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Phosphoinositides modulation of ion channels

Phosphoinositides modulation of ion channels. Gildas Loussouarn. Phosphoinositides modulation of ion channels. Requirements for biosensors Plasma membrane influences channel activity PIP 2 modulates many ion channels PIP 2 antagonizes channel rundown

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Phosphoinositides modulation of ion channels

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  1. Phosphoinositides modulation of ion channels Gildas Loussouarn

  2. Phosphoinositides modulation of ion channels • Requirements for biosensors • Plasma membrane influences channel activity • PIP2 modulates many ion channels • PIP2 antagonizes channel rundown • PIP2 and KATP channels: PIP2 modulates ATP sensitivity • PIP2 and KCNQ1 channels: PIP2 modulates voltage dependent activation • PIP2 and Kv channels: PIP2 modulates voltage dependent inactivation • PIP2 signal transduction • A major mechanism for PIP2 action: stabilization of the open state • Localization of PIP2 activation gate • Many residues critical for PIP2 regulation are facing the membrane • Mutations of membrane facing positive residues decrease the stabilization of the open state • Comparison between KATP and KCNQ1 • Biosensor durability and repeatability depends on PIP2 stability • Circumvent PIP2 modulation of ion channels

  3. Requirements for biosensors • durability : robustness, function guaranteed for long period of time • repeatability : a correct measure guaranteed for long period of time • easy calibration •  Compatibility with a complex sensor (ion channel + membrane)? From Shim and Gu, 2007, Anal. Chem. 79:2207-2213 Pancrazio et al, 1999, Annals of Biomedical Engineering. 27:697-711

  4. Kir1 • Plasma membrane influences channel activity • PIP2 modulates many ion channels Adapted from yu et al, 2005, Pharmacol Rev. 57:387-95

  5. Plasma membrane influences channel activity • PIP2 antagonizes channel rundown

  6. Plasma membrane influences channel activity • PIP2 antagonizes channel rundown

  7. Plasma membrane influences channel activity • PIP2 antagonizes channel rundown cell attached patch excision Inside-out patch excision KCNQ1 For many channels , patch excision leads ultimately to 0 current Loussouarn et al, 2003, EMBO J 22:5412-21

  8. cell attached patch excision Inside-out +PIP2 PIP2 • Plasma membrane influences channel activity • PIP2 antagonizes channel rundown Zhang et al, 2003, Neuron 37 963–975

  9. Kir1 • Plasma membrane influences channel activity • PIP2 modulates many ion channels Adapted from yu et al, 2005, Pharmacol Rev. 57:387-95

  10. cell attached patch excision Inside-out +PIP2 PIP2 • Plasma membrane influences channel activity • PIP2 antagonizes channel rundown Voltage-gated calcium channels KCNQ1 Wu et al, 2002, Nature 419:947-952 Loussouarn et al, 2003, EMBO J 22:5412-21

  11. Plasma membrane influences channel activity • PIP2 antagonizes channel rundown cell attached patch excision Inside-out +PIP2 PIP2 ATP KCNQ1 MgATP + PIP2 PIP2 MgATP Ctrl Loussouarn et al, 2003, EMBO J 22:5412-21

  12. Plasma membrane influences channel activity • PIP2 and KATP channels: PIP2 modulates ATP sensitivity KATP Shyng and Nichols, 1998, Science 282:1138-41

  13. Plasma membrane influences channel activity • PIP2 and KCNQ1 channels: PIP2 modulates voltage dependent activation Loussouarn et al, 2003, EMBO J 22:5412-21

  14. Plasma membrane influences channel activity • PIP2 and Kv channels: PIP2 modulates voltage dependent inactivation Closed Open Inactivated Adapted from Oliver et al, 2004, Science 304:265-70

  15. Plasma membrane influences channel activity • PIP2 and Kv channels: PIP2 modulates voltage dependent inactivation Adapted from Oliver et al, 2004, Science 304:265-70

  16. Plasma membrane influences channel activity • PIP2 signal transduction Gamper et al, 2004, J Neurosci 24:10980-92

  17. Plasma membrane influences channel activity • For many channels: • PIP2 is necessary for channel function : biosensor durability • PIP2 modulates channels sensitivity (to ATP, Vm…) : repeatability, calibration)  Are those two properties linked ?

