分子医学所现有研究员的研究领域与经历介绍

一、Principal Investigator：肖瑞平（Rui-Ping Xiao）

Personal Synopsis

Rui-Ping (Ping) Xiao was trained as a cardiologist and physiologist at Tong-Ji Medical University in Wuhan, China and the Medical School at University of Maryland at Baltimore (UMAB), where she earned her M.D. in  1984 and Ph.D. in 1995, respectively. She joined the Laboratory of Cardiovascular Science, National Institute of Aging, in 1990 as a postdoctoral fellow, and later in 1996 became a tenure-track investigator and the head of the Receptor Signaling Unit. In 2004, she was converted to Senior Investigator at National Institute of Health, USA. She is now a Senior Investigator and co-PI of the Laboratory of Cellular Signaling Network at IMM, PKU.

Research Interest

The scope of  her research work covers three intertwined programs: (I) b-adrenergic receptor subtype signaling in cardiovascular system;  (II) Modulation of cardiac excitation-contraction coupling by Ca/calmodulin-dependent protein kinase II (CaMKII) in normal and failing hearts;  and (III) Identification and characterization of cardiovascular disease-related genes.   Her main scientific focus has been G-protein coupled receptor (GPCR) signaling in the cardiovascular system. Using interdisciplinary approaches, including physiological and pharmacological techniques in conjunction with genetic manipulations (e.g. gene-targeted animal models or adenoviral gene transfer systems), her work revealed dual coupling of b₂-adrenergic receptor (b2AR) with two functionally opposite G-protein families, Gs and Gi proteins. This counterintuitive finding was the first demonstration that a given GPCR can couple to more than one class of G-proteins in a physiological context such as in intact cardiac myocytes.

Dr. Xiao’s research has demonstrated that the additional Gi coupling creates a microscopic compartmentalization of the concurrent Gs-cAMP signaling and, more importantly, dictates the opposing outcomes of bAR subtype stimulation with respect to cardiac cell survival and apoptotic cell death. 

Dr. Xiao envisioned and promoted the perception that b₁AR and b₂AR subtypes play distinctly different-even opposing-roles in the context of heart failure. Specifically, while b₁AR is widely recognized as a "foe," b₂AR might be a "friend" in need due to its concurrent anti-apoptotic effect and contractile support. This new perception of bAR signal transduction has been increasingly appreciated in the cardiovascular research community and provides a novel rationale for new therapeutic strategies, particularly a combination of b₁AR blockade with b₂AR activation for improving the function of the failing heart.

Dr. Xiao’s research has not been limited to G protein-coupled receptor signaling. She was also the first to characterize role of CaMKII in regulating cardiac L-type Ca²⁺ currents and in the control of cardiac pacemaker activity.  Her recent in vivo and in vitro studies have shown that activation of p38 MAPK exhibits a potent inhibitory effect on cardiac contractility. In addition, She has put considerable efforts to understand mechanisms underlying cardiac aging and heart failur. 

Human Genome Project has demonstrated that the family of G protein coupled receptors (GPCRs) is the largest gene family in human genome. The GPCR superfamily has also long been considered the most important target in the pharmaceutical industry. Remarkably, 70% of today’s therapeutic agents used for the treatment of cardiovascular diseases are targeted at GPCR signaling pathways. Thus, one of Dr. Xiao’s major future directions will be focused on identification and target validation of orphan GPCRs .  These studies will not only provide novel insights into  basic mechanisms of novel GPCRs actions, but also reveal new rationales for ligand screens as well as clinical applications.  Additionally, identification and characterization of cardiovascular disease-related genes is another new initiative of Dr. Xiao’s lab. 

Selected Publuications

1. Xiao, R.P., and Lakatta, E.G.: b₁-adrenoceptor stimulation and b₂-adrenoceptor stimulation differ in their effects on contraction, cytosolic calcium, and calcium current in single rat ventricular cells. Circ. Res. 73: 286-300, 1993.

2. Xiao, R.P., Spurgeon, H.A., O'Connor, F., and Lakatta, E.G.: Age-associated changes in b-adrenergic modulation on rat cardiac excitation-contraction coupling. J. Clin. Invest. 94: 2051-2059, 1994.

3. Xiao, R.P., Cheng, H., Lederer, W.J., Suzuki, T., and Lakatta, E.G.: Dual regulation of Ca²⁺/calmodulin-dependent Kinase II activity by membrane voltage and by calcium influx. Proc. Nat. Acad., Sci. USA 91: 9659-9663, 1994.

