Disheveled regulates precoupling of heterotrimeric G proteins to Frizzled 6
| Authors | |
|---|---|
| Year of publication | 2014 |
| Type | Article in Periodical |
| Magazine / Source | FASEB JOURNAL |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1096/fj.13-246363 |
| Field | Genetics and molecular biology |
| Keywords | GNAI1; GNAQ; GPCR; WNT-5A |
| Description | Frizzleds (FZDs) are classified as G-protein-coupling receptors, but how signals are initiated and specified through heterotrimeric G proteins is unknown. FZD6 regulates convergent extension movements, and its C-terminal Arg511Cys mutation causes nail dysplasia in humans. We investigated the functional relationship between FZD6, Disheveled (DVL), and heterotrimeric G proteins. Live cell imaging combined with fluorescence recovery after photobleaching (FRAP) revealed that inactive human FZD6 precouples to GALPHAi1 and GALPHAq but not to GALPHAoA,GALPHAs, and GALPHA12 proteins. G-protein coupling is measured as a 10-20% reduction in the mobile fraction of fluorescently tagged G proteins on chemical receptor surface cross-linking. The FZD6 Arg511Cys mutation is incapable of G-protein precoupling, even though it still binds DVL. Using both FRAP and Förster resonance energy transfer (FRET) technology, we showed that the FZD6-GALPHAi1 and FZD-GALPHAq complexes dissociate on WNT-5A stimulation. Most important, G-protein precoupling of FZD6 and WNT-5A-induced signaling to extracellular signal-regulated kinase1/2 were impaired by DVL knockdown or overexpression, arguing for a strict dependence of FZD6-G-protein coupling on DVL levels and identifying DVL as a master regulator of FZD/G-protein signaling. In summary, we propose a mechanistic connection between DVL and G proteins integrating WNT, FZD, G-protein, and DVL function. |
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