Biology subjects

Truong, K.

Publications and source records attributed to Truong, K..

6 recordsLinked to original sources

bioRxiv2026

Efficacy profiling of structurally diverse cannabinoid receptor ligands across transducer-coupling assays

The full efficacy range of ligands at CB1 and CB2 (i.e., inverse agonists, neutral agonists, partial agonists, full agonists, and high-efficacy agonists) has been reported collectively across numerous laboratories and assay platforms. Canonical Gi/o and {beta}-arrestin signaling have each been suggested to shape physiological effects differently via different classes of cannabinoid ligands. These prior efficacy classifications, however, were obtained in multiple assay systems, often using indirect, amplified readouts and different reference agonists, making them difficult to compare across ligands. Here we profiled a structurally diverse panel of 22 cannabinoid ligands: synthetic cannabinoid receptor agonists (SCRAs), {Delta}-tetrahydrocannabinol ({Delta}-THC) analogues, endocannabinoid analogues, and antagonists/inverse agonists at CB1 and CB2 receptors using bioluminescence resonance energy transfer (BRET) assays, measuring Gi1 engagement and {beta}-arrestin 2 recruitment and normalizing every response to the reference full agonist CP55,940. At CB1, SCRAs and {Delta}-THC analogues acted as high-efficacy agonists. At CB1, these high-efficacy agonists were also highly efficacious in {beta}-arrestin 2 recruitment. Across the panel, the most consistent trend was a loss of agonist efficacy from CB1 to CB2. Among antagonists, inverse agonists suppressed constitutive CB1 activity more than neutral antagonists. Together, these CP55,940-normalized measurements provide a common efficacy scale and a framework for interpreting pharmacodynamics of CB1 and CB2 cannabinoid receptors.

pharmacology and toxicology↗

bioRxiv2025

PIAS1/PIAS4-Mediated SUMOylation of TDP-43 is Induced by Oxidative Stress

Abstract/SummaryTAR DNA-binding protein 43 (TDP-43) is a conserved RNA and DNA binding protein that functions in transcriptional repression, pre-mRNA splicing and mRNA stabilization. Under pathological conditions found in multiple neurodegenerative diseases, TDP-43 shows aberrant mislocalization from the nucleus and cytoplasmic accumulation and aggregation. TDP-43 also appears to play a role in DNA damage repair, specifically in non-homologous end-joining (NHEJ), suggesting that nuclear depletion of TDP-43 may contribute towards the accumulation of DNA damage observed in TDP-43 proteinopathies. These TDP-43 pathological inclusions are decorated with post-translational modifications, most notably phosphorylation. SUMOylation (Small Ubiquitin-like Modifier) is a dynamic post-translational modification that regulates many protein properties and is implicated in neurodegenerative disease pathology. DNA damage repair proteins are commonly regulated through SUMOylation, and the SUMO E3 ligases PIAS1 and PIAS4 are required for efficient DNA repair of double-strand DNA breaks. Given these findings, we investigated TDP-43 SUMOylation and whether SUMO modification impacts TDP-43s DNA damage repair function. We show that TDP-43 can be modified by SUMO1 and SUMO2/3 and confirm SUMOylation in response to oxidative stress. We also determine which regions of TDP-43 are SUMOylated and show that this modification is facilitated by the SUMO E3 ligases PIAS1 and PIAS4. Etoposide-induced DNA damage did not promote SUMOylation of TDP-43; studies are ongoing to determine the impact of TDP-43 SUMOylation on DNA repair.

neuroscience↗

bioRxiv2025

Optimization and Comparative Evaluation of SimpliAmp and Bio-Rad Thermal Cyclers for PCR-Based Detection of Vibrio cholerae

Cholera continues to pose a significant public health risk in low- and middle-income countries (LMICs), necessitating quick, cost-effective, and dependable diagnostics for effective outbreak surveillance and management. In this study, we optimized and tested two PCR-based assays targeting a uniplex assay with the ompW gene, and a multiplex assay with ctxA, O1-rfb, and O139-rfb genes of Vibrio cholerae (V. cholerae) on two thermal cycler platforms with different cost: the Bio-Rad C1000 Touch, which is more expensive, and the SimpliAmp, which is cheaper. Cycling conditions, annealing temperatures, and primer concentrations were systematically optimized to improve efficiency and reagent use. We tested our assay sensitivity by serially diluting gBlock DNA from 2000 to 50 copies. Quo data software was used to estimate the limit of detection and Fishers exact tests with Holm-Bonferroni correction to assess any differences (p<0.05) across all dilution levels on both platforms. The ompW assay achieved identical performance on both platforms, with 100% detection down to 250 copies and an LOD of 523 copies (95% CI: 347- 786; p = 1.000). For the multiplex assay, O1-rfb showed slightly higher sensitivity on SimpliAmp (LOD= 509 copies, 95% CI: 339-766) than on Bio-Rad (LOD = 333 copies, 95% CI: 255-688; p = 0.217). The ctxA assay had an LOD of 684 copies (95% CI: 501-1323) on SimpliAmp and 974 copies (95% CI: 714-1784) on Bio-Rad (p = 0.089). For O139-rfb, SimpliAmp and Bio-Rad achieved LOD values of 639 (95% CI: 490-1251) and 1060 copies (95% CI: 719-1562), respectively (p = 0.179). In general, the differences in performance between platforms were not statistically significant. These results highlight the potential of SimpliAmp as a reliable, low-cost alternative for cholera diagnostics in LMICs and low-resource settings, supporting broader access to molecular tools for outbreak investigation and public health surveillance.

molecular biology↗

bioRxiv2021

In vivo serial passaging of human-simian immunodeficiency virus clones identifies viral characteristics that enhance persistent viral replication

