Showing papers by "Susan Lindquist published in 1991"
TL;DR: Hsp104 is a member of the highly conserved ClpA/ClpB protein family first identified in Escherlchla coli and that additional heat-inducible members of this family are present in Schizosaccharomyces pombe and in mammals.
Abstract: MOST eukaryotic cells produce proteins with relative molecular masses in the range of 100,000 to 110,000 after exposure to high temperatures1. These proteins have been studied only in yeast and mammalian cells. In Saccharomyces cerevisiae, heat-shock protein hsp104 is vital for tolerance to heat, ethanol and other stresses (ref. 2, and Y.S. et al., manuscript submitted). The mammalian hsp110 protein is nucleolar and redistributes with growth state, nutritional conditions and heat shock3,5. The relationships between hsp110, hsp104 and the high molecular mass heat-shock proteins of other organisms were unknown. We report here that hsp104 is a member of the highly conserved ClpA/ClpB protein family first identified in Escherlchla coli6 and that additional heat-inducible members of this family are present in Schizosaccharomyces pombe and in mammals. Mutagenesis of two putative nucleotide-binding sites in hsp104 indicates that both are essential for function in thermotolerance.
264 citations
Journal Article•
TL;DR: The results indicate that hsp70 plays a major role in both thermotolerance and regulation, and also indicate that these functions can be separated.
Abstract: To test the role of the heat shock protein hsp70 in induced thermotolerance and in the regulation of the heat-shock response, we established cell lines with altered expression of the Hsp70 gene. Underexpressing cells were created by transformation with antisense Hsp70 genes, and overexpressing cells by transformation with extra copies of the wild-type gene. Expression at normal temperatures was achieved by placing Hsp70 coding sequences under the control of the metallothionein promoter. Cells that expressed mutant hsp70s were created by transforming cells with deletion and frameshift mutations. The results indicate that hsp70 plays a major role in both thermotolerance and regulation. Surprisingly, they also indicate that these functions can be separated. Overexpression affected thermotolerance more than regulation; underexpression affected regulation more than thermotolerance. A carboxyl-terminal deletion of Hsp70 had a severe dominant-negative effect on thermotolerance but only a minor effect on regulation; an amino-terminal deletion strongly affected regulation but not thermotolerance. A model that explains these observations is presented.
141 citations
TL;DR: Exposure of pancreatic islets to rIL-1 beta is accompanied by specific alterations in the protein synthesis of the islet cells, and this alteration was predominantly associated with the endoplasmic reticulum fraction.
Abstract: Prolonged exposure to high concentrations of human recombinant interleukin-1 beta (rIL-1 beta) has been reported to exert both suppressive and cytotoxic effects on pancreatic beta-cells during culture in vitro. In order to investigate the molecular mechanism(s) underlying the actions of rIL-1 beta on the beta-cell, we have exposed isolated rat pancreatic islets for 3 or for 24 h to 25 U/ml of rIL-1 beta. Subsequently the biosynthesis of heat shock proteins, as assessed by western blot analysis, and total protein biosynthesis patterns were studied, using one and two-dimensional gel electrophoresis of [35S]methionine labelled islet proteins from different subcellular compartments. It was found that rIL-1 beta exerted no specific effects on protein synthesis when added during a 3 h incubation period. However, after a 24 h incubation period, the synthesis of a group of acidic proteins with the approximate molecular weight of 35 kD was specifically inhibited in the rIL-1 beta treated islets. This alteration was predominantly associated with the endoplasmic reticulum fraction. The cytokine also inhibited the synthesis of four cytosolic proteins with the molecular weights 75, 85, 95 and 120 kD. In contrast, rIL-1 beta increased the expression of the heat shock protein hsp70 both in the microsomal and cytosolic fractions, in contrast to the islet nuclei in which no increase was found. These results show that exposure of pancreatic islets to rIL-1 beta is accompanied by specific alterations in the protein synthesis of the islet cells.(ABSTRACT TRUNCATED AT 250 WORDS)
36 citations