RNA-induced silencing attenuates G protein-mediated calcium signals

Phospholipase C beta (PLC beta) is activated by G protein subunits in response to environmental stimuli to increase intracellular calcium. In cells, a significant portion of PLC beta is cytosolic, where it binds a protein complex required for efficient RNA-induced silencing called C3PO (component 3 promoter of RISC). Binding between C3PO and PLC beta raises the possibility that RNA silencing activity can affect the ability of PLC beta to mediate calcium signals. By use of human and rat neuronal cell lines (SK-N-SH and PC12), we show that overexpression of one of the main components of C3PO diminishes Ca2+ release in response to G alpha(q)/PLC beta stimulation by 30 to 40%. In untransfected SK-N-SH or PC12 cells, the introduction of siRNA(GAPDH) [small interfering RNA(glyceraldehyde 3-phosphate dehydrogenase)] reduces PLC beta-mediated calcium signals by similar to 30%, but addition of siRNA(Hsp90) (heat shock protein 90) had little effect. Fluorescence imaging studies suggest an increase in PLC beta-C3PO association in cells treated with siRNA(GAPDH) but not siRNA(Hsp90). Taken together, our studies raise the possibility that Ca2+ responses to extracellular stimuli can be modulated by components of the RNA silencing machinery.-Philip, F., Sahu, S., Golebiewska, U., Scarlata, S. RNA-induced silencing attenuates G protein-mediated calcium signals. www.fasebj.org