The overall objective of this project is to define the molecular mechanisms of how human corneal Limbal Stem/Progenitor (LS/P) and Corneal Epithelial (CE) cells respond to hypoxic stresses in physiological and pathological conditions. Our preliminary data show in human CE cells that hypoxia (1% O2) activates Polo-like kinase 3 (Plk3) cascades that phosphorylate a group of important determinants for regulating cell fates, such as Hif-1, p53, c-Jun/AP-1 and H2AX. Thus, larger responses to hypoxic stress based on the magnitude of increases in Plk3 activities result in CE cell apoptosis. By contrast, human corneal LS/P cells are resistant to hypoxia-induced apoptosis because hypoxia suppresses Plk3 expression and fails to induce phosphorylation of Hif-1, p53, c-Jun/AP-1 and H2AX in these cells. We reveal that hypoxia stimulates significant changes in microRNA (miRNA) expression profiles. These miRNAs specifically target the 3'-untranslated region (3'UTR) of Plk3 mRNA to suppress hypoxia-induced Plk3 signaling in corneal LS/P cells, but not in CE cells. Our central hypothesis is that exposure of human corneas to hypoxic conditions activates two distinct processes in corneal LS/P and CE cells including: 1) activation of a Plk3-mediated signaling pathway that in turn increases p53 phosphorylation and activations of c-Jun/AP-1 and H2AX resulting in CE cell apoptosis;and 2) activation of specific expressions of miRNAs that suppress Plk3 expression to down-regulate downstream targets resulting in hypoxic tolerance and to trigger differentiation of corneal LS/P cells. To identify the molecular mechanisms, we propose three aims: 1) To define how hypoxia-induced Plk3 activation affects and interacts with AP-1, p53 and H2AX. Hypoxia-induced p53 and c-Jun phosphorylation are directly relevant to apoptosis. We will determine whether hypoxia-induced Plk3 can directly activate p53, AP-1 and H2AX, and how hypoxia-induced ATM/ATR/Chk1/2 activation leads to Plk3 activation in CE cells. 2) To investigate how Plk3 is down-regulated in hypoxia-induced corneal LS/P cells. Hypoxia suppresses Plk3 expression through a novel mechanism by inducing high levels of Plk3-specific miRNAs. We will determine the hypoxia-induced miRNA profiles in corneal LS/P cells in hypoxic conditions, which of the hypoxia-sensitive miRNAs suppress the Plk3 signaling pathway in the LS/P cells, and how these miRNAs interact with Plk3 mRNA to affect its stability. 3) To determine roles of hypoxia-induced Plk3 activation in corneal epithelial wound healing. Effects of hypoxia on corneal LS/P cell differentiation and CE cell apoptosis through regulating the Plk3 signaling pathways will be integrated in this aim. We investigate the effects of altered Plk3 activities on hypoxia-induced LS/P cell differentiation and CE cell apoptosis, and how hypoxia-induced delay of the wound healing process is affected by altering Plk3 activity in LS/P cells and corneas of Plk3-/- mice. By achieving the goal of combined studies, we will provide novel mechanisms to advance our understanding of hypoxia-induced effects on LS/P and CE cell functions in corneal epithelial self-renewal and wound healing.

Public Health Relevance

In this application, we propose to investigate significant questions concerning how corneal hypoxia in physiological and pathological conditions affect human corneal limbal stem cell differentiation and epithelial cell replacement. We will determine whether the Polo-like kinase 3 (Plk3) pathway is responsible for regulating activities of downstream hypoxia-induced determinative factors that are critical for corneal epithelial self- renewal and for improving the wound healing process in normal and disease stages. .

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY022364-03
Application #
8722566
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Mckie, George Ann
Project Start
2012-09-01
Project End
2017-08-31
Budget Start
2014-09-01
Budget End
2015-08-31
Support Year
3
Fiscal Year
2014
Total Cost
Indirect Cost
City
Torrance
State
CA
Country
United States
Zip Code
90502
Restuccia, Agnese; Yang, Feikun; Chen, Changyan et al. (2016) Mps1 is SUMO-modified during the cell cycle. Oncotarget 7:3158-70
Shi, Ting; Li, Dachao; Li, Guoqing et al. (2016) Modeling and Measurement of Correlation between Blood and Interstitial Glucose Changes. J Diabetes Res 2016:4596316
Wang, Ling; González, Sheyla; Dai, Wei et al. (2016) Effect of Hypoxia-regulated Polo-like Kinase 3 (Plk3) on Human Limbal Stem Cell Differentiation. J Biol Chem 291:16519-29
Choi, Byeong Hyeok; Che, Xun; Chen, Changyan et al. (2015) WWP2 is required for normal cell cycle progression. Genes Cancer 6:371-7
Wang, Ling; Dai, Wei; Lu, Luo (2014) Osmotic stress-induced phosphorylation of H2AX by polo-like kinase 3 affects cell cycle progression in human corneal epithelial cells. J Biol Chem 289:29827-35
Tsui, S; Dai, W; Lu, L (2014) CCCTC-binding factor mediates effects of glucose on beta cell survival. Cell Prolif 47:28-37
Yao, Yixin; Lu, Yinghua; Chen, Wen-Chi et al. (2014) Cobalt and nickel stabilize stem cell transcription factor OCT4 through modulating its sumoylation and ubiquitination. PLoS One 9:e86620
Wang, Ling; Wu, Xiaolin; Shi, Ting et al. (2013) Epidermal growth factor (EGF)-induced corneal epithelial wound healing through nuclear factor κB subtype-regulated CCCTC binding factor (CTCF) activation. J Biol Chem 288:24363-71
Yang, Feikun; Yao, Yixin; Jiang, Yongping et al. (2012) Sumoylation is important for stability, subcellular localization, and transcriptional activity of SALL4, an essential stem cell transcription factor. J Biol Chem 287:38600-8
Tsui, Shanli; Gao, Jie; Wang, Charles et al. (2012) CTCF mediates effect of insulin on glucagon expression. Exp Cell Res 318:887-95

Showing the most recent 10 out of 12 publications