William J. Lehman, Ph.D.
Professor of Physiology and Biophysics
B.S. State University of New York at Stony Brook
Ph.D. Princeton University
We are involved in structural studies on the assembly and function of actin-containing thin filaments in striated and smooth muscles as well as on those present in non-muscle cells. Our principal goals are (1) to analyze and elucidate the mechanisms of thin filament-linked regulation of muscle contraction and (2) to determine the role of tropomyosin as the thin filament gatekeeper controlling access of additional actin-binding proteins onto actin filaments, thus controlling cytoskeletal architecture. To accomplish these goals, we use a combination of molecular biology, electron microscopy, electron tomography, and image reconstruction to better understand the structural interactions and dynamics of protein components of isolated and reconstituted thin filaments. More recently, we have initiated a new approach to characterize thin filament components using state-of-the-art computer simulation techniques involving Molecular Dynamics (MD) protocols. To date, our analysis of the electron microscopy of thin filament proteins and the results of the in silico Molecular Dynamics have in all cases been mutually supportive. In a number of instances, the MD simulations have yielded insights not easily obtained experimentally. We combine our studies on native thin filament components with corresponding ones on mutants to better understand abnormal filament function in disease processes.
Our laboratory confirmed the steric-blocking mechanism of muscle regulation by identifying the positions assumed by tropomyosin on actin in the presence and the absence of Ca2+ using cryo-electron microscopy and negative staining. We also have demonstrated that on activation tropomyosin moves away from myosin cross-bridge binding sites on actin in two steps, one induced by Ca2+ binding to troponin and a second induced by the binding of myosin to actin. We demonstrated that the shape of tropomyosin is designed to match the contours of the F-actin filament and that tropomyosin’s curved shape is semi-rigid, and thus capable of cooperative movement on thin filaments. Merging our experimental results and our computational chemistry, we developed the first all atoms model of the F-actin-tropomyosin filament.
Our laboratory is continuing the above-mentioned studies to obtain even greater resolution of the processes involved in regulating contractile and cytoskeletal filaments in striated and in smooth muscle filaments. At the same time, we are investigating the structural organization of troponin on thin filaments and the changes it undergoes on binding of Ca2+. We are also engaged in studies on the structural interactions of other actin binding proteins including α-actinin, caldesmon, calponin, cortactin, and native and mutant dystrophin, filamin, fimbrin, fascin, leiomodin and tropomodulin, namely proteins that play important roles in the organization of the cytoskeleton in striated and smooth muscles as well as in non-muscle cells.
The scientific contributions that we have made have had profound implications on current Biomedical and Translational research. For example, assays that we developed led to the discovery of myosin-phosphorylation as a regulator of smooth muscle contractility. Drugs to modulate the cascades associated with this process are much in demand and in development. We also now examine how the smooth muscle cell cytoskeleton is modulated to control vascular smooth muscle stiffness, which is a major contributor and leading risk factor in the development of cardiovascular dysfunction. Moreover, we have for the first time indicated at an atomic level how point mutations in tropomyosin associated with Hypertrophic Cardiomyopathies can lead to muscle dysfunction.
Skoumpla, K., A. T. Coulton, W. Lehman, M. A. Geeves & D. P. Mulvihill. (2007) Acetylation regulates tropomyosin function in the fission yeast Schizosaccharomyces pombe. J. Cell Sci. 120, 1635-1645. doi: 10.1242/10.1242/jcs.001115
Greenberg, M. J., C.-L. Wang, W. Lehman & J. R. Moore (2008) Modulation of actin mechanics by caldesmon and tropomyosin. Cell Motil. Cytoskeleton 65, 156-164. doi:10.1002/cm.20251
Lehman, W. & Craig, R. (2008) Tropomyosin and the Steric Mechanism of Muscle Regulation. Adv. Exp. Med. Biol. 644, 95-109. Review.
