Biology subjects

McIntyre, J. C.

Publications and source records attributed to McIntyre, J. C..

5 recordsLinked to original sources

bioRxiv2024

Behavioral and metabolic effects of extended hippocampal overexpression of the myokine Irisin in an Alzheimers Disease mouse model

Lifestyle interventions such as exercise are promising strategies to reduce the detrimental effects faced by aging populations. In particular, the exercise-induced myokine Irisin could act as a mediator of the positive effects of exercise, even as a potential therapeutic option for Alzheimers disease (AD). However, the fundamental roles of Irisin in counteracting AD neuropathology and other effects have not been fully determined. In addition, whether centrally produced Irisin has any effects is unclear. Here we examined the neurobehavioral effects of overexpressing Irisin directly in the hippocampus of an AD transgenic mouse line (TgCRND8), using adult male mice stereotaxically injected with Irisin-AAV vector. To further mimic chronic exercise, spatial memory and exploratory behaviors were assessed using the novel object recognition (NOR)/open field test (OFT) and Y-Maze tests after 8 weeks. Our results showed that Irisin expression led to several behavioral changes, including increased grooming behavior and slightly improved spatial memory performance in short interval NOR test in Tg mice. In the Y-Maze test however, we observed an increase in time spent in familiar spaces, which could indicate heightened anxiety-like behaviors in mice injected with Irisin-AAV. In addition, we observed significant differences in body and liver size, and in circulating metabolites such as ketone bodies, that were differentially regulated in NTg or Tg mice. Overall, our findings show important neurobehavioral effects of long-lasting overexpression of the exerkine Irisin in the hippocampus. Our results also raise questions about potential detrimental effects and thus warrant further studies to fully dissect how this exercise mediator affects the brain.

neuroscience↗

bioRxiv2023

Cilia loss on distinct neuron populations differentially alters cocaine-induced locomotion and reward

Neuronal primary cilia are being recognized for their role in mediating signaling associated with a variety of neurobehaviors, including responses to drugs of abuse. Primary cilia are microtubule-based organelles that project from the surface of nearly all mammalian cells, including neurons. They function as signaling hubs and are enriched with a diverse array of GPCRs, including several known to be associated with motivation and drug-related behaviors; however, our understanding of how cilia regulate neuronal function and behavior is still limited. The objective of the current study was to investigate the contributions of primary cilia on specific neuronal populations to behavioral responses to cocaine. To test the consequences of cilia loss on cocaine-induced locomotion and reward-related behavior, we selectively ablated cilia from dopaminergic or GAD2-GABAergic neurons in male and female mice. Cilia ablation on either population of neurons failed to significantly alter acute locomotor responses to cocaine at a range of doses. With repeated administration, mice lacking cilia on GAD2-GABAergic neurons exhibited greater locomotor sensitization to cocaine compared to wild-type littermates, whereas mice lacking cilia on dopaminergic neurons exhibited reduced locomotor sensitization to cocaine at 10 & 30mg/kg. Mice lacking cilia on GAD2-GABAergic neurons showed no difference in cocaine conditioned place preference (CPP), whereas mice lacking cilia on dopaminergic neurons exhibited reduced CPP compared to wild-type littermates. Combined with previous findings using amphetamine, our results show that behavioral effects of cilia ablation are cell-and drug type-specific, and that neuronal cilia contribute to modulation of both the locomotor-inducing and rewarding properties of cocaine.

neuroscience↗

bioRxiv2022

Physiological Condition Dependent Changes in Ciliary GPCR Localization in the Brain

