Staurosporine and NEM mainly impair WNK-SPAK/OSR1 mediated phosphorylation of KCC2 and NKCC1

• Published in: PloS one Vol. 15; no. 5; p. e0232967
• Main Authors: Zhang, Jinwei, Cordshagen, Antje, Medina, Igor, Nothwang, Hans Gerd, Wisniewski, Jacek R, Winklhofer, Michael, Hartmann, Anna-Maria
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 15.05.2020; Public Library of Science (PLoS)
• Subjects: Analysis; Animals; Antibodies; Binding Sites; Biology and Life Sciences; Cells, Cultured; Cellular signal transduction; Chloride channels; Chloride transport; Comparative analysis; Dephosphorylation; Diseases; Enzyme inhibitors; Ethylmaleimide - pharmacology; Health aspects; Health sciences; HEK293 Cells; Hippocampus; Hippocampus - cytology; Hippocampus - metabolism; Humans; K Cl- Cotransporters; Kinase inhibitors; Kinases; Life Sciences; Mass spectrometry; Mass spectroscopy; Medicine; Membrane proteins; Neurons; Neurons - drug effects; Neurons - metabolism; Neurons and Cognition; Neurotransmission; Phosphatase; Phosphatases; Phosphorylation; Phosphorylation - drug effects; Physiological aspects; Physiology; Post-transcription; Potassium-chloride cotransporter; Protein Kinases - metabolism; Protein Serine-Threonine Kinases - metabolism; Proteomics; Quantitative analysis; Rats; Reagents; Recombinant Proteins - metabolism; Regulatory mechanisms (biology); Research and Analysis Methods; Signal transduction; Signal Transduction - drug effects; Signaling; Solute Carrier Family 12, Member 2 - metabolism; Spectroscopy; Staurosporine; Staurosporine - pharmacology; Symporters - metabolism; Synaptic transmission; Testing; Transfection; WNK Lysine-Deficient Protein Kinase 1 - metabolism; Germany; France; Phosphorylation; Immunoprecipitation; Phosphatases; Neurons; Immunoblotting; Kinase inhibitors; Neurotransmission; Quantitative analysis
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0232967

The pivotal role of KCC2 and NKCC1 in development and maintenance of fast inhibitory neurotransmission and their implication in severe human diseases arouse interest in posttranscriptional regulatory mechanisms such as (de)phosphorylation. Staurosporine (broad kinase inhibitor) and N-ethylmalemide (NEM) that modulate kinase and phosphatase activities enhance KCC2 and decrease NKCC1 activity. Here, we investigated the regulatory mechanism for this reciprocal regulation by mass spectrometry and immunoblot analyses using phospho-specific antibodies. Our analyses revealed that application of staurosporine or NEM dephosphorylates Thr1007 of KCC2, and Thr203, Thr207 and Thr212 of NKCC1. Dephosphorylation of Thr1007 of KCC2, and Thr207 and Thr212 of NKCC1 were previously demonstrated to activate KCC2 and to inactivate NKCC1. In addition, application of the two agents resulted in dephosphorylation of the T-loop and S-loop phosphorylation sites Thr233 and Ser373 of SPAK, a critical kinase in the WNK-SPAK/OSR1 signaling module mediating phosphorylation of KCC2 and NKCC1. Taken together, these results suggest that reciprocal regulation of KCC2 and NKCC1 via staurosporine and NEM is based on WNK-SPAK/OSR1 signaling. The key regulatory phospho-site Ser940 of KCC2 is not critically involved in the enhanced activation of KCC2 upon staurosporine and NEM treatment, as both agents have opposite effects on its phosphorylation status. Finally, NEM acts in a tissue-specific manner on Ser940, as shown by comparative analysis in HEK293 cells and immature cultured hippocampal neurons. In summary, our analyses identified phospho-sites that are responsive to staurosporine or NEM application. This provides important information towards a better understanding of the cooperative interactions of different phospho-sites.