Maytum, R., M. Konrad, V. Hatch, W. Lehman & M. A. Geeves. (2008) Ultra short yeast tropomyosins show novel myosin regulation. J. Biol. Chem. 283, 1902-1910. doi:10.1074/jbc.M708593200
Galińska-Rakoczy, A., P. Engel, C. Xu, H.-S. Jung, R. Craig, L.S. Tobacman & W. Lehman. (2008) Structural basis for the regulation of muscle contraction by troponin and tropomyosin. J. Mol. Biol. 379, 929-935. doi:10.1016/j.jmb.2008.04.062
Holmes, K. C. & W. Lehman. (2009) Gestalt-binding of tropomyosin to actin filaments. J. Muscle Research Cell Motility 29, 213-219. doi: 10.1007/s10974-008-9157-6
Lehman, W., A. Galińska-Rakoczy, V. Hatch, L. S. Tobacman & R. Craig. (2009) Structural basis for the activation of muscle contraction by troponin and tropomyosin. J. Mol. Biol. 388, 673-681, doi:10.1016/j.jmb.2009.03.060
Cammarato, A., R. Craig, & W. Lehman (2010) Electron microscopy and three-dimensional reconstruction of native thin filaments reveal species-specific differences in regulatory strand densities. Biochem. Biophys. Res. Commun. 391, 193-197.
Li, X. E., K. C. Holmes & W. Lehman, H.-S. Jung & S. Fischer. (2010a) The shape and flexibility of tropomyosin coiled-coils: Implications for actin filament assembly and regulation. J. Mol. Biol. 395, 327-399.
Galińska, A., V. Hatch, R. Craig, A. M. Murphy, J. E. Van Eyk, C. L.-A. Wang & W. Lehman & D. B. Foster (2010). The C-terminus of cardiac troponin I stabilizes the Ca2+-activated state of tropomyosin on actin filaments. Circ. Res. 106, 705-711.
Li, X. E., W. Lehman, S. Fischer, & K. C. Holmes (2010b) Curvature variation along the tropomyosin molecule. J. Struct. Biol. 107, 307-312.
Li, X. E., W. Lehman, & S. Fischer (2010c) The relationship between curvature, flexibility and persistence length in the tropomyosin coiled-coil. J. Struct. Biol. 107, 313-318.
Sousa, D., A. Cammarato, K. Jang, P. Graceffa, L.S. Tobacman, X. E. Li, & W. Lehman (2010) Electron microscopy and persistence length analysis of semi-rigid smooth muscle tropomyosin strands. Biophys. J. 99, 1-7.
Coulton, A. T., D. A. East, A. Galińska-Rakoczy, W. Lehman, & D. P. Mulvihill (2010) The recruitment of acetylated and unacetylated tropomyosin to distinct actin polymers permits the discrete regulation of specific myosins in fission yeast. J. Cell Sci. 123, 3235-3243.
Li, X. E., L. S. Tobacman, J. Y. Mun, R. Craig, S. Fischer, & W. Lehman (2011) Tropomyosin position on F-actin revealed by EM reconstruction and computational chemistry. Biophys. J. 100, 1005-1013.
Gallant, C., S. Appel, P. Graceffa, P. Leavis, J. J.-C. Lin, P. Gunning, G. Schevzov, C. Chaponnier, J. DeGnore, W. Lehman, & K. Morgan (2011) Tropomyosin variants describe distinct functional subcellular domains in differentiated vascular smooth muscle cells. Am. J. Physiol. 300, C1356-C1365.
Mun, J.Y., J. Gulick, J. Robbins, J. Woodhead, W. Lehman, & R. Craig (2011) Electron microscopy and 3D reconstruction of F-actin decorated with cardiac myosin-binding protein C (cMyBP-C). J. Mol. Biol. 410, 214-225.
Collins, A., R. Huang, M. H. Jensen, Jeffrey Moore, W. Lehman C.-L. A. Wang (2011) Structural studies on maturing actin filaments. BioArchitecture 1, 127-133.
Moore, J., J. Nirody, X. E. Li, J. Sumida, S. Fischer, S. S Lehrer, W. Lehman (2011) Structural implications of conserved aspartate residues located in tropomyosin’s coiled-coil core. BioArchitecture 1, 127-133.
