We have discovered that RALBP1 (RLIP76), a Ral-binding Rho-GAP protein is a transporter of glutathione-conjugates as well as structurally unrelated toxic xenobiotics. Preliminary studies in RALBP1-/- mice show marked radiation sensitivity in these animals compared with the RALBP1+/+ wild-type C57 mouse, with 0/6 RALBP1-/- mice surviving by day 13 after whole body X-irradiation to a dose of 500 cGy. Administration of a single dose of liposomes containing purified recombinant human RALBP1 (RALBP1-liposomes) i.p. caused detectable levels of RALBP1 in all tissues examined including brain 48 h after administration of liposomes. Three doses of liposomes caused further accumulation of RALBP1 in all tissues. Whole body irradiation to 500 cGy in RALBP1-/- mice administered control liposomes i.p. at day -3, +3 and +5 with respect to time of irradiation resulted in 0/6 animals surviving after 13 days. In marked contrast, 6/6 RALBP1-/- mice treated with the RALBP1-liposomes survived after 44 days. These remarkable results as well as our published and preliminary studies in cultured cell lead us to hypothesize that RALBP1 provides protection to cells from diverse stresses including heat-shock, oxidants, chemotherapeutic agents, UV-irradiation and X-irradiation and lead us to propose that RALBP1 is a multifunctional transporter and signaling protein functioning as a xenobiotic/oxidative-stress/radiation defense mechanisrn. We propose to test our hypothesis in the RIP1 (mouse ortholog of RALBP1) knockout mice we have obtained from Lexicon Genetics. We will perform studies with specific aims addressing the following hypotheses: 1) RALBP1 knockout will result in sensitization to the toxicity of X-irradiation; 2) RALBP1 knockout will result in sensitization to xenobiotic toxins including alkylating agents and natural product chemotherapy agents; 3) The transport activity of RALBP1 is regulated by POB1, a RAL-binding protein which causes apoptosis in prostate cancer cells when over-expressed. Towards these aims, we have designed detailed toxicological, biochemical, genetic and mechanistic studies proposed in the present application. Results of these studies will lead to the recognition of RALBP1 as a major xenobiotic defense mechanism and advance the potential use of RALBP1-liposomes as pharmacological agent for use in humans as a defense from the toxicity of xenobiotics and radiation.
| Yadav, Abhishek; Janaratne, Thamara; Krishnan, Arthi et al. (2013) Regression of lung cancer by hypoxia-sensitizing ruthenium polypyridyl complexes. Mol Cancer Ther 12:643-53 |
| Singhal, Sharad S; Wickramarachchi, Dilki; Yadav, Sushma et al. (2011) Glutathione-conjugate transport by RLIP76 is required for clathrin-dependent endocytosis and chemical carcinogenesis. Mol Cancer Ther 10:16-28 |
| Nagaprashantha, Lokesh Dalasanur; Vatsyayan, Rit; Lelsani, Poorna Chandra Rao et al. (2011) The sensors and regulators of cell-matrix surveillance in anoikis resistance of tumors. Int J Cancer 128:743-52 |
| Vatsyayan, Rit; Lelsani, Poorna Chandra Rao; Awasthi, Sanjay et al. (2010) RLIP76: a versatile transporter and an emerging target for cancer therapy. Biochem Pharmacol 79:1699-705 |
| Singhal, Sharad S; Sehrawat, Archana; Sahu, Mukesh et al. (2010) Rlip76 transports sunitinib and sorafenib and mediates drug resistance in kidney cancer. Int J Cancer 126:1327-38 |
| Awasthi, Sanjay; Singhal, Sharad S; Yadav, Sushma et al. (2010) A central role of RLIP76 in regulation of glycemic control. Diabetes 59:714-25 |
| Singhal, Sharad S; Yadav, Sushma; Roth, Cherice et al. (2009) RLIP76: A novel glutathione-conjugate and multi-drug transporter. Biochem Pharmacol 77:761-9 |
| Singhal, Sharad S; Roth, Cherice; Leake, Kathryn et al. (2009) Regression of prostate cancer xenografts by RLIP76 depletion. Biochem Pharmacol 77:1074-83 |
| Vatsyayan, Rit; Chaudhary, Pankaj; Lelsani, Poorna Chandra Rao et al. (2009) Role of RLIP76 in doxorubicin resistance in lung cancer. Int J Oncol 34:1505-11 |
| Singhal, Sharad S; Sehrawat, Archana; Mehta, Amee et al. (2009) Functional reconstitution of RLIP76 catalyzing ATP-dependent transport of glutathione-conjugates. Int J Oncol 34:191-9 |
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