4. Xiao, R.P., Hohl, C., Altschuld, R., Jones, L., Livingston, B., Ziman, B., Tantini, B., and Lakatta, E.G.: b₂-adrenergic receptor-stimulated increase in cAMP in rat heart cells is not coupled to changes in Ca²⁺ dynamics, contractility, or phospholamban phosphorylation. J. Biol. Chem. 269: 19151-19156, 1994.

5. Xiao, R.P., Ji, X., and Lakatta, E.G.: Functional coupling of the b₂-adrenoceptor to a pertussis toxin-sensitive G protein in cardiac myocytes. Mol. Pharmacol. 47: 322-329, 1995.

6. Altschuld, R.A., Starling, R.C., Hamlin, R.L., Hensley, J., Castillo, L., Fertel, R.H., Hohl, C.M., Robitaille, P.M., Jones, L.R., Xiao, R.P., and Lakatta, E.G.: Response of failing canine and human heart cells to b₂-adrenergic stimulation. Circulation. 92: 1612-1618, 1995.

7. Xiao, R.P., Pepe, S., Capogrossi, M.C., Spurgeon, H.A., and Lakatta, E.G.: Opioid peptide receptor stimulation reverses b-adrenergic effects in rat heart cells. Am. J. Physiol. 272: H797-H805, 1997.

8. Pepe, S., Xiao, R.P., Hohl, C., Altschuld, R., and Lakatta, E.G.: "Cross-talk" between opioid peptide and b-adrenergic receptor signaling in rat heart. Circulation 95: 2122-2129, 1997.

9. Xiao, R.P., Valdivia, H.H., Bogdanov, K., Valdivia, C., Lakatta, E.G., and Cheng, H.: The Immunophilin FK506 binding protein (FKBP) modulates Ca²⁺ release channel closure in rat heart cells. J. Physiol. 500: 331-342, 1997.

10. 18. Zhou, Y.Y., Cheng, H., Bogdanov, K., Hohl, C., Altschuld, R., Lakatta, E.G., and Xiao R.P.: Localized cAMP-dependent pathway mediates b₂-adrenergic stimulation in rat ventricular myocytes. Am. J. Physiol. 273: H1611-1618, 1997.

11. Xiao, R.P., Tomhave, E.D., Ji, X., Boluyt, M.O., Cheng, H., Lakatta, E.G., and Koch, W.J.: Age-associated reductions in cardiac b₁- and b₂-adrenoceptor responses without changes in inhibitory G proteins or receptor kinases. J. Clin. Invest. 101: 1273-1282, 1998.

12. Xiao, R.P., Avdonin, P., Zhou, Y.Y., Cheng, H., Akhter, S.A., Eschenhagen, T., Lefkowitz, R.J., Koch, W.J., and Lakatta, E.G.: Coupling of b₂-adrenoceptor to G_i proteins and its physiological releavance in murine cardiac myocytes. Circ. Res. 84:43-52, 1999.

13. Kuschel, M., Bartel, S., Spurgeon, H.A., Zhou, Y.Y., Zhang, S.J., Krause, E.G., Lakatta, E.G., and Xiao, R.P.: Canine cardiac b₂-adrenergic signaling is localized to the sarcolemma membrane. Circulation 99:2458-2465, 1999.

14. Kuschel, M., Zhou, Y.Y., Cheng, H., Zhang, S.J., Chen-Izu, Y., Lakatta, E.G., and Xiao, R.P.: G_i protein-mediated functional compartmentalization of cardiac b₂-adrnergic signaling. J. Biol. Chem. 274: 22048-22052, 1999.

15. Zhou, Y.Y., Cheng, H., Song, L.S., Lakatta, E.G., and Xiao, R.P.: Differential regulation of cardiac L-type calcium channel current by constitutively active and agonist-activated b₂-adrenergic receptor signaling. Mol. Parmacol. 56: 485‑93, 1999.

16. Xiao, R.P., Cheng, H., Zhou, Y.Y., Kuschel, M., and Lakatta, E.G.: Recent advances in cardiac b-adrenergic receptor subtype signal transduction. Circ. Res. 85:1092-1100, 1999 (Invited Review).

17. Zhou, Y.Y., Song, L.S., Lakatta, E.G., Xiao, R.P., and Cheng, H.: Constitutive b₂-adrenergic signaling enhances SR calcium to augment contraction in mouse heart. J. Physiol. 521: 351-363, 1999.

