title: GPI-anchor and GPI-anchored protein expression in PMM2-CDG patients.
abstract: BACKGROUND
  Mutations in PMM2 impair phosphomannomutase-2 activity and cause the most frequent congenital disorder of glycosylation, PMM2-CDG. Mannose-1-phosphate, that is deficient in this disorder, is also implicated in the biosynthesis of glycosylphosphatidyl inositol (GPI) anchors.
  
  
  OBJECTIVE
  To evaluate whether GPI-anchor and GPI-anchored proteins are defective in PMM2-CDG patients.
  
  
  METHODS
  The expression of GPI-anchor and seven GPI-anchored proteins was evaluated by flow cytometry in different cell types from twelve PMM2-CDG patients. Additionally, neutrophil CD16 and plasma hepatic proteins were studied by Western blot. Transferrin glycoforms were evaluated by HPLC.
  
  
  RESULTS
  Patients and controls had similar surface expression of GPI-anchor and most GPI-anchored proteins. Nevertheless, patients displayed a significantly diminished binding of two anti-CD16 antibodies (3G8 and KD1) to neutrophils and also of anti-CD14 (61D3) to monocytes. Interestingly, CD16 immunostaining and asialotransferrin levels significantly correlated with patients' age. Analysis by flow cytometry of CD14 with MΦP9, and CD16 expression in neutrophils by Western blot using H-80 ruled out deficiencies of these antigens.
  
  
  CONCLUSIONS
  PMM2 mutations do not impair GPI-anchor or GPI-anchored protein expression. However, the glycosylation anomalies caused by PMM2 mutations might affect the immunoreactivity of monoclonal antibodies and lead to incorrect conclusions about the expression of different proteins, including GPI-anchored proteins. Neutrophils and monocytes are sensitive to PMM2 mutations, leading to abnormal glycosylation in immune receptors, which might potentially affect their affinity to their ligands, and contribute to infection. This study also confirms less severe hypoglycosylation defects in older PMM2-CDG patients.
authors.forename: Maria E
authors.initials: ME
authors.lastname: de la Morena-Barrio
authors.forename: Trinidad
authors.initials: T
authors.lastname: Hernández-Caselles
authors.affiliation: Centro Regional de Hemodonación Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Universidad de Murcia, Ronda de Garay S/N, 30003 Murcia, Spain. javier.corral@carm.es.
authors.forename: Javier
authors.initials: J
authors.lastname: Corral
authors.forename: Roberto
authors.initials: R
authors.lastname: García-López
authors.forename: Irene
authors.initials: I
authors.lastname: Martínez-Martínez
authors.forename: Belen
authors.initials: B
authors.lastname: Pérez-Dueñas
authors.forename: Carmen
authors.initials: C
authors.lastname: Altisent
authors.forename: Teresa
authors.initials: T
authors.lastname: Sevivas
authors.forename: Soren R
authors.initials: SR
authors.lastname: Kristensen
authors.forename: Encarna
authors.initials: E
authors.lastname: Guillén-Navarro
authors.forename: Antonia
authors.initials: A
authors.lastname: Miñano
authors.forename: Vicente
authors.initials: V
authors.lastname: Vicente
authors.forename: Jaak
authors.initials: J
authors.lastname: Jaeken
authors.forename: Maria L
authors.initials: ML
authors.lastname: Lozano
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002851:Chromatography, High Pressure Liquid; D018981:Congenital Disorders of Glycosylation; D005260:Female; D005434:Flow Cytometry; D017261:Glycosylphosphatidylinositols / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007223:Infant; D008297:Male; D009000:Monocytes / Q000378:metabolism; D009154:Mutation; D009504:Neutrophils / Q000378:metabolism; D017875:Phosphotransferases (Phosphomutases) / Q000235:genetics / Q000378:metabolism*
chemical_list: D017261:Glycosylphosphatidylinositols; D017875:Phosphotransferases (Phosphomutases); C519582:phosphomannomutase 2, human