title: Band 3 Courcouronnes (Ser667Phe): a trafficking mutant differentially rescued by wild-type band 3 and glycophorin A.
abstract: We describe a mutation in human erythrocyte band 3 (anion exchanger 1; SLC4A1) causing both hereditary spherocytosis and distal renal tubular acidosis. The proband developed a transfusion-dependent, hemolytic anemia following birth. Immunoblotting showed band 3 was reduced to approximately 35% of wildtype; other proteins of the band 3/Rh macrocomplex were also reduced. DNA sequence analysis revealed a novel homozygous mutation, c.2000C>T, leading to the amino acid substitution Ser667Phe. The parents were heterozygous for the same mutation. Sulfate influx in the patient's erythrocytes was approximately 40% wild type. The mutant band 3 produced very little chloride influx when expressed in Xenopus oocytes. Influx was partially rescued by coexpression of glycophorin A and also rescued by coexpression of wild-type band 3. At 2 years of age, an ammonium chloride challenge showed the child has incomplete distal renal tubular acidosis (dRTA). Stable expression of mutant kidney band 3 in both nonpolarized and polarized Madin-Darby canine kidney cells showed that most of the mutant protein was retained in the endoplasmic reticulum. Overall our results suggest that the Ser667Phe does not affect the anion transport function of band 3, but causes a trafficking defect in both erythrocytes and kidney cells.
authors.affiliation: Department of Biochemistry, University of Bristol, Bristol, United Kingdom. ash.m.toye@bristol.ac.uk
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Toye
authors.forename: Rosalind C
authors.initials: RC
authors.lastname: Williamson
authors.forename: Moudji
authors.initials: M
authors.lastname: Khanfar
authors.forename: Brigitte
authors.initials: B
authors.lastname: Bader-Meunier
authors.forename: Thérèse
authors.initials: T
authors.lastname: Cynober
authors.forename: Madeleine
authors.initials: M
authors.lastname: Thibault
authors.forename: Gil
authors.initials: G
authors.lastname: Tchernia
authors.forename: Michèle
authors.initials: M
authors.lastname: Déchaux
authors.forename: Jean
authors.initials: J
authors.lastname: Delaunay
authors.forename: Lesley J
authors.initials: LJ
authors.lastname: Bruce
mesh_terms: D000141:Acidosis, Renal Tubular / Q000235:genetics* / Q000503:physiopathology; D019943:Amino Acid Substitution; D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics* / Q000378:metabolism*; D015153:Blotting, Western; D002462:Cell Membrane / Q000737:chemistry; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000737:chemistry / Q000502:physiology; D005455:Fluorescent Antibody Technique; D005808:Genes, Recessive; D005838:Genotype; D006021:Glycophorins / Q000378:metabolism*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D020125:Mutation, Missense; D010375:Pedigree; D010641:Phenotype; D018807:Polymorphism, Single-Stranded Conformational; D021381:Protein Transport / Q000502:physiology; D013103:Spherocytosis, Hereditary / Q000235:genetics* / Q000503:physiopathology; D014981:Xenopus
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D006021:Glycophorins; C454201:SLC4A1 protein, human