Rayudu Gopalakrishna

Research Interests

Protein kinase C in cancer chemoprevention

My laboratory is interested in understanding the oxidative regulation of protein kinase C (PKC) and protein phosphatases (type 1 and 2A) by tumor promoters, and the counter regulation by dietary chemopreventive agents and anti-metastatic drugs. Work from this laboratory has demonstrated that oxidant tumor promoters by activating PKC and simultaneously inactivating protein phosphatases can induce an imbalance in protein phosphorylation. Rapid multiwell filtration methods have been developed to determine the activities of PKC and various protein phosphatases. These methodologies gave us the edge to study both protein kinases and phosphatases simultaneously.

Since PKC is a receptor for diverse structurally unrelated tumor promoters as well as involved in growth regulation, it is a logical target site for the action of antitumor promoters and antiproliferative agents. Among many natural products screened, calphostin C, hypericin, and chelerythrine have emerged as specific inhibitors for PKC. Our recent studies have demonstrated an involvement of the site-specific oxidations or alkylating mechanisms in the action of these agents. This further emphasized the functional role for unique thiol-rich regions in both regulatory(zinc finger) and catalytic domains of PKC. Currently the studies are in progress to elucidate mechanisms of actionof chemopreventive agents such as selenium, vitamin E succinate, and organosulfur agents from vegetables. These studies are carried out using PKC isoenzymes isolated from rat brain and also using recombinant PKC in which cysteine residues are substituted by site-directed mutagenesis.

Another area of interest is to understand the role of tumor promoters in cancer metastasis in addition to their known role in tumor promotion. Compared to experimental tumor promoters, phorbol esters, the oxidant-generating tumor promoters present in the tobacco smoke induced a stronger stimulation of metastasis of tumor cells at least in part by activating PKC. In view of inhibition of metastasis by structurally diverse inhibitors of PKC, this enzyme may be targeted for the design and development of anti-metastatic drugs. These studies are carried out using both in vitro and in vivo models, and breast carcinoma, melanoma, and glioma cell lines.

Degrees

University of Madras, PHD, 1979
Andhra Univiversity, MS, 1975

Fellowships

National Cancer Institute, 1981 - 1983

MEMBERSHIPS & AFFILIATIONS

Memberships

American Association for the Advancement of Science
American Society for Biochemistry and Molecular Biology
New York Academy of Sciences
American Chemical Society and IUPAC
The Protein Society
Oxygen Society and International Society for Free Radical Research
American Association for Cancer Research
International Society for Cancer and Nutrition
Carotenoid Research Interest Group
Journal Reviewer
Endocrine Journal
Analytical Biochemistry
Molecular and Cellular Neurosciences
Cancer Journal
American J. Physiology
Molecular Pharmacology
Free Radical Biology and Medicine
Journal of Neurochemistry
Consultant Millipore Corporation New York Medical Center (1998-present).

Gopatakrishna, R., Gundimeda, U., Fontana, J.A., and Clarke, R. (1999) Differential distribution of protein phosphatase 2A in human breast carcinoma cell lines and its relation to estrogen receptor status. Cancer Lett. 136, 143-1 S 1.

Gopalakrishna, R., Gundimeda, U., Anderson, W. B., and Colburn, N. H., and Slaga, T. J. (1999) Tumor promoter benzoyl peroxide induces sulfhydryl oxidation in protein kinase C: its reversibility is related to the cellular resistance to peroxide induced cytotoxicity. Arch. Biochem. Biophys. 363, 246-258.

Simard, M., Zhang, W., Hinton, D. R., Chen, T. C., Weiss,M.H., Gopalakrishna, R., Law, R. E., Couldwell, W. T. Protein kinase C inhibition and tamoxifen induce growth arrest and apoptosis in pituitary adenomas in vitro. Clin. Endocrinol. Metab. (in press).

Gopalakrishna, R., Bernardo, V., arid Gundimeda, U. (2000) P-Carotene induces modifications of cysteine residues in protein kinase C, affecting its kinase activity and phorbol ester binding: a potential new mechanism for inhibition of tumor promotion. FEBS Lett. (communicated)

Sakamoto, T., Hinton, D. R., Gopatakrishna, R., Gundimeda, U., Spee, C., Ishibashi, T., and Ryan, S. J. (1999) Interferon-0 affects RPE cell proliferation via protein kinase C pathways. Brain Res. (communicated)

Gopalakrishna, R., Gundimeda, U., Bertram, J.S., and Krinsky, N. 1. (1999) (3-Carotene oxidation products inactivate protein kinase C; role of apocarotenals in cancer chemoprevention. Proc. Am. Assoc. Cancer Res. 40, 259.

Gopalakrishna, R., and Gundimeda, U. (1999) Regeneration of activity for protein kinase C by thioredoxin reductase (poster). 6' Annual meeting of the Oxygen society, New Orleans, November 17-21.

Gundimeda, U., and Gopalakrishna, R. (1999) Oxidant tumor promoters induce the collapse of zinc-fingers in protein kinase C to generate apo-protein. Proc. Am. Assoc. Cancer Res. 40, 503.

Book Chapters Gopalakrishna, R., and Jaken, S. (2000) Protein kinase C signaling and oxidative stress. Form Review article. Free Rad. Biol. Med. 28, 1349-1361.

Alkana, R.L.., Davies, D.L., Marland, J., Parker, E.S. and Bejanian, M. Low level hyperbaric exposure antagonizes locomotor effects of ethanol and n-propanol, but not morphine, in C57/BL mice. Alcoholism: Clinical and Experimental Research 19:693-700, 1995.

Gopalakrishna, R., Chen, Z., and Gundimeda, U. (1993) Nitric oxide and nitric oxide generating agents induce a reversible inactivation of PKC J. Biol. Chem. 268, 27180-27185.

Gopalakrishna, R., Chen, Z. H and Gundimeda, U. (1994) Tobacco smoke tumor promoters, catechol and hydroquinone induce oxidative regulation of protein kinase C and influence invasion and metastasis of lung carcinoma cells Proc. Natl. Acad. Sci. USA 91, 12233-12237.

Gundimeda, U., Chen, Z., and Gopalakrishna, R. (1996) Tamoxifen modulates protein kinase C via oxidative stress in estrogen receptor-negative breast cancer cells. J. Biol. Chem. 271, 13504-13514.