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Faculty Profile

Jonathan R. Lai, Ph.D.

Dr. Jonathan R. Lai

Assistant Professor, Department of Biochemistry

 

Professional Interests

Broadly stated, the objective of our research is to understand principles governing molecular recognition by proteins and antibodies, with the long-term goal of developing new research tools and therapies.  Students and post-doctoral fellows can expect to gain expertise in new and traditional biochemical techniques including phage display (library design, synthesis, and screening), protein expression and purification, structural analysis by circular dichroism and X-ray crystallography, and viral neutralization assays.  We are currently engaged in two lines of research.

1. Antibody Recognition Explored by Phage Display.  Antibody phage display has emerged as a powerful alternative to hybridoma technology for the generation of monoclonal antibodies and analysis of their interactions with antigens.  It is now possible to select high-affinity antibodies against virtually any antigen from phage libraries that bear tailored diversity elements encoded by synthetic DNA ("synthetic antibodies").  This approach obviates the requirement for animal immunization, greatly reducing the labor and cost of antibody production.  Selective enrichment of high-affinity binders from phage antibody libraries under controlled conditions enhances the reliability of output antibodies, and permits selection of binding with user-specified stringency.  The expression of antibody domains on the surface of bacteriophage was first reported nearly two decades ago, but only recently have synthetic libraries (where diversity is not borne from natural source repertoires) become sophisticated enough for general use.  We are developing and testing new synthetic antibody technologies to produce therapeutic, diagnostic, or research agents.  Our strategy involves two aspects: first, we use high-throughput mutagenesis to interrogate physicochemical parameters of high-affinity antibody-antigen interactions; and second, we utilize the information obtained from these studies to engineer new synthetic libraries directed against targets that have resisted traditional antibody isolation methods.

2.  Dissecting Mechanisms of Viral Membrane Fusion.  The envelope glycoproteins of membrane-bound viruses such as HIV-1, influenza, and ebolavirus all catalyze viral entry into host cells using essentially the same mechanism.  Central to this mechanism are well-timed conformational changes of the envelope glycoprotein that result in formation of a six-helix bundle hemifusion intermediate.  Formation of this hemifusion intermediate provides the driving force for fusion of the virus and host cell membranes.  Small molecules, peptides, or proteins that bind viral envelope glycoproteins and prevent formation of the hemifusion intermediate have been used clinically as antiviral therapies.  In addition, antibodies arising from natural infection (or other sources) that prevent the formation of the hemifusion intermediate are able to effectively neutralize the virus, suggesting that conformational mimicry of viral glycoprotein in the prefusion states may serve as an avenue for vaccine development.  Using synthetic antibody technologies coupled with traditional biophysical and biochemical approaches, we seek to understand details of the viral membrane fusion process and which steps along the pathway are susceptible to inhibition by antibodies.  Information gained from these studies will pave the way for structure-based vaccine design.

 

