Ellen K. LeMosy, M.D., Ph.D. elemosy@mail.mcg.edu Telephone: 706.721.0876 Fax: 706.721.6120 Room: CB-2916
Assistant Professor, Department of Cellular Biology and Anatomy

Research Emphasis:

Growth factors activate cell surface receptors to regulate cellular behavior and fate.  Many growth factors, such as TGF-beta (transforming growth factor-beta) and HGF (hepatocyte growth factor), are themselves regulated after their secretion to control their site and strength of signaling, e.g., by proteolytic cleavage or by interaction with inhibitors or extracellular matrix glycoproteins and proteoglycans.  This regulation is vitally important during embryonic development, providing positional information key to patterning the embryonic axes, the vasculature, the nervous system, and other organs.  For example, local capture of secreted heparin-binding VEGF (vascular endothelial growth factor) to form a steep gradient of its activity is critical to the proper branching morphogenesis of capillaries; deletion of its heparin-binding domain results in a broad shallow gradient of VEGF that stimulates the incorporation of new endothelial cells into existing vessels, widening them, rather than forming branch points for new vessels [Ruhrberg et al. (2002) Genes and Development 16: 2684-2698].  A fuller understanding of the mechanisms by which growth factors are regulated will aid in preventing birth defects and diseases such as atherosclerosis and cancer.

The major focus of our lab is on the extracellular regulation of signaling molecules related to NGF (nerve growth factor) that define spatial coordinates of the early Drosophila embryo.  Relevance of this area to human biology is highlighted by the recent recognition that the related mammalian neurotrophins are regulated by extracellular cleavage [reviewed by Lu (2003) Neuron 39: 735-738].  The Drosophila system offers several advantages for these studies.  Many of the regulatory molecules are already known – although some key matrix components are not (see our work below) – and tools such as antibodies and mutants are available for their analysis.  The fly embryo can be manipulated directly by microinjection and observed for rescue or disruption of patterning, e.g., by site-directed mutant molecules or putative inhibitors, allowing a wide range of in vivo analyses.  These and other features of the powerful Drosophila genetic model allow for a thorough and sophisticated attack on the problem of growth factor regulation.

Project 1: Spatial control of proteolysis in dorsoventral polarity (NIH RO1)

Spätzle is an NGF-like ligand that activates an NF-kB related signaling pathway to establish the dorsoventral axis of the early Drosophila embryo.  Freely diffusible Spätzle is activated ventrally by proteolytic processing by a cascade of four enzymes similar to those involved in human blood clotting.  Our genetic and biochemical studies suggest that the first two proteases are active uniformly around the circumference of the embryo, while the final protease that actually processes Spätzle is only activated on the ventral side.  This indicates that the second or the third protease, or both, interacts with its substrate only on the ventral side of the embryo and provides key spatial regulation to this signaling event.  This could result from the presence of a ventral activator for that protease, or possibly the ventral inhibition of a diffusible protease inhibitor; no such modulator has yet been identified.

Our work focuses on identifying the first proteolytic event that is spatially regulated, as well as on identifying the ventrally localized modulator(s) of this activation step.  For the latter task, we are assisted by a wealth of genetic studies from the labs of David Stein, Trudi Schüpbach, and Kathryn Anderson that implicate a gene called pipe in spatial control of Spätzle activity.  This gene encodes an enzyme that adds sulfate groups to carbohydrate chains on glycoproteins before they are secreted and deposited into the extracellular space.  We and others hypothesize that a sulfated glycoprotein is laid down in the egg extracellular matrix during oogenesis and somehow acts to regulate the dorsoventral protease cascade in the early embryo [for reviews, see Anderson (1998) Cell 95: 439-442; Roth (1998) Current Biology 8: R906-R910; LeMosy et al. (1999) Trends in Cell Biology 9: 102-107].  Our biochemical strategies have tentatively identified species altered in pipe-mutant extracellular matrix and functional studies are in progress to determine if these glycoproteins are required for dorsoventral patterning.

