Role of leukocyte specific adaptor protein leupaxin in T cell migration

尽管白细胞的粘附和运动在很大程度上依赖于整合素，但白细胞通常缺乏可区分的局灶粘附（FAs），而后者在其他粘附细胞中充当信号中心。FAs的组装和拆卸是由局部产生的细胞内信号调节的，paxillin的酪氨酸磷酸化参与了这一过程。aleukcell特异性接头蛋白leupaxin是paxillin家族的成员，与paxillin具有相同的总体结构特征。Leupaxin由多个功能性小体组成，包括LD基序和LIM结构域，这表明Leupaxin也作为一个分子接头参与整合素介导的信号传导。然而，在整合素信号传导中，leupaxin和paxillin是相互合作还是相互拮抗，目前尚不清楚。我们发现leupaxin能有效抑制paxillin的酪氨酸磷酸化。当在结合ICAM-1的小鼠胸腺瘤BW5147细胞中表达时，leupaxin在细胞周围的FA样斑块中积累更多。在沿ICAM-1迁移的BW5147细胞中，leupaxin选择性地位于后缘。当在NIH3T3和hek293t细胞中表达时，leupaxin通过细胞与纤维连接蛋白的粘附定位到FAs上，并强烈抑制整合素诱导的paxillin酪氨酸磷酸化。在整合素刺激的hek293t细胞中，leupaxin的LIM3结构域对于选择性FA定位和抑制paxillin酪氨酸磷酸化至关重要。Leupaxin的LD3基序对于与FAK的稳定关联至关重要，对于Leupaxin的抑制能力是必不可少的。此外，leupaxin减少了NIH3T3细胞在纤连蛋白上的扩散，而纤连蛋白需要LD3基序和LIM3结构域。当在人白细胞K562细胞中表达时，leupaxin显著抑制整合素α5β1介导的细胞对纤维连接蛋白的粘附和paxillin的酪氨酸磷酸化。这些发现表明，在整合素信号传导过程中，leupaxin作为一种白细胞特异性对偶物有效地抑制paxillin的酪氨酸磷酸化

Although the adhesion and locomotion of leukocytes largely depend on integrins, leukocytes often lack the distinguishable focal adhesions (FAs) that serve as signaling centers in other adherent cells. The assembly and disassembly of FAs is regulated by locally produced intracellular signals, and tyrosine phosphorylation of paxillin has been implicated in this process. Aleukocyte-specific adaptor protein, leupaxin, is a member of the paxillin family and shares overall structural characteristics with paxillin. Leupaxin is composed of multiple functional trbodules, including LD motifs and LIM domains, suggesting that leupaxin also serves as a molecular adaptor that is involved in integrinmediated signaling. However, it remains unknown whether leupaxin and paxillin cooperate with or antagonize each other in integrin signaling. We found that leupaxin potently represses the tyrosine phosphorylation of paxillin. When expressed in mouse thymoma BW5147 cells bound to ICAM-1, leupaxin accumulate … More d in FA like patches in the cell periphery In BW5147 cells migrating on ICAM-1, leupaxin is selectively located at the trailing edge. When expressed in NIH3T3 and HEK293Tcells, leupaxin localized to FAs upon cell adhesion to fibronectin and strongly suppressed the integrin-induced tyrosine phosphorylation of paxillin. In integrin-stimulatecd HEK293Tcells, leupaxin's LIM3 domain appeared essential for the selective FA localization and the suppression of paxillin tyrosine phosphorylation. Leupaxin's LD3 motif, which is critical for stable association with FAK, was dispensable for leupaxin's suppressive ability. In addition, leupaxin reduced the spreading of NIH3T3 cells on fibronectin, which required both the LD3 motif and LIM3 domain. When expressed in human leukocytic K562 cells, leupaxin significantly suppressed integrin α5β1-mediated cell adhesion to fibronectin and the tyrosine phosphorylation of paxillin. These findings indicate that leupaxin functions as a leukocyte-specific counterpart that potently suppresses the tyrosine phosphorylarion of paxillin during integrin signaling Less