Biology subjects

DeCuzzi, N. L.

Publications and source records attributed to DeCuzzi, N. L..

4 recordsLinked to original sources

bioRxiv2026

The eIF4B RNA recognition motif promotes higher-order organization of the translation initiation machinery during stress granule assembly.

Cells respond to environmental stress by rapidly remodeling translation and assembling stress granules (SGs), which are dynamic ribonucleoprotein condensates that contain untranslated mRNAs, translation initiation factors, and 40S ribosomal subunits. Although the translation initiation factor eIF4B has been implicated in SG biology, the contribution of its highly conserved RNA recognition motif (RRM) to SG assembly has remained unclear. Here, we developed a quantitative live-cell imaging framework that resolves distinct kinetic phases of SG assembly at single-cell resolution and combines these measurements with single-cell analysis of protein synthesis. Using this approach, we show that disruption of the eIF4B RRM delays SG nucleation, slows SG assembly, and reduces the number of SGs formed, while having little effect on mature SG size. Biochemical analyses revealed that the RRM mutant retained high-affinity binding to both RNA and the 40S ribosomal subunit and exhibited only a modest reduction in eIF4A helicase stimulation activity but displayed altered RNA engagement, consistent with impaired RNA-dependent organization of the translation initiation machinery. Coupling SG kinetics with single-cell measurements of protein synthesis further revealed that delayed SG nucleation is associated with reduced translational repression during oxidative stress. Together, our findings identify the conserved eIF4B RRM as a regulator of productive higher-order organization of the translation initiation machinery and establish a quantitative framework for investigating how SG assembly and translational remodeling are coordinated during cellular stress.

cell biology↗

bioRxiv2026

A Far-Red FRET biosensor for AMPK enables multiplexed imaging of single-cell bioenergetic homeostasis

Metabolic homeostasis has been studied primarily at the tissue and organism level, identifying molecular control mechanisms such as the energy charge-sensing kinase AMPK. Feedback loops involving AMPK and other regulators align cellular ATP generation and consumption, determining energetic balance. Recent work has demonstrated surprising oscillatory dynamics in AMPK activity, revealing unidentified kinetic modulation in single-cell homeostatic behaviour. However, probing the kinetic mechanisms of intracellular feedback requires simultaneous observation of multiple energetic parameters, and such experiments are precluded by the shared wavelength band occupied by most metabolic biosensors. We have overcome this obstacle by constructing a red-shifted FRET-based AMPK activity biosensor, RAMPKAR2, that is comparable to existing FRET-based AMPK activity biosensors. Multiplexed imaging of RAMPKAR2 with PercevalHR, which detects ATP/ADP ratio, confirmed that the kinetics of AMPK activity and ATP/ADP ratio are tightly coupled, with a lag of less than 6 minutes at the single-cell level. Pairing of RAMPKAR with HYlight, which detects the glycolytic intermediate fructose 1,6-bisphosphate (FBP), revealed that glycolytic activity co-oscillates with AMPK, shifted by [~]1.5 hours, and that these oscillations are suppressed by sustained AMPK activity. Together these data advance a model in which temporally offset increases in glycolytic ATP supply and AMPK deactivation contribute to single-cell oscillations.

systems biology↗

bioRxiv2024

Two Novel Red-FRET ERK Biosensors in the 670-720nm Range.

Cell fate decisions are regulated by intricate signaling networks, with Extracellular signal-Regulated Kinase (ERK) being a central regulator. However, ERK is rarely the only signaling pathway involved, creating a need to study multiple signaling pathways simultaneously at the single-cell level. Many existing fluorescent biosensors for ERK and other pathways have significant spectral overlap, limiting their ability to be multiplexed. To address this limitation, we developed two novel red-FRET ERK biosensors, REKAR67 and REKAR76, which operate in the 670-720 nm range using miRFP670nano3 and miRFP720. REKAR67 and REKAR76 differ in fluorophore position, which impacts biosensor characteristics; REKAR67 displayed a higher dynamic range but greater signal variance than REKAR76. Mixed populations of REKAR67 or REKAR76 displayed similar Signal-to-Noise ratio (SNR), but in clonal cell populations, REKAR76 had a significantly higher SNR. Overall, our red-FRET ERK biosensors were highly consistent with existing ERK FRET biosensors and in reporting ERK activity and are spectrally compatible with CFP/YFP FRET and cpGFP -based biosensors. Both REKAR biosensors expand the available methods for measuring single-cell ERK activity.

cell biology↗

bioRxiv2024

Spatiotemporal Clusters of ERK Activity Coordinate Cytokine-induced Inflammatory Responses in Human Airway Epithelial Cells

RATIONALESpatially coordinated ERK signaling events ("SPREADs") transmit radially from a central point to adjacent cells via secreted ligands for EGFR and other receptors. SPREADs maintain homeostasis in non-pulmonary epithelia, but it is unknown whether they play a role in the airway epithelium or are dysregulated in inflammatory disease. OBJECTIVES(1) To characterize spatiotemporal ERK activity in response to pro-inflammatory ligands, and (2) to assess pharmacological and metabolic regulation of cytokine-mediated SPREADs. METHODSSPREADs were measured by live-cell ERK biosensors in human bronchial epithelial cell lines (HBE1 and 16HBE) and primary human bronchial epithelial (pHBE) cells, in both submerged and biphasic Air-Liquid Interface (ALI) culture conditions (i.e., differentiated cells). Cells were exposed to pro-inflammatory cytokines relevant to asthma and chronic obstructive pulmonary disease (COPD), and to pharmacological treatments (gefitinib, tocilizumab, hydrocortisone) and metabolic modulators (insulin, 2-deoxyglucose) to probe the airway epithelial mechanisms of SPREADs. Phospho-STAT3 immunofluorescence was used to measure localized inflammatory responses to IL-6. RESULTSPro-inflammatory cytokines significantly increased the frequency of SPREADs. Notably, differentiated pHBE cells display increased SPREAD frequency that coincides with airway epithelial barrier breakdown. SPREADs correlate with IL-6 peptide secretion and localized pSTAT3. Hydrocortisone, inhibitors of receptor signaling, and suppression of metabolic function decreased SPREAD occurrence. CONCLUSIONSPro-inflammatory cytokines modulate SPREADs in human airway epithelial cells via both secreted EGFR and IL6R ligands. SPREADs correlate with changes in epithelial barrier permeability, implying a role for spatiotemporal ERK signaling in barrier homeostasis and dysfunction during inflammation. The involvement of SPREADs in airway inflammation suggests a novel signaling mechanism that could be exploited clinically to supplement corticosteroid treatment for asthma and COPD. Brief SummaryCombining live-cell ERK biosensors with multiple human airway epithelial models, we demonstrate that pro-inflammatory cytokines cause spatiotemporally organized ERK signaling events called "SPREADs", correlating with conditions that disrupt epithelial barrier function. Additionally, common anti-inflammatory treatments tocilizumab, gefitinib, and hydrocortisone suppress cytokine-induced SPREADs. These findings suggest that localized ERK signaling coordinates the innate immune response via spatially restricted cytokine release and regulation of airway barrier permeability.

cell biology↗