MECHANISMS INVOLVED IN THE INTRACELLULAR RETENTION OF A2C ADRENERGIC RECEPTOR

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 最近的实验证据表明α2C肾上腺素能受体(AR)在雷诺现象(RP)中起着重要作用。在37℃时，该受体亚型在细胞膜上表达较弱，在内质网和高尔基体中聚集。冷暴露后，Alpha2C-AR到细胞表面的流量大大增加。结构分析表明，α2C-AR在第三胞内环和C末端有异常高数量的精氨酸(R)残基，由11个推测的精氨酸分类基序(RXR)组成。当嵌入其他蛋白质时，这个RXR基序已被证明可以诱导内质网滞留。我们的初步实验表明，从第三细胞内环中删除8个可能的RXR基序极大地促进了30oC下的α2C-AR转运。基于这一观察，我们的总体假设是，Alpha2C-AR中独特的结构基序调控其贩运。该实验计划旨在区分内质网停滞和高尔基体运输受阻对质膜的贡献，并将通过识别对α2C-AR运输具有温度敏感性的RXR基序并确定参与这些影响的分子机制来阐明α2C交通调制所涉及的机制。此外，还将研究Rab8和Rab14 GTP酶在温度敏感型α2C-AR受体质膜表达中的作用。这些研究将提供关于α2C-AR细胞内蓄积的分子决定因素的新的和重要的信息，并可能为设计更有效的雷诺现象治疗策略提供基础。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Recent experimental evidence indicates an important role of alpha2C adrenergic receptor (AR) in Raynaud Phenomenon (RP). This receptor subtype is poorly expressed at the plasma membrane at 37oC, accumulating in endoplasmic reticulum (ER) and Golgi apparatus. Alpha2C-AR traffic to the cell surface is greatly enhanced after cold exposure. Structural analysis indicate that alpha2C-AR has an unusual high number of arginine (R) residues in the third intracellular loop and in the C-terminus, organized in eleven putative arginine sorting motifs (RXR). When embedded in other proteins, this RXR motif has been shown to induce ER retention. Our preliminary experiments demonstrated that deletion of the eight putative RXR motifs from the third intracellular loop greatly enhanced alpha2C-AR transport at 30oC. Based on this observation, our overall hypothesis is that unique structural motifs in alpha2C-AR regulate its trafficking. The experimental plan aims to distinguish between the contributions of ER arrest and obstruction of transport from Golgi to the plasma membrane and it will elucidate the mechanisms involved in the alpha2C traffic modulation by identifying the RXR motifs conferring temperature sensitivity to alpha2C-AR transport and determining the molecular mechanisms involved in these effects. Further, the role of Rab8 and Rab14 GTPases in the temperature sensitive alpha2C-AR receptor plasma membrane expression will be studied. These studies will produce novel and important information regarding the molecular determinants of alpha2C-AR intracellular accumulation and may provide foundation for designing more effective therapeutic strategies in Raynaud Phenomenon.