Eye lens αA- and αB-crystallin: complex stability versus chaperone-like activity

Boekel, M.A.M. van; Lange, Frank de; Grip, W.J. de; Jong, Wilfried W. de

doi:10.1016/s0167-4838(99)00178-8

Cited by 51 publications

(51 citation statements)

References 41 publications

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“…Numerous studies implicate surface-exposed hydrophobic sites on ␣-crystallin and other sHSPs in binding to partially unfolded proteins (14 -23). The finding that increased exposure of hydrophobic surfaces on structurally perturbed ␣-crystallin is associated with increased chaperone-like function substantiates the role of hydrophobicity in the chaperone function of sHSP (14 -16, 21 with increased hydrophobicity with recombinant ␣A-and ␣B-crystallins (14,16). ␣A-and ␣B-crystallins differ not only in their hydrophobic character with temperature but also in their secondary and tertiary structure, molecular size, and other physicochemical properties (14 -16).…”

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confidence: 55%

Insights into Hydrophobicity and the Chaperone-like Function of αA- and αB-crystallins

Kumar

Kapoor

Sinha

et al. 2005

Journal of Biological Chemistry

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␣-Crystallin, composed of two subunits, ␣A and ␣B, has been shown to function as a molecular chaperone that prevents aggregation of other proteins under stress conditions. The exposed hydrophobic surfaces of ␣-crystallins have been implicated in this process, but their exact role has not been elucidated. In this study, we quantify the hydrophobic surfaces of ␣A-and ␣B-crystallins by isothermal titration calorimetry using 8-anilino-1-napthalenesulfonic acid (ANS) as a hydrophobic probe and analyze its correlation to the chaperone potential of ␣A-and ␣B-crystallins under various conditions. Two ANS binding sites, one with low and another with high affinity, were clearly detected, with ␣B showing a higher number of sites than ␣A at 30°C. In agreement with the higher number of hydrophobic sites, ␣B-crystallin demonstrated higher chaperone activity than ␣A at this temperature. Thermodynamic analysis of ANS binding to ␣A-and ␣B-crystallins indicates that high affinity binding is driven by both enthalpy and entropy changes, with entropy dominating the low affinity binding. Interestingly, although the number of ANS binding sites was similar for ␣A and ␣B at 15°C, ␣A was more potent than ␣B in preventing aggregation of the insulin B-chain. Although there was no change in the number of high affinity binding sites of ␣A and ␣B for ANS upon preheating, there was an increase in the number of low affinity sites of ␣A and ␣B. Preheated ␣A, in contrast to ␣B, exhibited remarkably enhanced chaperone activity. Our results indicate that although hydrophobicity appears to be a factor in determining the chaperone-like activity of ␣-crystallins, it does not quantitatively correlate with the chaperone function of ␣-crystallins.

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confidence: 55%

Insights into Hydrophobicity and the Chaperone-like Function of αA- and αB-crystallins

Kumar

Kapoor

Sinha

et al. 2005

Journal of Biological Chemistry

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“…This difference is not caused by their mode of purification, as demonstrated with His-Hsp22 purified under native conditions and with urea. Small Hsps of other organisms have also been reported to show differences in their chaperone activity; among others, this is the case for Xenopus laevis Hsp30C and Hsp30D (Abdulle et al 2002), for mammalian ␣A-crystallin and ␣B-crystallin (Datta and Rao 1999;Van Boekel et al 1999;Reddy et al 2000) and recently for mammalian Hsp22 (Chowdary et al 2004) and S. cerevisiae Hsp42 and Hsp26 (Haslbeck et al 2004). For example, despite the high degree of sequence homology and structural similarity of ␣A-and ␣B-crystallin, ␣A-crystallin is more efficient in preventing thermal aggregation of proteins whereas ␣B-crystallin performs better against reduction-induced aggregation of proteins (Datta and Rao 1999).…”

Section: Discussionmentioning

confidence: 98%

Differences in the chaperone-like activities of the four main small heat shock proteins of Drosophila melanogaster

