The lipoglycoproteins of the WNT family act on seven transmembrane-spanning Class Frizzled receptors. Here, we show that WNT-5A evokes a proliferative response in a mouse microglia-like cell line (N13), which is sensitive to pertussis toxin, thus implicating the involvement of heterotrimeric G proteins of the G(i/o) family. We continue to show that WNT-5A stimulation of N13 membranes and permeabilized cells evokes the exchange of GDP for GTP of pertussis toxin-sensitive G proteins employing [γ-(35)S]GTP assay and activity state-specific antibodies to GTP-bound G(i) proteins. Our functional analysis of the PTX-sensitivity of WNT-induced G protein activation and PCR analysis of G protein and FZD expression patterns suggest that WNT-5A stimulation leads to the activation of G(i2/3) proteins in N13 cells possibly mediated by FZD(5), the predominant FZD expressed. In summary, we provide for the first time molecular proof that WNT-5A stimulation results in the activation of heterotrimeric G(i2/3) proteins in mammalian cells with physiological protein stochiometry.
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