Abstract：
G protein-coupled receptors (GPCRs) are a family of cell membrane receptors that couple and activate heterotrimeric G proteins and their associated intracellular signalling processes after ligand binding. Although the carboxyl terminal of the receptors is essential for this action, it can also serve as a docking site for regulatory proteins such as the β-arrestins. Prokineticin receptors (PKR1 and PKR2) are a new class of GPCRs that are able to activate different classes of G proteins and form complexes with β-arrestins after activation by the endogenous agonists PK2. The aim of this work was to define the molecular determinants within PKR2 that are required for β-arrestin-2 binding and to investigate the role of β-arrestin-2 in the signalling pathways induced by PKR2 activation. Our data show that PKR2 binds constitutively to β-arrestin-2 and that this process occurs through the core region of the receptor without being affected by the carboxy-terminal region. Indeed, a PKR2 mutant lacking the carboxy-terminal amino acids retains the ability to bind constitutively to β-arrestin-2, whereas a mutant lacking the third intracellular loop does not. Overall, our data suggest that the C-terminus of PKR2 is critical for the stability of the β-arrestin-2-receptor complex in the presence of PK2 ligand. This leads to the β-arrestin-2 conformational change required to initiate intracellular signalling that ultimately leads to ERK phosphorylation and activation.
摘要：
G蛋白偶联受体（GPCRs）是细胞膜受体家族，在配体结合后偶联并激活异源三聚体G蛋白及其相关的细胞内信号传导过程。尽管受体的羧基末端对这种作用至关重要，它也可以作为调节蛋白如β-抑制素的对接位点。前动力蛋白受体（PKR1和PKR2）是一类新的GPCR，能够激活不同类型的G蛋白，并在内源性激动剂PK2激活后与β-抑制素形成复合物。这项工作的目的是定义PKR2内β-arrestin-2结合所需的分子决定簇，并研究β-arrestin-2在PKR2激活诱导的信号传导途径中的作用。我们的数据表明，PKR2与β-抑制蛋白2组成型结合，并且该过程通过受体的核心区发生，而不受羧基末端区的影响。的确,缺乏羧基末端氨基酸的PKR2突变体保留了与β-抑制蛋白-2组成型结合的能力,而缺乏第三胞内环的突变体则没有。总的来说,我们的数据表明,PKR2的C端对于在PK2配体存在下β-抑制蛋白-2-受体复合物的稳定性至关重要.这导致启动细胞内信号传导所需的β-抑制蛋白-2构象变化，最终导致ERK磷酸化和激活。