18. Zhang, S.J., Cheng, H., Zhou, Y.Y., Wang, D.J., Zhu, W., Ziman, B., Spurgeon, H., Lefkowitz, R.J., Lakatta, E.G., Koch, W.J., and Xiao, R.P.: Inhibition of spontaneous b₂-adrenergic activation rescues b₁-adrenergic contractile response in cardiomyocytes overexpressing b₂-adrenoceptor. J. Biol. Chem. 275: 21773-21779, 2000.

19. Hagemann, D., Kuschel, M., Kuromochi, T., Zhu, W., Cheng, H., and Xiao, R.P.: Frequency-encoding Thr¹⁷ phospholamban phosphorylation is independent of Ser¹⁶ phosphorylation in cardiac myocytes. J. Biol. Chem. 275: 22532-22536, 2000.

20. Vinogradova, T.M., Zhou, Y.Y., Bogdanov, K.Y., Kuschel, M., Cheng, H., and Xiao, R.P.: Sinoatrial node pacemaker activity requires Ca²⁺/calmodulin-dependent protein kinase II activation. Circ. Res. 87: 760-767, 2000.

21. Xiao, R.P.: Cell logic for dual coupling of a single class of receptors to G_s and G_i proteins. Cric. Res. 87:635-637, 2000 (Editorial).

22. Zhou, Y.Y., Zhu, W., Zhang, S..J., Wang, D.J., Kobilka, B., Lakatta, E.G., Cheng, H., and Xiao, R.P.: Ligand-independent activation of b₂- but not b₁-adrenoceptor overexpressed in b₁/b₂-adrenoceptor double knockout mouse cardiomyocytes. Mol. Pharmacol. 58: 887-894, 2000.

23. Zheng, M., Zhang, S.J., Zhu, W., Ziman, B., Kobilka, B.K., and Xiao, R.P.: adrenergic receptor-induced p38 MAPK activation is mediated by PKA rather than by G_i or G_b( in adult mouse cardiomyocytes. J. Biol. Chem. 275: 40635-40640, 2000.

24. Zhu, W.Z., Zheng, M., Lefkowitz, R.J., Koch, W.J., Kobilka, B., and Xiao, R.P.: Dual modulation of cardiac cell survival and cell death by b₂-adrenergic signaling in adult mouse heart cells. Proc. Nat. Acad., Sci. USA 98: 1607-1612, 2001.

25. Xiao, R.P.: β-adrenergic signaling in the heart: Dual coupling of the β₂-adrenergic receptor to G_s and G_i proteins. Science’s STKE. 16:RE15, 2001 (invited Review).

26. Liao, P., Wang, S.Q., Zheng, M., Zheng, M.Z., Cheng, H., Wang, Y., and Xiao, R.P.: p38 mitogen activated protein kinase mediates negative inotropic effect in cardiac myocytes. Circ. Res. 90:190-196, 2002.

27. Jo, S.H., Leblais, V., Crow, M.T., and Xiao, R.P.: Phosphatidylinositol 3-kinase functionally compartmentalizes the concurrent G_s signaling during b₂-adrenergic stimulation. Circ. Res. 91: 46-53, 2002.

28. Zhu, W.Z., Wang, S.Q., Chakir, K., Kolbilka, B.K., Cheng, H., and Xiao, R.P.: Linkage of b₁-adrenergic stimulation to apoptotic heart cell death through protein kinase A-independent activation of Ca²⁺/Calmodulin Kinase II. J. Clin. Invest. 111:617-625, 2003.

29. Xiao, R.P., Zhang, S.J. Kuschel, M., Zhou, Y.Y., Bond, R.A., Balke, C.W., Lakatta, E.G., and Cheng, H.: Enhanced G_i signaling mediates the diminution of b₂-adrenergic contractile response in failing spontaneous hypertensive rat heart. Circulation. 108:1633-1639, 2003.

30. Chakir, K., Xiang, Y., Zhang, S.J., Yang, D., Cheng, H., Kobilka, B.K., and Xiao, R.P.: The third intracellular loop and the carboxyl terminus of b₂-adrenergic receptor confer the receptor spontaneous activity. Mol. Pharmacol. 64:1048-58, 2003.

