1. PROBLEMA
4.3 DE LA DIDÁCTICA A LA MOTIVACIÓN DE LA LECTURA
b-AR blockade is one of the most effective treatments for heart failure. However, the use of b-AR blockers in patients with heart failure is counterintuitive, as they are known to decrease contractility in normal hearts. We have recently shown that systemic oral administration of a b-AR blocker reverses PKA hyperphosphorylation of RyR2, restores the stoichiometry of the RyR2 macromolecular complex and normalizes single channel function (Fig. 1D) in a canine model of heart failure (61). These results may, in part, explain the improved cardiac function observed in heart failure patients treated with b-AR blockers.
Conclusions and perspectives
Elucidation of the molecular basis of cardiac EC coupling has improved our understanding of basic mechanisms that regulate cardiac function. Applications of these new understandings to the problems of heart failure and cardiac arrhythmogenesis have provided additional new understandings with important therapeutic implications. Complicating these new understandings are the challenging problems of studying integrative physiology using reductionist models. Model systems, that are necessitated by the complexity of cellular and organ physiology, each provide additional challenges that must be overcome. As investigators our goal is to integrate data from all useful models and adapt hypotheses to fit new understandings. To deny the validity of new observations because at first blush they challenge closely held beliefs is an approach that likely leads one into darkness. Most often tomorrow’s investigations uncover new threads of understanding that tie together apparently disparate observations. Such an inclusive approach to investigation most often provides pathways towards the light and to lasting truths.
A better understanding of the potential role of PKA hyperphosphorylation of RyR2 in heart failure and its role in the generation of fatal cardiac arrhythmias
may emerge from studying the biophysical properties of RyR2 mutations linked to catecholamine-induced ventricular arrhythmias. However, integrating single channel data, cellular and animal physiology and emerging with a unifying mechanism that causes heart failure and SCD will be a challenge. Nevertheless, elucidating the molecular pathogenesis of heart failure and VT will be the basis for strategies that lead to novel therapeutics.
ACKNOWLEDGMENTS
The work described in this review was supported by grants from the NIH and the AHA. The author is a Doris Duke Foundation Distinguished Clinical Scientist.
References
1. Marx SO, Reiken S, Hisamatsu Y, et al.: PKA Phosphorylation Dissociates FKBP12.6 from the Calcium Release Channel (Ryanodine Receptor): Defective Regulation in Failing Hearts. Cell. 2000;101:365-376. 2. Priori SG, Napolitano C, Tiso N, et al.: Mutations in the
Cardiac Ryanodine Receptor Gene (hRyR2) Underlie Catecholaminergic Polymorphic Ventricular Tachycardia. Circulation. 2001;103:196-200.
3. Laitinen PJ, Brown KM, Piippo K, et al.: Mutations of the cardiac ryanodine receptor (RyR2) gene in familial polymorphic ventricular tachycardia. Circulation. 2001;103:485-490.
4. Tiso N, Stephan DA, Nava A, et al.: Identification of mutations in the cardiac ryanodine receptor gene in families affected with arrhythmogenic right ventricular cardiomyopathy type 2 (ARVD2). Hum Mol Genet. 2001;10:189-194.
5. Marks AR, Tempst P, Hwang KS, et al.: Molecular cloning and characterization of the ryanodine receptor/junctional channel complex cDNA from skeletal muscle sarcoplasmic reticulum. Proc. Natl. Acad. Sci. 1989;86:8683-8687.
6. Nakai J, Imagawa T, Hakamata Y, et al.: Primary structure and functional expression from cDNA of the cardiac ryanodine receptor/calcium release channel. FEBS. 1990;271:169-177.
7. Otsu K, Willard HF, Khanna VK, et al.: Molecular cloning of cDNA encoding the Ca2+ release channel (ryanodine
receptor) of rabbit cardiac muscle sarcoplasmic reticulum. J Biol Chem. 1990;265:13472-13483. 8. Hakamata Y, Nakai J, Takeshima H, et al.: Primary
Structure and distribution of a novel ryanodine receptor/calcium release channel from rabbit brain. FEBS. 1992;312:229-235.
9. Imagawa T, Smith J, Coronado R, et al.: Purified ryanodine receptor from skeletal muscle sarcoplasmic reticulum is the Ca2+-permeable pore of the calcium release channel. J. Biol. Chem. 1987;262:16636- 16643.