We previously reported that a human immunodeficiency virus type 1 with a simian immunodeficiency virus vif substitution (HSIV-vifNL4-3) could replicate in pigtailed macaques (PTMs), demonstrating that Vif is a species-specific tropism factor of primate lentiviruses. However, infections did not result in high peak viremia or setpoint plasma viral loads, as observed during SIV infection of PTMs. Here, we characterized variants isolated from one of the original infected animals with CD4 depletion after nearly four years of infection to identify determinants of increased replication fitness. In our studies, we found that the HSIV-vif clones did not express the HIV-1 Vpr protein due to interference from the vpx open reading frame in singly spliced vpr mRNA. To examine whether these viral genes contribute to persistent viral replication, we generated infectious HSIV-vif clones expressing either the HIV-1 Vpr or SIV Vpx protein. And then to determine viral fitness determinants of HSIV-vif, we conducted three rounds of serial in vivo passaging in PTMs, starting with an initial inoculum containing a mixture of CXCR4-tropic (Vpr- HSIV-vifNL4-3 isolated at 196 (C/196) and 200 (C/200) weeks post-infection from a PTM with depressed CD4 counts) and CCR5-tropic HSIV (Vpr+ HSIV-vif derivatives based NL-AD8 and Bru-Yu2 and a Vpx expressing HSIV-vifYu2). Interestingly, all infected PTMs showed peak plasma viremia close to or above 105 copies/ml and persistent viral replication for more than 20 weeks. The passage 3 PTM showed peak viral loads greater than 105 viral RNA copies/ml. Infectious molecular clones (IMCs) recovered from the passage 3 PTM (HSIV-P3 IMCs) included mutations required for HIV-1 Vpr expression and those mutations encoded by the CXCR4-tropic HSIV-vifNL4-3 isolates C/196 and C/200. The data indicate that the biological isolates selected during long-term infection acquired HIV-1 Vpr expression to enhance their replication fitness in PTMs. Further passaging of HSIV-P3 IMCs in vivo may generate pathogenic variants with higher replication capacity, which will be a valuable resource as challenge virus in vaccine and cure studies.

microbiology↗

bioRxiv2021

Interaction of micropatterned topographical and biochemical cues to direct neurite growth from spiral ganglion neurons

Functional outcomes with neural prosthetic devices, such as cochlear implants, are limited in part due to physical separation between the stimulating elements and the neurons they stimulate. One strategy to close this gap aims to precisely guide neurite regeneration to position the neurites in closer proximity to electrode arrays. Here, we explore the ability of micropatterned biochemical and topographic guidance cues, singly and in combination, to direct the growth of spiral ganglion neuron (SGN) neurites, the neurons targeted by cochlear implants. Photopolymerization of methacrylate monomers was used to form unidirectional topographical features of ridges and grooves in addition to multidirectional patterns with 90{degrees} angle turns. Microcontact printing was also used to create similar uni- and multi-directional patterns of peptides on polymer surfaces. Biochemical cues included peptides that facilitate (laminin, LN) or repel (EphA4-Fc) neurite growth. On flat surfaces, SGN neurites preferentially grew on LN-coated stripes and avoided EphA4-Fc-coated stripes. LN or EphA4-Fc was selectively adsorbed onto the ridges or grooves to test the neurite response to a combination of topographical and biochemical cues. Coating the ridges with EphA4-Fc and grooves with LN lead to enhanced SGN alignment to topographical patterns. Conversely, EphA4-Fc coating on the grooves or LN coating on the ridges tended to disrupt alignment to topographical patterns. SGN neurites respond to combinations of topographical and biochemical cues and surface patterning that leverages both cues enhance guided neurite growth.

bioengineering↗

bioRxiv2018

Live calcium imaging of Aedes aegypti neuronal tissues reveals differential importance of chemosensory systems for life-history-specific foraging strategies

Aedes aegypti have a wide variety of sensory pathways that have supported success as a species as well as a highly competent vector of numerous debilitating infectious pathogens. Investigations into mosquito sensory systems and their effects on behavior are valuable resources for the advancement of mosquito control strategies. Numerous studies have elucidated key aspects of mosquito sensory systems, however there remains critical gaps within the field. In particular, compared to that of the adult form, there has been a lack of studies directed towards the immature life stages. Additionally, although numerous studies have pinpointed specific sensory receptors as well as relevant response behaviors, there has been a lack of studies able to monitor both concurrently. To begin filling aforementioned gaps, here we engineered Ae. aegypti to ubiquitously express a genetically encoded calcium indicator, GCaMP6s. Using this strain, combined with advanced confocal microscopy, we were able to simultaneously measure live stimulus-evoked calcium responses in both neuronal and muscle cells with a wide spatial range and resolution. Moreover, by coupling in vivo calcium imaging with behavioral assays we were able to gain functional insights into how stimulus-evoked neural and muscle activities are represented, modulated, and transformed in mosquito larvae enabling us to elucidate mosquito sensorimotor properties important for life-history-specific foraging strategies.\n\nSignificance StatementUnderstanding mosquito sensory systems and resulting behavior has been a major factor in the advancement of mosquito control innovations. Aedes aegypti larvae offer an effective life stage for further elucidating information on mosquito sensory systems. Due to their relatively simplified nervous system, mosquito larvae are ideal for studying neural signal transduction, coding, and behavior. Moreover, a better understanding of the larval sensory system may enable the development of novel control methodologies able to target mosquitoes before they reach a vector-competent stage. Here we engineer Ae. aegypti to ubiquitously express a genetically encoded calcium indicator, GCaMP6s and use this tool to observe links between sensorimotor responses and behavior by exploiting live calcium imaging as well as live tracking based behavioral assays.

neuroscience↗