31. Xiao, R.P., and Balke, C,W,: Na⁺/Ca²⁺ Exchange Linking b₂-Adrenergic G_i Signaling to Heart Failure: Associated Defect of Adrenergic Contractile Support. J Mol. Cell. Cardiol. 36:7-11, 2004, (Editorial).

32. Ding, J.H., Xu, X., Yang, D., Chu, P.H., Dalton, N.D., Ye, Z., Yeakley, J.M., Cheng, H., Xiao, R.P., Ross, J., Chen, J., and Fu, X.D.: Dilated cardiomyopathy caused by tissue-specific ablation of SC35 in the heart. EMBO J. 23:885-96, 2004.

33. Patterson, A.J., Zhu, W., Chow, A., Kosek, J., Xiao, R.P., and Kobilka, B.K.: Protecting the myocardium: A role for the b₂-Adrenergic receptor in the heart. Critical Care Medicine. 32:1041-8, 2004.

34. Xiao, R.P., Zhu, W., Zheng, M., Bond, R., Lakatta, E.G., and Cheng, H.: Subtype-specific b-adrenergic signaling pathways and their clinical implications. Trends in Pharmacological Sciences (TiPS). 25: 358-365, 2004, (invited Review).

35. Pepe, S., van den Brink, O.W.V., Lakatta, E.G., and Xiao, R.P.: b-Adrenergic Receptor-Opioid Peptide Receptor Cross-talk: Cardiovascular Regulation and Adaptation in Health and Disease. Cardiovascular Research. 15;63:414-22, 2004, (invited Review).

36. Chen, K.H., Guo, X.M., Ma, D.L., Guo, Y.H., Li, Q., Li, P., Qiu, X., Xiao*, R.P., & Tang, J.: Dysregulation of A Novel Hyperplasia Suppressor Gene Triggers Vascular Proliferative Disorders. Nature Cell Biology, 6:872-83, 2004, (*the corresponding author).

37. Leblais, V., Jo, S.H., Chakir, K., Maltsev, V., Zheng, M., Crow, M.T., Wang, W., Lakatta, E.G., & Xiao, R.P. Phosphatidylinositol 3-Kinase Offsets cAMP-Mediated Positive Inotropic Effect via Inhibiting Ca2+ Influx in Cardiomyocytes. Circ. Res., 2004, 95:1183-90.

38. Zheng, M., Jo, S.H., Wersto, R., Han, Q., and Xiao, R.P.: Intracellular Acidosis-Induced p38 MAPK Activation and Its Pathophysiological Relevance in Cardiomyocyte Ischemia. FASEB J. 2005, 19:109-11.

二、Principal Investigator：程和平（He-ping Cheng）

Personal Synopsis

Heping (Peace) Cheng received degrees in applied mathematics and mechanics, physiology, and biomedical engineering from Peking University, China, where he served as a faculty member in the Department of Electrical Engineering before earning his Ph.D. degree in Physiology in 1995 from the University of Maryland at Baltimore. He then joined the NIH Intramural Research Program as a senior staff fellow in 1995 and was selected as a tenure-track investigator in 1998. In November, 2004, he became a senior investigator and the head of the Ca²⁺ Signaling Section in the Laboratory of Cardiovascular Science, National Institute on Aging, NIH. He is now a Senior Investigator and co-PI of the Calcium Signaling Laboratory at IMM, PKU.

Research Interest

In my early years at Peking University, recognizing the power of multidisciplinary integration, my mentors and I designed a unique career path beginning with rigorous training in physiology, mathematics, physics, and computer science. My dream was to pursue fundamental biomedical questions by seamless integration of the philosophy, theory, and craftsmanship of these different fields.

As a Ph.D. student at the University of Maryland at Baltimore, I was fascinated with the economy and simplicity of Ca²⁺ in biological systems. As a divalent cation, calcium undergoes neither catabolism or anabolism, yet it plays pivotal roles in nearly every aspect of biology. This paradox of simplicity and complexity became even more profound as I realized that the list for second messengers at work in any biological system is extremely short—cAMP, IP3, ROS, for example. What mechanisms bestow Ca²⁺, or any second messenger, with such amazing signaling specificity and versatility?

In my first English publication, my co-workers and I reported the discovery of "Ca²⁺ sparks" as the elementary events of intracellular Ca²⁺ signaling. Ca²⁺ sparks are brief openings of variable cohorts of from one to eight ryanodine receptor (RyR) Ca²⁺ release channels in the endoplasmic or sarcoplasmic reticulum (ER or SR). The summation of coordinated activation of Ca²⁺ sparks in space and time gives rise to complex global Ca²⁺ signals.

