A dynamic balance of steroid receptor signaling and cellular phosphorylation cascades coordinately control cell growth at key steps where these signal transduction pathways converge. Conceivably, the stringent regulation of such points of convergence confer responsiveness to anti-proliferative signals in normal cells, and may regulate the uncontrolled proliferation of transformed cells if appropriately induced or activated. Glucocorticoids, one class of steroid hormones, can strongly inhibit the in vivo and in vitro growth of Con8 rat mammary tumor cells, which are derived from a hormone responsive rat mammary adenocarcinoma. To identify the steroid regulated mediators of this growth arrest, subtractive cloning of glucocorticoid responsive genes from a mammary tumor cell cDNA library uncovered a novel serine/threonine protein kinase, sgk, that is transcriptionally regulated by glucocorticoids and serum. The existence of sgk suggests a new pathway of cross-talk between steroid hormones and cellular phosphorylation cascades. Analysis of sgk structure/function relationships by in vitro mutagenesis will be carried out to determine the role of specific protein coding domains in transphosphorylation, substrate specificity and as targets of cellular phosphorylation cascades. The role of sgk in the glucocorticoid growth suppression response in cultured cells and in mammary cell derived tumors will be examined by analyzing vectors encoding the wild type, mutant or anti-sense forms of this protein kinase gene. Finally, interactive cloning strategies, such as the yeast two hybrid system, will be employed to identify the sgk binding proteins uncovered by co-immunoprecipitation and their functional characterization carried out to elucidate the sgk intracellular signal transduction pathway. Thus, the overall goal is to define the precise functional relationships between the steroid regulated signaling mediated by sgk and the glucocorticoid growth arrest of mammary tumor cells.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA071514-04
Application #
2895599
Study Section
Physiological Chemistry Study Section (PC)
Program Officer
Sathyamoorthy, Neeraja
Project Start
1996-07-01
Project End
2001-12-31
Budget Start
1999-05-01
Budget End
2001-12-31
Support Year
4
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of California Berkeley
Department
Internal Medicine/Medicine
Type
Schools of Arts and Sciences
DUNS #
094878337
City
Berkeley
State
CA
Country
United States
Zip Code
94704
Maiyar, Anita C; Leong, Meredith L L; Firestone, Gary L (2003) Importin-alpha mediates the regulated nuclear targeting of serum- and glucocorticoid-inducible protein kinase (Sgk) by recognition of a nuclear localization signal in the kinase central domain. Mol Biol Cell 14:1221-39
Wang, J; Barbry, P; Maiyar, A C et al. (2001) SGK integrates insulin and mineralocorticoid regulation of epithelial sodium transport. Am J Physiol Renal Physiol 280:F303-13
Lee, E; Lein, E S; Firestone, G L (2001) Tissue-specific expression of the transcriptionally regulated serum and glucocorticoid-inducible protein kinase (Sgk) during mouse embryogenesis. Mech Dev 103:177-81
Bell, L M; Leong, M L; Kim, B et al. (2000) Hyperosmotic stress stimulates promoter activity and regulates cellular utilization of the serum- and glucocorticoid-inducible protein kinase (Sgk) by a p38 MAPK-dependent pathway. J Biol Chem 275:25262-72
Alliston, T N; Gonzalez-Robayna, I J; Buse, P et al. (2000) Expression and localization of serum/glucocorticoid-induced kinase in the rat ovary: relation to follicular growth and differentiation. Endocrinology 141:385-95
Gonzalez-Robayna, I J; Falender, A E; Ochsner, S et al. (2000) Follicle-Stimulating hormone (FSH) stimulates phosphorylation and activation of protein kinase B (PKB/Akt) and serum and glucocorticoid-lnduced kinase (Sgk): evidence for A kinase-independent signaling by FSH in granulosa cells. Mol Endocrinol 14:1283-300
Park, J; Leong, M L; Buse, P et al. (1999) Serum and glucocorticoid-inducible kinase (SGK) is a target of the PI 3-kinase-stimulated signaling pathway. EMBO J 18:3024-33
Buse, P; Tran, S H; Luther, E et al. (1999) Cell cycle and hormonal control of nuclear-cytoplasmic localization of the serum- and glucocorticoid-inducible protein kinase, Sgk, in mammary tumor cells. A novel convergence point of anti-proliferative and proliferative cell signaling pathways. J Biol Chem 274:7253-63
Gonzalez-Robayna, I J; Alliston, T N; Buse, P et al. (1999) Functional and subcellular changes in the A-kinase-signaling pathway: relation to aromatase and Sgk expression during the transition of granulosa cells to luteal cells. Mol Endocrinol 13:1318-37
Maiyar, A C; Phu, P T; Huang, A J et al. (1997) Repression of glucocorticoid receptor transactivation and DNA binding of a glucocorticoid response element within the serum/glucocorticoid-inducible protein kinase (sgk) gene promoter by the p53 tumor suppressor protein. Mol Endocrinol 11:312-29

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