Evidence that the two C1q binding membrane proteins, gC1q-R and cC1q-R, associate to form a complex.
Evidence that the two C1q binding membrane proteins, gC1q-R and cC1q-R, associate to form a complex.
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DOI：
10.4049/jimmunol.159.3.1429
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发表时间：
1997-08
影响因子：
4.4
通讯作者：
B. Ghebrehiwet;P. Lu;W. Zhang;S. Keilbaugh;L. E. Leigh;Paul Eggleton;Kenneth B. M. Reid;E. Peerschke
中科院分区：
文献类型：
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作者：
B. Ghebrehiwet;P. Lu;W. Zhang;S. Keilbaugh;L. E. Leigh;Paul Eggleton;Kenneth B. M. Reid;E. Peerschke
两种类型的广泛共表达，高酸性，细胞膜结合蛋白，显示优先的结构域特异性C1 q已被描述：一个60 kDa的钙网蛋白同源物，命名为cC 1 q-R，结合到胶原样的“茎”和33 kDa的糖蛋白与亲和力的球状“头”（gC 1 q-R）。尽管已知这两种分子在迄今为止检查的所有细胞类型上共表达，并且在纯化过程中经常共表达，但没有直接证据表明它们在膜上或在纯化系统中检查时彼此缔合。在这份报告中，我们提出了第一个证据，1）生物素化的cC 1 q-R结合重组以及天然gC 1 q-R，如固相ELISA评估：2）cC 1 q-R的结合位点位于N-末端残基76至93的成熟形式的gC 1 q-R和残基204至218内; 3）这种相互作用被两种mAb 60.11和46.23和mAb 74.5.2抑制，所述mAb 60.11和46.23主要识别gC 1 q-R的N末端内对应于残基74至96的表位，所述mAb 74.5.2识别残基204至218内的表位;和4）生物素化的cC 1 q-R与微量滴定固定的Raji和K562细胞结合，并且这种相互作用被mAb 60.11抑制。此外，Raji细胞膜与抗gC 1 q-R单克隆抗体的免疫共沉淀分析表明，除了gC 1 q-R外，还存在cC 1 q-R。综上所述，证据表明cC 1 q-R能够与gC 1 q-R形成复合物，并且可能与细胞表面上的gC 1 q-R缔合。
Two types of widely coexpressed, highly acidic, cell membrane binding proteins that display preferential domain specificity for C1q have been described: a 60-kDa calreticulin homologue, designated cC1q-R, that binds to the collagen-like "stalk" and a 33-kDa glycoprotein with affinity for the globular "heads" (gC1q-R). Although the two molecules are known to be coexpressed on all cell types examined to date and often coelute during purification, there is no direct evidence showing that they associate with each other either on the membrane or when examined in a purified system. In this report we present the first evidence that 1) biotinylated cC1q-R binds to recombinant as well as native gC1q-R, as assessed by solid phase ELISA; 2) binding sites for cC1q-R are located within N-terminal residues 76 through 93 of the mature form of gC1q-R and within residues 204 through 218; 3) this interaction is inhibited by two mAbs, 60.11 and 46.23, that recognize primarily epitopes within the N terminus of gC1q-R corresponding to residues 74 through 96 and by mAb 74.5.2 that recognizes epitopes within residues 204 through 218; and 4) biotinylated cC1q-R binds to microtiter-fixed Raji and K562 cells, and this interaction is inhibited by mAb 60.11. Furthermore, coimmunoprecipitation analysis of Raji cell membranes with anti-gC1q-R mAbs showed the presence of cC1q-R in addition to gC1q-R. Taken together, the evidence suggests that cC1q-R is able to form a complex with gC1q-R and may associate with gC1q-R on the cell surface.