Curcumin Prevents Palmitoylation of Integrin β4 in Breast Cancer Cells

May Curcumin Prevents Palmitoylation of Integrin 4 in Breast Cancer Cells David T. Coleman 0 1 2 3 Young Hwa Soung 0 1 2 3 Young-Joon Surh 0 1 2 3 James A. Cardelli 0 1 2 3 Jun Chung 0 1 2 3 0 Funding: This study is supported by American Cancer Society (RSG-09-091-01-CSM: JC) and National Institutes of Health-National Cancer Institute (R01CA163657-01A1: JC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript 1 Data Availability Statement: All relevant data are within the paper 2 Academic Editor: A R M Ruhul Amin, Winship Cancer Institute of Emory University , UNITED STATES 3 1 Department of Physiology and Stephenson Cancer Center, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States of America, 2 Department of Microbiology and FeistWeiller Cancer Center, Louisiana State University Health Sciences Center , Shreveport , Louisiana, United States of America, 3 College of Pharmacy, Seoul National University , Seoul , South Korea Curcumin has been shown to mitigate cancer phenotypes such as invasive migration, proliferation, and survival by disrupting numerous signaling pathways. Our previous studies showed that curcumin inhibits integrin 4 (ITG 4)-dependent migration by blocking interaction of this integrin with growth factor receptors in lipid rafts. In the current study, we investigated the possibility that curcumin inhibits ITG 4 palmitoylation, a post-translational modification required for its lipid raft localization and signaling activity. We found that the levels of ITG 4 palmitoylation correlated with the invasive potential of breast cancer cells, and that curcumin effectively reduced the levels of ITG 4 palmitoylation in invasive breast cancer cells. Through studies of ITG 4 palmitoylation kinetics, we concluded curcumin suppressed palmitoylation independent of growth factor-induced phosphorylation of key ITG 4 Ser and Tyr residues. Rather, curcumin blocked autoacylation of the palmitoyl acyltransferase DHHC3 that is responsible for ITG 4 palmitoylation. Moreover, these data reveal that curcumin is able to prevent the palmitoylation of a subset of proteins, but not indiscriminately bind to and block all cysteines from modifications. Our studies reveal a novel paradigm for curcumin to account for much of its biological activity, and specifically, how it is able to suppress the signaling function of ITG 4 in breast cancer cells. - Competing Interests: The authors have declared that no competing interests exist. Introduction Curcumin [chemical name: 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-hepadiene-3,5 dione], is a natural polyphenol component of turmeric (Curcuma longa) with demonstrated biological activity against a wide assortment of human pathologies. Chemopreventive and therapeutic properties of curcumin have been well established in vitro and in vivo for various types of human cancer [1,2]. The ability of curcumin to act selectively on cancer cells over normal cells highlights its potential as a useful cancer preventive or therapeutic modality with minimal toxicity [3]. However, the molecular mechanism by which curcumin influences various, seemingly unrelated, signaling pathways to selectively obstruct aggressive cancer cells is unknown. In previous reports, we showed that integrin 4 (ITG 4) is a target of curcumin in aggressive breast cancer cells [4]. Curcumin inhibited ITG 4-dependent signaling events important for breast cancer cell motility, invasion and anchorage-independent growth [4]. Our subsequent studies demonstrated that inhibition of ITG 4 signaling by curcumin is mediated by blocking localization of ITG 4 to lipid raft membrane domains and disrupting its interaction with growth factor receptors [5]. Mobilization of ITG 4 from hemidesmosomes into the leading edges and lipid rafts is thought to play an essential role for signaling competency of this integrin [68]. Post-translational modifications of the ITG 4 cytoplasmic domain play an important role in its trafficking and signaling competency. For example, a number of reports have shown that phosphorylation of key tyrosine and serine residues along the cytoplasmic tail contributes to hemidesmosome disassembly and subsequent activation of ITG 4 signaling in human cancer cells [911]. ITG 4 is also palmitoylated on five cysteine residues (C732/736/738/739/742) along a juxtamembrane segment of the cytoplasmic tail through a reversible thioester linkage to regulate its signaling and trafficking [8, 911]. The palmitoylation of ITG 4 is catalyzed by the palmitoyl acyltransferase DHHC3 [12, 13]. Palmitoylation of ITG 4 is necessary for incorporation of 64 into lipid rafts, where ITG 4 crosstalks with growth factor receptors and enhances invasive potential of cancer cells [5, 8]. Importantly, an alternative report suggests palmitoylation of ITG 4 is not required for raft association, but rather for incorporation into tetraspanin co (...truncated)