Bag-1 Protects Nucleus Pulposus Cells from Oxidative Stress by Interacting with HSP70
Kaori Suyama,
Daisuke Sakai,
Shogo Hayashi,
Ning Qu,
Hayato Terayama,
Daisuke Kiyoshima,
Kenta Nagahori,
Masahiko Watanabe
Affiliations
Kaori Suyama
Department of Anatomy and Cellular Biology, Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Kanagawa, Japan
Daisuke Sakai
Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Kanagawa, Japan
Shogo Hayashi
Department of Anatomy and Cellular Biology, Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Kanagawa, Japan
Ning Qu
Department of Anatomy and Cellular Biology, Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Kanagawa, Japan
Hayato Terayama
Department of Anatomy and Cellular Biology, Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Kanagawa, Japan
Daisuke Kiyoshima
Department of Anatomy and Cellular Biology, Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Kanagawa, Japan
Kenta Nagahori
Department of Anatomy and Cellular Biology, Basic Medical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Kanagawa, Japan
Masahiko Watanabe
Department of Orthopaedic Surgery, Surgical Science, Tokai University School of Medicine, 143 Shimokasuya, Isehara 259-1193, Kanagawa, Japan
Bcl-2-associated athanogene 1 (Bag-1) is a multifunctional prosurvival protein that binds to several intracellular targets and promotes cell survival. HSP70 and Raf-1 are important targets of Bag-1; however, the protective function of Bag-1 in nucleus pulposus (NP) cells remains unclear. In this study, we determined the effects of Bag-1 on NP cells under oxidative stress induced by treatment with hydrogen peroxide (H2O2). We found that Bag-1 was bound to HSP70, but Bag-1–Raf1 binding did not occur in NP cells. Bag-1 overexpression in NP cells enhanced cell viability and mitochondrial function and significantly suppressed p38/MAPKs phosphorylation during oxidative stress, although NP cells treated with a Bag-1 C-terminal inhibitor, which is the binding site of HSP70 and Raf-1, decreased cell viability and mitochondrial function during oxidative stress. Furthermore, the phosphorylation of the ERK/MAPKs was significantly increased in Bag-1 C-terminal inhibitor-treated NP cells without H2O2 treatment but did not change with H2O2 exposure. The phosphorylation of Raf-1 was not influenced by Bag-1 overexpression or Bag-1 C-terminal binding site inhibition. Overall, the results suggest that Bag-1 preferentially interacts with HSP70, rather than Raf-1, to protect NP cells against oxidative stress.