[Research Interests] [Representative Publications] [Lab Members] RESEARCH INTERESTSCalcium Signaling Mechanisms in Yeast and Human CellsCalcium signals regulate a large number of cellular processes including contraction of muscle fibers, release of hormones and neurotransmitters, programmed cell death, and gene expression. Surprisingly, most of the factors known to control or respond to calcium signals are widely conserved in nature and operating similarly in diverse species. Our primary goal is to help develop a complete understanding of calcium signaling in the budding yeast Saccharomyces cerevisiae, a simple organism that affords powerful genetic and genomic tools, and to apply this knowledge toward understanding and treating human diseases. The protein phosphatase calcineurin is highly conserved in nature and serves as a primary sensor and transducer of calcium signals. Calcineurin is crucial for normal immune response in humans: drugs that inhibit calcineurin, such as Cyclosporin A and FK506, are potent immunosuppressants that are used to prevent rejection of transplanted organs and to treat certain autoimmune diseases. These drugs have many undesirable side effects in other tissues, suggesting important roles for calcineurin in other cell types. To better understand how calcineurin works in cells, we used yeast to clone and characterize a new family of endogenous regulators of calcineurin (termed RCNs) that are conserved from yeast to humans. We found that low concentrations of either the yeast or human RCN proteins directly stimulate calcineurin activity whereas high doses and dephosphorylation of these RCNs can block calcineurin function much like the immunosuppressive drugs. RCNs may therefore become useful in gene therapies. We also noticed the human RCN called DSCR1 was expressed at extraordinarly high levels in the brains of individuals with Down syndrome, suggesting that inappropriate calcineurin regulation may contribute to mental retardation and Alzheimer’s disease observed in all Down syndrome individuals. Future work will focus on defining the detailed molecular mechanism of how RCNs affect calcineurin activity in vivo and developing new therapies for treating these diseases. Some of our other studies have revealed an interesting new stimulus that generates calcium signals in yeast as well as pathogenic fungi. We found that damage to components of the endoplasmic reticulum triggers calcium influx through the plasma membrane and activation of calcineurin. Human cells may have a similar regulatory mechanism linking the two membranes, so we are interested in defining the molecules and mechanism that interconnect them. Surprisingly, we found that calcium influx and calcineurin activation were necessary to prevent the death of yeast cells in response to azole-class antifungal drugs, the most commonly prescribed antibiotics for treatment of fungal infections. We are actively seeking the cell death factors functioning downstream of calcineurin in yeast because they may represent a new kind of cell death mechanism and they may be good targets for the development of new types of antifungal drugs. REPRESENTATIVE PUBLICATIONSZhang NN, Dudgeon DD, Paliwal S, Levchenko A, Grote E, Cunningham KW. 2006. Multiple signaling pathways regulate yeast cell death during the response to mating pheromones. Mol Biol Cell.(8):3409-22. Frederick RL, McCaffery JM, Cunningham KW, Okamoto K, Shaw JM.2004. Yeast Miro GTPase, Gem1p, regulates mitochondrial morphology via a novel pathway. J Cell Biol. 167(1):87-98. Hilioti Z, Gallagher DA, Low-Nam ST, Ramaswamy P, Gajer P, Kingsbury TJ, Birchwood CJ, Levchenko A, Cunningham KW.2004. GSK-3 kinases enhance calcineurin signaling by phosphorylation of RCNs. Genes Dev. 18(1):35-47. Gupta SS, Ton V-K, Beaudry V, Rulli S, Cunningham KW, and Rao R. 2003. Antifungal activity of amiodarone is mediated by disruption of calcium homeostasis. J. Biol. Chem. 278, 28831-28839. Bonilla, M., K. K. Nastase, and K. W. Cunningham 2002. Essential Role of Calcineurin in Response to Endoplasmic Reticulum Stress. EMBO J 21, 2343-2353. Muller, E., E. G. Locke, and K. W. Cunningham 2001. Differential regulation of two Ca2+ influx systems by pheromone signaling in Saccharomyces cerevisiae. Genetics 159, 1527-1538. Takita, Y., L. Engstrom, C. Ungerman, and K. W. Cunningham 2001. Inhibition of a vacuolar Ca2+ ATPase Pmc1p by the v-SNARE Nyv1p. J. Biol. Chem. 276, 6200-6206. Furuichi, T., K. W., Cunningham, S. MutO.2001. A puaTtive two pore channel AtPC1 mediates Ca2+ flux in Arabidopsis leaf cells. Plant Cell Physiol. 42, 900-905 Birchwood, C. B., J. D. Saba, R. C. Dickson, and K. W. Cunningham.2001. Calcium influx and signaling in yeast stimulated by intracellular sphingosine-1-phosphate accumulation. J. Biol. Chem. 276, 11,712-11,718 Ueoka-Nakanishi, H., T. Tsuchiya, M. Sasaki, Y. Nakanishi, K. W. Cunningham, and M. Maeshima 2000. Functional expression of mung bean Ca2+/H+ antiporter in yeast and its intracellular localization in the hypcotyl and tobacco cells. Eur. J. Biochem. 267, 3090-3098. Locke, E. G., L. Liang, M. Bonilla, Y. Takita, and K. W. Cunningham 2000. A homolog of Voltage-gated Ca2+ Channels Stimulated by Depletion of Secretory Ca2+ Pools in Yeast. Mol. Cell. Biol. 20, 6686-6694. Kingsbury, T. J., and K. W. Cunningham 2000. A conserved family of calcineurin regulators. Genes & Dev 14, 1595-1604. Fuentes, J. J., L. Genescà, T. J. Kingsbury, K. W. Cunningham, M. Pérez-Riba, X. Estivill, and S. de la Luna. 2000. DSCR1, overexpressed in Down syndrome, is an inhibitor of calcineurin-mediated signaling pathways. Hum. Mol. Gen. 9, 1681-1690. Lab MembersGraduate Students: |
