The Tor kinases are the targets of the potent antiproliferative and immunosuppressive drug rapamycin. Rapamycin has recently been approved by the FDA as an immunosuppressive drug, and phase III clinical trials are in progress for its use as a novel chemotherapy agent. In both yeast and mammalian cells, rapamycin action is mediated by its association with the peptidyl prolyl isomerase, FKBP12. The rapamycin-FKBP12 complex then binds to and inhibits the functions of the Tor kinases, which were first identified by genetic studies in yeast and subsequently discovered in human cells. The Tor kinases regulate cell proliferation, translation and transcription as well as cellular responses to nutrient availability, including autophagy, ribosome biogenesis, cell differentiation, and mating. The Tor pathway plays a major role in yeast in regulating ribosomal protein (RP), ribosomal RNA, and tRNA gene expression in response to nutrients. In addition, Tor controls expression of nutrient utilization genes and stress responsive genes. Although much is known about the mechanisms by which Tor regulates the expression of nutrient utilization and stress responsive genes, very little is known about how Tor controls RP gene expression. We have shown that Tor activity favors the recruitment of the Esa1 histone acetylase to RP gene promoters coincident with RP gene activation. More recently, studies from our group and another have suggested a possible crosstalk between the Tor and cAMP-PKA pathways in regulating RP gene expression in response to nutrients. Many of the functions of the Tor kinases are mediated via type 2A protein phosphatases (PP2A). In yeast the PP2A-like phosphatase, Sit4, is regulated by its association with Tap42 and a set of four related proteins known as the Saps. Our proposed studies seek to define the roles of the Sap proteins in Tor action, to determine if there is crosstalk between the Tor and cAMP-PKA pathways to control RP gene expression, and to define the molecular mechanisms by which Tor signaling controls recruitment of Esa1 to RP gene promoters. Our goal is to elucidate the mechanisms of rapamycin action, many of which are conserved from yeast to mammals, and thereby, provide the biochemical basis for further development of rapamycin and its derivatives as novel chemotherapeutic agents.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA114107-03
Application #
7185140
Study Section
Drug Discovery and Molecular Pharmacology Study Section (DMP)
Program Officer
Forry, Suzanne L
Project Start
2005-03-17
Project End
2010-01-31
Budget Start
2007-03-01
Budget End
2008-01-31
Support Year
3
Fiscal Year
2007
Total Cost
$259,550
Indirect Cost
Name
Duke University
Department
Genetics
Type
Schools of Medicine
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
Shertz, Cecelia A; Bastidas, Robert J; Li, Wenjun et al. (2010) Conservation, duplication, and loss of the Tor signaling pathway in the fungal kingdom. BMC Genomics 11:510
Morales-Johansson, Helena; Puria, Rekha; Brautigan, David L et al. (2009) Human protein phosphatase PP6 regulatory subunits provide Sit4-dependent and rapamycin-sensitive sap function in Saccharomyces cerevisiae. PLoS One 4:e6331
Bastidas, Robert J; Heitman, Joseph; Cardenas, Maria E (2009) The protein kinase Tor1 regulates adhesin gene expression in Candida albicans. PLoS Pathog 5:e1000294
Bastidas, Robert J; Reedy, Jennifer L; Morales-Johansson, Helena et al. (2008) Signaling cascades as drug targets in model and pathogenic fungi. Curr Opin Investig Drugs 9:856-64
Rohde, John R; Bastidas, Robert; Puria, Rekha et al. (2008) Nutritional control via Tor signaling in Saccharomyces cerevisiae. Curr Opin Microbiol 11:153-60
Rutherford, Julian C; Chua, Gordon; Hughes, Timothy et al. (2008) A Mep2-dependent transcriptional profile links permease function to gene expression during pseudohyphal growth in Saccharomyces cerevisiae. Mol Biol Cell 19:3028-39
Puria, Rekha; Zurita-Martinez, Sara A; Cardenas, Maria E (2008) Nuclear translocation of Gln3 in response to nutrient signals requires Golgi-to-endosome trafficking in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 105:7194-9
Puria, Rekha; Cardenas, Maria E (2008) Rapamycin bypasses vesicle-mediated signaling events to activate Gln3 in Saccharomyces cerevisiae. Commun Integr Biol 1:23-25
Zurita-Martinez, Sara A; Puria, Rekha; Pan, Xuewen et al. (2007) Efficient Tor signaling requires a functional class C Vps protein complex in Saccharomyces cerevisiae. Genetics 176:2139-50