10. Inui M, Saito A, Fleischer S: Purification of the ryanodine receptor and identity with feet structures of junctional terminal cisternae of sarcoplasmic reticulum from fast skeletal muscle. J.Biol. Chem. 1987;262:1740-1747.
11. Lai FA, Erickson HP, Rousseau E, et al.: Purification and reconstitution of the calcium release channel from skeletal muscle. Nature. 1988;331:315-319.
12. Inui M, Saito A, Fleischer S: Isolation of the ryanodine receptor from cardiac sarcoplasmic reticulum and identity with the feet structures. J. Biol. Chem. 1987;262:15637-15642.
13. Inui M, Fleischer S: Purification of Ca2+ release channel (ryanodine receptor) from heart and skeletal muscle sarcoplasmic reticulum. Methods in Enzymology. 1988;157:490-505.
14. Brillantes AB, Ondrias K, Scott A, et al.: Stabilization of calcium release channel (ryanodine receptor) function by FK506-binding protein. Cell. 1994;77:513-523. 15. Kobrinsky E, Ondrias K, Marks AR: Expressed ryanodine
receptor can substitute for the inositol 1,4,5- trisphosphate receptor in Xenopus laevis oocytes during progesterone- induced maturation. Dev. Biol. 1995;172:531-540.
16. Chen SR, Leong P, Imredy JP, et al.: Single-channel properties of the recombinant skeletal muscle Ca2+ release channel (ryanodine receptor). Biophys J. 1997;73:1904-1912.
17. Gaburjakova M, Gaburjakova J, Reiken S, et al.: FKBP12 binding modulates ryanodine receptor channel gating. J Biol Chem. 2001;276:16931-16935.
18. Bhat MB, Hayek SM, Zhao J, et al.: Expression and functional characterization of the cardiac muscle ryanodine receptor Ca(2+) release channel in Chinese hamster ovary cells. Biophys J. 1999;77:808-816. 19. Hymel L, Inui M, Fleischer S, et al.: Purified ryanodine
receptor of skeletal muscle forms Ca2+-activated
oligomeric Ca2+ channels in planar bilayers. Proc. Natl.
Acad. Sci. USA. 1988;85:441-444.
20. Lai F, Erickson H, Block B, et al.: Evidence for a Ca2+
channel within the ryanodine receptor complex from cardiac sarcoplasmic reticulum. Biochem. Biophys. Res. Commun. 1988;151:441-449.
21. Smith JS, Imagawa T, Ma J, et al.: Purified ryanodine receptor from rabbit skeletal muscle is the calcium release channel of sarcoplasmic reticulum. J. Gen. Physiol. 1988; 2:1-26.
22. Brillantes A-MB, Ondrias K, Jayaraman T, et al.: FKBP12 Optimizes function of the cloned expressed calcium release channel (ryanodine receptor). Biophysical Journal. 1994;66:A19.
23. Ondrias K, Brillantes AM, Scott A, et al.: Single channel properties and calcium conductance of the cloned expressed ryanodine receptor/calcium-release channel. Soc Gen Physiol. 1996;51:29-45.
24. Bezprozvanny I, Watras J, Ehrlich B: Bell-shaped calcium response curves of Ins(1,4,5)P3- and calcium- gated channels from endoplasmic reticulum of cerebellum. Nature. 1991;351:751-754.
25. Meissner G: Adenine nucleotide stimulation of Ca2+- induced Ca2+ release in sarcoplasmic reticulum. J Biol Chem. 1984;259:2365-2374.
26. Meissner G: Ryanodine receptor/Ca2+ release channels and their regulation by endogenous effectors. Annu Rev Physiol. 1994;56:485-508.
27. Chen SRW, Zhang L, MacLennan DH: Characterization of a Ca2+ Binding and Regulatory Site in the Ca2+ Release Channel (Ryanodine Receptor) of Rabbit Skeletal Muscle Sarcoplasmic Reticulum. J. Biol. Chem. 1992;267:23318-23326.
28. Fill M, Mejia-Alvarez R, Zorzato F, et al.: Antibodies as probes for ligand gating of single sarcoplasmic reticulum Ca2+-release channels. Biochem J. 1991;273:449-457.
