PAQR3 regulates Golgi vesicle fission and transport via the Gβγ-PKD signaling pathway

Heterotrimeric G proteins function at diverse subcellular locations, in addition to canonical signaling at the plasma membrane (PM). G beta gamma signals at the Golgi, via protein kinase D (PKD), to regulate fission of PM-destined vesicles. However, the mechanism by which G beta gamma, 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 G beta subunit and localizes G beta to the Golgi thereby inhibiting G beta gamma signaling at the PM. Herein we show that, in contrast to this inhibition of canonical G beta gamma signaling at the PM, PAQR3 promotes G beta gamma signaling at the Golgi. Expression of PAQR3 causes fragmentation of the Golgi, while a G beta binding-deficient mutant of PAQR3 does not cause Golgi fragmentation. Also, a C-terminal fragment of GRK2 (GRK2ct), which interacts with G beta gamma and inhibits G beta gamma signaling, and gallein, a small molecule inhibitor of G beta gamma are both able to inhibit PAQR3-mediated Golgi fragmentation. Furthermore, a dominant negative form of PKD (PKD-DN) and a pharmacological inhibitor of PKD, Go6976, also inhibit PAQR3-mediated fragmentation of the Golgi. Importantly, expression of the G beta 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 G beta gamma at the non-canonical subcellular location of the Golgi and thus for controlling Golgi-to-PM protein transport via the G beta gamma-PKD signaling pathway. (C) 2015 Elsevier Inc. All rights reserved.