Mechanism of differential adhesion by protocadherin-cadherin complexes

描述(由申请人提供)：通过协调细胞运动、区域分割、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。钙粘蛋白超家族包括大量的、多样化的细胞表面受体，包括经典的钙粘蛋白和原钙粘蛋白。经典钙粘附素和原钙粘附素都被认为在发育中的大脑中扮演着建立神经回路的角色。虽然经典的钙粘附素是已知的亲性细胞黏附分子，但原钙粘附素在细胞黏附中的作用仍不确定。在我们以前的工作中，我们发现原钙粘蛋白-19(Pcdh19)与N-钙粘蛋白(Ncad)结合形成了一个异构体顺式复合体。在初步数据中，我们表明Pcdh19作为Pcdh19-Ncad复合体的一部分介导了亲性黏附，尽管它本身不是黏附的。这一设想的主要假设是原钙粘附素与经典钙粘附素结合形成具有不同粘附性的顺式复合体。为了更详细地研究这一假设，我们提出了以下具体目标。在目标1中，我们将检验d-原钙粘附素家族成员与经典钙粘附素形成顺式复合体的假设，并确定这些复合体是否如我们对Pcdh19-Ncad所显示的那样介导亲水性黏附。在目标2中，我们将首先确定构成粘合界面的Pcdh19中的残基，然后确定这一机制是否适用于Pcdh-CDH络合物。从这些实验中获得的见解将阐明一种新的细胞黏附机制的分子基础，并将促进我们对原钙粘附素和钙粘附素功能的了解，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。 公共卫生相关性：原钙粘附素和钙粘附素与许多神经发育障碍有关，包括自闭症、精神分裂症、癫痫和智力低下。尽管原钙粘附素对神经发育很重要，但人们对它们的分子和细胞功能或发育作用知之甚少。我们的研究将极大地促进我们对原钙粘附素细胞黏附机制的了解，并为了解它们在脊椎动物神经系统发育中的作用提供基础。

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. PUBLIC HEALTH RELEVANCE: Protocadherins and cadherins have been implicated in a number of neurodevelopment disorders, including autism, schizophrenia, epilepsy and mental retardation. Despite the importance of protocadherins to neural development, very little is known about their molecular and cellular functions or developmental roles. Our studies will dramatically advance our knowledge of the mechanism of cell adhesion by the protocadherins and provide a foundation for understanding their roles in the development of the vertebrate nervous system.