Biology subjects

Lee, K.-Z.

Publications and source records attributed to Lee, K.-Z..

6 recordsLinked to original sources

bioRxiv2025

Nora virus proliferates in dividing intestinal stem cells and sensitizes flies to intestinal infection and oxidative stress

The digestive tract represents the most complex interface of an organism with its biotope. Food may be contaminated by pathogens and toxicants while an abundant and complex microbiota thrives in the gut lumen. The organism must defend itself against potentially noxious biotic or abiotic stresses while preserving its microbiota, provided it plays a beneficial role. The presence of intestinal viruses adds another layer of complexity. Starting from a differential sensitivity of two lines from the same Drosophila wild-type strain to ingested Pseudomonas aeruginosa, we report here that the presence of Nora virus in the gut epithelium promotes the sensitivity to this bacterial pathogen as well as to an ingested oxidizing xenobiotic. The genotype, age, nature of the ingested food and, to a limited extent, the microbiota are relevant parameters that influence the effects of Nora virus on host fitness. Mechanistically, we detect the initial presence of the virus essentially in progenitor cells. Upon stress such as infection, exposure to xenobiotics, aging or feeding on a rich-food diet, the virus is then detected in enterocytes, which correlates with a disruption of the intestinal barrier function in aged flies. Finally, we show that the virus proliferates only when ISCs are induced to divide. We propose that enterocytes essentially get infected through lineage from progenitor cells and are not directly infected. In conclusion, it is important to check that experimental strains are devoid of intestinal viruses when monitoring survival/life span of fly lines or when investigating the homeostasis of the intestinal epithelium as these viruses can constitute significant confounding factors.

immunology↗

bioRxiv2023

Acute hyperoxia improves spinal cord oxygenation and circulatory function following cervical spinal cord injury in the rat

Spinal cord injury is associated with spinal vascular disruptions that result in spinal ischemia and tissue hypoxia. This study evaluated the therapeutic efficacy of normobaric hyperoxia on spinal cord oxygenation and circulatory function at the acute stage of cervical spinal cord injury. Adult male Sprague-Dawley rats underwent dorsal cervical laminectomy or cervical spinal cord contusion. At 1-2 days after spinal surgery, spinal cord oxygenation was monitored in anesthetized and spontaneously breathing rats via the optical recording of oxygen sensor foils placed on the cervical spinal cord and pulse oximetry. The arterial blood pressure, heart rate, blood gases, and peripheral oxyhemoglobin saturation were also measured under hyperoxic (50% O2) and normoxic (21% O2) breathing. The results showed that contused animals had a significantly lower spinal cord oxygenation level than uninjured animals during normoxia. Cervical spinal cord contusion also significantly reduced peripheral oxyhemoglobin saturation, arterial oxygen partial pressure, and mean arterial blood pressure. Notably, the spinal oxygenation of contused rats could be improved to a level comparable to uninjured animals under hyperoxia. Furthermore, acute hyperoxia could elevate blood pressure, arterial oxygen partial pressure, and peripheral oxyhemoglobin saturation. These results suggest that normobaric hyperoxia can significantly improve spinal cord oxygenation and circulatory function during acute cervical spinal cord injury. We propose that adjuvant normobaric hyperoxia combined with other hemodynamic optimization strategies may prevent secondary damage after spinal cord injury and improve functional recovery.

physiology↗

bioRxiv2022

Membrane Protein Modification Modulates Big and Small Extracellular Vesicle Biodistribution and Tumorigenic Potential in Breast Cancers In Vivo

Extracellular vesicles (EVs) are released by cells to mediate intercellular communication under pathological and physiological conditions. While small EVs (sEVs; <100-200 nm, exosomes) are intensely investigated, the properties and functions of medium and large EVs (big EVs [bEVs]; >200 nm, microvesicles) are less well explored. Here, we identify bEVs and sEVs as distinct EV populations, and determine that bEVs are released in a greater bEV:sEV ratio in the aggressive human triple-negative breast cancer (TNBC) subtype. PalmGRET, bioluminescence resonance energy transfer (BRET)-based EV reporter, reveals dose- dependent EV biodistribution at non-lethal and physiological EV dosages, as compared to lipophilic fluorescent dyes. Remarkably, the bEVs and sEVs exhibit unique biodistribution profiles, et individually promote in vivo tumor growth in a syngeneic immunocompetent TNBC breast tumor murine model. The bEVs and sEVs share mass spectrometry (MS)- identified tumor progression-associated EV surface membrane proteins (tpEVSurfMEMs), which include SLC29A1, CD9 and CD44. tpEVSurfMEM depletion attenuates EV lung organotropism, alters biodistribution, and reduces protumorigenic potential. This study identifies distinct in vivo property and function of bEVs and sEVs in breast cancer, which suggest the significant role of bEVs in diseases, diagnostic and therapeutic applications.

cancer biology↗

bioRxiv2021

A prior exposure to Serratia marcescens or xenobiotics primes Drosophila enterocytes against a recurring cytoplasmic purge

