We are interested in understanding multiple molecular interactions that go awry during both inflammatory diseases and cancer progression. The novelty in our group’s approach is that we utilize highly integrative methods to probe interactions from atomic resolution techniques to cell-based techniques. When cellular and clinical studies are combined with molecular and biochemical studies, a complete understanding of the particular system under study can be drawn. This will allow our lab to utilize both rational and irrational-based approaches to block many of the proteins upregulated during disease progression. Several of these projects are described herein.
Cyclophilins and enzyme dynamics:
Understanding the intimacy between structure, dynamics and function is critical for fully characterizing macromolecules, especially for enzymes that depend on rapid conformational changes for catalysis. Recently, similar conformational changes that occur within active enzymes have also been identified in the absence of substrates and thus, may allow important conformations to be dynamically sampled such as those that initiate substrate binding and catalysis. This suggests that like sequence and structure, inherent motions of enzymes that are associated with catalysis may also be an evolutionary trait. We are currently studying numerous members of the human cyclophilin family of enzymes to understand how the inherent dynamics within this family is correlated to their catalytic function. Cyclophilins are involved in everything from protein folding to signal transduction and the prototypical cyclophilin, cyclophilin-A (CypA), comprises nearly 0.5% of the cytosolic protein. Not surprisingly, cyclophilins are involved in multiple diseases that include cancer and CypA is utilized by multiple pathogens for infection. While there has been great therapeutic interest in targeting cyclophilins, structure-based approaches have proven difficult, likely due to the fact that these enzymes are highly dynamic. Thus, understanding the dynamics of these moving targets may help bridge rational-based therapeutic strategies.
Extracellular cyclophilins and disease:
Intracellular cyclophilins are involved in multiple signal transduction pathways, yet the role of extracellular cyclophilins has recently emerged as a major contributor to disease progression that includes multiple cancers and inflammatory disorders. Together with several labs that include Dr. Michael Bukrinsky (Department of Microbiology and Tropical Medicine The George Washington University), we are characterizing the particular cyclophilins released from different cancer cells (i.e. leukemic, pancreatic cancer, and melanoma) as well as the particular proteins secreted in response to extracellular cyclophilins.
The EMMPRIN receptor and cell signaling:
The cellular receptor EMMPRIN (Extracellular Matrix Metalloproteinase Inducer or EMMPRIN, also known as CD147) plays a central role in numerous diseases and has more recently become a marker for several cancers. EMMPRIN plays several roles during disease progression that includes the stimulation of matrix metalloproteinases (MMPs), which are responsible for tumor invasion, and stimulation of many pro-inflammatory cytokines, which further contribute to tumor growth. EMMPRIN-mediated activity is regulated by both ligand independent and ligand dependent mechanisms, yet little is known about the molecular details of either mechanism. Interestingly, the EMMPRIN ligands are the cyclophilin class of extracellular enzymes and suggest that there is a catalytic role in EMMPRIN/cyclophilin interactions that lead to intracellular signaling. Thus, our lab is interested in characterizing both the ligand-independent and ligand-dependent role of EMMPRIN signaling at both the molecular and cellular level. Biophysical experiments that include nuclear magnetic resonance have revealed the molecular details of EMMPRIN self-association and its interactions with its cyclophilin enzyme ligands. Cell-based assays that include stable EMMPRIN knockdowns as well as stable transfected cell lines will allow us to relate the molecular details to several signaling events. Thus, our lab is the first to begin probing EMMPRIN directly in solution as well as to understand the relationship between cyclophilin-mediated catalysis of EMMPRIN on the outside of the cell to intracellular signaling.
Extracellular EMMPRIN and disease:
EMMPRIN is a unique receptor in that it mediates its activity as a transmembrane protein but is also excised from the cellular membrane as a soluble protein and released in its full-length form by microvesicle shedding. Once again, we are using a combination of biophysical, biochemical and cell-based techniques to reveal the particular extracellular EMMPRIN forms released from cancer cells and present within bodily fluids such as peripheral blood.