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Molecular characterization of respiratory epithelium specific Lynx3

Final Report Summary - LYNX3 (Molecular characterization of respiratory epithelium specific Lynx3.)

Tobacco use is the leading preventable cause of death in the world. Nicotine, which is the addictive ingredient of tobacco, exerts its addictive effect through nicotinic acetylcholine receptors (nAChRs) in the central nervous system (CNS). Besides mediating nicotine addiction, nAChRs have been implicated in Alzheimer’s disease, Parkinson’s disease, learning and memory, autism, anxiety disorders, depression, cell motility and cellular adhesion. Lynx1 has recently been identified as a modulator of nAChRs and it functions in nicotinic receptor mediated learning and neurodegeneration. Lynx1 is a member of Ly6 superfamily of proteins (Ly6SF), which is a large protein family that consists of proteins with a characteristic three-finger topology. Lynx family consists of ~100 kDa proteins that function mainly in the nervous system through nicotinic receptor modulation. We have recently identified Lynx2 as another modulator of nicotinic receptor activity which is involved in fear and anxiety related behavior. Lynx3 is a novel member of this family that is expressed in high levels in lung epithelial cells that are specifically important in mechanical sensation. In this project, we planned to characterize the molecular function of Lynx3 and its association to lung disease through molecular biological, physiological and behavioral techniques. Our work plan can be grouped under the following headings: 1) Characterization of Lynx3 expression in lung respiratory epithelia and other sensory epithelia. 2) Functional characterization of Lynx3 in vitro through immunoprecipitation experiments and electrophysiology. 3) Physiological analysis of Lynx3 function through targeted-deletion of Lynx3 in mouse models. Our previous work and cited literature suggest that nicotinic acetylcholine receptors are involved in lung physiology, specifically nicotinic receptor associated cellular motility and cell adhesion and Lynx3 is a potential modulator of this system. We have completed all phases of the project. Our results are currently being prepared for publication.
Barrier function and mucociliary clearance of the airway epithelia are innate defenses to protect the lungs from deleterious effects caused by inhaled pollutants and allergens. Cigarette smoking, induces aberrant airway epithelial structure and function, and slows cilia beating, however, the underlying mechanisms are poorly understood. In this study, we identified a novel nicotinic acetylcholine receptor modulator, Lynx3, specifically expressed in ciliated cells of the airway epithelia. Lynx3 knock-out mice exhibited attenuated responses to the aerosolized cholinergic bronchoconstrictor methacholine, but not to intravenous, methacholine treatment; suggesting that Lynx3 deficiency alters barrier function of airway epithelia. Compared to wild type mice, ciliated tracheal cells from Lynx3-/- null mice showed a small but significant increase in both basal cytosolic Ca2+ concentration and in Ca2+ mobilization in response to ATP, without changes in response to mild temperature or hypotonic conditions. Lynx3-/- ciliated cells also presented a faster increase in the ciliary beat frequency following stimulation with ATP but without changes either in basal ciliary beat frequency or in response to mild temperature and hypotonic conditions. Altogether, these findings identify a novel member of the Ly6/α neurotoxin superfamily with cholinergic activity as a modulator of Ca2+ signaling and barrier function in ciliated cells of the airways.
In addition to the scientific findings, the current IRG project has enabled the researcher to make a good start in establishing her own research group after her move from USA to Turkey. With the help of IRG support, she managed to start other research projects and publish several high impact scientific papers, in addition to mentoring several graduate students.

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