Epstein–Barr virus upregulates phosphorylated heat shock protein 27 kDa in carcinoma cells using the phosphoinositide 3‐kinase/Akt pathway

Abstract

Gastric cancer is the most common cancer in Japan and infection with Epstein-Barr virus (EBV) is responsible for about 10% of gastric cancers worldwide. Although EBV infection may be involved at an early stage of gastric carcinogenesis, the mechanisms underlying its involvement remain unknown. To investigate the role of EBV in gastric carcinogenesis, we performed proteomic analyses of an EBV-infected gastric carcinoma cell line NU-GC-3 (EBV(+)) and its uninfected control (EBV(-)). 2-DE was combined with MS to identify differentially expressed proteins. We found that EBV infection upregulated one of the phosphorylated heat shock protein 27 kDa (HSP27). The phosphorylated HSP27 isoform which increased in EBV(+) cells can be induced by both heat shock and arsenite. The increase of phosphorylated HSP27 in EBV(+) cells was reduced by treatment with the phosphoinositide 3-kinase (PI3K) inhibitors (LY294002 and wortmannin). In addition, we found increased levels of phosphorylated Akt in EBV(+) cells. These findings suggest that EBV infection upregulates the phosphorylation of HSP27 via the PI3K/Akt pathway. Thus, activation of the PI3K/Akt pathway may contribute to the establishment of a malignant phenotype in EBV-infected gastric carcinomas.

Heat shock protein 27 phosphorylation: kinases, phosphatases, functions and pathology

“…Several observations point to a role for Akt as Hsp25/27 kinase [94,[98][99][100][101][102]. First, the Akt1, Akt2, and Akt3 isoforms can bind directly to Hsp27 and can be found in a complex with p38 MAPK, MK2, and Hsp27 [98][99][100].…”

“…Second, Rane and colleagues showed that Akt could phosphorylate Hsp27 at Ser-82, but not Ser-15 or Ser-78, in vitro, while co-expression of an active Akt mutant and Hsp27 in HEK cells resulted in Hsp27 phosphorylation at the same residue [100]. Third, comparative proteomic analysis of the gastric carcinoma cell line NU-GC-3 with Epstein-Barr virus (EBV)-infected cells revealed increased phosphorylation of Hsp27 at Ser-82 in an Akt-dependent, but MEK/ERK-and p38 MAPK-independent, manner [101]. Total protein levels of phosphoAkt, but not Akt, MK2 or phosphoMK2, were increased, suggesting that phosphorylated (activated) Akt controls EBV-induced Hsp27 phosphorylation.…”

Phosphatidylinositol 3-Kinase/Akt Pathway Targets Acetylation of Smad3 through Smad3/CREB-binding Protein Interaction

“…To examine the possible involvement of the PI3-K/Akt pathway in TGF-␤1-induced EBV reactivation, the expression of EBV lytic proteins was analyzed in TGF-␤1-stimulated Mutu-I, Kem-I, and Sav-I cells, pretreated with increasing concentrations of wortmannin, a selective inhibitor of PI3-K activity (30,31), or Akt inhibitor X, a specific pharmacological inhibitor of Akt (32). As illustrated by Fig.…”

Characterization of hsp27 kinases activated by elevated aortic pressure in heart

“…Of the kinases shown to catalyze the phosphorylation of hsp27, PKC is lipid-dependent and the experiments conducted herein were performed without lipid and in the presence of EGTA plus a peptide inhibitor of PKA (PKI, 1 μM); hence, these kinases would not be active. PKB forms a complex with [50] and phosphorylates hsp27 [41,42]. However, activated PKB requires higher [NaCl] to elute from Mono Q than observed for the hsp27 kinase activities reported herein.…”

“…Hsp27 is phosphorylated by several protein kinases, including PKA [40], PKB [41,42], PKC [40,43], PKD [44], PKG [45], MK2 [46], MK3 [47], and MK5/PRAK [48,49] in vitro ( Fig. 1, reviewed in [8]).…”