Effect of methylglyoxal modification and phosphorylation on the chaperone and anti‐apoptotic properties of heat shock protein 27

Abstract

Heat shock protein 27 (Hsp27) is a stress-inducible protein in cells that functions as a molecular chaperone and also as an anti-apoptotic protein. Methylglyoxal (MGO) is a reactive dicarbonyl compound produced from cellular glycolytic intermediates that reacts non-enzymatically with proteins to form products such as argpyrimidine. We found considerable amount of Hsp27 in phosphorylated form (pHsp27) in human cataractous lenses. pHsp27 was the major argpyrimidine-modified protein in brunescent cataractous lenses. Modification by MGO enhanced the chaperone function of both pHsp27 and native Hsp27, but the effect on Hsp27 was at least three-times greater than on pHsp27. Phosphorylation of Hsp27 abolished its chaperone function. Transfer of Hsp27 using a cationic lipid inhibited staurosporine (SP)-induced apoptotic cell death by 53% in a human lens epithelial cell line (HLE B-3). MGO-modified Hsp27 had an even greater effect (62% inhibition). SP-induced reactive oxygen species in HLE-B3 cells was significantly lower in cells transferred with MGO-modified Hsp27 when compared to native Hsp27. In vitro incubation experiments showed that MGO-modified Hsp27 reduced the activity of caspase-9, and MGO-modified pHsp27 reduced activities of both caspase-9 and caspase-3. Based on these results, we propose that Hsp27 becomes a better anti-apoptotic protein after modification by MGO, which may be due to multiple mechanisms that include enhancement of chaperone function, reduction in oxidative stress, and inhibition of activity of caspases. Our results suggest that MGO modification and phosphorylation of Hsp27 may have important consequences for lens transparency and cataract development.

Heat Shock Proteins 27 and 70: Anti-Apoptotic Proteins with Tumorigenic Properties

“…We have demonstrated in vitro and in vivo that for the e have demonstrated in vitro and in vivo that for the HSP27 caspase-dependent antiapoptotic effect, large nonphosphorylated oligomers of HSP27 were the active form of the protein. 32 Confirming this result, Oya-Ito et al 34 have recently published that the methylglyoxal modification of HSP27, which is reported to favor large oligomers, exacerbates the antiapoptotic caspase-inhibitory properties of HSP27. In contrast, phosphorylated and small oligomers of HSP27 are particulary efficient in binding to F-actin and Daxx 76,85 and it is the phosphorylated form of HSP27 that protects from neurotoxicity.…”

“…33 MG provokes the formation of large HSP27 oligomers by inducing the formation of Arg-pyrimidine, an MG-arginine adduct. 34 HSP27 and HSP70 interfere with the action of key apoptotic Proteins. The cytoprotective effect of HSP70 and HSP27 is also related to their ability to disable apoptosis.…”

Small heat shock proteins in ageing and age-related diseases

“…HSBP1 was reported to be methylglyoxal modified in endothelial cells exposed to conditions of excessive glucose ). This methylglyoxal modification modulates the oligomeric population of HSPB1, increases its chaperone activity, reduces its interaction with cytochrome c and modulates its anti-apoptotic activity (Oya-Ito et al 2006;Padival et al 2003;Sakamoto et al 2002;van Heijst et al 2006). This can potentially contribute to endothelial dysfunction associated to metabolic syndrome and various cardiovascular diseases, such as atherosclerosis.…”

Apoptosis Versus Cell Differentiation

“…77 Confirming these results, it has recently been demonstrated that methylglyoxal modification of HSP27 induces large oligomers formation and increases the anti-apoptotic caspase-inhibitory properties of HSP27. 78 In contrast, for HSP27 interaction with the F-actin and with Daxx, phosphorylated and small oligomers of HSP27 were necessary 73,79 and it is its phosphorylated form that protects against neurotoxicity. 80…”