Metal ions contribute to fundamental biological processes, including maintenance of protein architecture, determination of enzyme catalytic activity and signal transduction. Transport mechanisms for trace metal ions are not well characterized, and no ion channel with the ability to permeate significant amounts of these ions has yet been described. Recently, a superfamily of the putative calcium-permeable cation channel family TRPC (transient receptor potential channels) has been identified. Our data characterize a novel and widely expressed ion channel of this superfamily, LTRPC7, which has an intriguing selectivity profile for trace metal ions. LTRPC7 is regulated by intracellular levels of Mg.ATP and is non-redundantly essential for cell viability. The current proposal characterizes this novel ion channel using electrophysiological and molecular biology techniques.
Specific Aim 1 focuses on the biophysical characterization of recombinant and native LTRPC7. First, the channel?s selectivity profile for trace metal ions will be analyzed. Second, since LTRPC7 is dependent on nucleotide triphosphates, these findings will be extended to include other phospho-nucleotides. Third, the involvement of phosphorylation in channel function will be tested.
Specific Aim 2 concentrates on the functional and molecular analysis of LTPRC7 and introduces targeted point mutations to evaluate the structural requirements that determine the selectivity and modulation of LTRPC7.
Specific Aim 3 addresses the physiological significance of LTRPC7 currents. It is hypothesized that endogenous LTRPC7 contributes to calcium influx pathways normally attributed to the ICRAC conductance in immune cells. Therefore, experiments have been designed addressing the dissociation of these two currents. Finally, the role of enhanced LTRPC7 expression and metal ion entry in pro-apoptotic events and cell death is assessed. The studies proposed above are based on the unique ion channel LTRPC7. By virtue of this channel?s sensitivity to Mg ATP levels and unusual selectivity to divalent ions, LTRPC7 seems to link fundamental processes that adjust plasma membrane divalent cation fluxes according to the metabolic state of the cell. Disturbing this delicate balance may induce LTRPC7-dependent cell death. These features predestine LTRPC7 to be a prominent player in pathophysiological situations mediating the detrimental divalent ion entry in ischaemic events. Detailed understanding of LTRPC7 physiological function will open new and fascinating possibilities to influence cell survival.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM065360-04
Application #
6877037
Study Section
Metallobiochemistry Study Section (BMT)
Program Officer
Shapiro, Bert I
Project Start
2002-04-01
Project End
2006-03-31
Budget Start
2005-04-01
Budget End
2006-03-31
Support Year
4
Fiscal Year
2005
Total Cost
$283,620
Indirect Cost
Name
Queen's Medical Center
Department
Type
DUNS #
054787481
City
Honolulu
State
HI
Country
United States
Zip Code
96813
Cheng, Henrique; Beck, Andreas; Launay, Pierre et al. (2007) TRPM4 controls insulin secretion in pancreatic beta-cells. Cell Calcium 41:51-61
Tani, Dawn; Monteilh-Zoller, Mahealani K; Fleig, Andrea et al. (2007) Cell cycle-dependent regulation of store-operated I(CRAC) and Mg2+-nucleotide-regulated MagNuM (TRPM7) currents. Cell Calcium 41:249-60
Bessac, Bret F; Fleig, Andrea (2007) TRPM7 channel is sensitive to osmotic gradients in human kidney cells. J Physiol 582:1073-86
Penner, R; Fleig, A (2007) The Mg2+ and Mg(2+)-nucleotide-regulated channel-kinase TRPM7. Handb Exp Pharmacol :313-28
Demeuse, Philippe; Penner, Reinhold; Fleig, Andrea (2006) TRPM7 channel is regulated by magnesium nucleotides via its kinase domain. J Gen Physiol 127:421-34
Peinelt, Christine; Vig, Monika; Koomoa, Dana L et al. (2006) Amplification of CRAC current by STIM1 and CRACM1 (Orai1). Nat Cell Biol 8:771-3
Vig, M; Peinelt, C; Beck, A et al. (2006) CRACM1 is a plasma membrane protein essential for store-operated Ca2+ entry. Science 312:1220-3
Beck, Andreas; Kolisek, Martin; Bagley, Leigh Anne et al. (2006) Nicotinic acid adenine dinucleotide phosphate and cyclic ADP-ribose regulate TRPM2 channels in T lymphocytes. FASEB J 20:962-4
Kolisek, Martin; Beck, Andreas; Fleig, Andrea et al. (2005) Cyclic ADP-ribose and hydrogen peroxide synergize with ADP-ribose in the activation of TRPM2 channels. Mol Cell 18:61-9
Takezawa, Ryuichi; Schmitz, Carsten; Demeuse, Philippe et al. (2004) Receptor-mediated regulation of the TRPM7 channel through its endogenous protein kinase domain. Proc Natl Acad Sci U S A 101:6009-14

Showing the most recent 10 out of 17 publications