Winks, Joanna Shaw; (2004) Agonist-induced inhibition of the M-current: involvement of the phosphoinositide cycle. Doctoral thesis (Ph.D), UCL (University College London).

Preview

Text Agonist-induced_inhibition_of_.pdf Download (12MB) | Preview

Abstract

M-type potassium channels are closed by activation of G protein-coupled receptors which couple to phospholipase C activation. I have investigated the proposed role of the hydrolysis and depletion of phosphatidylinositol-4,5-bisphosphate (PIP2) in the closure of these channels produced by two different agonists (the muscarinic agonist, oxotremorine-M, and the peptide, bradykinin) in primary mammalian sympathetic neurons. Simultaneous electrophysiological recording of the M-current and imaging of the localization of a fluorescent PIP2-binding construct, GFP-PLC-[delta] PH, has provided a valuable tool for investigation of the involvement of PIP2 levels in M-channel closure. I found that over-expression of the neuronal calcium-sensor protein NCS-1, which enhances PIP2 synthesis by increasing the activity of the enzyme PI4-kinase, reduced the net decrease in membrane PIP2 following application of bradykinin and, in parallel, reduced the sensitivity of M channels to closure by bradykinin. This reduction in sensitivity was partly reversed by the PI4-kinase inhibitor wortmannin. I also found that over-expression of the next enzyme in the synthetic pathway, PI5-kinase, reduced both the net decrease in membrane PIP2 and the sensitivity of the M channels to both agonists. This (plus other evidence) suggests that membrane PIP2 depletion is a key factor in the regulation of M channels by both of these agonists.

Download activity - last month

Export as CSVXMLJSON

Download activity - last 12 months

Export as XMLCSVJSON

Downloads by country - last 12 months

Export as JSONXMLCSV

Archive Staff Only

View Item