Semester of Graduation

Spring

Degree

Master of Science (MS)

Department

Entomology

Document Type

Dissertation/Thesis

Abstract

The tick salivary gland is a critical tissue that enables blood feeding, maintenance of the ionic gradients, and facilitates pathogen transmission. Therefore, the broad objective of this investigation was to leverage pharmacological approaches to investigate the role of potassium ion channels to salivary gland function of Amblyomma americanum in an effort to identify a tractable target site for therapeutic development.

Data collected in Chapter 2 clearly illustrated that the A. americanum salivary gland is reliant upon inward rectifier potassium (Kir) channels for fluid secretion, which was similar to previous work performed by our laboratory on Drosophila salivary gland. Therefore, the physiological role of Kir channels was further characterized in fluid secretion, osmoregulation, and feeding capability in live ticks.

Further characterization showed that a subtype of Kir channels, termed ATP-gated Kir channels (KATP channels), are critical for proper salivation because the agonists VU0071063 and pinacidil inhibited salivation with an IC50 of 2 µM and 200 µM, respectively. Importantly, the inhibitory effect was negated by pre-treatment with ATP, which is known to inhibit KATP channels and provides support that VU0071063 is indeed reducing salivation through modulation of KATP channels.

In Chapter 3, we tested the hypothesis that KATP channels are critical for ion secretion and absorption, thus osmoregulation. KATP channel agonists were found to increase the concentration of Na+, K+, and Cl- ions in the secreted saliva by 10-15 fold when compared to control. These data suggest that KATP channels are likely maintaining, at least in part, the intracellular loop currents that drive ion secretion and/or reabsorption during salivary gland activity.

In Chapter 4, we aimed to translate the in vitro data collected in chapters 2 and 3 into a functional study that tested the utility of KATP modulators to alter feeding and survivability to a live tick. Data show that both KATP agonists, pinacidil and VU0071063, increased the rate of detachments during blood feeding, reduced the volume of ingested blood, and lead to mortality. The data collected in this thesis provide significant support for targeting Kir/KATP channels in future therapeutic development campaigns to reduce the burden of tick vectored pathogens.

Date

3-26-2018

Committee Chair

Swale, Daniel

Available for download on Tuesday, March 26, 2019

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