Mechanism of differential adhesion by protocadherin-cadherin complexes

描述（由申请人提供）：通过协调的细胞运动、区域划分、轴突靶向和突触形成，需要选择性的细胞-细胞相互作用来建立脊椎动物神经系统的精确三维结构。钙粘蛋白超家族由大量不同的细胞表面受体组成，包括经典钙粘蛋白和原钙粘蛋白。经典钙粘蛋白和原钙粘蛋白都被认为在发育中的大脑中建立神经回路中起作用。虽然已知经典钙粘蛋白是亲同性细胞粘附分子，但原钙粘蛋白在细胞粘附中的作用仍不确定。在我们之前的工作中，我们发现原钙粘蛋白-19 （Pcdh19）与n-钙粘蛋白（Ncad）结合形成异聚顺式复合物。在初步数据中，我们发现Pcdh19作为Pcdh19- ncad复合体的一部分介导亲同源性粘附，尽管它本身不具有粘附性。本研究的主要假设是原钙粘蛋白与经典钙粘蛋白结合形成具有不同粘附特性的顺式配合物。为了更详细地研究这一假设，我们提出以下具体目标。在Aim 1中，我们将验证d-原钙粘蛋白家族成员与经典钙粘蛋白形成顺式复合物的假设，并确定这些复合物是否介导亲同源粘附，正如我们在Pcdh19-Ncad中所展示的那样。在Aim 2中，我们将首先确定Pcdh19中构成粘附界面的残基，然后确定该机制是否适用于Pcdh-Cdh配合物。从这些实验中获得的见解将阐明细胞粘附新机制的分子基础，并将推进我们对原钙粘蛋白和钙粘蛋白功能的认识，为理解这些分子在神经发育中的作用和阐明建立神经连接模式的机制提供必要的基础。

DESCRIPTION (provided by applicant): Selective cell-cell interactions are required to establish the precise three-dimensional architecture of the vertebrate nervous system through coordinated cell movements, regional partitioning, axon targeting and synapse formation. The cadherin superfamily comprises a large, diverse array of cell surface receptors that includes both the classical cadherins and the protocadherins. Both classical cadherins and protocadherins have been proposed to play roles in establishing neural circuitry in the developing brain. While the classical cadherins are known to be homophilic cell adhesion molecules, the involvement of protocadherins in cell adhesion remains uncertain. In our previous work, we showed that Protocadherin-19 (Pcdh19) associates with N-cadherin (Ncad) to form a heteromeric cis-complex. In preliminary data, we show that Pcdh19 mediates homophilic adhesion as part of the Pcdh19-Ncad complex, although it is not adhesive itself. The main hypothesis of this proposal is that protocadherins associate with classical cadherins to form cis-complexes with distinct adhesive properties. To investigate this hypothesis in more detail we propose the following Specific Aims. In Aim 1, we will test the hypothesis that members of the d-protocadherin family form cis-complexes with classical cadherins and determine whether these complexes mediate homophilic adhesion, as we have shown for Pcdh19-Ncad. In Aim 2, we will first determine the residues in Pcdh19 that constitute the adhesive interface, and then determine if this mechanism is general to Pcdh-Cdh complexes. Insights gained from these experiments will elucidate the molecular underpinnings of a novel mechanism of cell adhesion and will advance our knowledge of protocadherin and cadherin function, providing an essential foundation for understanding the roles of these molecules in neural development and elucidating the mechanisms that establish patterns of neural connectivity.