Characterization of the thermotolerant cell. I. Effects on protein synthesis activity and the regulation of heat-shock protein 70 expression.

Abstract

Abstract. Exposure of mammalian cells to a nonlethal heat-shock treatment, followed by a recovery period at 37~ results in increased cell survival after a subsequent and otherwise lethal heat-shock treatment. Here we characterize this phenomenon, termed acquired thermotolerance, at the level of translation. In a number of different mammalian cell lines given a severe 45~ shock and then returned to 37~ protein synthesis was completely inhibited for as long as 5 h. Upon resumption of translational activity, there was a marked induction of heat-shock (or stress) protein synthesis, which continued for several hours. In contrast, cells first made thermotolerant (by a pretreatment consisting of a 43~ shock and further recovery at 37~ and then presented with the 45~ shock exhibited considerably less translational inhibition and an overall reduction in the amount of subsequent stress protein synthesis. The acquisition and duration of such "translational tolerance" was correlated with the expression, accumulation, and relative half-lives of the major stress proteins of 72 and 73 kD. Other agents that induce the synthesis of the stress proteins, such as sodium arsenite, similarly resulted in the acquisition of translational tolerance. The probable role of the stress proteins in the acquisition of translational tolerance was further indicated by the inability of the amino acid analogue, L-azetidine 2-carboxylic acid, an inducer of nonfunctional stress proteins, to render cells translationally tolerant. If, however, analogue-treated cells were allowed to recover in normal medium, and hence produce functional stress proteins, full translational tolerance was observed. Finally, we present data indicating that the 72-and 73-kD stress proteins, in contrast to the other major stress proteins (of 110, 90, and 28 kD), are subject to strict regulation in the stressed cell. Quantitation of 72-and 73-kD synthesis after heat-shock treatment under a number of conditions revealed that "titration" of 72/73-kD synthesis in response to stress may represent a mechanism by which the cell monitors its local growth environment.

The DNA-binding activity of the human heat shock transcription factor is regulated in vivo by hsp70.

“…ment (30). These results suggest that cells are able to respond to the level of stress by measuring the intracellular S\ level of free hsp70.…”

“…This property has been observed in cells that have been made thermotolerant by a previous heat treatment (30) and in rat cells that constitutively overexpress a transfected hsp70 gene (29). The synthesis of hsp70 was elevated after the heat (8,33,60).…”

“…The point at which the synthesis of hsp70 is repressed correlated closely with the NS production of a specific quantity of hsp70. The amount of hsp70 initially synthesized is dependent upon the severity of the heat stress and the amount of preexisting hsp70 in the cells (30). For example, rat cells that had been given two identical heat shock treatments separated by a period of recovery synthesized less hsp70 after the second heat treat-"b.…”

Extracellular Hsp72 concentration relates to a minimum endogenous criteria during acute exercise-heat exposure

“…The human 72 kDa heat shock protein (Hsp72), HSPA1A (Kampinga et al 2009) is the highly inducible isoform of a large family of proteins with an important role as a molecular chaperone maintaining cellular homeostasis, particularly in response to thermal stimuli (Mizzen and Welch 1988). Research has identified extracellular changes in Hsp72 concentration within whole blood (Marshall et al 2006;Yamada et al 2007;Ogura et al 2008;Magalhães et al 2010;Périard et al 2012), and intracellular changes in total protein expression and/or gene transcription in monocytes and systemic tissue (McClung et al 2008;Selkirk et al 2009;Magalhães et al 2010;Amorim et al 2011) in response to thermal and exercise stress.…”

Role of the yeast acetyltransferase Mpr1 in oxidative stress: Regulation of oxygen reactive species caused by a toxic proline catabolism intermediate

“…AZC is transported into the cells via proline transporters (4)(5)(6). There it causes misfolding of proteins into which it is incorporated competitively with proline, thus inhibiting cell growth in both prokaryotic and eukaryotic cells (7)(8)(9). We believe that Mpr1 converts AZC into N-acetyl AZC (Fig.…”