Rab GTP-binding proteins are members of the Ras supergene family. Rab proteins are generally involved in protein transport/trafficking and determine the specificity of membrane transport steps within cell. We have identified a novel member of the Rab protein family, which we have named Nu-Rab, for its unique nuclear localization. Nu-Rab mRNA is highly expressed in most of cancer cell lines examined, and it is overexpressed in more than 60% of human primary breast cancers when compared to their matching normal tissues. The GFP- and Myc-tagged Nu-Rab mainly localizes to nucleus with some distribution noted in the cytoplasmic subcellular compartment. Immnunochemistry using Nu-Rab antibodies generated in our laboratory also detects that the endogenous Nu-Rab predominantly localizes to nucleus. Nu-Rab expression is down-regulated by apoptosis inducing agents such as ultraviolet radiation (UV), thapsigargin and sulindac sulfide. The PI3-kinase inhibitor LY294002, PI3-K phosphotase PTEN and dominant-negative mutant-Akt also down-regulate Nu-Rab mRNA expression, suggesting that Nu-Rab is a potential downstream target of the PI3-K/Akt signaling pathway. We are now proposing to further investigate the role of Nu-Rab in cell growth and/or survival and to elucidate the molecular basis of its overexpression in human breast cancer.
In specific aim 1, we will analyze a larger pool of fresh-frozen and paraffin-embedded tissue specimens to evaluate the expression of Nu-Rab at the mRNA and protein levels.
In specific aim 2, we will initiate functional studies to explore the effect of wild type-and GTP-binding mutants of Nu-Rab protein in oncogenic transformation. We will also explore whether Nu-Rab overexpression or deficiency effects apoptosis induced by genotoxic and non-genotoxic agents. Studies in specific aim 3 will be initiated to identify potential Nu-Rab effectors/regulator proteins in order to explore whether Nu-Rab plays a role in nuclear-cytoplasmic protein trafficking and study potential signaling events modulated by Nu-Rab. These are exploratory/developmental studies that, upon completion, will generate sufficient new data and reagents that will form the basis of future in-depth studies investigating the molecular mechanisms (s) of action of this novel GTP-binding protein in breast cancer development and/or progression. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21CA113868-02
Application #
7230197
Study Section
Cancer Molecular Pathobiology Study Section (CAMP)
Program Officer
Blair, Donald G
Project Start
2006-04-01
Project End
2010-03-31
Budget Start
2007-04-01
Budget End
2010-03-31
Support Year
2
Fiscal Year
2007
Total Cost
$115,491
Indirect Cost
Name
Upstate Medical University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
058889106
City
Syracuse
State
NY
Country
United States
Zip Code
13210
Lui, Ki; An, Jie; Montalbano, Joanne et al. (2013) Negative regulation of p53 by Ras superfamily protein RBEL1A. J Cell Sci 126:2436-45
Jiang, Lingyan; Rong, Rong; Sheikh, M Saeed et al. (2011) Cullin-4A·DNA damage-binding protein 1 E3 ligase complex targets tumor suppressor RASSF1A for degradation during mitosis. J Biol Chem 286:6971-8
Corcoran, Chad A; Montalbano, JoAnne; Sun, Hong et al. (2009) Identification and characterization of two novel isoforms of Pirh2 ubiquitin ligase that negatively regulate p53 independent of RING finger domains. J Biol Chem 284:21955-70
Montalbano, JoAnne; Lui, Ki; Sheikh, M Saeed et al. (2009) Identification and characterization of RBEL1 subfamily of GTPases in the Ras superfamily involved in cell growth regulation. J Biol Chem 284:18129-42
Lui, Ki; Huang, Ying (2009) RanGTPase: A Key Regulator of Nucleocytoplasmic Trafficking. Mol Cell Pharmacol 1:148-156
Corcoran, Chad A; He, Qin; Ponnusamy, Suriyan et al. (2008) Neutral sphingomyelinase-3 is a DNA damage and nongenotoxic stress-regulated gene that is deregulated in human malignancies. Mol Cancer Res 6:795-807
Montalbano, JoAnne; Jin, Weixin; Sheikh, M Saeed et al. (2007) RBEL1 is a novel gene that encodes a nucleocytoplasmic Ras superfamily GTP-binding protein and is overexpressed in breast cancer. J Biol Chem 282:37640-9
Rong, R; Jiang, L Y; Sheikh, M S et al. (2007) Mitotic kinase Aurora-A phosphorylates RASSF1A and modulates RASSF1A-mediated microtubule interaction and M-phase cell cycle regulation. Oncogene 26:7700-8