Research
Small molecule and antibody modulators of the immune system have proven efficacious in the treatment of cancer, infectious diseases and autoimmune disorders. These successes underline the need for other immunomodulatory agents, in particular cell-penetrating small molecules, that can target proteins inaccessible to monoclonal antibodies. Combining chemical proteomics and activity-based protein profiling (ABPP), we synthesize new probes and develop new methods to study and manipulate the human immune system.
Projects:
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I. Background: Caspase-mediated proteolytic signaling is a central regulator of the human immune system. Caspase-8 (C-8) is one member of a family of 12 cysteine proteases that cleave substrate proteins after certain aspartate residues. C-8 protease activity is essential for program programmed cell death (PCD) and for immune cell, particularly T cell, activation. The nature and scope of substrates cleaved by C-8 and the respective contributions of these cleavage events to T cell activation and death remain uncharacterized.
Approach: We use high throughput screening, activity based protein profiling and organic synthesis to identify and optimize selective small molecule inhibitors of C-8. Then we combine these inhibitors with proteomics to annotate the substrates of C-8 in primary human T cells to uncover specific cleavage events that are required for immune cell activation. |
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II. Background: The adaptive immune response is regulated by many key protein complexes, including, among many others, the major histocompatibility complexes (MHC-I and -II), the T cell receptor and the Fas-FADD death domain complex. The development of chemical probes targeting protein-protein interactions (PPIs), both for the development of immunomodulatory agents as well as more generally, is an area that would benefit from new approaches to ligand discovery. Given the prevalence of both lysine and cysteine (particularly redox sensitive cysteine) residues at interaction sites, covalent compounds tailored to react with cysteine or lysine residues are an attractive option for the development of PPI probes.
Approach: We synthesize and apply libraries of cysteine and lysine reactive compounds to identify new small molecules that target protein-protein interactions. Using a combination of isoTOP-ABPP chemical proteomics and new proteomics platforms developed in the lab, we can identify the targets of probe labeling and the identities of the complexes disrupted. We are particularly interested in applying these compound libraries and proteomics platforms to target PPIs involved in immune cell activation. |
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III. Background: Protein phosphorylation regulates a multitude of cellular functions: both activating and inactivating enzymes, inducing changes in subcellular location and mediating many PPIs that are central to various signaling processes, including receptor-mediated signal transduction involved in immune cell activation. Within the context of adaptive immune cell activation, phosphorylation on key tyrosine residues, including those found in the ITAMS region of the T cell receptor induce a signaling cascade that ultimately leads to transcription, cytokine production and cellular activation.
Approach: We synthesize new chemical probes and then, using quantitative chemical proteomics, we apply these probes to identify novel proteins involved in cell signaling cascades, in particular those cascades involved in T cell activation. |
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