Lux S E, John K M, Karnovsky M J
J Clin Invest. 1976 Oct;58(4):955-63. doi: 10.1172/JCI108549.
Irreversibly sickled cells (ISC's) are circulating erythrocytes in patients with sickle cell disease that retain a sickled shape even when oxygenated. Evidence points to a membrane defect that prevents the return of these cells to the normal biconcave shape. The erythrocyte membrane protein spectrin is believed to help control erythrocyte shape and deformability. Recent studies suggest that normally spectrin and an erythrocyte actin form a self-supporting, fibrillar, lattice-like network on the cytoplasmic membrane surface. When normal erythrocyte ghosts are extracted with Triton X-100 all the integral membrane proteins and most of the membrane lipids are removed, leaving a ghost-shaped residue composed principally of spectrin and actin. We concentrated ISC's from patients with sickle cell anemia and compared the morphology and protein composition of ghosts and Triton-extracted ghost residues prepared from these ISC's with similar preparations of reversibly sickable cells and normal cells. (a) Many ISC's formed ISC-shaped ghosts. (b) All ISC-shaped ghosts formed ISC-shaped Triton residues. (c) Spectrin, erythrocyte actin (Band 5), an unidentified Band 3 component, and Band 4.1 were the major protein components of the Triton residues. All membrane-associated sickle hemoglobin was removed by the Triton treatment. (d) No ISC-shaped ghosts or ISC-shaped Triton residues were formed when deoxygenated, sickled RSC's were lysed or Triton-extracted. ISC-shaped ghosts and Triton residues were never formed from normal cells. These observations suggest that a defect of the "spectrin-actin lattice" may be the primary abnormality of the ISC membrane. Since ISC's are rigid cells, the data support the postulate that spectrin is a major determinant of membrane deformability. Finally, they provide direct evidence that spectrin is important in determining erythrocyte shape.
不可逆性镰状细胞（ISC）是镰状细胞病患者循环中的红细胞，即使在氧合状态下也保持镰状形态。有证据表明存在一种膜缺陷，阻止这些细胞恢复正常的双凹形。红细胞膜蛋白血影蛋白被认为有助于控制红细胞的形状和可变形性。最近的研究表明，正常情况下血影蛋白和红细胞肌动蛋白在细胞质膜表面形成一个自支撑的、纤维状的、晶格状网络。当用Triton X - 100提取正常红细胞血影时，所有整合膜蛋白和大部分膜脂都被去除，留下一个主要由血影蛋白和肌动蛋白组成的血影状残余物。我们从镰状细胞贫血患者中浓缩了ISC，并将由这些ISC制备的血影和经Triton提取的血影残余物的形态和蛋白质组成与可逆性镰变细胞和正常细胞的类似制备物进行了比较。（a）许多ISC形成了ISC形状的血影。（b）所有ISC形状的血影形成了ISC形状的Triton残余物。（c）血影蛋白、红细胞肌动蛋白（带5）、一种未鉴定的带3成分和带4.1是Triton残余物的主要蛋白质成分。所有与膜相关的镰状血红蛋白都被Triton处理去除。（d）当脱氧的镰状可逆性镰变细胞（RSC）被裂解或经Triton提取时，未形成ISC形状的血影或ISC形状的Triton残余物。正常细胞从未形成ISC形状的血影和Triton残余物。这些观察结果表明，“血影蛋白 - 肌动蛋白晶格”的缺陷可能是ISC膜的主要异常。由于ISC是刚性细胞，这些数据支持血影蛋白是膜可变形性的主要决定因素这一假设。最后，它们提供了直接证据表明血影蛋白在决定红细胞形状方面很重要。
