Biology subjects

Hernandez-Lopez, R. A.

Publications and source records attributed to Hernandez-Lopez, R. A..

7 recordsLinked to original sources

bioRxiv2026

Subcellular transcriptome sequencing with single cell APEX-seq identifies regulators of cell-cell interactions

Single-cell RNA sequencing has transformed our understanding of tissue complexity and heterogeneous cell states, yet provides little information about the subcellular organization of transcriptomes - despite the central role of RNA localization in splicing, translation, and function. Here we introduce single-cell APEX-seq (scAPEX-seq), a proximity labeling-based method for mapping subcellular transcriptomes at single-cell resolution. Improvements in probe design and RNA recovery enable APEX integration with droplet-based RNA-seq to capture endoplasmic reticulum-associated transcripts from thousands of individual cells. Applied to tumor-macrophage co-cultures, ER-targeted scAPEX-seq revealed interaction-dependent cell states and transcriptomic signatures by enriching for cell surface and secretory transcripts that are poorly resolved by conventional scRNA-seq. We further applied scAPEX-seq to short- and long-term co-cultures of HER2+ tumor cells with human chimeric antigen receptor (CAR) T cells, resolving distinct activated CAR T cell states, including populations characterized by upregulated NT5E or CTSW expression. We showed that overexpression of CTSW, a cathepsin protease, in CAR T cells promotes stem-like phenotypes, long-term proliferation, and sustained tumor cell killing. scAPEX-seq provides a powerful and scalable approach for profiling subcellular RNA populations, enabling the discovery of cell-cell interaction regulators missed by conventional approaches.

cell biology↗

bioRxiv2025

Bispecific T cell engagers control solid tumors through clonal replacement and IL2-driven effector differentiation of CD8 T-cells

Bispecific T cell engagers (TCEs) often exhibit limited efficacy in solid tumors, in part due to immunosuppressive cues in the tumor microenvironment and low expression of targetable tumor antigens. Therapeutic strategies to improve TCE target sensitivity and enhance T cell effector functions therefore have significant translational potential. Here, we engineered TCEs that induce T cell activation in vitro against the low-abundance target antigens, TRP2/Kb and DLL3. Despite in vitro activity in these models, TCE monotherapy showed limited control of tumor growth in immunocompetent mice. Leveraging this in vivo model of TCE treatment failure, we discovered that co-treatment with TCE and a CD25-biased Interleukin-2 (IL2) rescues anti-tumor activity. Further, multimodal single-cell transcriptomic and immune repertoire analyses revealed that TCE-IL2 combination therapy controlled tumors by recruiting and activating new CD8+ T cells into the tumor microenvironment. These findings demonstrate that TCE-mediated anti-tumor responses function through a CD8+ T cell clonal replacement mechanism that can be augmented by cytokine therapy. One Sentence SummaryCombining TCE therapy with IL-2 enhances TCE efficacy in aggressive small-cell lung cancer and melanoma models with low target antigen density through T cell clonal replacement and CD8+ effector T cell differentiation.

cancer biology↗

bioRxiv2025

Surfaceome CRISPR activation screening uncovers ligands regulating tumor sensitivity to NK cell killing

Natural killer (NK) cell-based immunotherapies represent a promising avenue for cancer treatment due to their ability to eliminate cancer cells independently of antigen presentation and potential for "off-the-shelf" use. However, the molecular determinants governing tumor cell susceptibility to NK cell-mediated cytotoxicity remain incompletely understood. Here we employed CRISPR activation (CRISPRa) screening to systematically identify cancer cell surface regulators of NK cell killing across multiple cancer types. Using a comprehensive surfaceome-focused library, we screened human and murine cancer cell lines co-cultured with NK cells, identifying both known and novel ligands that modulate NK cell cytotoxicity. Our screens revealed established factors including CD43 (encoded by SPN), while uncovering previously uncharacterized regulators such as CD44, PDPN, and Siglec-1/CD169. Validation through complementary cDNA overexpression and genetic knockout approaches confirmed that disruption of CD43, CD44, PDPN, and Siglec-1 significantly altered cancer cell susceptibility to NK killing both in vitro and in humanized mouse models. Analysis of clinical datasets show that expression of identified factors correlates with patient survival outcomes in an NK-context dependent manner supporting their therapeutic relevance. Most notably, our mechanistic studies demonstrate that CD43-mediated NK cell resistance operates independently of its previously proposed interaction with Siglec-7 on NK cells. Furthermore, we find that targeting CD43 on either NK cells or engineered T cells substantially enhances their cytotoxic activity against leukemia cell lines. These results establish gain-of-function screening as a powerful approach for discovering immunoregulatory surface proteins and identify multiple promising targets for enhancing NK cell-based cancer immunotherapies.

