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Title: The physiological role for amyloid B protein as a modulator of potassium channels and their accessory subunits
Author: Kerrigan, Talitha Lynn
ISNI:       0000 0001 3597 7071
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2007
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Alzheimer's disease is the most common neurodegenerative disease in the western world. Its pathology is characterised by the deposition of aggregated amyloid ~ (A~) senile plaques. Ap is derived from sequential cleavage of the amyloid precursor protein by ~- and y-secretases. This enigmatic peptide may playa physiological role iJ:l normal cellular functioning and ion channel homeostasis. In the present study we investigated the mechanism by which Ap modulates the K+ channel current (lK) and its effect on accessory subunits. The whole-cell patch-clamp technique was used to measure IK in primary rat cerebellar granule neurones (CON). We found that chronic incubation (24h) of CON cells with physiological concentrations of rat and human AP,-Io (lOnM), produced using recombinant technology, were as effective as synthetically produced peptides at modulating IK, Both species of Ap augmented the fast inactivating 'A'-type current (lKA), with no effect on the delayed rectifier current (lKV). Using immunopharmacology we determined that the Ap-induced increase in IKA involved Kv4.2 usubunits and the Kv channel interacting protein, KChIP3. This Ap-induced increase was negated using arachidonic acid which eradicated the interaction of Kv4.2 with KChIP3, reversing the effects of the Ap-induced IK increases. We established that the mechanism underlying the increase in IK is Ca2+ dependent. When a calcium chelator was introduced in the presence of A~, IK was not increased suggesting that the modulation of IK by A~ involves a Ca2 + mediated pathway. Immunopharmacology was used to establish a novel role for the accessory protein NCS-I in the Ap-induced modulation of IK• The role of endogenous Ap in modulating IK was explored using shRNAi lentiviral technology silencing the BACE-I gene. IK was reduced in both untransfected human neuroblastoma SH-SY5Y and cells overexpressing mutant presenilin 1. This inhibitory response was reversed when cells were co-incubated with IOnM exogenous API-Io. suggesting that the Ap peptide plays a crucial role in the modulation ofK+ currents. We have demonstrated that the physiologically relevant concentrations of Ap peptide modulates IK through a mechanism that is Ca2+dependent, and involves the association of Kv a-subunits with accessory proteins such as KChIP3 and NCS-I.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available