While it is well-established that the endoplasmic reticulum (ER) plays a critical role in cellular homeostasis, its significant contribution to apoptosis is only now becoming apparent. This proposal aims at discovering the molecular mechanisms of the ER stress-induced apoptosis and of the antiapoptotic function of ER chaperone protein GRP78/BJP. We hypothesize that the ER stress-induced apoptosis initiates from the ER but is amplified through the mitochondria via multiple pathways and that one anti-apoptotic function of GRP78 relies on its prevention of activation of pro-apoptotic components that initiate the cell death program from the ER. Our hypothesis is based on the recent discovery that the ER is a site of convergence and regulation of both pro- and anti-apoptotic components, and that GRP78, a key regulator of the unfolded protein response, can protect cells against apoptosis induced by ER stress as well as DNA-damaging topoisomerase inhibitors. Further, GRP78 can exist as a transmembrane protein and interact with caspases inducible by ER stress or etoposide and block their activation. Towards understanding the underlying in vivo molecular mechanisms, we have three specific aims.
In Aim 1, through the use of Apaf-1 deficient and BAX/BAK double knock MEFs, we will assess the requirement of the mitochondrial branch for ER-initiated apoptotic pathways, the relationship between known ER apoptotic pathways and ER BAK/BAX activation. We will further identify the molecules linking ER stress to activation of mitochondrial apoptotic pathway and their induction mechanism by ER stress.
In Aim 2, we will identify steps of the ER-stress and etoposide-induced apoptotic pathway that is suppressed by GRP78 and test whether GRP78 is a novel inhibitor of BIK, an upstream regulator of BAX.
In Aim 3, we will determine whether the ER stress-induced apoptotic pathways are altered in cancer, and the cytoprotective function of GRP78 in amyloid-beta toxicity in neuroblastoma and endothelial cells within tumors. The proposed work will not only contribute novel information on basic cell biology but also has clinical relevance in eliminating drug-resistant cancers and neurodegeneration in patients.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA111700-04
Application #
7435219
Study Section
Development - 1 Study Section (DEV)
Program Officer
Salnikow, Konstantin
Project Start
2005-08-01
Project End
2011-05-31
Budget Start
2008-06-01
Budget End
2011-05-31
Support Year
4
Fiscal Year
2008
Total Cost
$270,000
Indirect Cost
Name
University of Southern California
Department
Biochemistry
Type
Schools of Medicine
DUNS #
072933393
City
Los Angeles
State
CA
Country
United States
Zip Code
90089
Chen, Wan-Ting; Lee, Amy S (2011) Measurement and modification of the expression level of the chaperone protein and signaling regulator GRP78/BiP in mammalian cells. Methods Enzymol 490:217-33
Ni, Min; Zhang, Yi; Lee, Amy S (2011) Beyond the endoplasmic reticulum: atypical GRP78 in cell viability, signalling and therapeutic targeting. Biochem J 434:181-8
Zhou, Hui; Zhang, Yi; Fu, Yong et al. (2011) Novel mechanism of anti-apoptotic function of 78-kDa glucose-regulated protein (GRP78): endocrine resistance factor in breast cancer, through release of B-cell lymphoma 2 (BCL-2) from BCL-2-interacting killer (BIK). J Biol Chem 286:25687-96
Pfaffenbach, Kyle T; Lee, Amy S (2011) The critical role of GRP78 in physiologic and pathologic stress. Curr Opin Cell Biol 23:150-6
Zhang, Yi; Liu, Ren; Ni, Min et al. (2010) Cell surface relocalization of the endoplasmic reticulum chaperone and unfolded protein response regulator GRP78/BiP. J Biol Chem 285:15065-75
Wang, M; Ye, R; Barron, E et al. (2010) Essential role of the unfolded protein response regulator GRP78/BiP in protection from neuronal apoptosis. Cell Death Differ 17:488-98
Baumeister, Peter; Dong, Dezheng; Fu, Yong et al. (2009) Transcriptional induction of GRP78/BiP by histone deacetylase inhibitors and resistance to histone deacetylase inhibitor-induced apoptosis. Mol Cancer Ther 8:1086-94
Wang, Miao; Wey, Shiuan; Zhang, Yi et al. (2009) Role of the unfolded protein response regulator GRP78/BiP in development, cancer, and neurological disorders. Antioxid Redox Signal 11:2307-16
Lee, Amy S (2009) The Par-4-GRP78 TRAIL, more twists and turns. Cancer Biol Ther 8:2103-5
Ni, Min; Zhou, Hui; Wey, Shiuan et al. (2009) Regulation of PERK signaling and leukemic cell survival by a novel cytosolic isoform of the UPR regulator GRP78/BiP. PLoS One 4:e6868

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