Vargas Elizabeth, Penkert Rhiannon R, Prehoda Kenneth E
Department of Chemistry and Biochemistry, Institute of Molecular Biology, 1229 University of Oregon, Eugene, Oregon, USA.
Department of Chemistry and Biochemistry, Institute of Molecular Biology, 1229 University of Oregon, Eugene, Oregon, USA.
J Biol Chem. 2025 Feb;301(2):108097. doi: 10.1016/j.jbc.2024.108097. Epub 2024 Dec 18.
The Par complex polarizes the plasma membrane of diverse animal cells using the catalytic activity of atypical PKC (aPKC) to pattern substrates. Two upstream regulators of the Par complex, Cdc42 and Par-3, bind separately to the complex to influence its activity in different ways. Each regulator binds a distinct member of the complex, Cdc42 to Par-6 and Par-3 to aPKC, making it unclear how they influence one another's binding. Here, we report the discovery that Par-3 binding to aPKC is regulated by aPKC autoinhibition and link this regulation to Cdc42 and Par-3 exchange. The Par-6 PDZ domain activates aPKC binding to Par-3 via a novel interaction with the aPKC kinase domain. Cdc42 and Par-3 have opposite effects on the Par-6 PDZ-aPKC kinase interaction: while the Par-6 kinase domain interaction competes with Cdc42 binding to the complex, Par-3 binding is enhanced by the interaction. The differential effect of Par-3 and Cdc42 on the Par-6 PDZ interaction with the aPKC kinase domain forms an allosteric relay that connects their binding sites and is responsible for the negative cooperativity that underlies Par complex polarization and activity.
Par复合物利用非典型蛋白激酶C（aPKC）的催化活性使多种动物细胞的质膜极化，从而对底物进行模式化。Par复合物的两个上游调节因子Cdc42和Par-3分别与该复合物结合，以不同方式影响其活性。每个调节因子都与复合物的一个不同成员结合，Cdc42与Par-6结合，Par-3与aPKC结合，这使得它们如何相互影响彼此的结合尚不清楚。在此，我们报告了一项发现，即Par-3与aPKC的结合受aPKC自身抑制的调节，并将这种调节与Cdc42和Par-3的交换联系起来。Par-6的PDZ结构域通过与aPKC激酶结构域的新型相互作用激活aPKC与Par-3的结合。Cdc42和Par-3对Par-6 PDZ-aPKC激酶相互作用具有相反的影响：虽然Par-6激酶结构域的相互作用与Cdc42与复合物的结合竞争，但Par-3的结合因这种相互作用而增强。Par-3和Cdc42对Par-6 PDZ与aPKC激酶结构域相互作用的不同影响形成了一个变构中继，连接它们的结合位点，并导致Par复合物极化和活性的负协同作用。