29. Chu A, Diaz-Munoz M, Hawkes M, et al.: Ryanodine as a probe for the functional state of the skeletal muscle sarcoplasmic reticulum calcium release channel. Mol. Pharmacol. 1990;37:735-741.
30. Hawkes MJ, Nelson TE, Hamilton SL: [3H]Ryanodine as a Probe of Changes in the Functional State of the Ca2+-release Channel in Malignant Hyperthermia. J. Biol. Chem. 1992;267:6702-6709.
31. Meissner G, El-Hashem A: Ryanodine as a functional probe of the skeletal muscle sarcoplasmic reticulum Ca2+ release channel. Mol and Cell. Biochem. 1992;114:119-123.
32. Chen SR, Zhang L, MacLennan DH: Asymmetrical blockade of the Ca2+ release channel (ryanodine receptor) by 12-kDa FK506 binding protein. Proc. Natl. Acad. Sci. 1994;91:11953-11957.
33. Kaftan E, Marks AR, Ehrlich BE: Effects of rapamycin on ryanodine receptor/Ca(2+)-release channels from cardiac
34. Marks AR: Immunophilin modulation of calcium channel gating. Methods: A Companion to Methods in Enzymology. 1996;9:177-187.
35. Fabiato A: Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum. Am J Physiol. 1983;245:C1-C14.
36. Nabauer M, Callewart G, Cleeman L, et al.: Regulation of calcium release is gated by calcium current, not gating charge, in cardiac, myocytes. Science. 1989;244:800-803.
37. Marx SO, Reiken S, Hisamatsu Y, et al.: Phosphorylation-dependent Regulation of Ryanodine Receptors. A novel role for leucine/isoleucine zippers. J Cell Biol. 2001;153:699-708.
38. Landschulz WH, Johnson PF, McKnight SL: The leucine zipper: a hypothetical structure common to a new class of DNA binding proteins. Science. 1988;240:1759- 1764.
39. Leung IW, Lassam N: Dimerization via tandem leucine zippers is essential for the activation of the mitogen- activated protein kinase kinase kinase, MLK-3. J Biol Chem. 1998;273:32408-32415.
40. Jayaraman T, Brillantes A-MB, Timerman AP, et al.: FK506 Binding Protein Associated with the Calcium Release Channel (Ryanodine Receptor). J. Biol. Chem. 1992;267:9474-9477.
41. Timerman AP, Jayaraman T, Wiederrecht G, et al.: The ryanodine receptor from canine heart sarcoplasmic reticulum is associated with a novel FK-506 binding protein. Biochem. Biophys. Res. Commun. 1994;198:701-706.
42. Marks AR: Cellular functions of immunophilins. Physiol. Rev. 1996;76:631-649.
43. Schreiber S: Chemistry and biology of the immunophilins and their immunosuppressive ligands. Science. 1991;251:283-287.
44. Timerman AP, Ogunbumni E, Freund E, et al.: The calcium release channel of sarcoplasmic reticulum is modulated by FK-506-binding protein. Dissociation and reconstitution of FKBP-12 to the calcium release channel of skeletal muscle sarcoplasmic reticulum. Journal of Biological Chemistry. 1993;268:22992- 22999.
45. Ahern GP, Junankar PR, Dulhunty AF: Subconductance states in single-channel activity of skeletal muscle ryanodine receptors after removal of FKBP12. Biophysical Journal. 1997;72:146-162.
46. Shou W, Aghdasi B, Armstrong DL, et al.: Cardiac defects and altered ryanodine receptor function in mice lacking FKBP12. Nature. 1998;391:489-492.
47. Chen L, Molinski TF, Pessah IN: Bastadin 10 Stabilizes the Open Conformation of the Ryanodine-sensitive Ca(2+) Channel in an FKBP12-dependent Manner. J Biol Chem. 1999;274:32603-32612.
48. Marx SO, Ondrias K, Marks AR: Coupled gating between individual skeletal muscle Ca2+ release
channels (ryanodine receptors). Science. 1998;281:818-821.
49. Marx SO, Gaburjakova J, Gaburjakova M, et al.: Coupled Gating Between Cardiac Calcium Release Channels (Ryanodine Receptors). Circ Res. 2001;in press.
