Yoonseong Park - US grants

DESCRIPTION (provided by applicant): Ticks are obligatory external parasites that feed on the blood of hosts, and often transmit pathogens, including bacteria, protozoa, and viruses. Tick-borne diseases cause huge economic losses in the animal industry as well as health risks to humans. The salivary secretions of the ticks play an important role in blood feeding by modulating the host response. We propose to investigate the peptidergic system as it relates to control of the salivary gland in the black-legged tick, Ixodes scapularis, which is one of the most important ticks in the northern U.S. as a risk to human heath. Our preliminary study suggests that at least two peptidergic systems are involved in neural control of the salivary gland: putatively, myoinhibitory peptide (MIP) and pigment dispersing hormone (PDF). Specific Aim 1 is to identify candidate neuropeptides relevant to salivary functions. While we already identified candidate neuropeptides in our preliminary study, we will expand the survey by using more comprehensive and combinatorial approaches, proteomics, bioinformatics and immunohistochemistry. Specific Aim 2 will further characterize the MIP which is the neuropeptide strongly supported for the function controlling the salivary glands in the preliminary studies. Cloning of the genes encoding MIP and its receptor will be followed by investigation of their expression patterns and function. This study will provide the first description of neuropeptides controlling the tick salivary gland and will provide a foundation for investigations into the roles of the peptidergic systems in salivary secretion in the next tier of study. The fundamental knowledge obtained from this research is expected to lead to the design of compounds and vaccines that disrupt the tick salivary function. The outcome of the proposed research will have high impacts on the studies in other tick species that have large negative impacts on the economy and health. PUBLIC HEALTH RELEVANCE The outcome of the proposed work will provide an understanding of the basic biology of neural control of the tick salivary gland, which will provide the principles for studying other species of tick, and provide rational approaches to develop environmentally benign acaricidal compounds/strategies. This research is eventually expected to lead to the design of compounds and vaccines to disrupt the salivary functions and to prevent disease transmissions by ticks, ultimately improving human health.

DESCRIPTION (provided by applicant): Ticks are obligatory ectoparasites that feed on the blood of vertebrate hosts and often transmit pathogens, including bacteria, protozoa, and viruses. Tick-borne diseases cause huge economic losses in the animal industry as well as health risks to humans. The salivary secretions of ticks play an important role in blood feeding by modulating the host response. We propose to investigate the neural mechanisms controlling salivary secretion in the black-legged tick, Ixodes scapularis, one of the most important ticks in the northern U.S. in terms of its risk to human health. Our preliminary studies, combined with previous studies, led to hypotheses attempting to explain the major mechanism involved in salivary gland control. We hypothesize that myoinhibitory peptide (MIP) and SIFamide control dopamine biosynthesis in the salivary glands. Dopamine, as a paracrine signal synthesized and secreted from basally located cells in the salivary gland acini, activates apical epithelial cells and granular cells in the acini for salivary secretion. To test these hypotheses, three Specific Aims are proposed in this proposal. Specific Aim 1 is to identify and characterize the receptors for each SIFamide and dopamine in the salivary glands. Specific Aim 2 is to investigate the biosynthesis of catecholamines in the salivary glands by biochemical analyses. Specific Aim 3 will be to investigate the functions of MIP, SIFamide, and dopamine signaling pathways in the salivary gland using RNAi and physiological assays. This study will contribute significantly to the body of knowledge that has accumulated in the last three decades with regard to the understanding of the mechanisms controlling the tick salivary gland. The fundamental knowledge obtained from this research is expected to lead to the design of compounds and vaccines that disrupt tick salivary function. The outcome of the proposed research will have a large impact on studies in other tick species that have negative impacts on the economy and human and animal health. PUBLIC HEALTH RELEVANCE: The proposed work will provide an understanding of the mechanism controlling tick salivary gland, which can have large impacts on studies of other tick species that have negative impacts on the economy, and human and animal health. The fundamental knowledge will offer rational approaches to the development of environmentally benign acaricidal compounds.