Project 2: Spatial regulation of a signaling molecule involved in patterning the embryo termini (March of Dimes, Startup)

Trunk appears to be an NGF-related molecule that activates a receptor tyrosine kinase pathway to specify the formation of head and tail (terminal) structures in the early Drosophila embryo.  Like Spätzle, Trunk is freely diffusible in the extracellular space but is somehow activated only at the anterior and posterior poles of the embryo; while Trunk is hypothesized to be activated by proteolytic cleavage, no known genes in the pathway encode proteases.  Capitalizing on proteomics and immunological techniques we’ve developed to identify ventral cue candidates, we have tentatively identified novel components of the egg extracellular matrix that localize to the anterior and posterior poles, so could be involved in Trunk activation [see Stevens et al. (2003) Current Biology 13: 1058-1063 and LeMosy (2003) Current Biology 13: R508-R510 for background].  Current work focuses on functional characterization of these molecules.

Project 3: Cell adhesion, migration, and epithelial morphogenesis

One current and one former member of our laboratory have initiated studies exploring extracellular matrix and cell adhesion molecules expressed by migrating cells in the Drosophila ovary.  This is a new project with general relevance to epithelial morphogenesis during development, and to metastasis of cancer cells.

 Keywords: protease, extracellular matrix, growth factor signaling, Drosophila, embryo, cell fate determination, carbohydrate modification

 Techniques:  confocal immunofluorescence microscopy, embryo microinjection, transgenics, in vivo rescue/disruption assays, RNA interference, site-directed mutagenesis, DNA cloning, RNA in situ hybridization, antibody production, Western blot, immunoprecipitation, transfection of cultured cells, mosaic analysis by FLP/FRT-mediated DNA recombination, genetic analysis.

 

Education and Training:

1984    B.S., Biology (summa cum laude), with Chemistry minor, University of  Central Florida, Orlando, FL
Homeotic mutations of the bithorax complex interacting with the tumorous-head enhancer in Drosophila (advisor, David T. Kuhn, Ph.D.)

1988    Physiology: Cellular and Molecular Biology Course, Marine Biological Laboratory, Woods Hole, MA

1993    M.D., Ph.D., Department of Cell Biology, Duke University, Durham, NC
Studies of the mammalian extracellular matrix proteins fibronectin, transglutaminase, and glial laminin (advisor, Harold P. Erickson, Ph.D.)

1994-2000    Postdoctoral Fellow, Department of Cell Biology, Yale University, New Haven, CT
Role of an extracellular serine protease cascade in defining embryonic dorsoventral pattern in Drosophila (advisor, Carl Hashimoto, Ph.D.)

 

Academic Positions:

2000-2001       Associate Research Scientist, Department of Cell Biology, Yale University, New Haven, CT (in Hashimoto lab)

2002-present   Assistant Professor, Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, GA

 

Awards and Honors:

1982-1984      American Cancer Society Summer Undergraduate Research Fellowships
1986              Eugene A. Stead Research Scholar, Duke University School of Medicine
1986-1993      Medical Scientist Training Program (NIH Predoctoral Training Program)
1995-1998      Individual NRSA Postdoctoral Fellowship, National Institute of Child Health and Human Development  Spatial regulation of an embryonic extracellular signal
1998-2000      American Heart Association Postdoctoral Fellowship, Heritage Affiliate   Initiation of a serine protease cascade defining dorsoventral polarity in Drosophila
 

Research Funding:

Current

4/04-8/09       NIH RO1, National Institute of General Medical Sciences Spatial control of proteolysis in dorsoventral polarity

Completed

2/03-5/05       Basil O’Connor Starter Scholar Research Award, March of Dimes Birth Defects Foundation
Spatial regulation of embryonic dorsoventral pattern by a proteoglycan

9/03-6/04       MCG/UGA Seed Grant Initiative on Diabetes, Obesity, and Related Disorders (co-investigator with Michael Bender, Dept. of Genetics, UGA)
Functional analysis of the prohormone processing protease amontillado (amon) during insulin signaling in Drosophila

 

Peer-Reviewed Publications:

LeMosy, E. K., Erickson, H. P., Beyer, W. F., Jr., Radek, J. T., Jeong, J.-M., Murthy, S. N. P. and Lorand, L. (1992)  Visualization of purified fibronectin-transglutaminase complexes. Journal of Biological Chemistry 267: 7880-7885.

