William J. Lehman, Ph.D.

Professor and Chair ad interim, Department of Physiology & Biophysics

William J. Lehman
  • Title Professor and
    Chair ad interim, Department of Physiology & Biophysics
  • Office W408E
  • Phone (617) 358-8484
  • Education B.S. State University of New York at Stony Brook
    Ph.D. Princeton University

Research

Fig1
Atomic model showing tropomyosin moving between three positions on actin. Red – Blocked; Yellow – Ca2+-activated; Green – Myosin-activated. From Poole et al., 2006.

We take a structural approach to study the assembly and function of actin-containing thin filaments in striated and smooth muscles. We also investigate thin filament architecture 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 actin-binding proteins onto actin filaments, thus controlling cytoskeletal function. To accomplish these goals, we use a combination of molecular biology, electron microscopy, and image reconstruction to better understand the structural interactions and dynamics of protein components of isolated and reconstituted thin filaments.

Cryo-EM structure of cardiac myosin making specific contact with actin and tropomyosin of thin filaments. From Doran et al., 2020.

We also characterize thin filament components using state-of-the-art computer simulation techniques involving Molecular Dynamics (MD) and Energy Landscape protocols. To date, our EM analysis of thin filament proteins and the results of the in silico computational procedure have been mutually supportive. In a number of instances, MD simulations and energy landscapes have yielded insights not always easily obtained experimentally.

We combine our studies on native thin filament components with corresponding ones on mutants to better understand abnormal filament function in myopathic disease processes. We also develop drugs to fit within pockets found in tropomyosin to readjust normal and aberrant thin filament on-off switching.

 

Molecular dynamics simulation and protein-protein docking describing the interaction of troponin-I with actin and tropomyosin of cardiac thin filaments under muscle relaxing conditions.
From Lehman et al., 2021

Fig4Our laboratory provided fundamental structural evidence supporting 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 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. In addition, we showed that the shape of tropomyosin is designed to match the contours of the Factin 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. The model indicates at an atomic level how point mutations in tropomyosin associated with Hypertrophic Cardiomyopathies can lead to muscle dysfunction.

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 have also engaged in studies on the structural interactions of other actin binding proteins including 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.

Fig5
Schematic of our general approach


Recent Publications:

Lehman W, Li X, Kiani FA, Moore JR, Campbell SG, Fischer S, Rynkiewicz MJ. Precise binding of tropomyosin on actin involves sequence-dependent variance in coiled-coil twisting. Biophys J. 2018;115(6):1082‐1092. doi:10.1016/j.bpj.2018.08.017 PMCID: PMC6139885

Farman GP, Rynkiewicz MJ, Orzechowski M, Lehman W, Moore JR. HCM and DCM cardiomyopathy-linked α-tropomyosin mutations influence off-state stability and crossbridge interaction on thin filaments. Arch Biochem Biophys. 2018;647:84‐92. doi:10.1016/j.abb.2018.04.002 PMCID: PMC5958618

Lehman W, Moore JR, Campbell SG, Rynkiewicz MJ. The effect of tropomyosin mutations on actin-tropomyosin binding: In search of lost time. Biophys J. 2019;116(12):2275‐2284. doi:10.1016/j.bpj.2019.05.009 PMCID: PMC6588729

Kiani FA, Lehman W, Fischer S, Rynkiewicz MJ. Spontaneous transitions of actin-bound tropomyosin toward blocked and closed states. J Gen Physiol. 2019;151(1):4‐8. doi:10.1085/jgp.201812188 PMCID: PMC6314389

Geeves MA, Lehrer SS, Lehman W. The mechanism of thin filament regulation: Models in conflict?. J Gen Physiol. 2019;151(11):1265‐1271. doi:10.1085/jgp.201912446 PMCID: PMC6829557

Janco M, Rynkiewicz MJ, Li L, Hook J, Eiffe E, Ghosh A, Böcking T, Lehman WJ, Hardeman EC, Gunning PW. Molecular integration of the anti-tropomyosin compound ATM-3507 into the coiled coil overlap region of the cancer-associated Tpm3.1. Sci Rep. 2019;9(1):11262. doi:10.1038/s41598-019-47592-9 PMCID: PMC6677793