The cytoplasmic extrusion of enterocytes is a fast response to an exposure to pore-forming toxin (PFT)-producing bacteria whereby their apical cytoplasm is extruded into the intestinal lumen. As a result of this purge, the intestinal epithelium becomes thin prior to a subsequent recovery. We report here that the ingestion of ethanol or caffeine induces a similar response, which suggests that a common purging process is triggered by bacterial toxins and abiotic toxicants. We also delineate an additional mechanism that is initiated by these stimuli that we refer to as priming. The initial exposure of the intestinal epithelium to either PFT or xenobiotics protects enterocytes against a further round of purging upon a second bacterial infection. Priming prevents the epithelium from being persistently thin in the context of chronic intestinal infections. We have identified the upper part of the p38b MAPK pathway as well as the homeobox-containing transcription factors E5/EMS as being required for priming and not for the regrowth of enterocytes after the cytoplasmic purge. Unexpectedly, the priming process appears to function cell-nonautonomously. Our findings suggest that the cytoplasmic purge extrusion has been selected because it constitutes a fast reaction to accidental exposure to bacterial toxins or toxicants.

physiology↗

bioRxiv2021

The amino acid transporter CG1139 is required for retrograde transport and fast recovery of gut enterocytes after Serratia marcescens intestinal infection

The intestinal tract is constantly exposed to microbes. Severe infections can arise following the ingestion of pathogenic microbes from contaminating food or water sources. The host directly fights off ingested pathogens with resistance mechanisms, the immune response, or withstands and repairs the damages inflicted either by virulence factors or the host immune effectors, through tolerance/resilience mechanisms. In a previous study, we reported the existence in Drosophila melanogaster of a novel evolutionarily conserved resilience mechanism to intestinal infections with a hemolysin-positive Serratia marcescens strain (SmDb11), the purge of the apical cytoplasm of enterocytes. The epithelium becomes very thin and recovers rapidly, regaining its normal thickness within several hours. Here, we found that this recovery of gut enterocyte morphology is based on the host internal reserves and not on ingested food. Indeed, we observed a retrograde transport of amino acids from the host hemolymph to the enterocytes. We have identified several amino acid transporters required for recovery and we focused on the SLC36 family transporter CG1139. CG1139 is required for the retrograde transport of amino acids. RNA sequencing revealed that genes involved in the positive regulation of growth were observed in wild-type but not CG1139 mutant guts, in which the expression of Myc and genes involved in Insulin signaling is down-regulated. Functional analysis revealed that Myc is also required for the recovery of the thick gut epithelium after infection. Altogether, our results show the importance of an amino acid transporter in the fast regrowth of the enterocytes upon infection. Unexpectedly, we found that this transporter acts non cell-autonomously and can regulate the transcription of other genes, suggesting a signaling function of CG1139 that therefore appears to act as a transceptor.

physiology↗

bioRxiv2020

Deficiency of cyclin-dependent kinase-like 5 causes spontaneous seizures in neonatal mice

Cyclin-dependent kinase-like 5 (CDKL5), an X-linked gene encoding a serine-threonine kinase, is enriched in the mammalian forebrain and critical for neuronal maturation and synaptic function. Mutations in this gene cause CDKL5 deficiency disorder (CDD) that is characterized by early-onset epileptic seizures, autistic behaviors and intellectual disability. Although numerous CDD symptoms have been recapitulated in mouse models, spontaneous seizures have not been reported in mice with CDKL5 deficiency. Here, we present the first systematic study of spontaneous seizures in a mouse model of CDD. Through wireless electroencephalographic (EEG) recording and simultaneous videotaping, we observed epileptiform discharges accompanied with ictal behaviors in pups lacking CDKL5 at a selective time window during the pre-weaning period. The seizure-like patterns of EEG showed robust increase in total number of spike events, the total number and duration of bursts in Cdkl5 null pups compared to wild-type littermate controls at the age of postnatal day 12 (P12). The mutants displayed not only jerky and spasm-like movements during the prolonged bursts of discharges at P12, but also strengthened ictal grasping in both juvenile stage and adulthood. In addition, loss of CDKL5 remarkably reduced the phosphorylation of K+/Cl- co-transporter 2, which may impede GABA-mediated inhibition, in the cortex of P12 mouse pups. Our study reveals previously unidentified phenotypes of early-onset seizures in CDKL5-deficient mice, highlights the translational value of mouse models of CDD and provides a potential molecular target for early diagnosis and treatment for CDD. Significance StatementCyclin-dependent kinase-like 5 (CDKL5) is an X-linked gene encoding a serine-threonine kinase. Mutations in this gene cause CDKL5 deficiency disorder (CDD), a rare disease characterized by developmental delays, autistic behaviors and early-onset epilepsy. Even though many symptoms of CDD patients have been phenocopied in mice, spontaneous seizures are yet to be reported in mouse models of CDD. Here, for the first time, we identified early-onset seizures and ictal behaviors in neonatal pups of CDKL5-deficient mice. Loss of CDKL5 also selectively reduced protein levels of phosphorylated K+/Cl-cotransporter 2 in neonatal cortex of mice. Our study reveals an indispensible role of CDKL5 in regulating neuronal excitability in developing brains and highlights the translational significance of the CDD mouse models.

neuroscience↗