Role of glutamine synthetase in angiogenesis beyond glutamine synthesis

Guy Eelen, Charlotte Dubois, Anna Rita Cantelmo, Jermaine Goveia, Ulrike Brüning, Michael DeRan, Gopala Jarugumilli, Jos van Rijssel, Giorgio Saladino, Federico Comitani, Annalisa Zecchin, Susana Rocha, Rongyuan Chen, Hongling Huang, Saar Vandekeere, Joanna Kalucka, Christian Lange, Francisco Morales-Rodriguez, Bert Cruys, Lucas Treps, Leanne Ramer, Stefan Vinckier, Katleen Brepoels, Sabine Wyns, Joris Souffreau, Luc Schoonjans, Wouter H Lamers, Yi Wu, Jurgen Haustraete, Johan Hofkens, Sandra Liekens, Richard Cubbon, Bart Ghesquière, Mieke Dewerchin, Francesco L Gervasio, Xuri Li, Jaap D van Buul, Xu Wu, Peter Carmeliet (see publication in Journal )


Glutamine synthetase, encoded by the gene GLUL, is an enzyme that converts glutamate and ammonia to glutamine. It is expressed by endothelial cells, but surprisingly shows negligible glutamine-synthesizing activity in these cells at physiological glutamine levels. Here we show in mice that genetic deletion of Glul in endothelial cells impairs vessel sprouting during vascular development, whereas pharmacological blockade of glutamine synthetase suppresses angiogenesis in ocular and inflammatory skin disease while only minimally affecting healthy adult quiescent endothelial cells. This relies on the inhibition of endothelial cell migration but not proliferation. Mechanistically we show that in human umbilical vein endothelial cells GLUL knockdown reduces membrane localization and activation of the GTPase RHOJ while activating other Rho GTPases and Rho kinase, thereby inducing actin stress fibres and impeding endothelial cell motility. Inhibition of Rho kinase rescues the defect in endothelial cell migration that is induced by GLUL knockdown. Notably, glutamine synthetase palmitoylates itself and interacts with RHOJ to sustain RHOJ palmitoylation, membrane localization and activation. These findings reveal that, in addition to the known formation of glutamine, the enzyme glutamine synthetase shows unknown activity in endothelial cell migration during pathological angiogenesis through RHOJ palmitoylation.