Biology subjects

Knight, K. M.

Publications and source records attributed to Knight, K. M..

5 recordsLinked to original sources

bioRxiv2026

Activity-Dependent Postsynaptic Mitochondrial ROS Signaling Drives Avoidance Plasticity in C. elegans

Reactive oxygen species (ROS) are signaling molecules involved in neuronal excitatory function, with mitochondrial ROS (mitoROS) playing key roles in metabolic regulation and stress responses. Studies have shown that neuronal activity upregulates mitoROS production through oxidative phosphorylation, but it remains unclear if and how acute elevations in mitoROS influence synaptic plasticity. Here, we develop an avoidance sensitization paradigm in C. elegans using optogenetic excitation and training of nociceptive ASH neurons to initiate avoidance reversals by downstream activation of the AVA command interneurons. Using this paradigm, we show that the probability of reversal to light stimulation increases 4-hours after optogenetic training, indicating behavioral sensitization. This avoidance sensitization is accompanied by an increase of surface glutamate receptor (GLR-1) levels at ASH-AVA synapses which is dependent on postsynaptic expression of GLR-1 and active transcription. Interestingly, we find that somatic and nerve ring mitochondria produce ROS after optogenetic training. We show that this mitochondrial ROS (mitoROS) peak is dependent on postsynaptic GLR-1 and MCU-1 function during optogenetic training and is necessary for avoidance sensitization. Finally, we demonstrate that postsynaptic signaling by mitoROS in AVA is sufficient to induce avoidance sensitization. Postsynaptic photoactivation of mitochondria-targeted Killer Red in AVA, calibrated to produce the mitoROS peak observed during training, induces avoidance sensitization bypassing optogenetic training and MCU-1 requirement. Our results indicate that activity-dependent mitoROS signaling can instruct synaptic strengthening and directly modulate circuit function and behavior. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/730457v2_ufig1.gif" ALT="Figure 1"> View larger version (113K): org.highwire.dtl.DTLVardef@91f9bborg.highwire.dtl.DTLVardef@1a274b1org.highwire.dtl.DTLVardef@9b394forg.highwire.dtl.DTLVardef@cf8b7d_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2026

Systems modeling identifies phenotype-determining signaling pathways controlled by phosphatase PTPRJ in diverse receptor tyrosine kinase activation settings

Protein tyrosine phosphatase receptor J (PTPRJ) restrains cell proliferation and migration by dephosphorylating receptor tyrosine kinases (RTKs) including the epidermal growth factor receptor (EGFR). PTPRJ is a purported tumor suppressor, and alterations to its expression and/or function are associated with colorectal, breast, lung, and other cancers. While there is interest in controlling PTPRJ-regulated phenotypes, efforts are limited by the complexity of PTPRJ-mediated signaling. PTPRJ dephosphorylates multiple RTKs, and the degree to which PTPRJ control of signaling and phenotypes depends on local cellular RTK activation profiles is unknown. To probe the context dependence of PTPRJ signaling regulation, we collected signaling measurements across 16 pathway nodes at two time points in a panel of HSC3 carcinoma cells engineered with different PTPRJ expression profiles. Cells were treated with three different RTK ligands, and paired phenotype measurements (viability, wound healing, xCELLigence cell index) were made. Partial least squares regression models were developed to predict relationships between PTPRJ-regulated signaling pathways and cell phenotypes. The model effectively separated contributions to variance arising from the PTPRJ expression background and growth factor context. In testing model predictions, we demonstrated that PTPRJ suppressed MET-induced cell cell proliferation via regulation of a HER3/AKT signaling axis that stabilized PTPRJ expression through an unanticipated feedback mechanism. We also found that PTPRJ regulated HSC3 cell migration via JNK signaling that was preferentially activated by MET. Our results identify new regulatory nodes through which PTPRJ influences cancer cell phenotypes and demonstrates that these processes preferentially occur in the context of distinct RTK activation states.

systems biology↗

bioRxiv2023

Activity-dependent Mitochondrial ROS Signaling Regulates Recruitment of Glutamate Receptors to Synapses

