Receptor-induced activation of Drosophila TRP γ by polyunsaturated fatty acids

Cellular calcium homeostasis is regulated by hormones and neurotransmitters, resulting in the activation of a variety of proteins, in particular, channel proteins of the plasma membrane and of intracellular compartments. Such channels are, for example, TRP channels of the TRPC protein family that are activated by various mediators from receptor-stimulated signaling cascades. In Drosophila, two TRPC channels, TRP and TRPL, are involved in phototransduction. In addition, a third Drosophila TRPC channel, TRP gamma, has been identified and described as an auxiliary subunit of TRPL. Beyond it, our data show that heterologously expressed TRP gamma formed a receptor-activated, outwardly rectifying cation channel independent from TRPL coexpression. Analysis of the activation mechanism revealed that TRP gamma is activated by various polyunsaturated fatty acids generated in a phospholipase C- and phospholipase A(2)- dependent manner. The most potent activator of TRP gamma, the stable analogue of arachidonic acid, 5,8,11,14-eicosatetraynoic acid, induced currents in single channel recordings. Here we show that upon heterologous expression TRP gamma forms a homomeric channel complex that is activated by polyunsaturated fatty acids as mediators of receptor- dependent signaling pathways. Reverse transcription PCR analysis showed that TRP gamma is expressed in Drosophila heads and bodies. Its body- wide expression pattern and its activation mechanism suggest that TRP gamma forms a fly cation channel responsible for the regulation of intracellular calcium in a variety of hormonal signaling cascades.