Subsequent research in "sparkology" has unraveled exquisite hierarchal architecture of Ca²⁺ signaling. On the basis of these findings, we have proposed that Ca²⁺ signaling is, in essence, a discrete, stochastic, and digital system, rather than a continuous, deterministic, analog system, as previously thought. This concept not only sheds new light on calcium’s complex simplicity, but also allows for unprecedented precision in the detection and definition of disease-related aberrant Ca²⁺ signaling.

In collaboration with M.T. Nelson, we uncovered a novel Ca²⁺ signaling pathway in which sparks relax vascular smooth muscles. In this pathway, subsurface sparks activate large-conductance Ca²⁺-sensitive K+ channels, which shut off L-type Ca²⁺ influx through hyperpolarization of the membrane. This leads to reduction of intracellular Ca²⁺ and muscle relaxation. This finding vividly illustrates that a single simple messenger, Ca²⁺, can serve different and even opposing roles in the same cell.

In heart muscle cells, Ca²⁺ entering through L-type Ca²⁺ channels traverses a 12-nm junctional cleft to activate RyRs in the SR, liberating stored Ca²⁺. This process is known as Ca²⁺-induced Ca²⁺ release (CICR). For years, many physiologists dreamed of "seeing" nanoscale, intermolecular CICR. Our team has now painstakingly accomplished the optical recording of single L-type channel Ca²⁺ currents or "Ca²⁺ sparklets." We went on to demonstrate that a single sparklet can trigger a spark in an all-or-none fashion. These steps made it possible to define the stoichiometry, kinetics, and fidelity of intermolecular signaling in real time and in live cells.

Most recently, we found that when a spark ignites, rapid and substantial decreases in Ca²⁺, called "Ca²⁺ blinks," develop within nanometer-sized stores—the junctional cisternae of the SR. The complementary spark-blink signal pairs in heart may be a prototype for similar reciprocal signals and suggest space-time organization of signaling from Ca²⁺ stores, including capacitive Ca²⁺ entry and ER/SR-dependent apoptotic signaling.

The aims of our current and future Ca2+ signaling research are to discover new phenomena, functions, and mechanisms—leading to new concepts and theories—as we develop novel methods, analytic tools, special reagents, and instruments for Ca²⁺ studies. We hope these "nuts and bolts" will broaden the frontier of technology for the field.

We will continue to focus on Ca²⁺ signaling in subcellular compartments and organelles (mitochondria, ER/SR, and nuclei) and in vivo imaging of biosensors at single-cell and single-molecule resolutions. But beyond this, we will consider the Ca²⁺ signalome as a whole, including synthesizing information gleaned from molecules, pathways, subcellular organelles, cells and organisms. This integration enlists the powerful addition of bioinformatics and system theory to our current research portfolio. In addition, through collaboration, we also hope to translate our findings to pertinent disease models, thereby advancing the understanding of the etiology and enlightening the treatment of human diseases.

Selected Publuications

1. Cheng, H., Lederer, W.J., Cannell., M.B., 1993, Calcium sparks: The elementary events underlying excitation-contraction coupling in heart muscle. Science 262, 740-744

2. Cheng, H., Lederer, W.J., Cannell, M.B., 1995, Partial inhibition of calcium current by D600 reveals spatial non-uniformities in [Ca²⁺]_i during excitation-contraction coupling in cardiac myocytes. Circ. Res. 76, 236-241

3. Cheng, H., Fill, M., Valdivia, H.H., Lederer, W.J., 1995, Models of calcium release channel adaptation, Science 267, 2009-2010

4. Cannell, M.B., Cheng, H., Lederer, W.J., 1995, The control of calcium release in heart muscle. Science 268, 1045-1050

5. Nelson, M.T., Cheng, H., Rubart, M., Santana, L.F., Bonev, A., Knot, H., Lederer, W.J., 1995, Relaxation of arterial smooth muscle by calcium sparks. Science 270, 633-637

6. Klein, M.G., Cheng, H.*, Santana, L.F., Lederer, W.J., Schneider, M.F., 1996, Discrete sarcomeric calcium release events activated by dual mechanisms in skeletal muscle. Nature 379, 455-458 (* the corresponding author)

