Abstract 5055: TOPK phosphorylation of Prx1 at Ser32 prevents UVB-induced apoptosis in RPMI7951 melanoma cells through regulation of its peroxidase activity and blockade of intracellular accumulation of H2O2

Abstract

Abstract A novel serine/threonine kinase, T-LAK cell-originated protein kinase (TOPK), is only expressed in a wide range of cancer cells. We previously showed that TOPK increases colorectal cancer growth in vivo and ex vivo and that melanoma cell lines with a high abundance of TOPK protein exhibit a marked resistance to As3+-induced apoptosis. Here we continue our investigation of the functional details of TOPK. LC/MS/MS data showed that TOPK can bind with peroxiredoxin 1 (Prx1), which regulates hydrogen peroxide-mediated signal transduction. The role of Prx1 phosphorylation induced by UV in melanoma is not clear. Here, we provide evidence that TOPK phosphorylates Prx1 at Ser32 in vitro. Analysis of the CD spectra of Prx1 and a mutant Prx1 (S32A) protein shows that the secondary structure of Prx1 was significantly altered by its phosphorylation at Ser32. UVB radiation induced phosphorylation of TOPK in a time-dependent manner in RPMI7951 human melanoma cells and phosphorylated TOPK co-localized with Prx1 in the nucleus. UVB treatment increased peroxidase activity of Prx1 in vitro and ex vivo. The level of H2O2 was increased in TOPK siRNA cells and in RPMI7951 cells stably overexpressing mutant Prx1 (S32A). In addition, apoptosis was dramatically increased in TOPK siRNA cells and decreased in WT-Prx1 stable cells after UVB treatment. Our results suggested that TOPK phosphorylation of Prx1 at Ser 32 prevents UVB-induced apoptosis in RPMI7951 melanoma cells through the regulation of Prx1 peroxidase activity by blocking intracellular accumulation of H2O2. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5055.