My work focuses on how host cells recognize and respond to Gram-negative bacterial-derived endotoxin (E). Host response to E depends on the ordered interaction of four host proteins: LBP, CD14, MD-2 and Toll-Like Receptor 4 (TLR4). Previous work has shown that monomeric E is extracted by CD14 in the presence of LBP, forming E:CD14. The E monomer is then transferred to MD-2 forming E:MD-2, which binds to TLR4 and triggers an intracellular signaling cascade. Signaling through TLR4 can proceed through the MyD88-dependent pathway, which involves the interaction of the intracellular mediators MyD88 and MAL, or through the TRIF-dependent pathway, which involves the intracellular mediators TRIF and TRAM. I am investigating the molecular requirements for activation of these pathways, and how the activation of a specific TLR4 signaling cascade can modulate the immune response and affect the overall outcome of infection. Currently I am utilizing the transformed human astrocytoma cell line U373 that expresses TLR4/MD-2 in the absence of CD14 to determine if CD14 is required for TRIF-dependent signaling in human cells. Our lab also has access to wild-type C57BL/6, MD-2-/- and CD14-/- mice that will be utilized in assays similar to those described above to determine the activation and magnitude of TRIF and MyD88-dependent responses in the presence or absence of CD14.

Gioannini TL, Teghanemt A, Zhang D, Esparza G, Yu L, Weiss J. Purified monomeric ligand.MD-2 complexes reveal molecular and structural requirements for activation and antagonism of TLR4 by Gram-negative bacterial endotoxins. Immunol Res. 2014 Jun 4. [Epub ahead of print] PubMed PMID: 24895101.

Esparza GA, Teghanemt A, Zhang D, Gioannini TL, Weiss JP. Endotoxin{middle dot}albumin complexes transfer endotoxin monomers to MD-2 resulting in activation of TLR4. Innate Immun. 2012 Jun;18(3):478-91. doi: 10.1177/1753425911422723. Epub 2011 Oct 12. PubMed PMID: 21994253.