7. Gomez, A.M., Valdivia, H.H., Cheng, H., Santana, L.F., Lederer, W.J., 1997, Defective excitation-contraction coupling in experimental cardiac hypertrophy and heart failure. Science 276, 800-806

8. Sham, J., Song, L.-S., Deng, L.H., Chen-Izu, Y., Lakatta, E.G., Stern, M.D., Cheng, H., 1998, Termination of Ca²⁺ release by local inactivation of ryanodine receptors in cardiac myocytes. Proc. Natl. Acad. Sci. USA 95, 15096-15101

9. Shirokova, N., Gonzalez, A., Kirsch, W.G., Rios, E., Pizarro, G., Stern, M.D., Cheng, H., 1999, Calcium sparks: release packets of uncertain origin and fundamental role. J. Gen. Physiol. 113, 377-384 (Invited Review)

10. Wang, S.Q., Song, L.-S., Lakatta, E.G., Cheng, H., 2001, Ca²⁺ signalling between single L-type Ca²⁺ channels and ryanodine receptors in heart cells. Nature 410, 592-596

11. Song, L.-S., Wang, S.Q., Xiao, R.-P., Spurgeon, H., Lakatta, E.G., Cheng, H., 2001, b-adrenergic stimulation synchronizes intracellular Ca²⁺ release during excitation-contraction coupling in cardiac myocytes. Circ. Res. 88, 794-801

12. Song, L.-S., Guia, A., Muth, J., Rubio, M., Wang, S.Q, Xiao, R.-P., Josephson, I.R., Schwartz, A., Lakatta, E.G., Cheng, H., 2002, Ca²⁺ signaling in cardiac myocytes overexpressing the α1-subunit of L-type Ca²⁺ channel. Circ. Res. 90, 174-181

13. Pan, Z., Yang, D., Nagaraj, R.Y., Nosek, T.A., Nishi, M. Takeshima, H., Cheng, H., Ma, J., 2002, Dysfunction of store-operated Ca²⁺ channel in muscle cells lacking mg29 gene. Nature Cell Biol. 4, 379-383

14. Yang, D., Song, L.-S., Zhu, W.Z., Chakir, K., Wang, W., Wu, C., Wang, Y., Xiao, R.-P., Chen, S.R.W., Cheng, H., 2003, Calmodulin regulation of excitation-contraction coupling in cardiac myocytes. Circ. Res. 92, 659-667

15. Wang, S.Q., Stern, M.D., Ríos, E., Cheng, H., 2004,The quantal nature of ca²⁺ sparks and in situ operation of the ryanodine receptor array in cardiac cells. Proc. Natl. Acad. Sci. USA 101, 3979-3984

16. Wang, S.Q., Wei, C.L., Gao, G. L., Brochet, D., Shen, J.X., Song, L.S., Wang, W., Yang, D.M., Cheng, H., 2004, Imaging microdomain Ca²⁺ in muscle cells. Circ. Res. 94, 1011-1022 (invited review)

17. Wang, W., Zhu, W., Wang, S. Q., Yang, D. M., Crow, M. T., Xiao, R. P., Cheng, H., 2004, Sustained b₁-adrenergic stimulation modulates cardiac contractility by Ca²⁺/calmodulin kinase signaling pathway. Circ. Res. 95,798-806.

18. Brochet, D. X. P., Yang, D., Di Maio, A., Lederer, W. J., Franzini-Armstrong, C., Cheng, H., 2005, Calcium blinks: Rapid nanoscopic store calcium signaling. Proc. Natl. Acad. Sci. USA, 102, 3099-3104

19. Ouyan, K., Wu, C. H., Cheng, H. (2005) Ca²⁺-induced Ca²⁺ release in sensory neurons: Low-gain amplification confers intrinsic stability. J. Biol. Chem. 280, 15898-15902

20. Wang, X., Collet, C., Weisleder, N., Zhou, J.S., Chu, Y., Brotto, M., Hirata, Y., Pan, Z., Cheng, H., Ma, J. (2005) Uncontrolled Ca²⁺ sparks as dystrophic signal for mammalian skeletal muscle. Nature Cell Biol. 7, 525-530

