The Transmembrane Domains of L-selectin and CD44 Regulate Receptor Cell Surface Positioning and Leukocyte Adhesion under Flow
The Transmembrane Domains of L-selectin and CD44 Regulate Receptor Cell Surface Positioning and Leukocyte Adhesion under Flow
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DOI：
10.1074/jbc.m110.102640
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发表时间：
2010-04-30
影响因子：
4.8
通讯作者：
Ley, Klaus
中科院分区：
文献类型：
--
作者：
Buscher, Konrad;Riese, Sebastian B.;Ley, Klaus
在炎症和免疫监视期间，自由流动的白细胞和内皮细胞之间的初始接触（栓系）至关重要地依赖于白细胞微绒毛上粘附受体l -选择素的呈现。然而，调节受体靶向微绒毛的决定因素在很大程度上是难以捉摸的。因此，我们系统地交换了l -选择素和CD44的细胞外（EC）、跨膜（TM）和细胞内（IC）结构域，CD44是一种透明质酸受体，在细胞体上表达，从微绒毛中排除。转染的人髓系K562细胞电镜显示，高度保守的TM结构域负责表面定位。l -选择素的TM片段迫使嵌合分子进入微绒毛，CD44 TM结构域在细胞体上引起表达，而IC和EC结构域几乎不影响表面定位。以微绒毛为基础的嵌合体的转染物在流动条件下的黏附率明显高于细胞体表达受体的细胞，而在静态条件下则没有。l -选择素的IC结构域的替换导致了白细胞拴系的减少，但表面分布没有变化，这表明微绒毛定位和细胞骨架锚定都有助于白细胞拴系。这些发现表明，l -选择素和CD44的TM结构域分别通过靶向受体到微绒毛或细胞体，在细胞流动粘附中起着至关重要的作用。
During inflammation and immune surveillance, initial contacts (tethering) between free-flowing leukocytes and the endothelium are vitally dependent on the presentation of the adhesion receptor L-selectin on leukocyte microvilli. Determinants that regulate receptor targeting to microvilli are, however, largely elusive. Therefore, we systematically swapped the extracellular (EC), transmembrane (TM), and intracellular (IC) domains of L-selectin and CD44, a hyaluronan receptor expressed on the cell body and excluded from microvilli. Electron microscopy of transfected human myeloid K562 cells showed that the highly conserved TM domains are responsible for surface positioning. The TM segment of L-selectin forced chimeric molecules to microvilli, and the CD44 TM domain evoked expression on the cell body, whereas the IC and EC domains hardly influenced surface localization. Transfectants with microvillus-based chimeras showed a significantly higher adhesion rate under flow but not under static conditions compared with cells with cell body-expressed receptors. Substitution of the IC domain of L-selectin caused diminished tethering but no change in surface distribution, indicating that both microvillus positioning and cytoskeletal anchoring contribute to leukocyte tethering. These findings demonstrate that TM domains of L-selectin and CD44 play a crucial role in cell adhesion under flow by targeting receptors to microvilli or the cell body, respectively.