WNT Stimulation Dissociates a Frizzled 4 Inactive-State Complex with Gα12/13

• Published in: Molecular pharmacology Vol. 90; no. 4; pp. 447 - 459
• Main Authors: Arthofer, Elisa, Hot, Belma, Petersen, Julian, Strakova, Katerina, Jäger, Stefan, Grundmann, Manuel, Kostenis, Evi, Gutkind, J Silvio, Schulte, Gunnar
• Format: Journal Article
• Language: English
• Published: United States The American Society for Pharmacology and Experimental Therapeutics 01.10.2016
• Subjects: Dishevelled Proteins - metabolism; Fluorescence Recovery After Photobleaching; Fluorescence Resonance Energy Transfer; Frizzled Receptors - chemistry; Frizzled Receptors - metabolism; Green Fluorescent Proteins - metabolism; GTP-Binding Protein alpha Subunits, G12-G13 - metabolism; HEK293 Cells; Humans; Medicin och hälsovetenskap; Protein Binding - drug effects; Protein Domains; Rho Guanine Nucleotide Exchange Factors - metabolism; Signal Transduction - drug effects; Wnt Proteins - pharmacology
• DOI: 10.1124/mol.116.104919
• ISSN: 0026-895X; 1521-0111

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.