三、Principal Investigator：周专（ Zhuan Zhou）

Personal Synopsis

Zhuan Zhou, 1984, B.S. Electronic instrumentation, Tongji University, Shanghai. 1990, Ph.D. (Prof. Huaguang Kang's lab) Biomedical Engineering, Huazhong University of Science and Technology (HUST), Wuhan. Nov. 1990-Feb. 1993, postdoctoral fellow (Dr. Erwin Neher's lab), Max-Planck-Institute for Biophysical Chemistry, Goettingen, Germany. Feb. 1993 - Oct. 1995, Research Instructor (Dr. Stanley Misler's lab), Departments of Physiology, Washington University. St. Louis, USA. Nov. 1995-97, Researcher Assistant Professor, Department of Physiology, Loyola University, Chicago, USA. Sep. 1997-99, professor and head, Department of Neuroscience and Biophysics, University of Science and Technology of China, Hefei. Apr. 1993-2000, professor and director, Nov. 1999-2004, Principle Investigator, Institute of Neuroscience, Chinese Academy of Sciences. Consul of Biophysical Society of China, Chair of Neurobiophysics Committee (2002-2006). Consul of Chinese Association of Physiological Society (2002-2006). He is now a Senior Investigator and PI of the Nerve-Circulation-interaction Laboratory at IMM, PKU.

Research Interests

Secretion is a principle function of a cell. Neurotransmitter and hormone secretion is triggered by increase in intracellular Ca concentration. We are interested in mechanisms of how intracellular Ca is regulated in single cell level by advanced methods including electrophysiological and optical fluorescence measurements. We investigate mechanisms of neurotransmitter, in particular catecholamines, release from soma (or synapse) of a cell by patch-clamp, membrane capacitance and carbon fiber electrodes (CFEs) and fluorescent optic measurements. We are interested in creating/modifying biophysical technologies for advanced experiments including Ca homeostasis, patch-clamp and stimulus-secretion-coupling. Our goal is to best understand how secretion is regulated in a living cell, and how catecholamine release (from adrenal chromaffin cells as well as catechonminergic CNS neurons, affect cardiac/vesicular function.

Ionic channels, action potentials and quantal secretion in single cells

Neurotransmitter release is primary triggered by Ca influx during action potentials in neuronal cells. Action potentials are generated and regulated by variety of ion channels on the cell membrane. We are interested in how action potential patterns are regulated by the ion channels, and how secretion is regulated by different encodes of the action potentials. We created a technique for membrane capacitance measurements using reconstituted codes of action potentials as stimulation protocol and we are studying the relation between action potential pattern and cell secretion in chromaffin cells.

We are interested in the kinetics of fusion pore, which release/uptake vesicle contents during an exocytotic/endocytotic event. In adrenal chromaffin cells, we discovered that the endogenous transmitter ATP can inhibits secretion via two pathways: Ca channel (50% of total inhibition) and fusion pore (the other 50% of total inhibition). ATP reduces the fusion pore open time or shift the mode of exocytosis to “kiss-and-run”. In astrocyte, a hippocampal glia, we study Ca dependent quantal secretion as well. In particular, the fusion pore kinetics in astrocytes is distinct in response to different stimulations.

Ion channels are molecular basis for action potentials. Ion channels studies in our lab including Na channel (inactivation), voltage and Ca dependent K channels (specific toxins against BK and SK channels) and HCN pacemaker channels. The role of HCN (or I_f, I_h) channels is to generate rhythmic action potentials in the host cells. In opposite to other voltage gated channels, these channels activate at negative potentials and thus depolarize the cell to fire next Na dependent action potential. This non-selective cation channel has a reversal potential at –30-40 mV and permeates Na⁺ and K⁺. Recently, we discovered that in addition to mono cation, HCN can permeate Ca²⁺ as well: 05% of total current is contributed by Ca²⁺. The Ca influx through I_h channels can modulate neuronal secretion in DRG neurons and action potential duration in cardiac cells.

Exocytosis and endocytosis in somata in DRG neurons

In sensory dorsal root ganglion (DRG) neurons, we have discovered a novel type of action potential triggered secretion in the soma, Ca independence but voltage dependent secretion (CIVDS). This means, depolarization can directly trigger exocytosis in the absence of both internal and external Ca²⁺. This finding was very surprising in the areas of stimulus-secretion coupling and synaptic transmission, because the dominant “Ca hypothesis” puts Ca²⁺ as the only trigger for exocytosis, the role of voltage depolarization is only to allow Ca influx through voltage gated Ca channels. CIVDS can be detected by membrane capacitance, electrochemical amperometry, and confocal single vesicle imaging assays. In DRG soma, membrane depolarization/action potential trigger both Ca dependent secretion (CDS) and CIVDS. Vesicle pool size of CIVDS is 20 % of that of CDS. After depletion of the, the recovery rate of the vesicle pool of CIVDS is fast (10 s). Compared with CDS, the onset rate of CIVDS is very fast. The voltage dependence of CIVDS is similar as a voltage-sensitive ion channel. These properties make CIVDS to be the major source of secretion in response to in low (< 5 Hz) frequency action potentials.

