Luxenburg, C. | bioRxiv Science

bioRxiv2024

Spectrin coordinates cortical actomyosin organization and differentiation essential for a functional epithelial barrier

Cell shape and fate are tightly linked, yet how the cortical cytoskeletal integrates regulation of shape and fate remains unclear. Using the epidermis as a paradigm where cell shape changes guide differentiation we identify spectrin as an essential organizer of the keratinocyte actomyosin cortex that integrates transitions in cell shape with spatial organization of signaling. Loss of II-spectrin (Sptan1) in the mouse epidermis altered cell shape in all layers and impaired differentiation, and barrier formation. High-resolution imaging and laser ablation revealed that E-cadherin guides differential gradients of actin and spectrin to regulate the layer-specific organization and mechanics of sub-membraneous spectrin-actomyosin networks. This organization is essential to dissipate tension, maintain structural integrity, and retain active growth factor receptor EGFR and the cation channel TRPV3 at the membrane in upper layers to induce terminal differentiation. Together, these findings reveal how organization of the cortical cytoskeleton coordinates changes in cell shape and cell fate at the tissue scale necessary to establish epithelial barriers.

cell biology↗

bioRxiv2020

Transient cell-in-cell formation underlies tumor resistance to immunotherapy

Despite the remarkable success of immunotherapy in cancer, most patients will develop resistant tumors. While the main conceptual paradigm suggests that relapsed clones emerge through a process of clonal selection and immunoediting, currently little evidence directly demonstrates this process in epithelial cancers. To study this process, we established several mouse models in which tumors drastically regress following immunotherapy, yet resistant tumors relapse within a few weeks of treatment cessation. Whole exome analyses indicated that relapsed tumors share hundreds of neo-antigens with the primary tumors and are comparably killed by reactive T cells. Examination of tumor cells that survive immunotherapies revealed that they structure a transient cell-in-cell formation, which is impenetrable to immune-derived cytotoxic compounds and to chemotherapies. This formation is mediated predominantly by a cell-membrane protein on activated T cells, which subsequently induces epidermal growth factor receptors and STAT3 phosphorylation in tumors cells. In contrast to previous reports on cell-in-cell formations, here both cells remain alive and can disseminate into single tumor cells once T cells are no longer present. Overall, this work highlights a powerful resistance mechanism which enable tumor cells to survive immune pressure and provides a new theoretical framework for combining chemotherapies and immunotherapies.

immunology↗