2006

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The Drosophila melanogaster family of small heat shock proteins (sHsps) is composed of 4 main members (Hsp22, Hsp23, Hsp26, and Hsp27) that display distinct intracellular localization and specific developmental patterns of expression in the absence of stress. In an attempt to determine their function, we have examined whether these 4 proteins have chaperone-like activity using various chaperone assays. Heat-induced aggregation of citrate synthase was decreased from 100 to 17 arbitrary units in the presence of Hsp22 and Hsp27 at a 1:1 molar ratio of sHsp to citrate synthase. A 5 M excess of Hsp23 and Hsp26 was required to obtain the same efficiency with either citrate synthase or luciferase as substrate. In an in vitro refolding assay with reticulocyte lysate, more than 50% of luciferase activity was recovered when heat denaturation was performed in the presence of Hsp22, 40% with Hsp27, and 30% with Hsp23 or Hsp26. These differences in luciferase reactivation efficiency seemed related to the ability of sHsps to bind their substrate at 42ЊC, as revealed by sedimentation analysis of sHsp and luciferase on sucrose gradients. Therefore, the 4 main sHsps of Drosophila share the ability to prevent heat-induced protein aggregation and are able to maintain proteins in a refoldable state, although with different efficiencies. The functional reasons for their distinctive cell-specific pattern of expression could reflect the existence of defined substrates for each sHsp within the different intracellular compartments.

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“…In contrast, the properties of homo-and hetero-oligomeric ␣-crystallin complexes differ, because it was reported that these complexes have different lens plasma membrane-binding properties (47). It was also shown that ␣A and ␣B-crystallin homooligomers possess unique chaperone activities that are additionally differently modulated in response to temperature changes (48,49).…”

Section: Discussionmentioning

confidence: 99%

The Small Heat Shock Protein IbpA of Escherichia coli Cooperates with IbpB in Stabilization of Thermally Aggregated Proteins in a Disaggregation Competent State

Matuszewska

Kuczyńska-Wiśnik

Laskowska

et al. 2005

Journal of Biological Chemistry

105

108

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The small heat shock proteins are ubiquitous stress proteins proposed to increase cellular tolerance to heat shock conditions. We isolated IbpA, the Escherichia coli small heat shock protein, and tested its ability to keep thermally inactivated substrate proteins in a disaggregation competent state. We found that the presence of IbpA alone during substrate thermal inactivation only weakly influences the ability of the bi-chaperone Hsp70-Hsp100 system to disaggregate aggregated substrate. Similar minor effects were observed for IbpB alone, the other E. coli small heat shock protein. However, when both IbpA and IbpB are simultaneously present during substrate inactivation they efficiently stabilize thermally aggregated proteins in a disaggregation competent state. The properties of the aggregated protein substrates are changed in the presence of IbpA and IbpB, resulting in lower hydrophobicity and the ability of aggregates to withstand sizing chromatography conditions. IbpA and IbpB form mixed complexes, and IbpA stimulates association of IbpB with substrate.The proper conformation of proteins is challenged by stress conditions. Exposure to extreme heat shock conditions results in a massive aggregation of proteins inside both prokaryotic and eukaryotic cells (1-3). Chaperones from the Hsp100 family, that is ClpB in Escherichia coli and Hsp104 in the yeast Saccharomyces cerevisiae, were implicated in the disaggregation reaction, because aggregated proteins were not eliminated in either clpB or HSP104 deletion strains (1-3). Additionally, the clpB and HSP104 gene products were identified as factors conferring thermotolerance in E. coli and S. cerevisiae (4 -7). However, in vitro studies on the reactivation of aggregated proteins showed that chaperones from the Hsp100 family alone are not sufficient for disaggregation and refolding. Other chaperone proteins are also involved in this process. E. coli Hsp70 (DnaK) and its cochaperones (DnaJ and GrpE) cooperate with ClpB and form a bi-chaperone system capable of efficient disaggregation of aggregated proteins (3,8,9). Analogous Hsp100-Hsp70 bi-chaperone systems able to disaggregate denatured protein substrates in vitro were established using chaperones from other bacterial species (10), as well as from yeast cytosol (11) and mitochondria (12, 13). However, the efficiency of refolding reaction catalyzed by these bichaperone systems depends strongly on the physical properties of protein aggregates. It was proposed that small heat shock proteins (sHsps) 1 associate with aggregated proteins and change their physical properties in such a way that chaperone-mediated disaggregation and refolding become much more efficient (14 -19). However, little is known about the molecular mechanism of these processes.Small heat shock proteins are widely distributed both in prokaryotes and eukaryotes. Members of this diverse protein family are characterized by relatively low monomeric molecular masses (15-43 kDa) and a conserved stretch of ϳ100 amino acid residues (reviewed in Refs. 20 and ...

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Eye lens αA- and αB-crystallin: complex stability versus chaperone-like activity

Cited by 51 publications

References 41 publications

Insights into Hydrophobicity and the Chaperone-like Function of αA- and αB-crystallins

Insights into Hydrophobicity and the Chaperone-like Function of αA- and αB-crystallins

Differences in the chaperone-like activities of the four main small heat shock proteins of Drosophila melanogaster

The Small Heat Shock Protein IbpA of Escherichia coli Cooperates with IbpB in Stabilization of Thermally Aggregated Proteins in a Disaggregation Competent State

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