Biology subjects

Hayes, C. A.

Publications and source records attributed to Hayes, C. A..

5 recordsLinked to original sources

bioRxiv2021

IGF-1 Differentially Modulates Glutamate-Induced Toxicity and Stress in Cells of the Neurogliovascular Unit

The age-related reduction in circulating levels of insulin-like growth factor-1 (IGF-1) is associated with increased risk of stroke and neurodegenerative diseases in advanced age. Numerous reports highlight behavioral and physiological deficits in blood-brain barrier function and neurovascular communication when IGF-1 levels are low. Administration of exogenous IGF-1 reduces the extent of tissue damage and sensorimotor deficits in animal models of ischemic stroke, highlighting the critical role of IGF-1 as a regulator of neurovascular health. The beneficial effects of IGF-1 in the nervous system are often attributed to direct actions on neurons; however, glial cells and the cerebrovasculature are also modulated by IGF-1, and systemic reductions in circulating IGF-1 likely influence the viability and function of the entire neuro-glio-vascular unit. We recently observed that reduced IGF-1 led to impaired glutamate handling in astrocytes. Considering glutamate excitotoxicity is one of the main drivers of neurodegeneration following ischemic stroke, the age-related loss of IGF-1 may also compromise neural function indirectly by altering the function of supporting glia and vasculature. In this study, we assess and compare the effects of IGF-1 signaling on glutamate-induced toxicity and reactive oxygen species (ROS)-produced oxidative stress in primary neuron, astrocyte, and brain microvascular endothelial cell cultures. Our findings verify that neurons are highly susceptible to excitotoxicity, in comparison to astrocytes or endothelial cells, and that a prolonged reduction in IGFR activation increases the extent of toxicity. Moreover, prolonged IGFR inhibition increased the susceptibility of astrocytes to glutamate-induced toxicity and lessened their ability to protect neurons from excitotoxicity. Thus, IGF-1 promotes neuronal survival by acting directly on neurons and indirectly on astrocytes. Despite increased resistance to excitotoxic death, both astrocytes and cerebrovascular endothelial cells exhibit acute increases in glutamate-induced ROS production and mitochondrial dysfunction when IGFR is inhibited at the time of glutamate stimulation. Together these data highlight that each cell type within the neuro-glio-vascular unit differentially responds to stress when IGF-1 signaling was impaired. Therefore, the reductions in circulating IGF-1 observed in advanced age are likely detrimental to the health and function of the entire neuro-glio-vascular unit.

neuroscience↗

bioRxiv2021

Adulthood Deficiency of the Insulin-like Growth Factor-1 Receptor in Hippocampal Neurons Impairs Cell Structure and Spatial Learning and Memory in Male and Not Female Mice

Reductions in insulin-like growth factor-1 (IGF-1) are associated with cognitive impairment and increased risk of neurodegenerative disease in advanced age. In mouse models, reduced IGF-1 early-in-life leads to memory impairments and synaptic dysfunction; however, these models are limited by systemic reductions in IGF-1. We hypothesized that IGF-1 continues to promote hippocampal neuron structure and function after development, and as such, the loss of IGF-1 signaling in adult neurons would lead to impaired spatial learning and memory. To test this, the IGF-1 receptor (IGF-1R) was genetically targeted in hippocampal neurons of adult male and female mice. Male mice deficient in neuronal IGF-1R exhibited spatial learning impairments as evidenced by increased pathlength and errors in the radial arm water maze. No differences in learning and memory were observed in female mice. Golgi-Cox staining revealed a reduced number of dendritic boutons of neurons the CA1 region of the hippocampus in male mice. Decreased MAPK and increased ROCK activity were also observed in these tissues. In vitro studies revealed that impaired neurite outgrowth due to inhibited IGF-1R signaling could be rescued by pharmacological inhibitors of ROCK. However, ROCK inhibition in neuronal IGF-1R-deficient mice did not fully rescue learning impairments or bouton numbers. Together, our study highlights that IGF-1 continues to support spatial learning and memory and neuronal structure in adulthood.

neuroscience↗

bioRxiv2017

The Nucleoid Occlusion Protein SlmA Is A Direct Transcriptional Activator Of Chitobiose Utilization In Vibrio cholerae

