title: Expression analysis revealing destabilizing mutations in phosphomannomutase 2 deficiency (PMM2-CDG): expression analysis of PMM2-CDG mutations.
abstract: Deficiency of phosphomannomutase (PMM2, MIM#601785) is the most common congenital disorder of glycosylation. Herein we report the genetic analysis of 22 Spanish PMM2 deficient patients and the functional analysis of 14 nucleotide changes in a prokaryotic expression system in order to elucidate their molecular pathogenesis. PMM2 activity assay revealed the presence of six protein changes with no enzymatic activities (p.R123Q, p.R141H, p.F157S, p.P184T, p.F207S and p.D209G) and seven mild protein changes with residual activities ranging from 16 to 54% (p.L32R, p.V44A p.D65Y, p.P113L p.T118S, p.T237M and p.C241S) and also one variant change with normal activity (p.E197A). The results obtained from Western blot analysis, degradation time courses of 11 protein changes and structural analysis of the PMM2 protein, suggest that the loss-of-function of most mutant proteins is based on their increased susceptibility to degradation or aggregation compared to the wild type protein, considering PMM2 deficiency as a conformational disease. We have identified exclusively catalytic protein change (p.D209G), catalytic protein changes affecting protein stability (p.R123Q and p.R141H), two protein changes disrupting the dimer interface (p.P113L and p.T118S) and several misfolding changes (p.L32R, p.V44A, p.D65Y, p.F157S, p.P184T, p.F207S, p.T237M and p.C241S). Our current work opens a promising therapeutic option using pharmacological chaperones to revert the effect of the characterized misfolding mutations identified in a wide range of PMM2 deficient patients.
authors.affiliation: Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid / Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.
authors.forename: Ana Isabel
authors.initials: AI
authors.lastname: Vega
authors.forename: Celia
authors.initials: C
authors.lastname: Pérez-Cerdá
authors.forename: David
authors.initials: D
authors.lastname: Abia
authors.forename: Alejandra
authors.initials: A
authors.lastname: Gámez
authors.forename: Paz
authors.initials: P
authors.lastname: Briones
authors.forename: Rafael
authors.initials: R
authors.lastname: Artuch
authors.forename: Lourdes R
authors.initials: LR
authors.lastname: Desviat
authors.forename: Magdalena
authors.initials: M
authors.lastname: Ugarte
authors.forename: Belén
authors.initials: B
authors.lastname: Pérez
mesh_terms: D002460:Cell Line; D018981:Congenital Disorders of Glycosylation / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D004252:DNA Mutational Analysis; D004795:Enzyme Stability / Q000235:genetics; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D006801:Humans; D020125:Mutation, Missense / Q000502:physiology*; D017875:Phosphotransferases (Phosphomutases) / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D017510:Protein Folding
chemical_list: D017875:Phosphotransferases (Phosphomutases); C519582:phosphomannomutase 2, human