Pannexin 3 inhibits proliferation of osteoprogenitor cells by regulating Wnt and p21 signaling [Developmental Biology]

December 12th, 2013 by Ishikawa, M., Iwamoto, T., Fukumoto, S., Yamada, Y.

Canonical Wnt signaling and BMP promote the proliferation and differentiation of osteoprogenitors, respectively. However, the regulatory mechanism involved in the transition from proliferation to differentiation is unclear. Here, we show that pannexin 3 (Panx3) plays a key role in this transition by inhibiting the proliferation and promoting the cell cycle exit. Using primary calvarial cells and explants, C3H10T1/2 cells, and C2C12 cells, we found that Panx3 expression inhibited cell growth, whereas the inhibition of endogenous Panx3 expression increased it. We also found that the Panx3 hemichannel inhibited cell growth by promoting β-catenin degradation through GSK3β activation. Additionally, the Panx3 hemichannel inhibited cyclin D1 transcription and Rb phosphorylation through reduced cAMP/PKA/CREB signaling. Furthermore, the Panx3 endoplasmic reticulum (ER) Ca2+ channel induced the transcription and phosphorylation of p21, through the calmodulin/Smad pathway, and resulted in the cell cycle exit. Our results reveal that Panx3 is a new regulator that promotes the switch from proliferation to differentiation of osteoprogenitors via multiple Panx3 signaling pathways.