Modulation and Targeting of Kainate Receptors

说明： 谷氨酸对NMDA、AMPA和海人酸亲离子受体具有门控作用。对于凯恩特 受体，相对较少知道它们的功能是如何调节的 通过亚单位组成或锚定分子，如突触后密度 蛋白质(PSD/SAP)。我们最近的工作表明，PSD-95/SAP9O是协同定位的 与突触上的海人酸受体结合，结合海人酸受体Ka2和GIuR6 亚基，并显著修改GluR6和Ka2/G1uR6生理学(Garcia et Al.，1998)。我们发现酪氨酸磷酸化与 生理反应和潜在调节分子的修饰， SRC和MSS4(一种鸟核苷酸交换因子)优先关联 分别使用Ka2和PSD-95/SAP90。此外，我们还发现，两者 关联受Ka2-PSD-95/SAP9O相互作用的调节，以及 此外，SAP97不能与含有Ka2的受体结合。一起， 这些结果表明，PSD蛋白可能不仅在锚定中起作用 受体在突触部位，但也在调节受体的活动，其中 受体亚型存在于给定的部位。 该提案将建立PSD-95/SAP9O监管海人酸的机制 受体功能和靶向。我们将评估它是如何调节受体的 活性以及调节是否依赖于受体亚单位组成，决定 激动剂亲和力、脱敏特性和对抑制剂的敏感性。 对于可能的机制，我们将研究配体的结合，如GKAP， GK结构域可促进PSD-95的SH3结构域与 决定酪氨酸的KA2和PSD-95上的分子位点 磷酸化，以及MSS4和PSD-95/SAP9O上调节的位点 将确定MSS4-PSD-95/SAP9O-Ka2相互作用。生理学 这些相互作用和src对Ka2和PSD-95的影响将是 通过表达带有受体亚基的活性和非活性酶而建立的 (野生型与突变型)。确定MSS4对受体的潜在调节作用 靶向、受体的表面表达和受体分布 (集群化与非集群化)将进行评估。这些研究预计将 提供有关如何确定功能属性的新颖信息 通过控制受体聚集/靶向的机制 特定的亚基组成。

DESCRIPTION: Glutamate gates NMDA, AMPA and kainate ionotropic receptors. For kainate receptors, comparatively little is known about how their function is regulated by subunit composition or anchoring molecules such as postsynaptic density proteins (PSD/SAP). Our recent work demonstrates that PSD-95/SAP9O colocalizes with kainate receptors at synapses, binds the kainate receptor KA2 and GIuR6 subunits, and significantly modifies GluR6 and KA2/G1uR6 physiology (Garcia et al., 1998). We find that tyrosine phoshorylation correlates with the modification of physiological response and that potential regulatory molecules, src and mss4 (a guanine nucleotide exchange factor) preferentially associate with, respectively, KA2 and PSD-95/SAP9O. Furthermore, we also find that both associations are regulated by the KA2-PSD-95/SAP9O interaction, and additionally that SAP97 is unable to bind KA2-containing receptors. Together, the results imply that PSD proteins may function not only in anchoring receptors at synaptic Sites, but also in regulating receptor activity and which receptor subtypes are present in a given site. This proposal will establish mechanisms by which PSD-95/SAP9O regulates kainate receptor function and targeting. We will assess how it regulates receptor activity and if regulation depends on receptor subunit composition, determining agonist affinities, desensitization properties and sensitivity to inhibitors. For potential mechanisms, we will examine how binding of ligands, such as GKAP, to the GK domain may promote the association of the SH3 domain of PSD-95 with KA2, the molecular sites on KA2 and PSD-95 that determine tyrosine phosphorylation, as well as the sites on mss4 and PSD-95/SAP9O that regulate mss4-PSD-95/SAP9O-KA2 interactions will be identified. The physiological effects of these interactions and those of src on KA2 and PSD-95, will be established by expressing active and inactive enzymes with receptor subunits (wild-type vs. mutated). To determine potential mss4 regulation of receptor targeting, the surface expression of receptors and receptor distribution (clustered vs. unclustered) will be evaluated. These studies are expected to provide novel information on how functional properties can be determined through mechanisms controlling the clustering/targeting of receptors of specific subunit composition.