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David E. Levin 72 East Concord Street, Evans, room 430 Boston, MA 02118-2394 |
education
Ph. D.: University of California, Berkeley 1984
Postdoctoral Training: University of California, San Francisco 1984-1988
research description
Stress signaling and cell wall biogenesis in fungi
We use baker’s yeast, Saccharomyces cerevisiae, as a model genetic organism in which to study the molecular mechanisms of stress signaling. The biomedical relevance of our work is centered on the identification of potential antifungal drug targets. One project concerns the dissection of the Cell Wall Integrity (CWI) signaling pathway, which detects and responds to cell wall stress during growth and morphogenesis. Because animal cells lack cell walls, this structure is an attractive target in fungal pathogens. Disruption of the fungal cell wall results in cell lysis. The CWI pathway uses a set of cell surface sensors that are connected to a small G-protein (Rho1), which activates signaling through a MAP kinase cascade. We have found in recent studies that the Mpk1 MAP kinase of the CWI pathway has a non-catalytic function in transcription initiation and elongation, in addition to its catalytic activity as a protein kinase. We are now working to understand this novel mechanism for transcriptional regulation.
A second project exploits the need of fungal cells to maintain osmotic homeostasis through the regulation of intracellular glycerol concentration. We have identified a pair of genes, named GCA1 and GCA2 (for Glycerol Channel Activators) whose function is to control the activity of the Fps1 glycerol channel, which acts as a plasma membrane vent that decreases turgor pressure by releasing glycerol from the cell. The fungal kingdom is replete with members of the Gca family of proteins, but they have not been found in metazoan organisms. For this reason, and because mutants in these genes undergo cell lysis as a result of excess turgor pressure, the Gca proteins may be suitable antifungal targets. Current studies are centered on understanding the biochemical function of Gca1/2 and their mode of regulation in response to osmotic stress.
A third project concerns the regulation of glycosylphosphatidylinositol (GPI)-anchor production by the G-protein Ras. GPI-anchors are attached to proteins in the endoplasmic reticulum (ER) that are destined for the cell surface. This regulation is unusual because it involves Ras signaling at the ER, rather than at the plasma membrane, its well-studied site of action. We found that Ras inhibits the first step in GPI-anchor biosynthesis and have identified and mutated the site of Ras interaction with its target enzyme at the ER. This has allowed us to initiate studies on the biological consequences of this regulation.
recent publications
Beese, S. E., T. Negishi, and D. E. Levin. Identification of activators of the yeast Fps1 glycerol channel. Submitted.
Truman, A. W., K-Y. Kim, and D. E. Levin. Mechanism of Mpk1 MAPK binding to the Swi4 transcription factor and its regulation by a novel caffeine-induced phosphorylation. Submitted.
Kim, K-Y., A. W. Truman, S. Caesar, G. l. Schlenstedt, and D. E. Levin. Yeast Mpk1 cell wall integrity MAPK regulates nucleocytoplasmic shuttling
of the Swi6 transcriptional regulator. Submitted.
Kim, K-Y., A. W. Truman, and D. E. Levin (2008). Yeast Mpk1 MAPK activates transcription through Swi4/Swi6by a non-catalytic mechanism that requires upstream signal. Mol. Cell. Biol. 28: 2579-2589.
Kim, K-Y., I. C. Cosano, D. E. Levin, M. Molina and H. Martín (2007). Dissecting the transcriptional activation function of the cell wall integrity MAP kinase. Yeast 24: 335-342.
Newman, H. A., M. J. Romeo, S. E. Lewis, B. C. Yan, P. Orlean, and D. E. Levin (2005). Gpi19, the Saccharomyces cerevisiae homologue of mammalian PIG-P, is a subunit of the initial enzyme for glycosylphosphatidylinositol anchor biosynthesis. Euk. Cell 4:1801-1807.
Levin, D. E. (2005). Cell wall integrity signaling in Saccharomyces cerevisiae. Micro. Mol. Biol. Rev. 69: 262-291.
Vay, H. A., B. Philip, and D. E. Levin (2004). Mutational analysis of the cytoplasmic domain of the Wsc1 cell wall stress sensor. Microbiology 150: 3281-3288.
Sobering, A. K., R. Watanabe, M. J. Romeo, B. C. Yan, C. A. Specht, P. Orlean, H. Riezman, and D. E. Levin (2004). Yeast Ras regulates the complex that catalyzes the first step in GPI-anchor biosynthesis at the ER. Cell 117: 637-648.