Cynthia Leifer - Cornell Veterinary Medicine

Dr. Leifer, an Assistant Professor in the Department of Microbiology and Immunology, received her Bachelor of Science from the University of Maryland College Park and her PhD from the Weill Graduate School of Medical Sciences, Cornell University. While a post-doctoral fellow at the National Cancer Institute in Bethesda Maryland she began work on the intracellular localization and trafficking of receptors critical for innate immune responses.

Research Interests | Graduate Fields | Lab Members | Related Links | Selected References

Research Interests

The identification of a signaling receptor for Gram-negative bacterial lipopolysaccharide (LPS) in the late 1990's resulted in an explosion of information in the field of innate immunity. The receptor for LPS, Toll-like receptor 4 (TLR4), is one member of a family of receptors that recognize various conserved microbial patterns. At least 11 TLRs recognize patterns from microorganisms as diverse as viruses, bacteria, and parasites. Some TLRs even recognize endogenous inflammatory mediators. To better understand how the immune system fights infection and what goes wrong during overzealous immune responses that lead to immunopathology and autoimmunity, my lab studies the molecular mechanisms of action of TLRs.

While several TLRs, including TLR4, are expressed at the cell surface, TLRs 3, 7, 8 and 9 are expressed intracellularly. The lab uses TLRs 3, 7, 8 and 9 as a unique tool to examine the role that receptor localization plays in the intracellular recognition of microorganisms. This sub-family of TLRs recognizes different nucleic acids such as dsRNA (by TLR3), ssRNA (by TLRs 7 and 8) and CpG containing bacterial and viral DNA (by TLR9). Recently, we have demonstrated that TLR9 is retained in the endoplasmic reticulum (ER) prior to ligand exposure (Leifer et al., 2004). This came as a surprise since TLR9 had been shown to localize with its ligand, CpG DNA, in lysosomes. Chimeric proteins revealed specific sequences in TLR9 that were required for ER retention and vesicle targeting.

These studies have led to three main projects in the lab.

1) Specific sequences in the cytoplasmic tail of TLR9 have been identified which regulate ER retention and vesicle targeting. The first project seeks to identify cytoplasmic proteins that bind to these localization motifs and evaluate the role of these proteins in TLR9 signaling.

2) While the ligands for TLRs 3, 7, 8 and 9 all seem to require intracellular recognition, TLRs 3, 7 and 8 do not share the identified localization motifs with TLR9. A second project seeks to determine if TLRs 3, 7 and 8 are also retained in the ER and what the control mechanisms are for ER retention.

3) Recently the structure of TLR3's ecto-domain has been solved and several surfaces for potential ligand interactions have been proposed. There have also been polymorphisms found in several TLRs that disrupt ligand-induced signaling. A third area of research in the lab uses mutagenesis and binding studies to determine the ligand-binding domains of various nucleic acid recognizing TLRs.

Dr. Leifer is a member of the following Graduate Fields:

Program in Infection and Pathobiology

Selected References

Leifer CA, Kennedy MN, Mazzoni A, Lee CW, Kruhlak MJ, Segal DM. (2004). Tlr9 is localized in the ER prior to stimulation. J.

Bell JK, Mullen GED, Leifer CA, Mazzoni A, Davies DR, Segal DM. (2003). Leucine-rich repeats and pathogen recognition in Toll-like receptors. Trends. Immunol. 24: 528-533.

Takeshita F*, Leifer CA*, Gursel I, Ishii KJ, Takeshita S, Gursel M, Klinman DM. (2001). Cutting edge: Role of Toll-like receptor 9 in CpG DNA-induced activation of human cells. J.

Klinman DM, F Takeshitsa, I Gursel, C Leifer, KJ Ishii, D Verthelyi, M Gursel. (2002). CpG DNA: Recognition by and activation of monocytes. Microbes Infect. 4: 897-901.

Bafica, A., CA Scanga, CG Feng, CA Leifer, A Cheever, A Sher. (2005). TLR9 regulates Th1 responses and cooperates with TLR2 in mediating optimal resistance to Mycobacterium tuberculosis. J. Exp. Med. 202:1715-1724.

Leifer CA*, JC Brooks, K Hoelzer, JL Lopez, MN Kennedy, A Mazzoni, DM Segal. (2006). Cytoplasmic targeting motifs control localization of Toll-like receptor 9. J. Biol. Chem. 281: 35585-35592.