T Cell Receptor Forces: From Molecular Mapping to Cancer Therapeutic Triggering

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T cells migrate through tissues, scanning cell surfaces and selectively destroying infected or malignant cells. The T cell interacts with other cells through the T cell receptor (TCR), recognizing antigen peptide fragment bound to the major histocompatibility complex (pMHC), on target cells. The TCR-pMHC bond is extremely specific, recognizing a single target pMHC among a myriad of other antigens. Despite the extreme importance of the TCR-pMHC bond to cancer prevention and immune surveillance, the origin of TCR specificity remains unclear. There is indirect evidence that TCR recognition of antigen utilizes uses mechanical force, specifically piconewton forces parallel the T cell membrane, to differentiate foreign antigen from self-antigen. Additionally, only one or two TCR-pMHC molecular bonds may be sufficient to trigger T cell activation, but tools to map pN mechanical events and to measure the orientation of these forces of do not exist, hindering progress in understanding T cell mechanobiology. My PhD research focuses on developing tools for molecular mechanobiology. I have invented a technique, Molecular Force Microscopy, capable of mapping the 3D orientation of piconewton molecular forces. I have also invented tension-PAINT, a super-resolved imaging technique capable of mapping single molecule cellular forces with ~10 nm spatial resolution. My F99 research has two focuses. First, I will apply Molecular Force Microscopy in conjunction with biochemical markers of T cell activation (e.g. Zap70-EGFP and calcium signaling) to test the hypothesis that TCR prefers forces parallel to the cell membrane to activate in response to antigen. Second, I will apply tension-PAINT to T cell forces to test the hypothesis that molecular forces recruit co-receptors in a force-dependent manner during T cell activation. This research will provide vital mechanistic details about force-mediated T cell activation. For my postdoctoral (K00) work, I will transition to developing immunotherapuetics. Immunotherapies, including engineered immune cells and PD-L1 blocking antibodies, have been deployed as anti-tumor therapies. However, immunotherapy is ineffective in many cancers. I hypothesize that TCR forces at the T cell-tumor junction can be leveraged to create new, force-activated immunotherapeutics. I will create a DNA-based container which I have termed the DNA origami antigen (DOA). The DOA will bind to tumor cells via cancer-specific antibodies. T cell forces will open the container, revealing a highly immunogenic payload that will stimulate cytotoxic T cell killing of cancer therapeutic. This research will result in a novel class of molecular force activated immunotherapeutics to combat cancer.