title: High mobility group box-1 is phosphorylated by protein kinase C zeta and secreted in colon cancer cells.
abstract: High mobility group box-1 (HMGB1), a nuclear protein, is overexpressed and secreted in cancer cells. Phosphorylation on two different nuclear localization signal regions are known to be important for the nuclear-to-cytoplasmic transport and secretion of HMGB1. However, little is known about the biochemical mechanism of HMGB1 modifications and its subsequent secretion from cancer cells. To identify the specific enzyme and important sites for HMGB1 phosphorylation, we screened the protein kinase C (PKC) family in a colon cancer cell line (HCT116) for HMGB1 binding by pull-down experiments using a 3XFLAG-HMGB1 construct. Strong interactions between atypical PKCs (PKC-ζ, λ, and ι) and cytoplasmic HMGB1 were observed in HCT116 cells. We further identified the most critical PKC isotype that regulates HMGB1 secretion is PKC-ζ by using PKC inhibitors and siRNA experiments. The serine residues at S39, S53 and S181 of HMGB1 were related to enhancing HMGB1 secretion. We also demonstrated overexpression and activation of PKC-ζ in colon cancer tissues. Our findings suggest that PKC-ζ is involved in the phosphorylation of HMGB1, and the phosphorylation of specific serine residues in the nuclear localization signal regions is related to enhanced HMGB1 secretion in colon cancer cells.
authors: Department of Pathology, Yonsei University College of Medicine, 134 Shinchon-Dong, Seodaemoon-Ku, Seoul, Republic of Korea.
authors: Hanna
authors: H
authors: Lee
authors: Minhee
authors: M
authors: Park
authors: Nara
authors: N
authors: Shin
authors: Gamin
authors: G
authors: Kim
authors: Yun Gi
authors: YG
authors: Kim
authors: Jeon-Soo
authors: JS
authors: Shin
authors: Hoguen
authors: H
authors: Kim
mesh_terms: D021581:Active Transport, Cell Nucleus; D003110:Colonic Neoplasms / Q000378:metabolism*; D045325:HCT116 Cells; D024243:HMGB1 Protein / Q000378:metabolism*; D006801:Humans; D019913:Nuclear Localization Signals / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D000099221:Protein Kinase C zeta
chemical_list: D024243:HMGB1 Protein; D019913:Nuclear Localization Signals; D011493:Protein Kinase C; D012694:Serine; D000099221:Protein Kinase C zeta