Nicholas Till

All Publications

• Mapping the nanoscale organization of the human cell surface proteome reveals new functional associations and surface antigen clusters. bioRxiv : the preprint server for biology Floyd, B. M., Schmidt, E. L., Till, N. A., Yang, J. L., Liao, P., George, B. M., Flynn, R. A., Bertozzi, C. R. 2025

  Abstract

  The cell surface is a dynamic interface that controls cell-cell communication and signal transduction relevant to organ development, homeostasis and repair, immune reactivity, and pathologies driven by aberrant cell surface phenotypes. The spatial organization of cell surface proteins is central to these processes. High-resolution fluorescence microscopy and proximity labeling have advanced studies of surface protein associations, but the spatial organization of the complete surface proteome remains uncharted. In this study, we systematically mapped the surface proteome of human T-lymphocytes and B-lymphoblasts using proximity labeling of 85 antigens, identified from over 100 antibodies tested for binding to surface-exposed proteins. These experiments were coupled with an optimized data-independent acquisition mass spectrometry workflow to generate a robust dataset. Unsupervised clustering of the resulting interactome revealed functional modules, including well-characterized complexes such as the T-cell receptor and HLA class I/II, alongside novel clusters. Notably, we identified mitochondrial proteins localized to the surface, including the transcription factor TFAM, suggesting previously unappreciated roles for mitochondrial proteins at the plasma membrane. A high-accuracy machine learning classifier predicted over 6,000 surface protein associations, highlighting functional associations such as IL10RB's role as a negative regulator of type I interferon signaling. Spatial modeling of the surface proteome provided insights into protein dispersion patterns, distinguishing widely distributed proteins, such as CD45, from localized antigens, such as CD226 pointing to active mechanisms of regulating surface organization. This work provides a comprehensive map of the human surfaceome and a resource for exploring the spatial and functional dynamics of the cell membrane proteome.

  View details for DOI 10.1101/2025.02.12.637979

  View details for PubMedID 40027624

  View details for PubMedCentralID PMC11870420

• The modified RNA base acp3U is an attachment site for N-glycans in glycoRNA. Cell Xie, Y., Chai, P., Till, N. A., Hemberger, H., Lebedenko, C. G., Porat, J., Watkins, C. P., Caldwell, R. M., George, B. M., Perr, J., Bertozzi, C. R., Garcia, B. A., Flynn, R. A. 2024

  Abstract

  GlycoRNA consists of RNAs modified with secretory N-glycans that are presented on the cell surface. Although previous work supported a covalent linkage between RNA and glycans, the direct chemical nature of the RNA-glycan connection was not described. Here, we develop a sensitive and scalable protocol to detect and characterize native glycoRNAs. Leveraging RNA-optimized periodate oxidation and aldehyde ligation (rPAL) and sequential window acquisition of all theoretical mass spectra (SWATH-MS), we identified the modified RNA base 3-(3-amino-3-carboxypropyl)uridine (acp3U) as a site of attachment of N-glycans in glycoRNA. rPAL offers sensitivity and robustness as an approach for characterizing direct glycan-RNA linkages occurring in cells, and its flexibility will enable further exploration of glycoRNA biology.

  View details for DOI 10.1016/j.cell.2024.07.044

  View details for PubMedID 39173631

• Tumor Immune Cell Targeting Chimeras (TICTACs) For Targeted Depletion of Macrophage-Associated Checkpoint Receptors. bioRxiv : the preprint server for biology Morimoto, M., Till, N. A., Bertozzi, C. R. 2023

  Abstract

  Immune cells in the tumor microenvironment are not only powerful regulators of immunosuppression and tumorigenesis, but also represent a dominant cell type, with tumor-associated macrophages (TAMs) comprising up to 50% of total cell mass in solid tumors. Immunotherapies such as immune checkpoint inhibitors (ICIs) derive their efficacy from this cancer-immune cell interface, however, immune-related adverse events resulting from systemic blockade remain a significant challenge. To address this need for potent, yet highly tumor-specific immunotherapies, we developed Tumor-Immune Cell Targeting Chimeras (TICTACs), antibody conjugates that are capable of selectively depleting immune checkpoint receptors such as SIRPa from the surface of TAMs. These chimeric molecules consist of a synthetic glycan ligand that binds the C-type lectin CD206, a well-established TAM marker, conjugated to a non-blocking antibody that binds but does not inhibit the checkpoint receptor. By engaging CD206, which constitutively recycles between the plasma membrane and early endosomes, TICTACs facilitate robust removal of the checkpoint receptors from the surface of CD206high macrophages, while having no effect on CD206low macrophages. By decoupling antibody selectivity from its blocking function, we present a new paradigm for developing highly tumor-specific immunotherapies.

  View details for DOI 10.1101/2023.12.06.570444

  View details for PubMedID 38106036

  View details for PubMedCentralID PMC10723462