Selected Publications

 Selected Publications

  1. Koellhoffer, J. F.; Malashkevich, V. N.; Harrison, J. S.; Toro, R.; Bhosle, R. C.; Chandran, K.; Almo, S. C.; Lai J. R.  Crystal Structure of the Marburg Virus Core Domain in its Post-Fusion Conformation.  Biochemistry, In press.
  2. Harrison, J. S.; Koellhoffer, J. K.; Chandran, K.; Lai, J. R.  Marburg Virus Glycoprotein GP2: pH-Dependent Stability of the Ectodomain alpha-Helical Bundle.  Biochemistry, 2012, 51, 2515-2525.
  3. Stewart, A.; Liu, Y.; Lai, J. R.  A Strategy for Phage Display Selection of Functional Domain-Exchanged Immunoglobulin Scaffolds with High Affinity for Glycan Targets.  J. Immunol. Methods., 2012, 376, 150-155.
  4. Liu, Y.; Regula, L. K.; Stewart, A.; Lai, J. R. Synthetic Fab Fragments that Bind the HIV-1 gp41 Heptad Repeat Regions.  Biochem. Biophys. Res. Commun., 2011, 413, 611-615.
  5. Harrison, J. S.; Higgins, C. D.; Chandran, K.; Lai, J. R. Designed Protein Mimics of the Ebola Virus GP2 alpha-Helical Bundle: Stability and pH Effects.  Protein Sci.  2011, 20, 1587-1596.
  6. Miller, E. H.; Harrison, J. S.; Radoshitzky, S. R.; Higgins, C. D.; Chi, X.; Dong, L.; Kuhn, J. H.; Bavari, S.; Lai, J. R.; Chandran, K.  Inhibition of Ebola Virus Entry by a C-Peptide Targeted to Endosomes.  J. Biol. Chem.  2011, 286, 15854-15861.
  7. Da Silva, G. F.; Harrison, J. S.; Lai, J. R.  Contribution of Light Chain Residues to High Affinity Binding in an HIV-1 Antibody Explored by Combinatorial Scanning Mutagenesis.  Biochemistry.  2010,49 5464-5472.
  8. Pomerantz, W. C., Grygiel, T. L. R.; Lai, J. R., Gellman, S. H.  Distinctive Circular Dichroism Signature for 14-Helix-Bundle Formation by β-Peptides.  Org. Lett.  2008, 10, 1799-1802.
  9. Fischbach, M. A.; Lai, J. R.; Roche, E. D.; Walsh, C. T.; Liu, D. R.  Directed Evolution Can Rapidly Improve the Activity of Chimeric Assembly-Line Enzymes.  Proc. Natl. Acad. Sci. USA, 2007, 104, 11951-11956.
  10. Zhou, Z.; Lai, J. R.; Walsh, C. T. Directed Evolution of Aryl Carrier Proteins: Determinants of Recognition in the Enterobactin Synthetase.  Proc. Natl. Acad. Sci. USA, 2007, 104, 11621-11626.
  11. Lai, J. R.; Koglin, A.; Walsh, C. T.  Carrier Protein Structure and Recognition in Polyketide and Nonribosomal Peptide Biosynthesis.  Biochemistry.  2006, 45, 14869-14879.
  12. Lai, J. R.; Fischbach, M. A.; Liu, D. R.; Walsh, C. T.  Localized Protein Interaction Surfaces on the EntB Carrier Protein Revealed by Combinatorial Mutagenesis and Selection.  J. Am. Chem. Soc.  2006, 128, 11002-11003
  13. Zhou, Z.; Lai, J. R.; Walsh, C. T.  Interdomain Communication Involving the Thiolation Domain of EntF Explored by Combinatorial Mutagenesis and Selection.  Chem. Biol.  2006, 13, 1-11.
  14. Lai, J. R.; Fischbach, M. A.; Liu, D. R.; Walsh, C. T.  A Protein Interaction Surface in Nonribosomal Peptide Synthesis Mapped by Combinatorial Mutagenesis and Selection.  Proc. Natl. Acad. Sci. USA  2006, 103, 5314-5319.
  15. Lai, J. R.; Epand, R. F.; Weisblum, B.; Epand, R. M.; Gellman, S. H.  Role of Salt and Conformation in the Biological and Physicochemical Behavior of Protegrin-1 and Designed Analogues: Correlation of Antimicrobial, Hemolytic and Lipid Bilayer-Perturbing Activities.  Biochemistry.  2006, 45, 15718-15730.
  16. Lai, J. R.; Fisk, J. D.; Weisblum, B.; Gellman, S. H.  Hydrophobic Core Repacking in a Coiled-Coil Dimer via Phage Display: Insights into Plasticity and Specificity at a Protein-Protein Interface.  J. Am. Chem. Soc.  2004, 126, 10514-10515.
  17. Lai, J. R.; Gellman, S. H.  Reinvestigation of the Proposed Folding and Self-Association of the Neuropeptide Head Activator.  Prot. Sci.  2003, 12, 560-566.
  18. Lai, J. R.; Huck, B. R.; Weisblum, B.; Gellman, S. H.  Design of Non-Cysteine-Containing Antimicrobial β-Hairpins: Structure-Activity Relationship Studies with Linear Protegrin-1 Analogues.  Biochemistry, 2002, 41, 12835-12842.


 

More Information About Dr. Jonathan Lai

Lai Group Webpage

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Contact

Albert Einstein College of Medicine
Jack and Pearl Resnick Campus
1300 Morris Park Avenue
Forchheimer Building, Room 320
Bronx, NY 10461

Tel: 718.430.8641
Fax: 718.430.8565
jon.lai@einstein.yu.edu

 
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