Electron microscopic and physicobiochemical studies on disorganization of the cytoskeletal network and integral protein (band 3) in red cells of band 4.2 deficiency with a mutation (codon 142: GCT-->ACT).
The role of band 4.2 deficiency in the pathogenesis of red cell membrane dysfunctions was studied in seven unrelated patients with complete band 4.2 deficiency with a point mutation (142 GCT-->ACT; 142 Ala-->Thr) on the cDNA of the band 4.2 gene. Two major types of abnormalities were detected in these patients; (A) abnormalities of the cytoskeletal network in the horizontal dimension, and (B) abnormalities of band 3 in the vertical dimension. Electron microscopy by the surface replica method and the quick-freeze deep-etching method demonstrated the markedly impaired cytoskeletal network (a disorganized cobblestone pattern, uneven distribution of junctional units, and the appearance of bulky aggregates after heat treatment). Ektacytometry showed a markedly decreased red cell deformability especially at 48 degrees C, although the cytoskeletal proteins themselves were essentially normal with normal mechanical stability of the Triton-shells. Electron microscopy by the freeze fracture method revealed a decreased number and a random distribution of intramembrane particles (IMPs) with a shift of the IMPs to a larger size. Fluorescence recovery after photobleaching studies on band 3 indicated the marked increase of its mobile fraction. The extractability of band 3 by Triton X in vitro was markedly enhanced, although the physico-biochemical properties of band 3 itself (the cleavage pattern of band 3 fragments, and the binding properties of band 3 to band 4.2 or ankyrin) were basically normal. These findings demonstrate that band 4.2 plays a crucial role in the maintenance of the normal structure and functions of both the cytoskeletal and integral proteins (band 3).
Department of Medicine, Kawasaki Medical School, Kurashiki City, Japan.
T
T
Inoue
A
A
Kanzaki
A
A
Yawata
A
A
Tsuji
K
K
Ata
N
N
Okamoto
H
H
Wada
I
I
Higo
T
T
Sugihara
O
O
Yamada
D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism*; D001483:Base Sequence; D001798:Blood Proteins / Q000172:deficiency* / Q000235:genetics*; D003062:Codon; D003598:Cytoskeletal Proteins; D003599:Cytoskeleton / Q000648:ultrastructure; D004910:Erythrocyte Membrane / Q000378:metabolism / Q000648:ultrastructure*; D005613:Freeze Etching; D005614:Freeze Fracturing; D006801:Humans; D008565:Membrane Proteins; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D017354:Point Mutation
D001457:Anion Exchange Protein 1, Erythrocyte; D001798:Blood Proteins; D003062:Codon; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; C044791:erythrocyte membrane band 4.2 protein