Dissertation
AMPK-HDAC5 pathway facilitates nuclear accumulation of HIF-1[alpha] and functional activation of HIF-1 by deacetylating Hsp70 in the cytosol
Doctor of Philosophy (Ph.D.), Drexel University
01 Mar 2015
DOI:
https://doi.org/10.17918/etd-6331
Abstract
Hypoxia-inducible factor 1 (HIF-1) is a major transcriptional regulator of adaptation to hypoxia at both cellular and tissue levels. As such, HIF-1 plays an important role in the pathogenesis of cancer and ischemic disorders including heart disease and cerebral ischemia. The expression of HIF-1[alpha], the functional determining subunit of HIF-1 increases in the majority of cancers, and up-regulation of HIF-1[alpha] is associated with increased risk of mortality in a variety of cancer types. Therefore HIF-1 is a potential target for the treatment of both cancer and ischemic disorders. Accumulating evidence suggests that histone deacetylase (HDAC) activity is critical for HIF-1[alpha] stability and HIF-1 activation. However, the underlying mechanism remains unclear. In this thesis, I demonstrate that the cytosolic HDAC5 increases HIF-1[alpha] stability by deacetylating heat shock protein-70kD (Hsp70). Specifically, HDAC knockdown screening revealed that only knockdown of HDAC5 impairs hypoxic HIF-1[alpha] accumulation and HIF-1 activity (Chapter 2 and Chapter 3). Overexpression of cytosol-localized and enzymatic active HDAC5 stabilizes HIF-1[alpha] and promotes HIF-1 function (Chapter 4 and Chapter 5). To identify the cytosolic substrate of HDAC5 that is responsible for HIF-1[alpha] stabilization, I knocked down HDAC5, and examined the acetylation statue of HIF-1[alpha], Hsp70 and Hsp90. I found that only the acetylation level of Hsp70 was increased by HDAC5 knockdown. Moreover, hyperacetylatation of Hsp70 led to accelerated degradation of HIF-1[alpha] and poor nuclear accumulation of HIF-1[alpha]. I further show that AMPK-triggered cytosolic translocation of HDAC5, which facilitated HIF-1[alpha] stabilization and promoted cell survival under stressful conditions (Chapter 7). Finally, I show an HDAC5 inhibitor, LMK235, disrupted the nuclear accumulation of HIF-1[alpha] and tumor cell proliferation under hypoxic conditions. Taken together, my findings demonstrate that the HDAC5-induced deacetylation of Hsp70 facilitates a rapid nuclear accumulation of HIF-1[alpha], indicating that AMPK-induced cytosolic translocation of HDAC5 plays an active role in cells' energy homeostasis during hypoxia and ischemia associated nutrient insufficiency.
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Details
- Title
- AMPK-HDAC5 pathway facilitates nuclear accumulation of HIF-1[alpha] and functional activation of HIF-1 by deacetylating Hsp70 in the cytosol
- Creators
- Shuyang Chen - DU
- Contributors
- Nianli Sang (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Biology; College of Arts and Sciences; Drexel University
- Other Identifier
- 6331; 991014632711704721