Our understanding of mitochondrial signaling in the nervous system has been limited by the technical challenge of analyzing mitochondrial function in vivo. In the transparent genetic model Caenorhabditis elegans, we were able to manipulate and measure mitochondrial signaling as well as neuronal activity in vivo. Using this approach, we provide evidence supporting a novel role for mitochondrial signaling in dendrites. Specifically, we show that dendritic mitochondria take up calcium (Ca2+) via the mitochondrial Ca2+ uniporter MCU-1 causing an upregulation of mitochondrial reactive oxygen species (mitoROS) production. We also observed that mitochondria are positioned in close proximity to synaptic clusters of GLR-1, the C. elegans ortholog of the AMPA subtype of glutamate receptors that mediate neuronal excitation. We show that synaptic recruitment of GLR-1 is downregulated by mitoROS signaling resulting from mitochondrial Ca2+ uptake via MCU-1. Thus, postsynaptic mitochondria provide a means of negative feedback that regulates excitatory synapse function which may be vital for neuronal homeostasis by preventing excitotoxicity and energy depletion.

neuroscience↗

bioRxiv2022

A Dual Role for LAR-RPTP in Regulating Long-distance Transport and Synaptic Retention of AMPARs, Essential for Long Term Associative Memory

The AMPA subtype of ionotropic glutamate receptors (AMPARs) plays an essential role in excitatory synaptic transmission, learning, and memory. The majority of AMPARs are made in the cell body and are transported by molecular motors to synapses. Maintaining the proper number of synaptic receptors requires coordinated regulation of receptor production, export from the soma and delivery at synapses. This major logistical process is essential for circuit function and behavior. Although recent studies have shown that long-distance synaptic transport is regulated by neuronal activity, little is known about the mechanisms that coordinate somatic export or synaptic delivery and removal. Here we show that loss of the PTP-3A isoform of the receptor tyrosine phosphatase PTP-3 (the C. elegans homologue of vertebrate LAR-RPTP) leads to a [~]60% decrease in AMPAR transport; this affects synaptic delivery of AMPARs and synaptic functions necessary for long-term associative olfactory memory in C. elegans. Interestingly, while complete loss of PTP-3A leads to defects in transport and local synaptic trafficking of AMPARs, loss of only PTP-3 phosphatase function affects local synaptic recycling and retention of AMPARs. Finally, we show that the N-terminus of PTP-3A regulates transport, whereas the C-terminal regulates synaptic retention of AMPARs. Altogether, our results suggest a model in which the two domains of PTP-3/LAR-RPTPs have specific, complementary roles in coordinating somatic export and local retention of AMPARs essential for long-term associative memory.

neuroscience↗

bioRxiv2020

A Universal Allosteric Mechanism for G Protein Activation

G proteins play a central role in signal transduction and pharmacology. Signaling is initiated by cell-surface receptors, which promote GTP binding and the dissociation of G from the G{beta}{gamma} subunits. Structural studies have revealed the molecular basis for subunit association with receptors, RGS proteins and downstream effectors. In contrast, the mechanism of subunit dissociation is poorly understood. We used cell signaling assays, MD simulations, biochemistry and structural analysis to identify a conserved network of amino acids that dictates subunit release. In the presence of the terminal phosphate of GTP, a glycine forms a polar network with an arginine and glutamate, putting torsional strain on the subunit binding interface. This "G-R-E motif" secures GTP and, through an allosteric link, discharges the G{beta}{gamma} dimer. Replacement of network residues prevents subunit dissociation, regardless of agonist or GTP binding. These findings reveal the molecular basis for the final committed step of G protein activation. HIGHLIGHTSO_LIReceptors promote GTP-GDP exchange and dissociation of G protein and {beta}{gamma} subunits C_LIO_LIWe find an allosteric network linking the {gamma} phosphate of GTP with release of G{beta}{gamma} C_LIO_LIThe network consists of a conserved Gly-Arg-Glu "activation triad" C_LIO_LITriad mutations prevent subunit dissociation, regardless of agonist or GTP binding C_LIO_LITriad mutations are responsible for human endocrine and neurological disorders C_LI

biochemistry↗