Biology subjects

Kuffner, C. J.

Publications and source records attributed to Kuffner, C. J..

3 recordsLinked to original sources

bioRxiv2026

ProNotch converts extracellular protease activity into programmable transcriptional outputs

Synthetic receptors that convert extracellular protease activity into programmable transcriptional outputs would expand the toolkit of mammalian cell biology and cell engineering, yet modular platforms for directly coupling extracellular proteolysis to gene expression remain limited. Here we introduce ProNotch, a receptor architecture that harnesses protease-gated derepression of a mutant Notch1 negative regulatory region (NRR) to drive user-defined gene expression. ProNotch tethers destabilized NRR mutants to inhibitory anti-NRR single-chain variable fragments (scFvs) via protease-cleavable linkers. NRR engagement by high-affinity scFvs simultaneously rescues surface trafficking of mutant receptors and suppresses basal signaling until linker cleavage releases the inhibitory scFv module, permitting the destabilized NRR to initiate ligand-independent signaling. Linker substitution reprogrammed protease specificity across diverse enzymes, and tandem substrate repeats enhanced sensitivity without increasing basal activity. Single-chain receptor designs enabled OR and AND logic gates, allowing integration of multi-protease inputs into a single transcriptional output. ProNotch detected endogenous MMP-14 activity from cancer cell lines in cis and in trans and drove protease-dependent cell-state transitions in C3H/10T1/2 fibroblasts. The scFv-NRR module also functioned as a protease-activated pro-antibody that conditionally inhibited DLL4-dependent signaling and ligand-independent activation of mutant NOTCH1 in the T cell acute lymphoblastic leukemia cell line HPB-ALL. Together, these results establish ProNotch as a modular platform for engineering protease-responsive cells and demonstrate that its regulatory module can be extended to a soluble, conditionally activated inhibitor of NOTCH1 signaling.

synthetic biology↗

bioRxiv2024

RNA-Stabilized Coat Proteins for Sensitive and Simultaneous Imaging of Distinct Single mRNAs in Live Cells

RNA localization and regulation are critical for cellular function, yet many live RNA imaging tools suffer from limited sensitivity due to background emissions from unbound probes. Here, we introduce conditionally stable variants of MS2 and PP7 coat proteins (which we name dMCP and dPCP) designed to decrease background in live-cell RNA imaging. Using a protein engineering approach that combines circular permutation and degron masking, we generated dMCP and dPCP variants that rapidly degrade except when bound to cognate RNA ligands. These enhancements enabled the sensitive visualization of single mRNA molecules undergoing differential regulation within various sub-compartments of live cells. We further demonstrate dual-color imaging with orthogonal MS2 and PP7 motifs, allowing simultaneous low-background visualization of distinct RNA species within the same cell. Overall, this work provides versatile, low-background probes for RNA imaging, which should have broad utility in the imaging and biotechnological utilization of MS2- and PP7-containing RNAs.

bioengineering↗

bioRxiv2024

Fluorescein-Based SynNotch Adaptors for Regulating Gene Expression Responses to Diverse Extracellular Cues

We introduce an adaptor-based strategy for regulating fluorescein-binding synthetic Notch (SynNotch) receptors using ligands based on conjugates of fluorescein isomers and analogs. To develop a versatile system, we evaluated the surface expression and activities of multiple constructs containing distinct extracellular fluorescein-binding domains. Using an optimized receptor, we devised ways to regulate signaling via fluorescein-based chemical transformations, including an approach based on a bio-orthogonal chemical ligation and a spatially controllable strategy via the photo-patterned uncaging of an o-nitrobenzyl-caged fluorescein conjugate. We further demonstrate that fluorescein-conjugated extracellular matrix (ECM)-binding peptides can regulate SynNotch activity depending on the folding state of collagen-based ECM networks. Treatment with these conjugates enabled cells to distinguish between folded versus denatured collagen proteins and enact dose-dependent gene expression responses depending on the nature of the signaling adaptors presented. To demonstrate the utility of these tools, we applied them to control the myogenic conversion of fibroblasts into myocytes with spatial and temporal precision and in response to denatured collagen-I, a biomarker of multiple pathological states. Overall, we introduce an optimized fluorescein-binding SynNotch as a versatile tool for regulating transcriptional responses to extracellular ligands based on the widely used and clinically-approved fluorescein dye.

synthetic biology↗