Dokainish Hatem, Gavicherla Balramakrishna, Shen Yang, Ireton Keith
Department of Medical Genetics and Microbiology, University of Toronto, Toronto, ON, M5S 1A8, Canada.
Cell Microbiol. 2007 Oct;9(10):2497-516. doi: 10.1111/j.1462-5822.2007.00976.x.
The intracellular bacterial pathogen Listeria monocytogenes causes food-borne illnesses leading to gastroenteritis, meningitis or abortion. Listeria induces its internalization into some mammalian cells through binding of the bacterial surface protein InlB to its host receptor, the Met Receptor Tyrosine Kinase. InlB-induced activation of Met stimulates host signal transduction pathways that culminate in cell surface changes driving pathogen engulfment. One mammalian protein with the potential to couple Met to downstream signalling is the adaptor CrkII. CrkII contains an unusual carboxyl-terminal SH3 domain (SH3C) that promotes entry of Listeria. However, binding partners or downstream effectors of SH3C remain unknown. Here, we use RNA interference and overexpression studies to demonstrate that SH3C affects bacterial uptake, at least in part, through stimulation of host phosphatidylinositide (PI) 3-kinase. Experiments with latex beads coated with InlB protein indicated that one potential role of SH3C and PI 3 kinase is to promote changes in the F-actin cytoskeleton necessary for particle engulfment. Taken together, our results indicate that the CrkII SH3C domain engages a cellular ligand that regulates PI 3 kinase activity and host cell surface rearrangements.
细胞内细菌病原体单核细胞增生李斯特菌可引发食源性疾病，导致肠胃炎、脑膜炎或流产。李斯特菌通过其表面蛋白InlB与宿主受体——甲硫氨酸受体酪氨酸激酶（Met）结合，诱导自身内化进入某些哺乳动物细胞。InlB诱导的Met激活会刺激宿主信号转导通路，最终导致细胞表面变化，促使病原体被吞噬。一种有可能将Met与下游信号传导相偶联的哺乳动物蛋白是衔接蛋白CrkII。CrkII含有一个不寻常的羧基末端SH3结构域（SH3C），该结构域可促进李斯特菌的进入。然而，SH3C的结合伴侣或下游效应器仍不清楚。在此，我们利用RNA干扰和过表达研究来证明，SH3C至少部分地通过刺激宿主磷脂酰肌醇（PI）3激酶来影响细菌摄取。用包被InlB蛋白的乳胶珠进行的实验表明，SH3C和PI 3激酶的一个潜在作用是促进颗粒吞噬所需的F-肌动蛋白细胞骨架的变化。综上所述，我们的结果表明，CrkII的SH3C结构域与一种调节PI 3激酶活性和宿主细胞表面重排的细胞配体相互作用。
