Department of Molecular Biology and Genetics, 107 Biotechnology Building, Cornell University, Ithaca, NY 14853, USA.
Dev Biol. 2010 Apr 1;340(1):88-98. doi: 10.1016/j.ydbio.2010.01.023. Epub 2010 Feb 1.
PAR-6 is a conserved protein important for establishment and maintenance of cell polarity in a variety of metazoans. PAR-6 proteins function together with PAR-3, aPKC and CDC-42. Mechanistic details of their interactions, however, are not fully understood. We studied the biochemical interactions between C. elegans PAR-6 and its binding partners and tested the requirements of these interactions in living worms. We show that PB1 domain-mediated binding of PAR-6 to PKC-3 is necessary for polarity establishment and PAR-6 cortical localization in C. elegans embryos. We also show that binding of PAR-6 and PAR-3 is mediated in vitro by a novel type of PDZ-PDZ interaction; the betaC strand of PAR-6 PDZ binds the betaD strand of PAR-3 PDZ1. However, this interaction is dispensable in vivo for PAR-6 function throughout the life of C. elegans. Mutations that specifically abolish conventional ligand binding to the PAR-6 PDZ domain also failed to affect PAR-6 function in vivo. We conclude that PAR-6 binding to PKC-3, but not to PAR-3 nor to a conventional PDZ ligand, is required for PAR-6 cortical localization and function in C. elegans.
PAR-6 是一种保守的蛋白质，对各种后生动物细胞极性的建立和维持很重要。PAR-6 蛋白与 PAR-3、aPKC 和 CDC-42 一起发挥作用。然而，它们相互作用的机制细节还不完全清楚。我们研究了秀丽隐杆线虫 PAR-6 与其结合伴侣之间的生化相互作用，并在活体蠕虫中测试了这些相互作用的要求。我们表明，PAR-6 与 PKC-3 的 PB1 结构域介导的结合对于线虫胚胎极性的建立和 PAR-6 皮质定位是必要的。我们还表明，PAR-6 和 PAR-3 的结合在体外是由一种新型 PDZ-PDZ 相互作用介导的；PAR-6 PDZ 的 betaC 链结合 PAR-3 PDZ1 的 betaD 链。然而，这种相互作用在体内对于线虫的整个生命周期中 PAR-6 的功能是可有可无的。专门消除 PAR-6 PDZ 结构域与传统配体结合的突变也未能影响 PAR-6 在线虫体内的功能。我们得出的结论是，PAR-6 与 PKC-3 的结合，而不是与 PAR-3 或与传统 PDZ 配体的结合，对于 PAR-6 在秀丽隐杆线虫中的皮质定位和功能是必需的。
