Liu S C, Palek J, Yi S J, Nichols P E, Derick L H, Chiou S S, Amato D, Corbett J D, Cho M R, Golan D E
Department of Biomedical Research, St Elizabeth's Medical Center of Boston, Tufts University Medical School, MA 02135, USA.
Blood. 1995 Jul 1;86(1):349-58.
Southeast Asian ovalocytosis (SAO) is an asymptomatic trait characterized by rigid, poorly deformable red cells that resist invasion by several strains of malaria parasites. The underlying molecular genetic defect involves simple heterozygous state for a mutant band 3 protein, which contains a deletion of amino acids 400 through 408, linked with a Lys 56-to-Glu substitution (band 3-Memphis polymorphism). To elucidate the contribution of the mutant SAO band 3 protein to increased SAO red blood cell (RBC) rigidity, we examined the participation of the mutant SAO band 3 protein in increased band 3 attachment to the skeleton and band 3 oligomerization. We found first that SAO RBC skeletons retained more band 3 than normal cells and that this increased retention preferentially involved the mutant SAO band 3 protein. Second, SAO RBCs contained a higher percentage of band 3 oligomer-ankyrin complexes than normal cells, and these oligomers were preferentially enriched by the mutant SAO protein. At the ultrastructural level, the increased oligomer formation of SAO RBCs was reflected by stacking of band 3-containing intramembrane particles (IMP) into longitudinal strands. The IMP stacking was not reversed by treating SAO RBCs in alkaline pH (pH 11), which is known to weaken ankyrin-band 3 interactions, or by removing the cytoplasmic domain of band 3 from SAO membranes with trypsin. Finally, we found that band 3 protein in intact SAO RBCs exhibited a markedly decreased rotational mobility, presumably reflecting the increased oligomerization and the membrane skeletal association of the SAO band 3 protein. We propose that the mutant SAO band 3 has an increased propensity to form oligomers, which appear as longitudinal strands of IMP and exhibit increased association with membrane skeleton. This band 3 oligomerization underlies the increase in membrane rigidity by precluding membrane skeletal extension, which is necessary for membrane deformation.
东南亚椭圆形红细胞增多症（SAO）是一种无症状性状，其特征是红细胞僵硬、变形性差，能抵抗多种疟原虫菌株的侵袭。潜在的分子遗传缺陷涉及突变的带3蛋白的简单杂合状态，该蛋白包含400至408位氨基酸的缺失，并与赖氨酸56到谷氨酸的替换（带3 - 孟菲斯多态性）相关。为了阐明突变的SAO带3蛋白对SAO红细胞（RBC）刚性增加的作用，我们研究了突变的SAO带3蛋白在增加带3与骨架的附着以及带3寡聚化中的参与情况。我们首先发现，SAO红细胞骨架比正常细胞保留了更多的带3，并且这种增加的保留优先涉及突变的SAO带3蛋白。其次，SAO红细胞中带3寡聚体 - 锚蛋白复合物的百分比高于正常细胞，并且这些寡聚体优先富集了突变的SAO蛋白。在超微结构水平上，SAO红细胞中增加的寡聚体形成表现为含带3的膜内颗粒（IMP）堆积成纵向链。通过在碱性pH（pH 11）下处理SAO红细胞（已知这会削弱锚蛋白 - 带3相互作用）或用胰蛋白酶从SAO膜上去除带3的细胞质结构域，IMP堆积并未逆转。最后，我们发现完整的SAO红细胞中的带3蛋白表现出明显降低的旋转流动性，这可能反映了SAO带3蛋白寡聚化增加以及与膜骨架的结合增加。我们提出，突变的SAO带3形成寡聚体的倾向增加，这些寡聚体表现为IMP的纵向链，并与膜骨架的结合增加。这种带3寡聚化通过阻止膜骨架伸展（这是膜变形所必需的）导致膜刚性增加。