Project Summary/Abstract Numerous species of mosquitoes are vectors of many pathogens that cause devastating infectious diseases, such as malaria, Dengue, yellow fever, and Zika fever. More than 1 million deaths and up to 700 million cases of infections by mosquito-borne vector diseases (nearly 10% of the total world population) are reported each year. The use of chemical insecticides has been a highly efficient method for the disruption of the pathogen transmission cycle by suppressing the vector population, whereas the evolution of insecticide resistance has hampered the efficacy of currently available classes of insecticides. We propose to establish a new approach for the development of a novel class of mosquitocidal compounds. In the era of new biotechnology, the search for small bioactive compounds using high throughput screening (HTS) is now a robust and accessible technology that can offer substantive dividends for users. The target molecule for the HTS assay we propose is a G protein-coupled receptor (GPCR), named ecdysis-triggering hormone receptor (ETH-R), which is a receptor for a crucial hormone in the unique biology of arthropods for shedding of their external cuticle during molting and for regulation of another crucial endocrine factor juvenile hormone in mosquito. The ETH-R is an ideal target that will allow for the identification of an effective product with significantly improved selectivity toward mammals and even different orders of insects, which will permit the suppression of the mosquito population without significant environmental damage. Target-based discovery of insecticidal compounds will provide a novel example of a biorational approach for the development of pesticide. In this proposal, we aim to identify compounds that act on ETH receptor of the most devastating malaria mosquito (Anopheles gambiae, AgETH-R) by using HTS. We will also identify the structure of the peptide ligands ETH to understand the chemical interaction of the ligand on the binding pocket of the ETH-R. Four investigators in two different Universities will collaborate for the Specific Aims that require diverse areas of disciplines. The specific aims are: 1) High throughput screening for identifying agonists and antagonists acting on AgETH-R [Drs. Roy and Park], 2) Nuclear magnetic resonance (NMR) spectroscopy to determine the structures of AgETH and similar peptide ligands [Drs. Prakash and Park], and 3) Cheminformatics to identify the chemical signature of the hits and the chemical clusters for further tests [Drs. Huan and Park].

Project Summary Ticks are obligatory ectoparasites that feed on vertebrates and transmit pathogens during blood feeding, causing health problems globally in animals and humans. Ticks transmit a wide variety of pathogens, including bacteria (e.g., rickettsia), protozoa, and viruses, and directly damage their hosts. A most significant tick physiology that allows ticks survive in the field is maintaining water balance throughout the lifetime including the off-host periods. The osmoregulatory mechanisms in Metastriata ticks include: 1) directly drinking water through the gut and the salivary glands, 2) losing large amounts of water through dermal secretion, and 3) losing water with excretion of metabolic wastes. The central dogma in this proposal is using the tick water drinking behavior as a route of delivering toxic agents to disrupt the osmoregulatory pathway, which is a vulnerable toxicological target in off-host ticks. Ample preliminary data provides the proof of the concept. Tick deaths could be induced by voluntary drinking of phosphate-rich iso-osmotic solutions and also by thermally induced exhaustive dermal secretion. The aims of the proposals are to develop the tick- specific osmoregulation disruptor (Aim 1) and to investigate the physiology of water loss through tick dermal secretion (Aim 2). In the Aim 1, we will study the physiology of the inorganic phosphate metabolism and phosphate-mediated electrochemical imbalance in the excretory system, which function as a significant osmoregulatory disruptor. Aim2 will uncover the mechanisms of dermal secretion including serotonin-mediated regulation and ion transport mechanisms in the dermal glands, which is a unique organ associated with a loss of large amount (~300 nL) of fluid within a second upon thermal/mechanical stimulation. The strategy using an osmoregulatory disruptor fits well in the hot and dry season in the Midwest and Southwest area of the U.S. where numerous Metastriata ticks, Amblyomma, Dermacentor, Rhipicephalus, and Haemaphysalis, and the pathogen transmission have been reported. The current proposal is to expand the knowledge of the target physiology, linking to the long-term goal in the development of environmentally compatible tick control measures.