Under physiological conditions, the low frequency of action potential may trigger

Following CIVDS, there is a rapid endocytosis termed CIVDS-RE. Compared to other endocytosis in neurons, CIVDS-RE has several distinct properties: (1) like CIVDS, RE is Ca independent; (2) RE is dynamin independent; (3) RE depends on frequency of action potentials; (4) RE is dependent of PKA, which is activated by high (not low) frequency of action potentials.

In addition to voltage-triggered exocytosis and endocytosis, we are interested in ligand-triggered exocytosis and endocytosis. Compared to Ca²⁺ influx through Ca channels, the caffeine sensitive Ca stores (or Ca sparks) alone have a lower efficiency to trigger secretion. However, Ca stores provide an important synergistic role to enhance depolarization induced secretion. Finally, we are studying ligand-induced endocytosis and their signal tranduction with high spatial and temporal resolution by using capacitance and single vesicle imaging. These studies may have potential applications in GPCR-mediated signaling in neurons and cardiac cells.

Stimulus-secretion-coupling between neurons in the brain slice and in living brain

Currently, majority studies on stimulus-secretion-coupling are performed in culture cells. This is because the culture cells offer relative simple techniques to record secretion in single cells. However, interaction between neurons and other cell environment maintain better in brain slice or in vivo. To understand how synaptic transmission and cell secretion occur in brain slice and/or in vivo, we are developing new carbon fiber electrodes (CFEs) and studying neurotransmitter release in slice and in living animals. We determine the common and different features of stimulus-secretion coupling between neurons in culture, in slice and in vivo. These studies may lead new insights into exocytosis/endocytosis in response to stimuli under more physiological conditions.

Development of novel microprobes to detect neuropeptides secretion from single cells with high spatial-temporal sensitivity

Neuropeptides are important modulators for fundamental brain functions. Unlike other ligands such as ACh, glutamate etc, there are few neuropeptide-gated ion channels, which can be recorded by patch-clamp. Thus, to detect neuropeptide new probes are needed. Since several years we are working on new types of electrodes, which may sense release of neuropeptides. Our goal is to use the new peptide-electrodes to study how, when and where neuropeptides are released from culture single cells, brain slices and living brains.

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Selected Publuications

1. Chen Zhang, Wei Xiong, Hui Zheng, Liecheng Wang, Bai Lu and Zhuan Zhou (2004) Calcium- and dynamin-independent endocytosis in dorsal root ganglion neurons. Neuron, 42: 225–236

2. Yu X, Duan KL, Shang CF, Yu HG and Zhou Z (2004) Calcium influx through hyperpolarization-activated cation channels ( Ih channels) contributes to activity-evoked neuronal secretion. Proc Natl Acad Sci U S A., 101:1051-1056.

3. Duan KL, Yu X, Zhang C, and Zhou Z (2003) Control of Secretion by Temporal Patterns of Action Potentials in Adrenal Chromaffin Cells. J. Neurosci., 23(35):11235-43

4. Xuelin Lou, Xiao Yu, Xiao-Ke Chen, Liming He, Kai-Lai Duan, Anlian Qu, Tao Xu and Zhuan Zhou. (2003) Na channel inactivation: a comparison study between pancreatic islet ß-cells and adrenal chromaffin cells in rat. J. Physiol (Lond) 548: 191-202.

5. Chong-Xu Fan, Xiao-Ke Chen, Chen Zhang, Li-Xiu Wang, Kai-Lai Duan, Lin-Lin He, Ying Cao1, Shang-Yi Liu, Ming-Nai Zhong, Chris Ulens, Jan Tytgat, Ji-Sheng Chen, Cheng-Wu Chi and Zhuan Zhou. (2003) A Novel Conotoxin from Conus betulinus, k-BtX, unique in Cysteine Pattern and in Function as a specific BK Channel Modulator. J. Biol. Chem. 278:12624-33

6. Lan Bao, Shan-Xue Jin, Chen Zhang, Li-Hua Wang, Zhen-