Red cell membrane polypeptides under normal conditions and in genetic disorders.
Broadly speaking, the red cell membrane is comprised of --a cholesterol-rich phospholipid bilayer that is studded by a large number of trans-bilayer proteins, --of glycosylphosphatidylinositol-anchored proteins (GPI-proteins) standing outside, and --an important protein assembly, the erythrocyte or membrane skeleton, that laminates the inner surface of the bilayer. Among the trans-bilayer proteins, one finds the anion exchanger, the glycophorins, the glucose transporter, a variety of cation transporters and pumps, and of course proteins carrying the epitopes of many blood groups. Among the GPI-proteins, one encounters the acetylcholinesterase and the decay-accelerating factor (CD 55). Among the skeletal proteins, finally, one recognises spectrin, actin (and a number of actin-binding proteins other than spectrin: dematin, tropomyosin, tropomodulin, etc.), protein 4.1 and protein p55. Spectrin heterotetramer organizes into a bidimensional network with a hexagonal mesh on the average. This network is linked to trans-bilayer proteins, through the complex beta-spectrin-ankyrin-anion exchanger (+ protein 4.2) on the one hand and, on the other hand, through the triangular interaction between protein 4.1, glycophorin C and protein p55. The sequence of the above proteins and the exon-intron organisation of their genes are known in most cases. Many proteins have a widespread tissue distribution in the form of variants adapted to their local functions. Such variants may be the products of multigene families (anion exchanger, ankyrin, spectrin), or derive from a single gene (protein 4.1, protein 4.2), the transcripts of which undergo cell-specific alternative splicing. It has been established that many congenital haemolytic anaemias result from mutations altering the above-mentioned genes. We will provide two examples. Hereditary elliptocytosis stems from an array of mutations located at, or near the head-to-head self-association region of two spectrin alpha beta dimers, or from mutations which, most often, yield a reduction (heterozygous state) or the lack (homozygous state) of protein 4.1. The aggravation of elliptocytosis associated with alpha-spectrin mutations frequently yields poikilocytosis and usually stems from the occurrence, in trans, of a low expression allele, allele alpha LELY. Hereditary spherocytosis derives from mutations in the ankyrin gene (80% of the cases), the anion exchanger gene (10-15% of the cases), the protein 4.2 gene (rare cases) and the alpha- and beta-spectrin genes (rare cases). Anion exchanger mutations usually cause the decrease in this protein (heterozygous state).(ABSTRACT TRUNCATED AT 250 WORDS)
Laboratoire de génétique humaine, CNRS URA 1171, Institut Pasteur de Lyon, France.
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Delaunay
D001457:Anion Exchange Protein 1, Erythrocyte / Q000235:genetics; D017487:Ankyrins / Q000235:genetics; D001483:Base Sequence; D001798:Blood Proteins / Q000235:genetics*; D003598:Cytoskeletal Proteins; D004612:Elliptocytosis, Hereditary / Q000097:blood / Q000235:genetics; D004910:Erythrocyte Membrane / Q000737:chemistry*; D030342:Genetic Diseases, Inborn / Q000097:blood* / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009479:Neuropeptides; D017354:Point Mutation; D013049:Spectrin / Q000235:genetics; D013103:Spherocytosis, Hereditary / Q000097:blood / Q000235:genetics
D001457:Anion Exchange Protein 1, Erythrocyte; D017487:Ankyrins; D001798:Blood Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D009479:Neuropeptides; C028841:erythrocyte membrane band 4.1 protein; C120557:erythrocyte membrane protein band 4.1-like 1; D013049:Spectrin