The role of Junctional Adhesion Molecule-A (JAM-A) in cell polarity and mitosis

脊椎动物的上皮细胞和内皮细胞嵌入在排列在身体内表面的细胞膜中。单个细胞有不同的膜区，一个顶区是自由的，另一个是与其他细胞和细胞外基质接触的基侧区；这通常被称为尖基底膜极性。顶端和基侧膜域在细胞-细胞接触部位的顶端区域被紧密连接(TJ)分开。最近的证据表明，TJs的信号转导调节细胞的增殖、分化和凋亡。我们的兴趣集中在定位于TJ的一小类细胞黏附分子，即连接黏附分子(JAMs)。我们以前已经鉴定了几个与JAM相关的PDZ结构域蛋白，包括细胞极性蛋白PAR-3，我们发现了间接证据表明，同亲的JAM-A相互作用诱导了TJ和基底膜极性形成所需的信号事件。在初步实验中，我们发现JAM-A在体外和体内都被PKC磷酸化。本提案的具体目的是：(1)分析JAM-A同亲相互作用诱导的信号通路；(2)分析JAM-A磷酸化在TJ和细胞极性形成中的作用；(3)分析JAM-A和JAM-A磷酸化在有丝分裂过程中的作用。

Vertebrate epithelial and endothelial cells are embedded in cellular sheets that line the inner surfaces of the body. The individual cells have distinct membrane domains, an apical domain which is free and a basolateral domain which is in contact with other cells and the extracellular matrix; this is commonly referred to as apico-basal membrane polarity. The apical and basolateral membrane domains are separated by tight junctions (TJ) at the apical region of the cell-cell contact sites. Recent evidence indicates that signaling from and to TJs regulates cell proliferation, differentiation and apoptosis. Our interest is focused on a small family of cell adhesion molecules localized at TJs, the Junctional Adhesion Molecules (JAMs). We have previously identified several PDZ domain proteins associated with JAMs including the cell polarity protein PAR-3, and we have found indirect evidence that homophilic JAM-A interactions induce signalling events required for TJ and apico-basal membrane polarity formation. In preliminary experiments, we have found that JAM-A is phosphorylated by PKC in vitro and in vivo. The specific aims of the present proposal is: (1) to analyze the signaling pathway induced by JAM-A homophilic interactions, (2) to analyze the role of JAM-A phosphorylation for TJ and cell polarity formation, (3) to analyze the role of JAM-A and JAM-A phosphorylation during mitosis.