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Participation of Gq alpha subunit in PKD1-dependent intracellular trafficking regulation Coria, Andrea Soledad; Masseroni, María Luján; and Díaz Añel, Alberto Marcelo Instituto de Investigación Médica "Mercedes y Martín Ferreyra", Córdoba, Argentina We have previously described the role of heterotrimeric G proteins bg subunits in the regulation of vesicle fission at the Trans-Golgi Network (TGN), where they activate a pathway that consist of Phospholipase C b3 (PLCb3), PKCh and PKD1. Since Gq a subunits are also able to activate PLCbs, we have decided to study the involvement of these proteins in traffic regulation. Our results showed that constitutive active mutants of Gaq (QL mutants) were able to induce vesicle fission at the Golgi level, leading to a complete fragmentation of this organelle, while other GaQL mutants (s, i2) did not have any effect in fission. This vesiculation was accompanied with the activation of PKD1 by phosphorylation in its activation loop. Specific PLC and PKC inhibitors, and an inactive PKD1 mutant (PKD kinase dead) were able to block the effect of GaqQL in membrane fission, suggesting that these subunits participate in the same or in a similar pathway as the one initiated by bg subunits. On the other hand, a non-palmytoylated mutant of GaqQL could not induce Golgi fragmentation, demonstrating that its localization in membranes is necessary to be completely effective. Finally, Pasteurella multocida toxin, a Gaq activator, produced an augment in transport due to an increase in vesicle fission, confirming the participation of these G protein subunits on the regulation of TGN to cell surface trafficking.