Functional analysis of FAK tyrosine kinase in intracellular signaling pathways

FAK蛋白酪氨酸激酶在脊椎动物细胞粘附中起重要作用。利用基于PCR的克隆策略，我们克隆了一个果蝇基因，该基因与脊椎动物FAK蛋白酪氨酸激酶家族同源。我们将该基因命名为Dfak 56，并对其基因产物进行了表征。Dfak 56的蛋白质结构和推导的氨基酸序列与FAK和PYK 2有很大的相似性。Dfak 56在体外对酪氨酸残基具有自磷酸化活性。Dfak 56 mRNA和蛋白质的表达被观察到在中枢神经系统和肌肉-表皮附着位点的胚胎，果蝇的位置特异性整合素定位。结果表明，像脊椎动物中的FAK一样，Dfak 56在整合素下游发挥作用。Dfak 56在细胞与细胞外基质的整合素依赖性附着后被酪氨酸磷酸化。我们的结论是Dfak 56酪氨酸激酶参与整合素介导的细胞粘附信号，因此，是脊椎动物FAK的功能同源物。

The FAK protein-tyrosine kinase plays important roles in cell adhesion in vertebrates. Using PCR-based cloning strategy, we cloned a Drosophila gene that was homologous to the vertebrate FAK family of protein-tyrosine kinases. We designated this gene Dfak56, and characterized its gene product. The overall protein structure and deduced amino acid sequence of Dfak56 showed significant similarity to FAK and PYK2. Dfak56 had in, vitro autophosphorylation activity on tyrosine residues. Expression of the Dfak56 mRNA and the protein was observed in the central nervous system and muscle-epidermis attachment site in the embryo, where Drosophila position-specific integrins are localized. The results suggest that like FAK in vertebrates, Dfak56 functions downstream of integrins. Dfak56 was tyrosine-phosphorylated upon integrin-dependent attachment of the cell to the extracellular matrix. We conclude that the Dfak56 tyrosine kinase is involved in integrin-mediated cell adhesion signaling and thus, is a functional homolog of vertebrate FAK.