Transfection of the CD20 cell surface molecule into ectopic cell types generates a Ca2+ conductance found constitutively in B lymphocytes.
Transfection of the CD20 cell surface molecule into ectopic cell types generates a Ca2+ conductance found constitutively in B lymphocytes.
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DOI：
10.1083/jcb.121.5.1121
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发表时间：
1993-06
期刊：
影响因子：
--
通讯作者：
Tedder TF
中科院分区：
文献类型：
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作者：
Bubien JK;Zhou LJ;Bell PD;Frizzell RA;Tedder TF
CD20是一种仅由B淋巴细胞表达的质膜磷酸化蛋白。mAb结合CD20改变细胞周期进程和分化，表明CD20在B淋巴细胞功能中起重要作用。利用全细胞膜片钳和荧光显微镜分别测量质膜离子电导和胞质游离Ca2+活性，直接检测CD20的功能。用CD20 cDNA转染人T和小鼠前b淋巴母细胞样细胞系，随后CD20的稳定表达特异性地增加了跨膜Ca2+电导。转染CD20 cDNA并随后在非淋巴样细胞（人K562红白血病细胞和小鼠NIH-3T3成纤维细胞）中表达CD20也诱导了相同的跨膜Ca2+电导的表达。CD20特异性单抗与CD20+淋巴母细胞的结合也增强了Ca2+的跨膜传导。在CD20转染的细胞中，单克隆抗体增强的Ca2+电流与CD20相关的Ca2+电流具有相同的电导特性。C20在结构上与几种离子通道相似；每个CD20单体具有四个跨膜结构域，氨基端和羧基端都位于细胞质内。细胞表面分子的生化交联和随后的CD20免疫沉淀分析表明，CD20可能以多聚体低聚物的形式存在于膜内，就像几种已知的膜通道一样。综上所述，这些发现表明CD20直接调节B淋巴细胞的跨膜Ca2+传导，并提示CD20的多聚复合物可能在B淋巴样细胞的质膜中形成Ca2+传导离子通道。
CD20 is a plasma membrane phosphoprotein expressed exclusively by B lymphocytes. mAb binding to CD20 alters cell cycle progression and differentiation, indicating that CD20 plays an essential role in B lymphocyte function. Whole-cell patch clamp and fluorescence microscopy measurements of plasma membrane ionic conductance and cytosolic-free Ca2+ activity, respectively, were used to directly examine CD20 function. Transfection of human T and mouse pre-B lymphoblastoid cell lines with CD20 cDNA and subsequent stable expression of CD20 specifically increased transmembrane Ca2+ conductance. Transfection of CD20 cDNA and subsequent expression of CD20 in nonlymphoid cells (human K562 erythroleukemia cells and mouse NIH-3T3 fibroblasts) also induced the expression of an identical transmembrane Ca2+ conductance. The binding of a CD20-specific mAb to CD20+ lymphoblastoid cells also enhanced the transmembrane Ca2+ conductance. The mAb-enhanced Ca2+ currents had the same conductance characteristics as the CD20- associated Ca2+ currents in CD20 cDNA-transfected cells. C20 is structurally similar to several ion channels; each CD20 monomer possesses four membrane spanning domains, and both the amino and carboxy termini reside within the cytoplasm. Biochemical cross-linking of cell-surface molecules with subsequent immunoprecipitation analysis of CD20 suggests that CD20 may be present as a multimeric oligomer within the membrane, as occurs with several known membrane channels. Taken together, these findings indicate that CD20 directly regulates transmembrane Ca2+ conductance in B lymphocytes, and suggest that multimeric complexes of CD20 may form Ca2+ conductive ion channels in the plasma membrane of B lymphoid cells.