Stress protein flux during recovery from simulated ischemia: Induced heat shock protein 70 confers cytoprotection by suppressing JNK activation and inhibiting apoptotic cell death

Abstract

Multiple stress proteins are recruited in response to stress in living cells. There are limited reports in the literature analyzing multiple stress protein shifts and their functional consequences on stress response. Using two-dimensional electrophoresis we have analyzed shifts in stress protein profiles in response to energy deprivation as a model of ischemic injury to kidneys. A group of chaperones and stress-induced mitogen activated protein (MAP) kinases were analyzed. In addition to examining stress protein induction and phosphorylation we have also examined the mechanism of cytoprotection by heat shock protein 70 (Hsp70). Our results show that, of the different stress proteins examined, only binding protein (BiP) and Hsp70 were significantly induced upon energy deprivation. Other stress proteins, including Hsp27, calnexin, Hsp90 and ERp57 showed alterations in their phosphorylation profiles. Three different MAP kinases, namely p38, extracellular signal regulated kisase and c-jun N-terminal kinase (JNK) were activated in response to energy deprivation. While JNK activation was linked to apoptosis, activated-p38 was involved in phosphorylation of Hsp27. Study of inhibitors of Hsp70 induction or pre-induction of Hsp70 indicated that induced Hsp70 was involved in the suppression of JNK activation thereby inhibiting apoptotic cell death. Our results provide important insights into the flux in stress protein profiles in response to simulated ischemia and highlight the antiapoptotic, cytoprotective mechanism of Hsp70 action.

Proteomic Profiling of Hepatic Endoplasmic Reticulum-associated Proteins in an Animal Model of Insulin Resistance and Metabolic Dyslipidemia

“…A shift to the acidic end of the pH gradient (the left side of the gel) correlated directly with the level of protein phosphorylation. Therefore, protein at the basic end of the isoform string represents the unmodified form of the protein (14,16). This raises the question of functional differences between isoforms.…”

“…The different spots corresponding to single protein species were found in all cases to correspond to the same molecular mass but possess slightly different isoelectric points. Because phosphorylation is known to occur in the ER (13)(14)(15)(16), these may represent different phosphoisoforms of the same protein. A shift to the acidic end of the pH gradient (the left side of the gel) correlated directly with the level of protein phosphorylation.…”

Hsp70/nitric oxide relationship in apoptotic modulation during obstructive nephropathy

“…Nevertheless, it has been proposed that HSPs also act by means of a mechanism independent of Bcl-2, intervening at several points to halt progression of the apoptotic cascade (Strasser and Anderson 1995). Previous studies have indicated that at least some of the antiapoptotic activity of Hsp70 can be attributed to its ability to suppress the activity of JUN-kinase (Kumar and Tatu 2003;Gabai et al 1997). Activation of stress-activated protein kinase SAPK/c-Jun N-terminal kinase (JNK) has been strongly inhibited in cells in which Hsp70 was induced to a high level, indicating that Hsp70 blocks apoptosis by inhibiting signaling events upstream of SAPK/JNK activation.…”

Huperzine A derivative M3 protects PC12 cells against sodium nitroprusside-induced apoptosis

“…Some of the anti-apoptotic activity of Hsp70 could be attributed to its ability to suppress the activity of JUN-kinase or Bid proteins [16,17] . Thus, the decreased activation of caspase-3 in the M3 treated group might be due to the inhibition of the JNK/Bim pathway by the induction of Hsp70.…”