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Glutathione Transferase P1 (GSTP1) is Modified by Palmitate
Author(s) -
Marensi Vanessa,
Yap Megan,
Ji Yuhuan,
Lin Cheng,
Berthiaume Luc,
Leslie Elaine M
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1196.5
Subject(s) - palmitoylation , chemistry , gstp1 , thioester , biochemistry , glutathione , cysteine , transferase , mutant , cytosol , microbiology and biotechnology , enzyme , biology , gene
Glutathione transferase P1 (GSTP1) protects cells from carcinogens by catalyzing their conjugation with the tripeptide glutathione (γ‐Glu‐Cys‐Gly). GSTP1 is also involved in cell signaling, proliferation and apoptosis. Overexpression of GSTP1 in tumors and single nucleotide polymorphic variants are associated with anti‐cancer drug resistance and poor prognosis. In contrast, inactivation of GSTP1 due to epigenetic promoter silencing increases susceptibility to certain cancer types, with prostate cancer as the best studied example. GSTP1 is classically described as a cytosolic enzyme; however, we have reported that it is strongly associated with the plasma membrane and the strength is comparable to the integral membrane protein Na + /K + ‐ATPase. We hypothesize that the addition of a hydrophobic component is required to allow its strong interaction with membranes. Palmitoylation is the reversible post‐translational addition of a 16‐C saturated fatty acid to proteins, most commonly on Cys residues through a thioester bond. We found that GSTP1 is modified by palmitate. However, Cys‐less (Cys to Ser or Cys to Ala) mutants expressed in MCF7 cells surprisingly retained palmitoylation. In addition, treatment of palmitoylated GSTP1 with NaOH, which cleaves thioester bonds, did not remove palmitate. These data suggested that GSTP1 is modified by palmitate on at least one non‐Cys residue. We also demonstrated that GSTP1 can be non‐catalytically palmitoylated (or autoplamitoylated). Peptide sequencing by ESI‐MS/MS of the autopalmitoylated GSTP1 revealed that Cys48 and Cys102 undergo S‐ palmitoylation and Lys103 undergoes N‐ palmitoylation. N ‐palmitoylation of an internal Lys residue is a rare observation and provides an explanation for the resistance of GSTP1 palmitoylation to NaOH treatment. In conclusion, we have identified palmitoylation as a novel post‐translational modification of GSTP1. This research lays the foundation for understanding the fundamental biology of GSTP1 and how palmitoylation may influence its structure, function and membrane association. Support or Funding Information Canadian Institute of Health Research (CIHR), Alberta Innovates Health Solutions (AIHS) and Alberta Cancer Foundation (ACF)