Cooperating Graduate Faculty:  Cross-Appointed from Other Departments
Research Description

	Andrea Fleig Associate Professor and Associate Director of Research, Department of Cell and Molecular Biology Phone:  (808) 537-7931 Fax:  (808) 537-7899 Email:  afleig@hawaii.edu
Queen's Medical Center & University of Hawai’i at Manoa Center for Biomedical Research UHT 809 Laboratory of Cell and Molecular Signaling 1356 Lusitana Street, _Honolulu, Hawaii _96813

Ph.D. Neurosciences, University of Hawaii at Manoa 1993
M.S. Biology and English, University Konstanz, Germany 1989

Cellular Physiology

Cellular Calcium and Magnesium Homeostasis

Calcium as Second Messenger. Calcium plays a pivotal role in various cell signaling events, ranging from muscle contraction to apoptosis. Calcium is employed as a second messenger in electrically excitable cells such as neurons or endocrine cells. Non-excitable cells such as blood cells or cells from the immune system also depend on this ion to be readily available.

Our recent work has concentrated on various aspects of calcium signaling in electrically excitable as well as non-excitable cells using patch-clamp electrophysiology, fluorimetry, flow cytometry and immunofluorescence. Changes in intracellular calcium concentration ([Ca2+]i) are employed by practically every cell type to control vital cellular responses such as secretion, contraction, enzyme regulation, gene expression, etc.  The sources from which calcium is mobilized can be either intracellular stores or the extracellular medium.  Depending on the cell type, there are different short- and long-term mechanisms by which increases in [Ca2+]i are accomplished.

In addition to its role as an important physiological signaling mechanism, it is also becoming increasingly evident that calcium plays a crucial role in many pathological situations.  Excessive Ca2+ influx is known to cause cell damage, even cell death (it appears to be one of the main detrimental factors in stroke).  Aberrant Ca2+ signaling can also cause cell transformation and tumor development.  It is becoming apparent that most of the neurodegenerative diseases such as Alzheimer’s, Multiple Sclerosis, and stroke have strong immunological components.  Modulating the activation of immune cells offers the intriguing possibility to alleviate the devastating auto-immune attacks in these diseases. Based on these premises one of our projects involves the role of calcium homeostasis in immune cells.  In addition, we study the regulation of magnesium homeostasis in immune cells and the role thereof in cell proliferation.  In a very recent project we have started to elucidate the physiological function of four novel magnesium- and/or calcium-conducting ion channels of the TRP-family expressed in human immune cells. Selected Publications 1.  Hermosura, M.C., Takeuchi, H., Fleig, A., Riley, A.M., Potter, B.V.L., Hirata, M. and Penner, R. 2000. Inositol 1,3,4,5-tetrakisphosphate facilitates store-operated calcium influx by inhibition of inositol 1,4,5-trisphosphate 5-phosphatase. Nature 408:735-740. 2.  Nadler, M.J.S., Hermosura, M.C., Inabe, K., Perraud, A.-L., Zhu, Q., Stokes, A.J., Kurosaki, T., Kinet, J.-P., Penner, R., Scharenberg, A. M. and Fleig, A. 2001. LTRPC7 is a Mg·ATP-regulated divalent cation channel required for cell viability. Nature 411:590-595. 3.  Perraud, A.-L., Fleig, A., Dunn, C.A., Bagley, L.A., Launay, P., Schmitz, C., Stokes, A.J., Zhu, Q., Bessmann, M.J., Penner, R., Kinet, J.-P. and Scharenberg, A.M. 2001. ADP-ribose gating of the calcium-permeable LTRPC2 channel revealed by Nudix motif homology. Nature 411:595-599. 4.  Hermosura, M.C., Monteilh-Zoller, M.K., Scharenberg, A.M., Penner, R. and Fleig, A. 2002. Dissociation of the store-operated calcium current ICRAC and the Mg2+-nucleotide-regulated metal ion current MagNuM. Journal of Physiology 539.2:445-458. 5.  Launay, P., Fleig, A., Perraud, A.L., Scharenberg, A.M., Penner, R. and Kinet, J.P. 2002. TRPM4 is a Ca2+ activated nonselective cation channel mediating cell membrane depolarization. Cell 109:397-407. 6.  Monteilh-Zoller, M.K., Hermosura, M.C., Nadler, M.J.S., Scharenberg, A.M., Penner, R. and Fleig, A. 2003. TRPM7 provides an ion channel mechanism for cellular entry of trace metal ions. Journal of General Physiology 121:49-60. 7.  Schmitz, C., Perraud, A.L., Johnson, C.O., Inabe, K., Smith, M.K., Penner, R., Kurosaki, T., Fleig, A. and Scharenberg, A.M. 2003. Regulation of vertebrate cellular Mg2+ homeostasis by TRPM7. Cell 114:191-200. 8.  Launay, P., Cheng, H., Srivatsan, S., Penner, R., Fleig, A. and Kinet, J.P. 2004. TRPM4 regulates calcium oscillations after T cell activation. Science 19:1374-1377. 9.  Takezawa, R., Schmitz, C., Demeuse, P., Scharenberg, A., Penner, R., and Fleig, A. 2004. Receptor-regulation of the TRPM7 channel through its kinase domain. Proceedings of the National Academy of Sciences USA 101:6009-6014. 10.  Fleig, A. 2004. TRPM cation channels, an unlikely family. Nova Acta Leopoldina 336, Band 89:53-60. 11.  Fleig, A. and Penner, R. 2004. The TRPM Ion Channel Subfamily: Molecular, Biophysical and Functional Features. Trends in Pharmacological Sciences 25:633-639. 12.  Kolisek, M., Beck, A., Fleig, A. and Penner, R. 2005. Cyclic ADP-ribose and hydrogen peroxide synergize with ADP-ribose in the activation of TRPM2 channels. Molecular Cell 18:61-69. 13.  Demeuse, P., Penner, R. and Fleig A. 2006. TRPM7 channel is regulated by magnesium nucleotides via its kinase domain. Journal of General Physiology 127:421-434. 14.  Stokes, A.J., Wakano, C., Koblan-Huberson, M., Adra, C.N., Fleig, A. and Turner H. 2006. TRPA1 is a substrate for de-ubiquitination by the tumor suppressor CYLD. Cell Signal (in press). 15.  Peinelt, C., Vig, M., Koomoa, D.L., Beck, A., Nadler, M., Koblan-Huberson, M., Lis, A., Fleig, A., Penner, R. and Kinet, J.P. Amplification of Ca2+ release-activated Ca2+ (CRAC) current by STIM1 and CRACM1 (ORAI1). Nature Cell Biology (in press). 16.  Vig, M., Peinelt, C., Beck, A., Koomoa, D.L., Rabah, D., Koblan-Huberson, M., Kraft, S., Turner, H., Fleig, A., Penner, R. and Kinet, J.P. CRACM 1 is a plasma-membrane protein essential for store-operated Ca2+ entry. Science (in press).