Biology subjects

Carney, K. R.

Publications and source records attributed to Carney, K. R..

7 recordsLinked to original sources

bioRxiv2025

ERK builds a population of short-lived nascent adhesions that produce persistent edge protrusion and cell migration

Cell migration is realized through the fast and persistent protrusion of a leading edge in the direction of movement. The actin and adhesion structures that build edge protrusions are integrated such that pro-migration signaling pathways must control both assemblies to induce protrusion. Understanding the contribution of adhesion regulation has been complicated by the inability to selectively assay the nascent adhesions that promote edge protrusion. Here, we dissect how the core RAS[->]RAF[->]MEK[->]ERK pathways control of nascent adhesions contributes to edge protrusion and cell migration by targeting an ERK FRET biosensor to adhesions and quantifying ERKs spatial and temporal activity. We find that ERK is activated in the assembling, membrane-proximal region of nascent adhesions through adhesion scaffold paxillin, which interacts with the ERK activator MEK. Tracking nascent adhesion dynamics during cell migration showed that ERK promotes both nascent adhesion assembly and disassembly to create a population of nascent adhesions with short lifetimes. MEK inhibition is partially complemented by expression of a talin R8vvv mutant that increases the nascent adhesion population, demonstrating the significance of ERKs adhesion regulation for edge protrusion and migration persistence. These findings suggest that when new adhesions initiate, the ERK activation level dictates adhesion assembly and disassembly rates to specifically build nascent adhesions that rapidly turnover, an adhesion population that promotes protrusion persistence and migration. SignificanceCell migration is essential for development, healing, and cancer spread. To move, cells need to build and break tiny structures called nascent adhesions, specifically at their edge that protrudes in the direction of movement. We discovered that ERK, a key signaling protein activated during development and cancer, helps create a fast-turning-over population of these adhesions, which supports steady movement. Using new biosensors and adhesion tracking, we showed ERK is active in the assembling part of the adhesion, where it promotes both assembly and disassembly. Increasing the nascent adhesion population helps cells move when ERK is blocked. This work reveals how ERK controls cell movement by balancing adhesion dynamics and introduces tools to study similar processes in other signaling pathways.

cell biology↗

bioRxiv2025

Mechanism of ERK-mediated Rho Activation and Stress Fiber Assembly for Cell Migration

The growth factor-activated RAS/Extracellular Regulated Kinase (ERK) pathway is a fundamental regulatory pathway that induces cell migration. ERK supports protrusion of a leading edge and also activates the small GTPase Rho, which induces actin assembly into contractile stress fibers that pull the cell body forward. Yet, the mechanism behind ERKs induction of Rho in the cell body has remained elusive. We discover here that ERK controls Rho activity and contractile stress fibers by inhibiting Ezrin, a protein that physically links proximal actin filaments to the plasma membrane, but which also inhibits Rho by recruiting and activating ARHGAP18. ERK specifically reduces Ezrin activity in the cell body by phosphorylating the C-terminal tail of the Ezrin-activating kinase lymphocyte-oriented kinase (LOK). This phosphorylation inhibits LOKs activation of Ezrin, thereby releases Ezrins inhibition of Rho and stress fibers. The ERK-LOK-Ezrin-ARHGAP18-Rho signal provides key mechanistic insight into how ERK, activated during development, wound healing, and cancer, induces Rho activity and stress fibers for cell migration.