immunology↗

bioRxiv2025

Programmable microparticles rewire CAR signaling to enable super-physiological expansion of human T cells in vitro

T cell proliferative capacity and persistence critically determine the therapeutic success of chimeric antigen receptor (CAR) T cells. However, it remains unknown if and how human CAR-T cells can be externally programmed to reach maximal proliferative capacity. Here, we use programmable PLGA microparticles functionalized with CAR-antigens and CD28-costimulatory antibodies (CAREp) to repeatedly stimulate human CD8+ CAR-T cells in vitro. CAREp-stimulated CAR-T cells expanded continuously for over 100 days--versus [~]30 days with tumor cell stimulation--and achieved up to 1018-fold cumulative expansion, greatly surpassing CD3/28-Dynabeads. Early-phase transcriptomic responses-- upregulation of DNA repair, cell cycle, telomere maintenance, and mitochondrial pathways--aligned with long-term outcomes: massive proliferation, telomere stability, robust respiration, and preserved progenitor phenotype by single-cell sequencing. Differentiation and exhaustion signals were broadly suppressed. Transient telomerase activity further supported physiologic expansion. These findings demonstrate that nanoscale-controlled extracellular cues can rewire intracellular signaling to drive durable, super-physiological expansion of functional CAR-T cells.

immunology↗

bioRxiv2024

Directed evolution of the multicopper oxidase laccase for cell surface proximity labeling and electron microscopy

Enzymes that oxidize aromatic substrates have shown utility in a range of cell-based technologies including live cell proximity labeling (PL) and electron microscopy (EM), but are associated with drawbacks such as the need for toxic H2O2. Here, we explore laccases as a novel enzyme class for PL and EM in mammalian cells. LaccID, generated via 11 rounds of directed evolution from an ancestral fungal laccase, catalyzes the one-electron oxidation of diverse aromatic substrates using O2 instead of toxic H2O2, and exhibits activity selective to the surface plasma membrane of both living and fixed cells. We show that LaccID can be used with mass spectrometry-based proteomics to map the changing surface composition of T cells that engage with tumor cells via antigen-specific T cell receptors. In addition, we use LaccID as a genetically-encodable tag for EM visualization of cell surface features in mammalian cell culture and in the fly brain. Our study paves the way for future cell-based applications of LaccID.

biochemistry↗

bioRxiv2021

Multimodal tubulin binding by the yeast kinesin-8, Kip3, underlies its motility and depolymerization

The microtubule (MT) cytoskeleton is central to cellular processes including axonal growth, intracellular transport, and cell division, all of which rely on precise spatiotemporal control of MT organization. Kinesin-8s play a key role in regulating MT length by combining highly processive directional motility with MT-end disassembly. However, how kinesin-8 switches between these two apparently opposing activities remains unclear. Here, we define the structural features underlying this molecular switch through cryo-EM analysis of the yeast kinesin-8, Kip3 bound to MTs, and molecular dynamics simulations to approximate the complex of Kip3 with the curved tubulin state found at the MT plus-end. By integrating biochemical and single-molecule biophysical assays, we identified specific intra- and intermolecular interactions that modulate processive motility and MT disassembly. Our findings suggest that Kip3 undergoes conformational changes in response to tubulin curvature that underlie its unique ability to interact differently with the MT lattice than with the MT-end.

biophysics↗

bioRxiv2021

T cell circuits that sense antigen density with an ultrasensitive threshold

Overexpressed tumor associated antigens (e.g. HER2 and EGFR) are attractive targets for therapeutic T cells, but toxic cross-reaction with normal tissues expressing low antigen levels has been observed with Chimeric Antigen Receptor (CAR) T cells targeting such antigens. Inspired by natural ultrasensitive response circuits, we engineer a two-step positive feedback circuit that allows T cells to discriminate targets based on a sigmoidal antigen density threshold. In this circuit, a low affinity SynNotch receptor for HER2 controls the expression of a high affinity CAR for HER2. Increasing HER2 density thus has cooperative effects on T cells it both increases CAR expression and activation leading to a sigmoidal response. T Cells with this circuit show sharp discrimination between target cells expressing normal and disease levels of HER2, both in vitro and in vivo. One Sentence SummaryA two-step positive feedback circuit generates engineered T cells capable of killing target cells with an ultrasensitive antigen density threshold.

synthetic biology↗