  18. Closed Open • A major mechanism for PIP2 action: stabilization of the open state • Localization of PIP2 activation gate Adapted from Yang et al, 2003, Nature Neuroscience 6:811-818 And Nishida et al, 2007, EMBO J Epub ahead of print]

  19. A major mechanism for PIP2 action: stabilization of the open state • Localization of PIP2 activation gate Adapted from Yang et al, 2003, Nature Neuroscience 6:811-818

  20. A major mechanism for PIP2 action: stabilization of the open state • Many residues critical for PIP2 gating are facing the membrane Adapted from Nishida et al, 2007, EMBO J Epub ahead of print]

  21. A major mechanism for PIP2 action: stabilization of the open state • Many residues critical for PIP2 gating are facing the membrane Kir3.1 Kir1.1 Logothetis et al, 2007, J Physiol

  22. A major mechanism for PIP2 action: stabilization of the open state • Mutations of membrane facing positive residues decrease the stabilization of the open state Kir1.1=ROMK1 Lopes et al, 2002, Neuron 34, 933–944

  23. A major mechanism for PIP2 action: stabilization of the open state • Mutations of membrane facing positive residues decrease the stabilization of the open state WT Kir6.2=KATP R177A Shyng and Nichols, 1998, Science 282:1138-41

  24. A major mechanism for PIP2 action: stabilization of the open state • Mutations of membrane facing positive residues decrease the stabilization of the open state Shyng and al, 2000, 116 : 599–607

  25. PIP2 4 4 CATP C O ATP Enkvetchakul et al 2000, Biophys J, 78:2334-2348 PIP2 V CS4off O CS4on Loussouarn et al 2003, EMBO J, 22:5412-5421 • A major mechanism for PIP2 action: stabilization of the open state • Comparison between KATP and KCNQ1

  26. A major mechanism for PIP2 action: stabilization of the open state • Comparison between KATP and KCNQ1 Enkvetchakul and al, 2001, Biophysical Journal 80 719–728

  27. A major mechanism for PIP2 action: stabilization of the open state • Biosensor durability and repeatability depends on PIP2 stability Enkvetchakul and al, 2001, Biophysical Journal 80 719–728

  28. A major mechanism for PIP2 action: stabilization of the open state • For many channels: • PIP2 is necessary for channel function : biosensor durability • PIP2 modulates channels sensitivity (to ATP, Vm…) : repeatability, calibration) •  And those two properties are linked

  29. R T P Q S • Circumvent PIP2 modulation of ion channels KCNQ1 mutation provokes the Long QT syndrome WT KCNQ1 mut KCNQ1 INa ICa,L ICa,T INa/Ca Ito1 Ito2 IKs IKr GIRK KCNQ1 IK1

  30. Circumvent PIP2 modulation of ion channels

  31. Circumvent PIP2 modulation of ion channels

  32. Circumvent PIP2 modulation of ion channels

  33. Circumvent PIP2 modulation of ion channels Personnal communication from A. Thomas and R. Brasseur, Centre de Biophysique Moléculaire Numérique, Université de Gembloux

  34. Circumvent PIP2 modulation of ion channels

  35. CONCLUSION • durability : robustness, function guaranteed for long period of time • repeatability : a correct measure guaranteed for long period of time • easy calibration : PIP2? • Compatibility with a complex sensor (ion channel + membrane)? PKA,PKC, MgATP…. PIP2

  36. Acknowledgements Julien Piron Frank Choveau Nicolas Rodriguez +Isabelle Baró Collaborators: Thierry Rose (Institut Pasteur) ANR, GRRC (F. Choveau), AFM (J. Piron)

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