cell biology↗

bioRxiv2025

Chemical propulsion of hemozoin crystal motion in malaria parasites

Malaria parasites infect red blood cells where they digest host hemoglobin and release free heme inside a lysosome-like organelle called the food vacuole. To detoxify excess heme, parasites form hemozoin crystals that rapidly tumble inside this compartment. Hemozoin formation is critical for parasite survival and central to antimalarial drug activity. Although the static structural properties of hemozoin have been extensively investigated, crystal motion and its underlying mechanism have remained puzzling. We used quantitative image analysis to determine the timescale of motion, which requires the intact vacuole but does not require the parasite itself. Using single particle tracking and Brownian dynamics simulations with experimentally derived interaction potentials, we found that hemozoin motion exhibits unexpectedly tight confinement but is much faster than thermal diffusion. Hydrogen peroxide, which is generated at high levels in the food vacuole, has been shown to stimulate the motion of synthetic metallic nanoparticles via surface-catalyzed peroxide decomposition that generates propulsive kinetic energy. We observed that peroxide stimulated the motion of isolated crystals in solution and that conditions that suppress peroxide formation slowed hemozoin motion inside parasites. These data suggest that surface-exposed metals on hemozoin catalyze peroxide decomposition to drive crystal motion. This work reveals hemozoin motion in malaria parasites as a biological example of an endogenous self-propelled nanoparticle. This mechanism of propulsion likely serves a physiological role to reduce oxidative stress to parasites from hydrogen peroxide produced by large-scale hemoglobin digestion during blood-stage infection. Significance statementHemozoin crystal formation is a major antimalarial drug target as it is essential for survival of Plasmodium parasites that cause malaria, one of the worlds most devastating infectious diseases. Hemozoin crystals rapidly tumble inside the parasite food vacuole, and the mechanism and significance of this motion have been mysterious. Using quantitative live-cell imaging and computational modeling, we discovered that hemozoin motion is driven by catalytic decomposition of hydrogen peroxide on the crystal surface, a mechanism analogous to synthetic nanomotors. Hemozoin crystals have been viewed as inert detoxification products. Our work reframes the physiological role of these crystals as catalytically active nanoparticles whose mechanism of propulsion helps to neutralize toxic hydrogen peroxide generated by parasite digestion of hemoglobin during blood-stage infection.

biophysics↗

bioRxiv2024

Tenascin-C in the early lung cancer tumor microenvironment promotes progression through integrin activation and FAK

Pre-cancerous lung lesions are commonly initiated by activating mutations in the RAS pathway, but do not transition to lung adenocarcinomas (LUAD) without additional oncogenic signals. Here, we show that expression of the extracellular matrix protein Tenascin-C (TNC) is increased in and promotes the earliest stages of LUAD development in oncogenic KRAS-driven lung cancer mouse models and in human LUAD. TNC is initially expressed by fibroblasts and its expression extends to tumor cells as the tumor becomes invasive. Genetic deletion of TNC in the mouse models reduces early tumor burden and high-grade pathology and diminishes tumor cell proliferation, invasion, and focal adhesion kinase (FAK) activity. TNC stimulates cultured LUAD tumor cell proliferation and migration through engagement of v-containing integrins and subsequent FAK activation. Intringuingly, lung injury causes sustained TNC accumulation in mouse lungs, suggesting injury can induce additional TNC signaling for early tumor cell transition to invasive LUAD. Biospecimens from patients with stage I/II LUAD show TNC in regions of FAK activation and an association of TNC with tumor recurrence after primary tumor resection. These results suggest that exogenous insults that elevate TNC in the lung parenchyma interact with tumor-initiating mutations to drive early LUAD progression and local recurrence.

cancer biology↗

bioRxiv2022

Mechanics of lung cancer: A finite element model shows strain amplification during early tumorigenesis

