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A dual phosphorylation switch controls 14-3-3-dependent cell surface expression of TASK-1.

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Citation

Kilisch, M., Lytovchenko, O., Arakel, E. C., Bertinetti, D., & Schwappach, B. (2016). A dual phosphorylation switch controls 14-3-3-dependent cell surface expression of TASK-1. Journal of Cell Science, 129(4), 831-842. doi:10.1242/jcs.180182.


Cite as: https://hdl.handle.net/11858/00-001M-0000-0029-CCA9-A
Abstract
The transport of the K+ channels TASK-1 and TASK-3 (also known as KCNK3 and KCNK9, respectively) to the cell surface is controlled by the binding of 14-3-3 proteins to a trafficking control region at the extreme C-terminus of the channels. The current model proposes that phosphorylation-dependent binding of 14-3-3 sterically masks a COPI-binding motif. However, the direct effects of phosphorylation on COPI binding and on the binding parameters of 14-3-3 isoforms are still unknown. We find that phosphorylation of the trafficking control region prevents COPI binding even in the absence of 14-3-3, and we present a quantitative analysis of the binding of all human 14-3-3 isoforms to the trafficking control regions of TASK-1 and TASK-3. Surprisingly, the affinities of 14-3-3 proteins for TASK-1 are two orders of magnitude lower than for TASK-3. Furthermore, we find that phosphorylation of a second serine residue in the C-terminus of TASK-1 inhibits 14-3-3 binding. Thus, phosphorylation of the trafficking control region can stimulate or inhibit transport of TASK-1 to the cell surface depending on the target serine residue. Our findings indicate that control of TASK-1 trafficking by COPI, kinases, phosphatases and 14-3-3 proteins is highly dynamic.