Stimulation of the Gαq/phospholipase Cβ1 signaling pathway returns differentiated cells to a stem-like state.

Phospholipase C beta 1 is activated by G alpha q to generate calcium signals in response to hormones and neurotransmitters. Besides carrying out this plasma membrane function, PLC beta 1 has a cytosolic population that helps to drive the differentiation of PC12 cells by inhibiting a nuclease that promotes RNA-induced silencing (C3PO). Here, we show that down-regulating PLC beta 1 or reducing its cytosolic population by activating G alpha q to localize it to the plasma membrane returns differentiated PC12 and SK-N-SH cells to an undifferentiated state. In this state, PC12 cells have a spherical morphology, resume proliferation, and express the stem cell transcription factors nanog and Oct4. Similar changes are seen when C3PO is down-regulated. This return to a stem-like state is accompanied by shifts in multiple miR populations. Surprisingly, de-differentiation can be induced by extended stimulation of G alpha q where cells return to a spherical morphology and levels of specific miRs return to their undifferentiated values. In complementary studies, we followed the real-time hydrolysis of a fluorescent-tagged miR in cells where PLC beta 1 or C3PO were down-regulated in PC12 cells and find substantial differences in miR processing in the undifferentiated and differentiated states. Taken together, our studies suggest that PLC beta 1, through its ability to regulate C3PO and endogenous miR populations, mediates the differentiation of two types of cultured neuronal cells.