Early lung cancer lesions develop within a unique microenvironment that undergoes constant cyclic stretch from respiration. While tumor stiffening is an established driver of tumor progression, the contribution of stress and strain to lung cancer is unknown. We developed tissue scale finite element models of lung tissue to test how early lesions alter respiration-induced strain. We found that an early tumor, represented as alveolar filling, amplified the strain experienced in the adjacent alveolar walls. Tumor stiffening further increased the amplitude of the strain in the adjacent alveolar walls and extended the strain amplification deeper into the normal lung. In contrast, the strain experienced in the tumor proper was less than the applied strain, although regions of amplification appeared at the tumor edge. Measurements of the alveolar wall thickness in clinical and mouse model samples of lung adenocarcinoma (LUAD) showed wall thickening adjacent to the tumors, consistent with cellular response to strain. Modeling alveolar wall thickening by encircling the tumor with thickened walls moved the strain amplification radially outward, to the next adjacent alveolus. Simulating iterative thickening in response to amplified strain produced tracks of thickened walls. We observed such tracks in early-stage clinical samples. The tracks were populated with invading tumor cells, suggesting that strain amplification in very early lung lesions could guide pro-invasive remodeling of the tumor microenvironment. The simulation results and tumor measurements suggest that cells at the edge of a lung tumor and in surrounding alveolar walls experience increased strain during respiration that could promote tumor progression. Author SummaryLung cancer is the leading cause of cancer-related death in the world. Efforts to identify and treat patients early are hampered by an incomplete understanding of the factors that drive early lesion progression to invasive cancer. We aimed to understand the role of mechanical strain in early lesion progression. The lung is unique in that it undergoes cyclic stretch, which creates strain across the alveolar walls. Computational models have provided fundamental insights into the stretch-strain relationship in the lung. In order to map the strain experienced in the alveolar walls near a tumor, we incorporated a tumor into a tissue scale model of the lung under stretch. We used finite element modeling to apply physiological material behavior to the lung and tumor tissue. Based on reported findings and our measurements, tumor progression was modeled as stiffening of the tumor and thickening of the tumor-adjacent alveolar walls. We found that early tumors amplified the strain in the tumor-adjacent alveolar walls. Strain amplification also arose at the tumor edges. Simulating strain-mediated wall stiffening generated tracks of thickened walls. We experimentally confirmed the presence of tracks of thickened extracellular matrix in clinical samples of LUAD. Our model is the first to interrogate the alterations in strain in and around a tumor during simulated respiration and suggests that lung mechanics and strain amplification play a role in early lung tumorigenesis.

cancer biology↗

bioRxiv2021

Nascent adhesions differentially regulate lamellipodium velocity and persistence

Cell migration is essential to physiological and pathological biology. Migration is driven by the motion of a leading edge, in which actin polymerization pushes against the edge and adhesions transmit traction to the substrate while membrane tension increases. How the actin and adhesions synergistically control edge protrusion remains elusive. We addressed this question by developing a computational model in which the Brownian ratchet mechanism governs actin filament polymerization against the membrane and the molecular clutch mechanism governs adhesion to the substrate (BR-MC model). Our model predicted that actin polymerization is the most significant driver of protrusion, as actin had a greater effect on protrusion than adhesion assembly. Increasing the lifetime of nascent adhesions also enhanced velocity, but decreased the protrusions motional persistence, because filaments maintained against the cell edge ceased polymerizing as membrane tension increased. We confirmed the model predictions with measurement of adhesion lifetime and edge motion in migrating cells. Adhesions with longer lifetime were associated with faster protrusion velocity and shorter persistence. Experimentally increasing adhesion lifetime increased velocity but decreased persistence. We propose a mechanism for actin polymerization-driven, adhesion-dependent protrusion in which balanced nascent adhesion assembly and lifetime generates protrusions with the power and persistence to drive migration.

cell biology↗

bioRxiv2019

LongAxis: a MATLAB-based program for 3D quantitative analysis of epithelial cell shape and orientation

Epithelial morphogenesis, a fundamental aspect of development, generates 3-dimensional tissue structures crucial for organ function. Underlying morphogenetic mechanisms are, in many cases, poorly understood, but mutations that perturb organ development can affect epithelial cell shape and orientation - difficult features to quantify in three dimensions. The basic structure of the eye is established via epithelial morphogenesis: in the embryonic optic cup, the retinal progenitor epithelium enwraps the lens. We previously found that loss of the extracellular matrix protein laminin-alpha1 (lama1) led to mislocalization of apical polarity markers and apparent misorientation of retinal progenitors. We sought to visualize and quantify this phenotype, and determine whether loss of the apical polarity determinant pard3 might rescue the phenotype. To this end, we developed LongAxis, a MATLAB-based program optimized for the retinal progenitor neuroepithelium. LongAxis facilitates 3-dimensional cell segmentation, visualization, and quantification of cell orientation and morphology. Using LongAxis, we find that retinal progenitors in the lama1-/- optic cup are misoriented and slightly less elongated. In the lama1;MZpard3 double mutant, cells are still misoriented, but larger. Therefore, loss of pard3 does not rescue loss of lama1, and in fact uncovers a novel cell size phenotype. LongAxis enables population-level visualization and quantification of retinal progenitor cell orientation and morphology. These results underscore the importance of visualizing and quantifying cell orientation and shape in three dimensions within the retina.

developmental biology↗