title: Protein phosphatase 1 activation and alternative splicing of Bcl-X and Mcl-1 by EGCG + ibuprofen.
abstract: Epigallocatechin-3-gallate (EGCG) and ibuprofen synergistically act to suppress proliferation and enhance apoptosis of prostate cancer cell lines, PC-3 and LNCaP. The purpose of this study was to investigate the mechanism of underlying this synergism. Most interestingly, EGCG + ibuprofen treatment in PC-3 cells resulted in altering the ratio of the splice variants of Bcl-X and Mcl-1, downregulating the mRNA levels of anti-apoptotic Bcl-X(L) and Mcl-1(L) with a concomitant increase in the mRNA levels of pro-apoptotic Bcl-X(s) and Mcl-1(s). However, there were no apparent changes in splicing variants in either ibuprofen or EGCG treated cells. Induction of alternative splicing was correlated with increased activity of protein phosphatase 1 (PP1) in EGCG + ibuprofen-treated cells, since pretreatment with calyculin A and tautomycin blocked EGCG + ibuprofen-induced alternative splicing in PC-3 cells in contrast to pretreatment with okadaic acid. On the other hand, EGCG + ibuprofen treatment in LNCaP cells did not alter splicing variants of Bcl-X and Mcl-1, despite the increase in protein phosphatase activity. In both cell lines, EGCG + ibuprofen inhibited cell proliferation synergistically. Taken together, this study demonstrate for the first time that EGCG + ibuprofen upregulated PP1 activity, which in turn induced alternative splicing of Bcl-X and Mcl-1 in a cell-type specific manner. Our study also demonstrates that the activation of PP1 contributes to the alternative splicing of Mcl-1.
authors.affiliation: Department of Molecular Biology and Immunology, University of North Texas Health Science Center, Fort Worth, Texas 76107, USA. mkim@hsc.unt.edu
authors.forename: Myoung H
authors.initials: MH
authors.lastname: Kim
mesh_terms: D017398:Alternative Splicing / Q000187:drug effects*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D045744:Cell Line, Tumor; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007052:Ibuprofen / Q000494:pharmacology* / Q000627:therapeutic use; D008297:Male; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D011471:Prostatic Neoplasms / Q000473:pathology; D054645:Protein Phosphatase 1 / Q000235:genetics*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D051020:bcl-X Protein / Q000235:genetics*
chemical_list: D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D002392:Catechin; C045651:epigallocatechin gallate; D054645:Protein Phosphatase 1; D007052:Ibuprofen