PT  - JOURNAL ARTICLE
AU  - Arthofer, Elisa
AU  - Hot, Belma
AU  - Petersen, Julian
AU  - Strakova, Katerina
AU  - Jäger, Stefan
AU  - Grundmann, Manuel
AU  - Kostenis, Evi
AU  - Gutkind, J. Silvio
AU  - Schulte, Gunnar
TI  - WNT Stimulation Dissociates a Frizzled 4 Inactive-State Complex with G<em>α</em><sub>12/13</sub>
AID  - 10.1124/mol.116.104919
DP  - 2016 Oct 01
TA  - Molecular Pharmacology
PG  - 447--459
VI  - 90
IP  - 4
4099  - http://molpharm.aspetjournals.org/content/90/4/447.short
4100  - http://molpharm.aspetjournals.org/content/90/4/447.full
SO  - Mol Pharmacol2016 Oct 01; 90
AB  - Frizzleds (FZDs) are unconventional G protein–coupled receptors that belong to the class Frizzled. They are bound and activated by the Wingless/Int-1 lipoglycoprotein (WNT) family of secreted lipoglycoproteins. To date, mechanisms of signal initiation and FZD–G protein coupling remain poorly understood. Previously, we showed that FZD6 assembles with Gαi1/Gαq (but not with Gαs, Gαo and Ga12/13), and that these inactive-state complexes are dissociated by WNTs and regulated by the phosphoprotein Dishevelled (DVL). Here, we investigated the inactive-state assembly of heterotrimeric G proteins with FZD4, a receptor important in retinal vascular development and frequently mutated in Norrie disease or familial exudative vitreoretinopathy. Live-cell imaging experiments using fluorescence recovery after photobleaching show that human FZD4 assembles—in a DVL-independent manner—with Gα12/13 but not representatives of other heterotrimeric G protein subfamilies, such as Gαi1, Gαo, Gαs, and Gαq. The FZD4–G protein complex dissociates upon stimulation with WNT-3A, WNT-5A, WNT-7A, and WNT-10B. In addition, WNT-induced dynamic mass redistribution changes in untransfected and, even more so, in FZD4 green fluorescent protein–transfected cells depend on Gα12/13. Furthermore, expression of FZD4 and Gα12 or Gα13 in human embryonic kidney 293 cells induces WNT-dependent membrane recruitment of p115-RHOGEF (RHO guanine nucleotide exchange factor, molecular weight 115 kDa), a direct target of Gα12/13 signaling, underlining the functionality of an FZD4-Gα12/13-RHO signaling axis. In summary, Gα12/13-mediated WNT/FZD4 signaling through p115-RHOGEF offers an intriguing and previously unappreciated mechanistic link of FZD4 signaling to cytoskeletal rearrangements and RHO signaling with implications for the regulation of angiogenesis during embryonic and tumor development.