseases. METHODS: We addressed the kinetics of anti-MOG immunoglobulins in a prospective study comprising 77 pediatric patients. This was supplemented by a cross-sectional study analyzing 126 pediatric patients with acute demyelination and 62 adult patients with multiple sclerosis (MS). MOG-transfected cells were used for detection of antibodies by flow cytometry. RESULTS: Twenty-five children who were anti-MOG immunoglobulin (Ig) positive at disease onset were followed for up to 5 years. Anti-MOG antibodies rapidly and continuously declined in all 16 monophasic patients with acute disseminated encephalomyelitis and in one patient with clinically isolated syndrome. In contrast, in 6 of 8 patients (75%) eventually diagnosed with childhood MS, the antibodies to MOG persisted with fluctuations showing a second increase during an observation period of up to 5 years. Antibodies to MOG were mainly IgG 1 and their binding was largely blocked by pathogenic anti-MOG antibodies derived from a spontaneous animal model of autoimmune encephalitis. The cross-sectional part of our study elaborated that anti-MOG Ig was present in about 25% of children with acute demyelination, but in none of the pediatric or adult controls. Sera from 4/62 (6%) adult patients with MS had anti-MOG IgG at low levels. CONCLUSIONS: The persistence or disappearance of antibodies to MOG may have prognostic relevance for acute childhood demyelination.
Subject(s)
Autoantibodies/analysis , Encephalomyelitis, Acute Disseminated/immunology , Myelin-Associated Glycoprotein/immunology , Adolescent , Adult , Binding, Competitive , Cell Line , Child , Child, Preschool , Cohort Studies , Cross-Sectional Studies , Female , Flow Cytometry , Humans , Immunoglobulin G/analysis , Immunoglobulins/analysis , Infant , Kinetics , Longitudinal Studies , Male , Multiple Sclerosis/immunology , Multiple Sclerosis/metabolism , Myelin Proteins , Myelin-Oligodendrocyte Glycoprotein , Prospective Studies , TransfectionABSTRACT
BACKGROUND: 12-Oxophytodienoate reductase (OPR) is a flavin mononucleotide (FMN)-dependent oxidoreductase in plants that belongs to the family of Old Yellow Enzyme (OYE). It was initially characterized as an enzyme involved in the biosynthesis of the plant hormone jasmonic acid, where it catalyzes the reduction of the cyclic fatty acid derivative 9S,13S-12-oxophytodienoate (9S,13S-OPDA) to 1S,2S-3-oxo-2(2'[Z]-pentenyl)-cyclopentane-1-octanoate. Several isozymes of OPR are now known that show different stereoselectivities with regard to the four stereoisomers of OPDA. RESULTS: Here, we report the high-resolution crystal structure of OPR1 from Lycopersicon esculentum and its complex structures with the substrate 9R,13R-OPDA and with polyethylene glycol 400. OPR1 crystallizes as a monomer and folds into a (betaalpha)(8) barrel with an overall structure similar to OYE. The cyclopentenone ring of 9R,13R-OPDA is stacked above the flavin and activated by two hydrogen bonds to His187 and His190. The olefinic bond is properly positioned for hydride transfer from the FMN N(5) and proton transfer from Tyr192 to Cbeta and Calpha, respectively. Comparison of the OPR1 and OYE structures reveals striking differences in the loops responsible for binding 9R,13R-OPDA in OPR1. CONCLUSIONS: Despite extensive biochemical characterization, the physiological function of OYE still remains unknown. The similar catalytic cavity structures and the substrate binding mode in OPR1 strongly support the assumption that alpha,beta-unsaturated carbonyl compounds are physiological substrates of the OYE family. The specific binding of 9R,13R-OPDA by OPR1 explains the experimentally observed stereoselectivity and argues in favor of 9R,13R-OPDA or a structurally related oxylipin as natural substrate of OPR1.