LeMosy, E. K., Lightner, V. A. and Erickson, H. P. (1996) Structural analysis of a human glial variant laminin. Experimental Cell Research 227: 80-88.

LeMosy, E. K., Kemler, D. and Hashimoto, C. (1998) Role of Nudel protease activation in triggering dorsoventral polarization of the Drosophila embryo. Development 125: 4045-4053.

LeMosy, E. K., Leclerc, C. L. and Hashimoto, C. (2000) Biochemical defects of mutant nudel alleles causing early arrest or dorsalization of the Drosophila embryo. Genetics 154: 247-257.

LeMosy, E. K. and Hashimoto, C. (2000) The Nudel protease of Drosophila is required for eggshell biogenesis in addition to embryonic patterning. Developmental Biology 217: 352-361.

Han, J.-H., Lee, S. H., Tan, Y.-Q., LeMosy, E. K. and Hashimoto, C. (2000) GD is a serine protease involved in activating the receptor Toll to polarize the Drosophila embryo. Proceedings of the National Academy of Sciences U.S.A. 97: 9093-9097.

LeMosy, E. K., Tan, Y.-Q. and Hashimoto, C. (2001) Activation of a protease cascade involved in patterning the Drosophila embryo. Proceedings of the National Academy of Sciences U.S.A. 98: 5055-5060.

Rose, T., LeMosy, E. K., Cantwell, A. M., Banerjee-Roy, D., Skeath, J. B. and Di Cera, E. (2003) Three-dimensional models of proteases involved in patterning of the Drosophila embryo: Crucial role of predicted cation binding sites. Journal of Biological Chemistry 278: 11320-11330.

Fakhouri, M., Elalayli, M., Sherling, D., Hall, J. D., Miller, E., Sun, X., Wells, L., and LeMosy, E. K. (2006) Minor proteins and enzymes of the Drosophila eggshell matrix.  Developmental Biology 293: 127-141.

LeMosy, E. K. (2006) Spatially dependent activation of the patterning protease, Easter.  FEBS Letters 580: 2269-2272.

Elalayli, M.^*, Hall, J. D.^*, Zhu, X., Ellison, T. T., Fakhouri, M., Stein, D., and LeMosy, E. K. Palisade, a protein required in the Drosophila ovary for formation and function of the protective vitelline membrane. ^*equal contributors (working title, manuscript in preparation, Fall 2006)

Fratto, V. M., Dinkins, M. B., and LeMosy, E. K.  Cell adhesion molecule expression and localization in migrating cells of the Drosophila ovary.  (working title, manuscript in preparation, Fall 2006)

 

Reviews and Book Chapters:

LeMosy, E. K., Hong, C. C. and Hashimoto. C. (1999) Signal transduction by a protease cascade. Trends in Cell Biology 9: 102-107.

LeMosy, E. K. (2003) Pattern formation: the eggshell holds the cue. Current Biology 13: R508-R510.

LeMosy, E. K. (2004) The Nudel protease of Drosophila. In The Handbook of Proteolytic Enzymes, Second Edition, A.J. Barrett, N.D. Rawlings, and J.F. Woessner, Editors, Academic Press, Orlando, Florida.

LeMosy, E. K. Proteolytic regulatory mechanisms in the formation of extracellular morphogen gradients.  Birth Defects Research, Part C: Embryo Today (invited review, in press August 2006)