G protein activation is the mechanism by which extracellular molecular signals are converted into intracellular responses and was previously thought to be exclusively triggered by extracellular stimuli. But, in October 21 Cell, Matthias Schaefer and colleagues from the Research Institute of Molecular Pathology in Vienna show the first in vivo evidence for G protein activation solely by an intracellular protein.

Schaefer et al. studied the mechanism Drosophila employs to orient cell division in the nervous system. They found that asymmetric activation of heterotrimeric G proteins by a receptor-independent mechanism controls asymmetric cell divisions in different cell types. The G protein subunit Gαi localized apically in neuroblasts and anteriorly in sensory organ precursor cells before and during mitosis. In addition, subunit Gαi was colocalized and associated with the Pins (Partner of Inscuteable) protein that induces the release of the βγ subunit. They conclude that Pins could act as a...

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