Publication Date

2014-06-06

Availability

Embargoed

Embargo Period

2016-06-05

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Neuroscience (Medicine)

Date of Defense

2014-05-27

First Committee Member

Miguel A. Perez-Pinzon

Second Committee Member

Carlos T. Moraes

Third Committee Member

Antoni Barrientos

Fourth Committee Member

Grace Zhai

Abstract

Mitochondrial dysfunction following cerebral ischemia is a major contributor to tissue injury and neurodegeneration. Therefore, investigating the pathways that lead to mitochondrial protection following cerebral ischemic injury represents a major strategy in the development of therapeutic approaches. The PKCepsilon enzyme has been shown to translocate to the mitochondria where it is involved in providing global mitochondrial protection against ischemic insults. The goal of this study was to better understand the downstream pathways that drive PKCepsilon-mediated mitochondrial neuroprotection which may facilitate therapeutic approaches to cerebral ischemic injury. Initial experiments performed in vitro revealed that PKCepsilon functionally cooperates with the transcriptional regulator AMPK, another master regulator of mitochondrial function. AMPK and PKCepsilon were shown to reciprocally regulate each other’s activity and require each other to provide ischemic neuroprotection. Further investigations both in vitro and in vivo showed that the PKCepsilon-AMPK pathway is involved in enhancing mitochondrial-localized Nampt. Furthermore, PKCepsilon was shown to be crucial for the upregulation or translocation of mitochondrial pools of Nampt following AMPK activation, IPC or resveratrol treatment. PKCepsilon regulation of Nampt was both sufficient and necessary to increase the mitochondrial NAD+/NADH ratio, a redox signal involved in promoting sirtuin activity. The PKCepsilon-Nampt-NAD+ pathway enhanced SIRT5 desuccinylase activity, which was shown to regulate mitochondrial respiration and was required for PKCepislon-mediated ischemic neuroprotection against apoptosis and necrosis. Collectively, the results of this study identify a novel pathway by which PKCepsilon regulates wide-scale mitochondrial function through activation of SIRT5.

Keywords

SIRT5; Apoptosis; Stroke; Mitochondrial Metabolism; NADH; Cerebral Ischemia

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