Competing activities of heterotrimeric G proteins in Drosophila wing maturation

Drosophila genome encodes six alpha-subunits of heterotrimeric G proteins. The Galphas alpha-subunit is involved in the post-eclosion wing maturation, which consists of the epithelial-mesenchymal transition and cell death, accompanied by unfolding of the pupal wing into the firm adult flight organ. Here we show that another alpha-subunit Galphao can specifically antagonize the Galphas activities by competing for the Gbeta13F/Ggamma1 subunits of the heterotrimeric Gs protein complex. Loss of Gbeta13F, Ggamma1, or Galphas, but not any other G protein subunit, results in prevention of post-eclosion cell death and failure of the wing expansion. However, cell death prevention alone is not sufficient to induce the expansion defect, suggesting that the failure of epithelial-mesenchymal transition is key to the folded wing phenotypes. Overactivation of Galphas with cholera toxin mimics expression of constitutively activated Galphas and promotes wing blistering due to precocious cell death. In contrast, co-overexpression of Gbeta13F and Ggamma1 does not produce wing blistering, revealing the passive role of the Gbetagamma in the Galphas-mediated activation of apoptosis, but hinting at the possible function of Gbetagamma in the epithelial-mesenchymal transition. Our results provide a comprehensive functional analysis of the heterotrimeric G protein proteome in the late stages of Drosophila wing development.