Chitin utilization by the cholera pathogen Vibrio cholerae is required for its persistence and evolution via horizontal gene transfer in the marine environment. Genes involved in the uptake and catabolism of the chitin disaccharide chitobiose are encoded by the chb operon. The orphan sensor kinase ChiS is critical for regulation of this locus, however, the mechanisms downstream of ChiS activation that result in expression of the chb operon are poorly understood. Using an unbiased transposon mutant screen, we uncover that the nucleoid occlusion protein SlmA is a regulator of the chb operon. SlmA has not previously been implicated in gene regulation. Also, SlmA is a member of the TetR family of proteins, which are generally transcriptional repressors. In vitro, we find that SlmA binds directly to the chb operon promoter, and in vivo, we show that this interaction is, surprisingly, required for transcriptional activation of this locus and for chitobiose utilization. Using point mutations that disrupt distinct functions of SlmA, we find that DNA-binding, but not nucleoid occlusion, is critical for transcriptional activation. This study identifies a novel role for SlmA as a transcriptional regulator in V. cholerae in addition to its established role as a cell division licensing factor.\n\nAUTHOR SUMMARYThe cholera pathogen Vibrio cholerae is a natural resident of the aquatic environment and causes disease when ingested in the form of contaminated food or drinking water. In the aquatic environment, the shells of marine zooplankton, which are primarily composed of chitin, serve as an important food source for this pathogen. The genes required for the utilization of chitin are tightly regulated in V. cholerae, however, the exact mechanism underlying this regulation is currently unclear. Here, we uncover that a protein involved in regulating cell division is also important for regulating the genes involved in chitin utilization. This is a newly identified property for this cell division protein and the significance of a common regulator for these two disparate activities remains to be understood.

microbiology↗

bioRxiv2017

Systematic Genetic Dissection Of Chitin Degradation And Uptake In Vibrio cholerae

Vibrio cholerae is a natural resident of the aquatic environment, where a common nutrient is the chitinous exoskeletons of microscopic crustaceans. Chitin utilization requires chitinases, which degrade this insoluble polymer into soluble chitin oligosaccharides. These oligosaccharides also serve as an inducing cue for natural transformation in Vibrio species. There are 7 predicted endochitinase-like genes in the V. cholerae genome. Here, we systematically dissect the contribution of each gene to growth on chitin as well as induction of natural transformation. Specifically, we created a strain that lacks all 7 putative chitinases and from this strain, generated a panel of strains where each expresses a single chitinase. We also generated expression plasmids to ectopically express all 7 chitinases in our chitinase deficient strain. Through this analysis, we found that low levels of chitinase activity are sufficient for natural transformation, while growth on insoluble chitin as a sole carbon source requires more robust and concerted chitinase activity. We also assessed the role that the three uptake systems for the chitin degradation products GlcNAc, (GlcNAc)2, and (GlcN)2, play in chitin utilization and competence induction. Cumulatively, this study provides mechanistic details for how this pathogen utilizes chitin to thrive and evolve in its environmental reservoir.\n\nORIGINALITY-SIGNIFICANCE STATEMENTVibrio cholerae, the causative agent of the diarrheal disease cholera, interacts with the chitinous shells of crustacean zooplankton in the aquatic environment, which serves as an environmental reservoir for this pathogen. It degrades and utilizes chitin-derived products as a source of carbon and nitrogen. Also, chitin serves as an inducing cue for natural transformation - an important mechanism of horizontal gene transfer in this species. Here, we systematically dissect the genes required for chitin degradation and uptake, and characterize the role of these genes for growth on chitin as a nutrient and during chitininduced natural transformation. Thus, this study provides mechanistic details for how this pathogen utilizes chitin to thrive and evolve in its environmental reservoir.

microbiology↗

bioRxiv2017

Multiplex genome editing for synthetic biology in Vibrio natriegens

Vibrio natriegens has recently emerged as an alternative to Escherichia coli for molecular biology and biotechnology, but low-efficiency genetic tools hamper its development. Here, we uncover how to induce natural competence in V. natriegens and describe methods for multiplex genome editing by natural transformation (MuGENT). MuGENT promotes integration of large genome edits at high-efficiency on unprecedented timescales, which will extend the utility of this species for diverse applications.\n\nV. natriegens is the fastest growing organism known, with a doubling time of <10 min1,2. With broad metabolic capabilities, lack of pathogenicity, and its rapid growth rate, it is an attractive alternative to E. coli for diverse molecular biology and biotechnology applications3. Methods for classical genetic techniques have been developed for V. natriegens, but these are rel ...

synthetic biology↗