ERK and RSK are necessary for TRH-induced inhibition of r-ERG potassium currents in rat pituitary GH(3) cells

作者：Carretero Luis; Llavona Pablo; Lopez Hernandez Alejandro; Casado Pedro; Cutillas Pedro R; de la Pena Filar; Barros Francisco; Dominguez Pedro^*

来源：Cellular Signalling, 2015, 27(9): 1720-1730.

DOI：10.1016/j.cellsig.2015.05.014

• Kv (voltage-gated potassium channels)
• Thyrotropin-releasing hormone
• Phosphorylation
• Phosphoproteomics
• ERK (extracellular-signal-regulated kinase)
• RSK (ribosomal S6 kinase)

The transduction pathway mediating the inhibitory effect that TRH exerts on r-ERG channels has been thoroughly studied in GH(3) rat pituitary cells but some elements have yet to be discovered, including those involved in a phosphorylation event(s). Using a quantitative phosphoproteomic approach we studied the changes in phosphorylation caused by treatment with 1 mu M TRH for 5 min in GH(3) cells. The activating residues of Erk2 and Erk1 undergo phosphorylation increases of 526 and 4.87 fold, respectively, in agreement with previous reports of ERK activation by TRH in GH(3) cells. Thus, we studied the possible involvement of ERR pathway in the signal transduction from TRH receptor to r-ERG channels. The MEK inhibitor U0126 at 0.5 mu M caused no major blockade of the basal r-ERG current, but impaired the TRH inhibitory effect on r-ERG. Indeed, the TRH effect on r-ERG was also reduced when GH(3) cells were transfected with siRNAs against either Erk1 or Erk2. Using antibodies, we found that TRH treatment also causes activating phosphorylation of Rsk. The TRH effect on r-ERG current was also impaired when cells were transfected with any of two different siRNAs mixtures against Rsk1. However, treatment of GH(3) cells with 20 nM EGF for 5 min, which causes ERK and RSK activation, had no effect on the r-ERG currents. Therefore, we conclude that in the native GH(3) cell system, ERK and RSK are involved in the pathway linking TRH receptor to r-ERG channel inhibition, but additional components must participate to cause such inhibition.

• 出版日期2015-9