Egge N, Arneaud SLB, Wales P, Mihelakis M, McClendon J, Fonseca RS, Savelle C, Gonzalez I, Ghorashi A, Yadavalli S, Lehman WJ, Mirzaei H, Douglas PM. Age-onset phosphorylation of a minor actin variant promotes intestinal barrier dysfunction. Dev Cell. 2019;51(5):587‐601.e7. doi:10.1016/j.devcel.2019.11.001 PMCID: PMC6897307

Lehman W, Maéda Y. Introducing a special issue of the Journal of Muscle Research and Cell Motility on actin and actin-binding proteins. J Muscle Res Cell Motil. 2020;41(1):1‐2. doi:10.1007/s10974-019-09569-z, PMID: 31865487, PMCID: not provided by journal.

Lehman W, Rynkiewicz MJ, Moore JR. A new twist on tropomyosin binding to actin filaments: perspectives on thin filament function, assembly and biomechanics. J Muscle Res Cell Motil. 2020;41(1):23‐38. doi:10.1007/s10974-019-09501-5 PMCID: PMC6697252

Viswanathan MC, Schmidt W, Franz P, Rynkiewicz MJ, Newhard CS, Madan A, Lehman W, Swank DM, Preller M, Cammarato A. A role for actin flexibility in thin filament-mediated contractile regulation and myopathy. Nat Commun. 2020;11(1):2417. doi:10.1038/s41467-020-15922-5 PMCID: PMC7229152

Sundar S, Rynkiewicz MJ, Ghosh A, Lehman W, Moore JR. Cardiomyopathy mutation alters end-to-end junction of tropomyosin and reduces calcium sensitivity. Biophys J. 2020;118(2):303‐312. doi:10.1016/j.bpj.2019.11.3396 PMCID: PMC6976805

Pavadai E, Rynkiewicz MJ, Ghosh A, Lehman W. Docking troponin T onto the tropomyosin overlapping domain of thin filaments. Biophys J. 2020;118(2):325‐336. doi:10.1016/j.bpj.2019.11.3393 PMCID: PMC6976810

Pavadai E, Lehman W, Rynkiewicz MJ. Protein-protein docking reveals dynamic interactions of tropomyosin on actin filaments. Biophys J. 2020; 119(1):77-86. doi.org/10.1016/j.bpj.2020.05.017 PMCID: PMC7335911

Doran MH, Pavadai E, Rynkiewicz MJ, Walklate J, Bullitt E, Moore JR, Regnier M, Geeves MA, Lehman W. Cryo-EM and molecular docking shows myosin loop 4 contacts actin and tropomyosin on thin filaments. Biophys J. 2020; 119(4) 821-830. doi: 10.1016/j.bpj.2020.07.006 PMCID: PMC7451941

Racca AW, Rynkiewicz MJ, LaFave N, Ghosh A, Lehman W, Moore JR. M8R tropomyosin disrupts actin-binding and filament regulation. The beginning affects the middle and the end. J Biol Chem. 2020; 295(50):17128-17137. doi: 10.1074/jbc.RA120.014713. PMID: 33020181.

Lehman W, Pavadai E, Rynkiewicz MJ. C-terminal troponin-I residues trap tropomyosin in the muscle thin filament blocked-state. Biochem Biophys Res Commun. 2021; 551:27-32. doi: 10.1016/j.bbrc.2021.03.010. PMID: 33714756.

Earlier publications are listed on: https://www.ncbi.nlm.nih.gov/myncbi/william.lehman.1/bibliography/public/

We collaborate with colleagues in several laboratories with similar interests including:

Dr. Stuart Campbell, School of Engineering and Applied Science, Yale University.
Dr. Anthony Cammarato, Department of Medicine, Johns Hopkins University.
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. Peter Gunning, School of Medical Sciences, University of New South Wales, Sydney, Australia.
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 Biological Sciences, University of Massachusetts-Lowell.
Dr. Larry Tobacman, Departments of Biochemistry and Medicine, University of Illinois at Chicago.

Links:

BU Profile
ResearchGate

Contact Us

William J. Lehman
Department of Physiology & Biophysics
Boston University School of Medicine
700 Albany Street, W408E
Boston MA 02118-2526

Phone:(617) 358-8484
e-mail: wlehman@bu.edu

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