East, D. A., D. Sousa, S. R. Martin, T. A. Edwards, W. Lehman, & D. P. Mulvihill. (2011) Altering the stability of the Cdc8 overlap region modulates the ability of this tropomyosin to bind cooperatively to actin and regulate myosin. Biochem. J. 438, 265-273.
Cammarato, A., X. E. Li, M. C. Reedy, C. F. Lee, W. Lehman, & S. I. Bernstein (2011) Structural basis for myopathic defects engendered by alterations in the myosin rod. J. Mol. Biol. 414, 474-484.
Rao, J. N., X. E. Li, R. Rivera-Santiago, W. Lehman, & R. Dominguez (2012) Structural study of smooth muscle tropomyosin alpha and beta isoforms. J. Biol. Chem. 359, 3165-3174.
Jensen, M. H., J. Watt, J. Hodgkinson, C. Gallant, S. Appel, M. El-Mezgueldi, T. E. Angelini, K. G. Morgan, W. Lehman, & Jeffrey R. Moore (2012) Effects of basic calponin on the flexural mechanics and stability of F-actin. Cytoskeleton 69, 49-58.
Lehman, W. & K. G. Morgan (2012) Structure and dynamics of the actin-based smooth muscle contractile and cytoskeletal apparatus. J. Muscle Research Cell Motility (in press)
X. E. Li, W. Suphamungmee, Miro Janco, M. A. Geeves, S. B. Marston, S. Fischer, & W. Lehman. (2012) The flexibility of two tropomyosin mutants, D175N and E180G, that cause hypertrophic cardiomyopathy. Biochem. Biophys. Res. Commun. (in press).
• To top
We collaborate closely with several laboratories with similar interests including:
Dr. Roger Craig, Department of Cell Biology, University of Massachusetts Medical School.
Dr. Roberto Dominguez, Department of Physiology, University of Pennsylvania School of Medicine.
Dr. Stefan Fischer, Computational Biochemistry Group, University of Heidelberg, Heidelberg, Germany.
Dr. Michael Geeves, School of BioSciences, University of Kent, Canterbury, UK.
Dr. Kenneth C. Holmes, Max Planck Institut fϋr Medizinische Forschung, Heidelberg (Germany).
Dr. Steven B. Marston, National Heart and Lung Institute, Imperial College, London, UK.
Dr. Kathleen Morgan, Department of Health Sciences, Sargent College, Boston University.
Dr. Jeffrey Moore, Department of Physiology & Biophysics, Boston University School of Medicine.
Dr. Dan Mulvihill, Department of Biosciences, University of Kent, Canterbury, UK.
Dr. Stefan Raunser, Max Planck Inst of Molecular Physiology, Dortmund, Germany.
Dr. Larry Tobacman, Departments of Biochemistry and Medicine, University of Illinois at Chicago.
Dr. Albert Wang, Department of Muscle Research, Boston Biomedical Research Institute.
- Senior Electron Microscopy Technician
- Postdoctoral Fellow
A Postdoctoral Research Fellow and a Senior Electron Microscopy Technician are sought to carry out research work on the structure of actin filament complexes that (1) are associated with cardiac and skeletal muscle regulatory proteins to control muscle activity and (2) interact with smooth muscle actin-binding proteins to modulate the assembly of the smooth muscle cytoskeleton. Applicants must have several years of experience in high-resolution EM work and first-rate facility with computer-assisted image analysis. Prior familiarity with preserving and recording macromolecular assemblies in negative stain and by cryo-EM methods would be invaluable. Experience in supervising graduate students and postdoctoral fellows would also be important.
Interested applicants should send their CV with three references to:
Dr. William Lehman
Professor of Physiology & Biophysics
Department of Physiology & Biophysics
Boston University School of Medicine
72 East Concord Street
Boston, MA 02118
Or email: firstname.lastname@example.org
William J. Lehman
Department of Physiology and Biophysics
Boston University School of Medicine
72 East Concord Street
Boston MA 02118-2526
Fax: (617) 638-4273