Heterologous Expression of a Plant Small Heat-Shock Protein Enhances Escherichia coliViability under Heat and Cold Stress1

Abstract

A small heat-shock protein (sHSP) that shows molecular chaperone activity in vitro was recently purified from mature chestnut (Castanea sativa) cotyledons. This protein, renamed here as CsHSP17.5, belongs to cytosolic class I, as revealed by cDNA sequencing and immunoelectron microscopy. Recombinant CsHSP17.5 was overexpressed in Escherichia coli to study its possible function under stress conditions. Upon transfer from 37°C to 50°C, a temperature known to cause cell autolysis, those cells that accumulated CsHSP17.5 showed improved viability compared with control cultures. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of cell lysates suggested that such a protective effect in vivo is due to the ability of recombinant sHSP to maintain soluble cytosolic proteins in their native conformation, with little substrate specificity. To test the recent hypothesis that sHSPs may be involved in protection against cold stress, we also studied the viability of recombinant cells at 4°C. Unlike the major heat-induced chaperone, GroEL/ES, the chestnut sHSP significantly enhanced cell survivability at this temperature. CsHSP17.5 thus represents an example of a HSP capable of protecting cells against both thermal extremes. Consistent with these findings, high-level induction of homologous transcripts was observed in vegetative tissues of chestnut plantlets exposed to either type of thermal stress but not salt stress.

Small heat-shock proteins regulate membrane lipid polymorphism

“…In mammalian cells, sHsp expression confers increased thermotolerance, as does expression of plant class I sHsp or ␣B-crystallin in E. coli (36,37). More interestingly, expression of sHsp from chestnut (Castanea sativa) in E. coli enhanced cell viability not only to heat stress but also to low temperature (4°C) (38). Clearly, these findings fundamentally question the view that the ability of sHsps to attenuate both heat-and cold-induced cell injury is solely due to their chaperone function.…”

Chemical Signals of Vector Beetle Facilitate the Prevalence of a Native Fungus and the Invasive Pinewood Nematode

“…1), as expected because high temperature is the classic inducer of sHSP, suggesting that CeHSP17 may play an important role in preventing the natural host from thermal stress damage or may assist to repair the damages caused by such thermal insult. Similarly, C. elegans HSP16 (Dixon et al, 1990) and other sHSP from mammalian cells (Landry et al, 1989), plants (Soto et al, 1999;Basha et al, 2004), and prokaryotes (Torok et al, 2001) have been demonstrated to be induced by heat, and correlated with protection against thermal stress.…”

Synechocystis HSP17 is an amphitropic protein that stabilizes heat-stressed membranes and binds denatured proteins for subsequent chaperone-mediated refolding

“…There is growing evidence that both ␣B-crystallin and mammalian HSP27 provide protection against ischemic injury in cardiac myocytes (11). Several experiments support a role for sHSPs in the acquisition of thermotolerance in mammalian cells, yeast, plants, and prokaryotes (6,12,13). A causal link between the level of sHSPs and thermotolerance in a cyanobacterium, Synechocystis sp.…”