50. Marks AR: Cardiac intracellular calcium release channels: role in heart failure. Circ Res. 2000;87:8-11. 51. Marks AR: Ryanodine Receptors/Calcium Release
channels in Heart Failure and Sudden Cardiac Death. J Mol Cell Cardiol. 2001;33:615-624.
52. Hain J, Onoue H, Mayrleitner M, et al.: Phosphorylation modulates the function of the calcium release channel of sarcoplasmic reticulum from cardiac muscle. J Biol Chem. 1995;270:2074-2081.
53. Hohenegger M, Suko J: Phosphorylation of the purified cardiac ryanodine receptor by exogenous and endogenous protein kinases. Biochem J. 1993;296:303-308.
54. Islam MS, Leibiger I, Leibiger B, et al.: In situ activation of the type 2 ryanodine receptor in
pancreatic beta cells requires cAMP-dependent phosphorylation. Proc Natl Acad Sci U S A. 1998;95:6145-6150.
55. Lokuta AJ, Rogers TB, Lederer WJ, et al.: Modulation of cardiac ryanodine receptors of swine and rabbit by a phosphorylation-dephosphorylation mechanism. J. Phys. 1995;487:609-622.
56. Takasago T, Imagawa T, Shigekawa M: Phosphorylation of the cardiac ryanodine receptor by cAMP-dependent protein kinase. J Biochem (Tokyo). 1989;106:872-877. 57. Takasago T, Imagawa T, Furukawa K, et al.: Regulation
of the cardiac ryanodine receptor by protein kinase- dependent phosphorylation. J Biochem (Tokyo). 1991;109:163-170.
58. Valdivia HH, Kaplan JH, Ellis-Davies GC, et al.: Rapid adaptation of cardiac ryanodine receptors: modulation by Mg2+ and phosphorylation. Science. 1995;267:1997-2000.
59. Yoshida A, Takahashi M, Imagawa T, et al.: Phosphorylation of ryanodine receptors in rat myocytes during beta-adrenergic stimulation. J Biochem (Tokyo). 1992;111:186-190.
60. Bers DM. Excitation-Contraction Coupling and Cardiac Contractile Force. Boston: Kluwer Academic Publishers; 1991.
61. Reiken S, Gaburjakova M, Gaburjakova J, et al.: Beta adrenergic receptor blockers restore cardiac calcium release channel (ryanodine receptor) structure and function in heart failure. Circulation. 2001;in press. 62. Tanaka H, Nishimaru K, Sekine T, et al.: Two-
dimensional millisecond analysis of intracellular Ca2+ sparks in cardiac myocytes by rapid scanning confocal microscopy: increase in amplitude by isoproterenol. Biochem Biophys Res Commun. 1997;233:413-418. 63. Witcher DR, Strifler BA, Jones LR: Cardiac-specific
phosphorylation site for multifunctional Ca2+/calmodulin-dependent protein kinase is conserved in the brain ryanodine receptor. J. Biol. Chem. 1992;267:4963-4967.
64. Trafford AW, Diaz ME, Sibbring GC, et al.: Modulation of CICR has no maintained effect on systolic Ca2+: simultaneous measurements of sarcoplasmic reticulum and sarcolemmal Ca2+ fluxes in rat ventricular myocytes. J Physiol (Lond). 2000;522 Pt 2:259-270. 65. Litwin SE, Zhang D, Bridge JH: Dyssynchronous Ca(2+)
Sparks in Myocytes From Infarcted Hearts. Circ Res. 2000;87:1040-1047.
66. Gomez AM, Valdivia HH, Cheng H, et al.: Defective excitation-contraction coupling in experimental cardiac hypertrophy and heart failure. Science. 1997;276:800- 806.
67. Hobai IA, O'Rourke B: Decreased sarcoplasmic reticulum calcium content is responsible for defective excitation-contraction coupling in canine heart failure. Circulation. 2001;103:1577-1584.
Correspondence: Andrew R. Marks
Center for Molecular Cardiology, Box 65
Columbia University College of Physicians & Surgeons, Rm 9-401 630 West 168th Street New York, NY 10032 tel 212 305-0270 fax 212 305-3690 E-mail: [email protected]
Running title: Ryanodine receptors, PKA and FKBP12
Key words: calcium, excitation-contraction coupling, heart failure