Testing the specificity of the inhibitory effects of Aβ42, an Alzheimer’s related protein, to ion channels Cav 3.2 and Kv 4.2
Persistent URL
Author(s)
Appiah-Agyeman, Lilly
Date Issued
April 3, 2017
Abstract
Alzheimer’s Disease (AD) is a neurodegenerative disorder characterized by the degradation of neurons and synapses in areas of the brain involved with memory. Unfortunately, there is not a known cure for AD, in part because verifying a person’s AD can only be done by locating Amyloid beta (Aβ) plaque deposits in the brain during postmortem examination. Aβ42, the most prevalent isoform of Aβ, is linked to AD because it has two hydrophobic amino acids (Isoleucine and Alanine) that give it the ability to aggregate with other Aβ to produce different forms (oligomer, fibril, etc.). These forms can eventually become the Aβ plaques that are readily expressed in AD patients and localized in areas of the brain involved with memory. Presence of extracellular Aβ plaques does not directly align with progression of AD symptoms. Thus, it is important to examine different conformation and locations of Aβ42. In addition, although it is not clear the exact neurological pathway Aβ42 undergoes to induce symptoms of AD, it is hypothesized that Aβ42 is interacting with ion channels. A previous Allegheny College Comprehensive Thesis showed that 0.1 nM of Aβ42 inhibited the maximum current of the BK channel hSlo1.1 expressed in oocytes. I hypothesize that the inhibitory effect of the monomeric form of 0.1 nM of Aβ42 would be specific to the BK channel hSlo1.1 expressed in Xenopus oocytes as compared to Kv 4.2, an A-type voltage-gated potassium channel and Cav.3.2, a T-type calcium channel. Two-electrode voltage clamp (TEVC) recordings were conducted on each RNA and water-inject oocyte. A voltage electrode held the oocyte at a voltage from-50mV to +40 mV in increments of +10mV and a current electrode measuring current at each step. The maximum current of Kv4.2 and water-inject oocytes was noted at +40mV while the maximum current of Cav3.2 was noted between -50 mV and -40 mV. Intracellular applications of Aβ42 were conducted by applying the Aβ42 to the current electrode and allowing the Aβ42 to diffuse into the oocyte for 5 minutes before TEVC recordings were conducted. Extracellular applications of Aβ42 were conducted by applying Aβ42 to the recording bath solution and allowing it to diffuse into the bath before TEVC recordings were conducted. The intracellular and extracellular recordings were analyzed using an independent t- test and matched pair t-test, respectively. It was found that 0.1 nM of Aβ42 did not inhibit the maximum current of Kv4.2 and Cav3.2, both intracellularly and extracellularly. These results prove that the inhibitory effects of 0.1nM of Aβ42 was specific to hSlo1.1. Although 0.1 µM of Aβ42 did not inhibit the maximum current of Cav3.2 and Kv4.2, these findings are important because it eliminates the possible ion channels that Aβ42 affects in the pathway to AD. Therefore, researchers can focus on their time on other ion channels affected by Aβ42 to uncover how they relate to AD.
Major
Neuroscience
Honors
Neuroscience, 2017
First Reader(s)
French, Lauren
Type of Publication
Senior Project Paper
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Name
2016_17_Appiah-Ageyman_inhibitoryeffects.pdf
Description
Main Document
Size
1.43 MB
Format
Adobe PDF
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