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Calcium-dependent gating of Voltage-gated Ca 2+ channels

Calcium-dependent gating of Voltage-gated Ca 2+ channels. Regulation by Calmodulin. Other stimuli. D Membrane potential. D Gates. Ion fluxes. Ca 2+ fluxes. Other transport mechanisms. D Internal free calcium. D Effect. Ca 2+ Ions Transduce Signals.

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Calcium-dependent gating of Voltage-gated Ca 2+ channels

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  1. Calcium-dependent gating of Voltage-gated Ca2+ channels Regulation by Calmodulin

  2. Other stimuli DMembrane potential DGates Ion fluxes Ca2+ fluxes Other transport mechanisms DInternal free calcium DEffect Ca2+ Ions Transduce Signals Ion Channels of Excitable Membranes, 3rd Edition, 2001

  3. Ca++ Ca++ Berne & Levy, Cardiovascular Physiology 6th Edition (1992) Ca2+ current controls the plateau phase of the cardiac action potential Journal of Physiology (2000) 525.2, pp. 285-298

  4. Ca2+ channels control neurotransmitter release CALCIUM CHANNEL Ca2+ Annu. Rev. Cell Dev. Biol. 2000. 16:521–55

  5. Ca2+ channels regulate gene expression in hippocampal neurons Current Opinion in Neurobiology 1997, 7:419–429 NATURE |VOL 401 | 14 OCTOBER 1999 |703

  6. Ca2+ channel Structure Annu. Rev. Cell Dev. Biol. 2000. 16:521–55

  7. L-type P/Q-type Family of Voltage-Gated Ca2+ Channels Neuron, Vol. 25, 533–535, March, 2000

  8. Ca2+ channel inactivation is relatively slow ICa,L Circ Res. 2001; 89:944-956.

  9. Ca2+-dependent gating of the L-type Ca2+ Channel

  10. The permeating ion affects Ca2+ channel inactivation: Calcium Dependent Inactivation (CDI) SCIENCE, VOL. 202, 15 DECEMBER 1978

  11. +20 mV Voltage -90 100 ms CDI in a heterologous system Ca2+ Current Ba2+

  12. Conditional open probability analysis (COPA): Ca2+ entry enhances inactivation Ba2+ Ca2+ SCIENCE, VOL. 250, 21 DECEMBER 1990

  13. Ca2+ Ba2+ CDI is greatest at membrane potentials eliciting peak inward Ca2+ current Ca2+ Ba2+ SCIENCE • VOL. 270 • 1502

  14. CDI in L-type channels reconstituted in bilayers 100 mM Ba2+ out Biophysical Journal Volume 66 April 1994 1051-1060

  15. Ca2+ sensing apparatus resides within CaV1.2 (a1C) • Rapid effects (< 5 msec) • CDI in bilayers • Minimal effects of Ca2+ chelators

  16. EF-hand Early candidate: EF-hand in C-terminus EF-hand

  17. EF-hand region from a1C: necessary and sufficient CE EC SCIENCE VOL 270 1 DECEMBER 1995 1502

  18. Ca2+-binding in the EF-hand is not necessary Proc. Natl. Acad. Sci. USA Vol. 94, pp. 2301–2305, March 1997

  19. EF-hand: an essential for CDI independent of Ca2+ binding Biophysical Journal Volume 78 April 2000 1906–1920

  20. THE JOURNAL OF BIOLOGICAL CHEMISTRY Vol. 272, No. 6, Issue of February 7, pp. 3560–3566, 1997 Proc. Natl. Acad. Sci. USA Vol. 95, pp. 3287–3294, March 1998 Other region(s) in the C-terminus

  21. IQ motif IQ motif / calmodulin (CaM) binding domain: CaM as the Ca2+ sensor NATURE |VOL 399 | 13 MAY 1999 | 159

  22. IQ motif is the CaM effector site NATURE |VOL 399 | 13 MAY 1999 | 159

  23. CaM binds to the IQ motif in the C-tail NATURE |VOL 399 | 13 MAY 1999 | 159

  24. 1477-1592 1592-1875 1551-1660 WT 4- WT 4- WT 4- CaM is constitutively bound to a1C N C THE JOURNAL OF BIOLOGICAL CHEMISTRY Vol. 276, No. 33, Issue of August 17, pp. 30794–30802, 2001

  25. CDI correlates with the affinity of the divalent ion for CaM Comparison of cation binding affinities of Calmodulin EF hands EC50 values (mM) Mol Pharmacol 26:75-82, 1984

  26. Calcium Dependent Inactivationof L-type Ca2+ Channels • Calmodulin is the Ca2+ sensor • CaM is pre-associated with a1C • The IQ motif is the effector domain in a1C • The EF-hand is a structural, non Ca2+-sensing domain

  27. Gene expression in hippocampal neurons: LTCs and CaM SCIENCE VOL 294 333 12 OCTOBER 2001 SCIENCE VOL 294 318 12 OCTOBER 2001

  28. 100 ms Frequency-dependent stimulation of L-type Ca2+ current: Calcium Dependent Facilitation 2.0 Hz Journal of Physiology (1990), 428, pp. 653-671

  29. Force-Frequency Relationship Treppe Contraction or “Staircase” Effect Pharm. Rev. 15:601 (1963)

  30. CDF is Regulated by CaMKII Proc. Natl. Acad. Sci. USA Vol. 91, pp. 9659-9663, September 1994

  31. CaMKII phosphorylation controls CDF NATURE CELL BIOLOGY | VOL 2 | MARCH 2000 | 173

  32. Ca2+/CaM-dependent kinase II (CaMKII): A molecular clock JBC 275: 14354, 2000

  33. Calcium Dependent Facilitation is also controlled by the IQ Motif IleAla NATURE |VOL 399 | 13 MAY 1999 | 159

  34. CaM is also the Ca2+ sensor for CDF NATURE |VOL 399 | 13 MAY 1999 | 159

  35. Calcium Dependent Facilitationof L-type Ca2+ Channels • Calmodulin is the Ca2+ sensor • The IQ motif is the effector domain in a1C • Phosphorylation by CaMKII leads to increased Po

  36. Ca2+-dependent gating of P/Q-type Ca2+ Channels

  37. CDI and CDF in P/Q channels NATURE |VOL 411 | 24 MAY 2001 |485

  38. CaM is the Ca2+ sensor? NATURE |VOL 411 | 24 MAY 2001 |485

  39. NATURE |VOL 411 | 24 MAY 2001 |485 NATURE |VOL 399 | 13 MAY 1999 |155 Different kinetics: different effector site?

  40. Different kinetics: different Ca2+ sensor? nature neuroscience • volume 5 no 3 • march 2002 • 210

  41. Ionic Dependence of IpCa Inactivation is it really CaM? Neuron, Vol. 20, 797–807, April, 1998

  42. Calcium Dependent Gating of P/Q Ca2+ Channels • Kinetics of inactivation and facilitation differ from L-type channel gating • Calmodulin appears to be the Ca2+ sensor and the IQ motif is one effector domain in a1A • CBD may be another effector domain • The Ca2+-binding protein CaBP1 regulates inactivation in a Ca2+-independent manner

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