Primary cilia are small immotile cellular appendages which mediate diverse types of singling and are found on most mammalian cell types including throughout the central nervous system. Cilia are known to localize certain G protein-coupled receptors (GPCRs) and are critical for mediating the signaling of these receptors. Several of these neuronal GPCRs have recognized roles in feeding behavior and energy homeostasis. Heterologous cell line and model systems like C. elegans and Chlamydomonas have implicated both dynamic GPCR cilia localization and cilia length and shape changes as key for signaling. However, it is unclear if mammalian ciliary GPCRs utilize similar mechanisms in vivo and under what physiological conditions these processes may occur. Here, we use the ciliary GPCRs, melanin concentrating hormone receptor 1 (MCHR1) and neuropeptide-Y receptor 2 (NPY2R) as model ciliary receptors to determine if dynamic localization to cilia occurs. We tested physiological conditions in which these GPCRs have been implicated such as feeding behavior, obesity, and circadian rhythm. Cilia were imaged using confocal microscopy and analyzed with a computer assisted approach allowing for unbiased and high throughput analysis of cilia. We analyzed GPCR positive cilia, cilia frequency as well as cilia length and receptor occupancy. Interestingly we observed changes in ciliary length, receptor occupancy, and cilia frequency under different conditions, but no consistent theme across GPCRs or brain nuclei was observed. A better understanding of the subcellular localization dynamics of ciliary GPCRs could reveal unrecognized molecular mechanisms regulating behaviors like feeding. Significance StatementOften, primary cilia localize specific G protein-coupled receptors (GPCRs) for subcellular signaling. Cell lines and model systems have indicated that cilia deploy dynamic GPCR localization and change their shape or length to modulate signaling. We used mice to assess neuronal cilia GPCRs under physiological conditions associated with both the receptors known functions and ciliopathy clinical features like obesity. We show that certain cilia with specific GPCRs appear to dynamically alter their length while others appear relatively stable under these conditions. These results implicate multiple themes across cilia GPCR mediated signaling and indicate that not all cilia modulate GPCR signaling using the same mechanisms. These data will be important for potential pharmacological approaches to target cilia GPCR-mediated signaling.

neuroscience↗

bioRxiv2021

An N-terminal Fusion Allele to Study Melanin Concentrating Hormone Receptor 1

Cilia on neurons play critical roles in both the development and function of the central nervous system (CNS). While it remains challenging to elucidate the precise roles for neuronal cilia, it is clear that a subset of G-protein-coupled receptors (GPCRs) preferentially localize to the cilia membrane. Further, ciliary GPCR signaling has been implicated in regulating a variety of behaviors. Melanin concentrating hormone receptor 1 (MCHR1), is a GPCR expressed centrally in rodents known to be enriched in cilia. Here we have used MCHR1 as a model ciliary GPCR to develop a strategy to fluorescently tag receptors expressed from the endogenous locus in vivo. Using CRISPR/Cas9, we inserted the coding sequence of the fluorescent protein mCherry into the N-terminus of Mchr1. Analysis of the fusion protein (mCherryMCHR1) revealed its localization to neuronal cilia in the CNS, across multiple developmental time points and in various regions of the adult brain. Our approach simultaneously produced fortuitous in/dels altering the Mchr1 start codon resulting in a new MCHR1 knockout line. Functional studies using electrophysiology show a significant alteration of synaptic strength in MCHR1 knockout mice. A reduction in strength is also detected in mice homozygous for the mCherry insertion, suggesting that while the strategy is useful for monitoring the receptor, activity could be altered. However, both lines should aid in studies of MCHR1 function and contribute to our understanding of MCHR1 signaling in the brain. Additionally, this approach could be expanded to aid in the study of other ciliary GPCRs.

neuroscience↗

bioRxiv2019

Inhibitory signaling in mammalian olfactory transduction potentially mediated by Gαo

Olfactory GPCRs (ORs) in mammalian olfactory receptor neurons (ORNs) mediate excitation through the Gs family member Golf. Here we tentatively associate a second G protein, Go, with inhibitory signalling in mammalian olfactory transduction by first showing that odor evoked phosphoinositide 3-kinase (PI3K)-dependent inhibition of signal transduction is absent in the native ORNs of mice carrying a conditional OMP-Cre based knockout of Go. We then identify an OR from native rat ORNs that are activated by octanol through cyclic nucleotide signaling and inhibited by citral in a PI3K-dependent manner. We show that the OR activates cyclic nucleotide signaling and PI3K signaling in a manner that reflects its functionality in native ORNs. Our findings lay the groundwork to explore the interesting possibility that ORs can interact with two different G proteins in a functionally identified, ligand-dependent manner to mediate opponent signaling in mature mammalian ORNs.

neuroscience↗