14-3-3θ facilitates plasma membrane delivery and function of mechanosensitive connexin 43 hemichannels

Intracellular signaling in osteocytes activated by mechanical loading is important for bone formation and remodeling. These signaling events are mediated by small modulators released from C×43 hemichannels (HC). We have recently shown that integrin α5 senses the mechanical stimulation and induces the opening of C×43 HC; however, the underlying mechanism is unknown. Here, we show that both C×43 and integrin α5 interact with 14-3-3θ, and this interaction is required for the opening of C×43 HC upon mechanical stress. The absence of 14-3-3θ prevented the interaction between C×43 and integrin α5, and blocked HC opening. Furthermore, it decreased the transport of C×43 and integrin α5 from the Golgi apparatus to the plasma membrane. Mechanical loading promoted the movement of C×43 to the surface which was associated not only with an increase in 14-3-3θ levels but also its interaction with C×43 and integrin α5. This stimulatory effect on forward transport by mechanical loading was attenuated in the absence of 14-3-3θ and the majority of the C×43 accumulated in the Golgi. Disruption of the Golgi by brefeldin A reduced the association of C×43 and integrin α5 with 14-3-3θ, further suggesting that the interaction is likely to occur in the Golgi. Together, these results define a previously unidentified, scaffolding role of 14-3-3h in assisting the delivery of C×43 and integrin α5 to the plasma membrane for the formation of mechanosensitive HC in osteocytes.