Hara Takahiko, Ishida Hiroshi, Raziuddin Razi, Dorkhom Stephan, Kamijo Keiju, Miki Toru
Molecular Tumor Biology Section, Basic Research Laboratory, National Cancer Institute, Bethesda, Maryland, 20892-4255, USA.
Mol Biol Cell. 2004 Mar;15(3):1172-84. doi: 10.1091/mbc.e03-07-0531. Epub 2003 Dec 10.
Dynamic rearrangements of cell-cell adhesion underlie a diverse range of physiological processes, but their precise molecular mechanisms are still obscure. Thus, identification of novel players that are involved in cell-cell adhesion would be important. We isolated a human kelch-related protein, Kelch-like ECT2 interacting protein (KLEIP), which contains the broad-complex, tramtrack, bric-a-brac (BTB)/poxvirus, zinc finger (POZ) motif and six-tandem kelch repeats. KLEIP interacted with F-actin and was concentrated at cell-cell contact sites of Madin-Darby canine kidney cells, where it colocalized with F-actin. Interestingly, this localization took place transiently during the induction of cell-cell contact and was not seen at mature junctions. KLEIP recruitment and actin assembly were induced around E-cadherin-coated beads placed on cell surfaces. The actin depolymerizing agent cytochalasin B inhibited this KLEIP recruitment around E-cadherin-coated beads. Moreover, constitutively active Rac1 enhanced the recruitment of KLEIP as well as F-actin to the adhesion sites. These observations strongly suggest that KLEIP is localized on actin filaments at the contact sites. We also found that N-terminal half of KLEIP, which lacks the actin-binding site and contains the sufficient sequence for the localization at the cell-cell contact sites, inhibited constitutively active Rac1-induced actin assembly at the contact sites. We propose that KLEIP is involved in Rac1-induced actin organization during cell-cell contact in Madin-Darby canine kidney cells.
细胞间黏附的动态重排是多种生理过程的基础，但其精确的分子机制仍不清楚。因此，鉴定参与细胞间黏附的新分子将具有重要意义。我们分离出一种人类kelch相关蛋白，即kelch样ECT2相互作用蛋白（KLEIP），它含有广泛复合体、tramtrack、bric-a-brac（BTB）/痘病毒、锌指（POZ）基序和六个串联的kelch重复序列。KLEIP与F-肌动蛋白相互作用，并集中在Madin-Darby犬肾细胞的细胞间接触部位，在那里它与F-肌动蛋白共定位。有趣的是，这种定位在细胞间接触诱导过程中短暂发生，在成熟连接部位则未观察到。在置于细胞表面的E-钙黏蛋白包被的珠子周围诱导了KLEIP募集和肌动蛋白组装。肌动蛋白解聚剂细胞松弛素B抑制了E-钙黏蛋白包被的珠子周围的这种KLEIP募集。此外，组成型活性Rac1增强了KLEIP以及F-肌动蛋白向黏附部位的募集。这些观察结果强烈表明KLEIP定位于接触部位的肌动蛋白丝上。我们还发现，KLEIP的N端半段缺乏肌动蛋白结合位点，但含有在细胞间接触部位定位的足够序列，它抑制了组成型活性Rac1诱导的接触部位肌动蛋白组装。我们提出KLEIP参与了Madin-Darby犬肾细胞细胞间接触过程中Rac1诱导的肌动蛋白组织。
