PT  - JOURNAL ARTICLE
AU  - Elisa Arthofer
AU  - Belma Hot
AU  - Julian Petersen
AU  - Katerina Strakova
AU  - Stefan Jager
AU  - Manuel Grundmann
AU  - Evi Kostenis
AU  - Silvio J Gutkind
AU  - Gunnar Schulte
TI  - WNT stimulation dissociates a Frizzled 4 inactive state complex with Gα12/13
AID  - 10.1124/mol.116.104919
DP  - 2016 Jan 01
TA  - Molecular Pharmacology
PG  - mol.116.104919
4099  - http://molpharm.aspetjournals.org/content/early/2016/07/22/mol.116.104919.short
4100  - http://molpharm.aspetjournals.org/content/early/2016/07/22/mol.116.104919.full
AB  - Frizzleds are unconventional G protein-coupled receptors (GPCRs) that belong to the Class Frizzled. They are bound and activated by the 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 Gα12/13 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 (FEVR). Live cell imaging experiments employing fluorescence recovery after photobleaching (FRAP) 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 (DMR) changes in untransfected and - even more so - in FZD4-GFP transfected cells depend on Gα12/13. Furthermore, expression of FZD4 and Gα12 or Gα13 in HEK293 cells induces WNT-dependent membrane recruitment of p115-RHOGEF, a direct target of Gα12/13 signaling, underlining the functionality of a 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.