Functional kinomics establishes a critical node of volume-sensitive cation-Cl^- cotransporter regulation in the mammalian brain

This is the final version of the article. Available from the publisher via the DOI in this record.There is another record in ORE for this publication: http://hdl.handle.net/10871/33424Cell volume homeostasis requires the dynamically regulated transport of ions across the plasmalemma. While the ensemble of ion transport proteins involved in cell volume regulation is well established, the molecular coordinators of their activities remain poorly characterized. We utilized a functional kinomics approach including a kinome-wide siRNA-phosphoproteomic screen, a high-content kinase inhibitor screen, and a kinase trapping-Orbitrap mass spectroscopy screen to systematically identify essential kinase regulators of KCC3 Thr991/Thr1048 phosphorylation – a key signaling event in cell swelling-induced regulatory volume decrease (RVD). In the mammalian brain, we found the Cl−-sensitive WNK3-SPAK kinase complex, required for cell shrinkage-induced regulatory volume decrease (RVI) via the stimulatory phosphorylation of NKCC1 (Thr203/Thr207/Thr212), is also essential for the inhibitory phosphorylation of KCC3 (Thr991/Thr1048). This is mediated in vivo by an interaction between the CCT domain in SPAK and RFXV/I domains in WNK3 and NKCC1/KCC3. Accordingly, genetic or pharmacologic WNK3-SPAK inhibition prevents cell swelling in response to osmotic stress and ameliorates post-ischemic brain swelling through a simultaneous inhibition of NKCC1-mediated Cl− uptake and stimulation of KCC3-mediated Cl− extrusion. We conclude that WNK3-SPAK is an integral component of the long-sought “Cl−/volume-sensitive kinase” of the cation-Cl− cotransporters, and functions as a molecular rheostat of cell volume in the mammalian brain.We thank the excellent technical support of the MRC-Protein Phosphorylation and Ubiquitylation Unit (PPU) DNA Sequencing Service (coordinated by Nicholas Helps), the MRC-PPU tissue culture team (coordinated by Laura Fin), the Division of Signal Transduction Therapy (DSTT) antibody purification teams (coordinated by Hilary McLauchlan and James Hastie). We are grateful to the MRC PPU Proteomics facility (coordinated by David Campbell, Robert Gourlay and Joby Varghese). We thank for support the Medical Research Council (MC_UU_12016/2; DRA) and the pharmaceutical companies supporting the Division of Signal Transduction Therapy Unit (AstraZeneca, Boehringer-Ingelheim, GlaxoSmithKline, Merck KGaA, Janssen Pharmaceutica and Pfizer; DRA). We thank Thomas J. Jentsch (Max-Delbrück-Centrum für Molekulare Medizin) for providing the KCC1/3 double KO mice and his reading of this manuscript. We thank Nathaniel Grey (Harvard) for providing the kinase inhibitor library used in this study (NIH LINCS Program grant U54HL127365). This work was also supported by a Harvard-MIT Neuroscience Grant (to KTK/SJE)

Octyl Gallate Inhibits ATP-induced Intracellular Calcium Increase in PC12 Cells by Inhibiting Multiple Pathways

Phenolic compounds affect intracellular free Ca2+ concentration ([Ca2+]i) signaling. The study examined whether the simple phenolic compound octyl gallate affects ATP-induced Ca2+ signaling in PC12 cells using fura-2-based digital Ca2+ imaging and whole-cell patch clamping. Treatment with ATP (100 µM) for 90 s induced increases in [Ca2+]i in PC12 cells. Pretreatment with octyl gallate (100 nM to 20 µM) for 10 min inhibited the ATP-induced [Ca2+]i response in a concentration-dependent manner (IC50=2.84 µM). Treatment with octyl gallate (3 µM) for 10 min significantly inhibited the ATP-induced response following the removal of extracellular Ca2+ with nominally Ca2+-free HEPES HBSS or depletion of intracellular Ca2+ stores with thapsigargin (1 µM). Treatment for 10 min with the L-type Ca2+ channel antagonist nimodipine (1 µM) significantly inhibited the ATP-induced [Ca2+]i increase, and treatment with octyl gallate further inhibited the ATP-induced response. Treatment with octyl gallate significantly inhibited the [Ca2+]i increase induced by 50 mM KCl. Pretreatment with protein kinase C inhibitors staurosporin (100 nM) and GF109203X (300 nM), or the tyrosine kinase inhibitor genistein (50 µM) did not significantly affect the inhibitory effects of octyl gallate on the ATP-induced response. Treatment with octyl gallate markedly inhibited the ATP-induced currents. Therefore, we conclude that octyl gallate inhibits ATP-induced [Ca2+]i increase in PC12 cells by inhibiting both non-selective P2X receptor-mediated influx of Ca2+ from extracellular space and P2Y receptor-induced release of Ca2+ from intracellular stores in protein kinase-independent manner. In addition, octyl gallate inhibits the ATP-induced Ca2+ responses by inhibiting the secondary activation of voltage-gated Ca2+ channels

Calcium and cancer: targeting Ca2+ transport

Ca2+ is a ubiquitous cellular signal. Altered expression of specific Ca2+ channels and pumps are characterizing features of some cancers. The ability of Ca2+ to regulate both cell death and proliferation, combined with the potential for pharmacological modulation, offers the opportunity for a set of new drug targets in cancer. However, the ubiquity of the Ca2+ signal is often mistakenly presumed to thwart the specific therapeutic targeting of proteins that transport Ca2+. This Review presents evidence to the contrary and addresses the question: which Ca2+ channels and pumps should be targeted