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Zinc-dependent potassium channel modulation mediates neuronal apoptosis.

Redman, Patrick Timothy (2008) Zinc-dependent potassium channel modulation mediates neuronal apoptosis. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The liberation of zinc from intracellular stores during pathophysiological conditions, especially those in which reactive oxygen and nitrogen species have been implicated, is central to the progression of neuronal injury. In addition, cellular efflux of a second ionic species, potassium, is similarly responsible for facilitating apoptotic cell death downstream of the initial oxidant-induced zinc liberation. Potassium efflux is mediated by Kv2.1-encoded potassium channels in apoptotic neurons. Here, I have characterized several critical molecular components that link zinc liberation to the loss of cytoplasmic potassium following oxidative injury. First, electrophysiological and viability studies using Kv2.1 channel mutants identified a p38 phosphorylation site at serine 800 (S800) that is required for Kv2.1 membrane insertion, potassium current enhancement, and cell death. In addition, a phospho-specific antibody for S800 detected a p38-dependent increase in Kv2.1 phosphorylation in apoptotic neurons, and reveals phosphorylation of S800 in immunopurified channels incubated with active p38. Next, I present data indicating that an N-terminal tyrosine of Kv2.1 (Y124), which is targeted by src, is also critical for the apoptotic current surge. These latter studies suggest that Y124 works in concert with the C-terminal serine (S800) target of p38 MAPK to regulate Kv2.1-mediated current enhancement. While zinc was previously shown to activate p38 and src, I demonstrate here that this metal inhibits cytoplasmic protein tyrosine phosphatase å (Cyt-PTPå), which targets Y124 and antagonizes the actions of src. Therefore, I have identified two requisite phosphorylation sites on Kv2.1, at Y124 and S800, that cooperatively mediate apoptotic potassium current enhancement. Importantly, disruption of either phosphorylation event is neuroprotective. The work presented here provides a more complete understanding of neuronal apoptotic processes by revealing the intracellular signaling events linking intracellular zinc liberation and cytoplasmic potassium efflux.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Redman, Patrick Timothyptr3@pitt.eduPTR3
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairLevitan, Edwin Slevitan@server.pharm.pitt.eduELEVITAN
Committee MemberDeFranco, Donald Bdod1@pitt.eduDOD1
Committee Member Aizenman, Eliasredox@pitt.eduREDOX
Committee MemberTamkun, Michael
Committee Member Meriney, Stephen Dmeriney@pitt.eduMERINEY
Committee Member Hastings, Teresa Gthasting@pitt.eduTHASTING
Date: 21 November 2008
Date Type: Completion
Defense Date: 17 October 2008
Approval Date: 21 November 2008
Submission Date: 11 November 2008
Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Neurobiology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: apoptosis; Kv2.1; p38; potassium; src; tyrosine phosphatase epsilon; zinc
Other ID:, etd-11112008-162403
Date Deposited: 10 Nov 2011 20:04
Last Modified: 15 Nov 2016 13:51


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