Hewavitharana Thamara, Wedegaertner Philip B
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, 233 S. 10th St., 839 BLSB, Philadelphia, PA 19107, United States.
Cell Signal. 2015 Dec;27(12):2444-51. doi: 10.1016/j.cellsig.2015.08.017. Epub 2015 Aug 29.
Heterotrimeric G proteins function at diverse subcellular locations, in addition to canonical signaling at the plasma membrane (PM). Gβγ signals at the Golgi, via protein kinase D (PKD), to regulate fission of PM-destined vesicles. However, the mechanism by which Gβγ is regulated at the Golgi in this process remains elusive. Recent studies have revealed that PAQR3 (Progestin and AdipoQ Receptor 3), also called RKTG (Raf Kinase Trapping to the Golgi), interacts with the Gβ subunit and localizes Gβ to the Golgi thereby inhibiting Gβγ signaling at the PM. Herein we show that, in contrast to this inhibition of canonical Gβγ signaling at the PM, PAQR3 promotes Gβγ signaling at the Golgi. Expression of PAQR3 causes fragmentation of the Golgi, while a Gβ binding-deficient mutant of PAQR3 does not cause Golgi fragmentation. Also, a C-terminal fragment of GRK2 (GRK2ct), which interacts with Gβγ and inhibits Gβγ signaling, and gallein, a small molecule inhibitor of Gβγ, are both able to inhibit PAQR3-mediated Golgi fragmentation. Furthermore, a dominant negative form of PKD (PKD-DN) and a pharmacological inhibitor of PKD, Gö6976, also inhibit PAQR3-mediated fragmentation of the Golgi. Importantly, expression of the Gβ binding-deficient mutant of PAQR3 inhibits the constitutive transport of the model cargo protein VSV-G from the Golgi to the PM, indicating the involvement of PAQR3 in Golgi-to PM vesicle transport and a dominant negative role for this mutant. Collectively, these results reveal a novel role for the newly characterized, Golgi-localized PAQR3 in regulating Gβγ at the non-canonical subcellular location of the Golgi and thus for controlling Golgi-to-PM protein transport via the Gβγ-PKD signaling pathway.
异源三聚体G蛋白除了在质膜（PM）进行经典信号传导外，还在不同的亚细胞位置发挥作用。Gβγ通过蛋白激酶D（PKD）在高尔基体发出信号，以调节运往质膜的囊泡的分裂。然而，在此过程中Gβγ在高尔基体中被调节的机制仍不清楚。最近的研究表明，PAQR3（孕激素和脂联素受体3），也称为RKTG（Raf激酶被困于高尔基体），与Gβ亚基相互作用并将Gβ定位于高尔基体，从而抑制质膜上的Gβγ信号传导。在此我们表明，与这种对质膜上经典Gβγ信号传导的抑制相反，PAQR3促进高尔基体处的Gβγ信号传导。PAQR3的表达导致高尔基体碎片化，而PAQR3的Gβ结合缺陷突变体不会导致高尔基体碎片化。此外，与Gβγ相互作用并抑制Gβγ信号传导的GRK2的C末端片段（GRK2ct）和Gβγ的小分子抑制剂加列因都能够抑制PAQR3介导的高尔基体碎片化。此外，PKD的显性负性形式（PKD-DN）和PKD的药理学抑制剂Gö6976也抑制PAQR3介导的高尔基体碎片化。重要的是，PAQR3的Gβ结合缺陷突变体的表达抑制了模型货物蛋白VSV-G从高尔基体到质膜的组成型转运，表明PAQR3参与高尔基体到质膜的囊泡运输以及该突变体的显性负性作用。总的来说，这些结果揭示了新鉴定的高尔基体定位的PAQR3在高尔基体非经典亚细胞位置调节Gβγ从而通过Gβγ-PKD信号通路控制高尔基体到质膜的蛋白质运输中的新作用。
