Clusterin is an extracellular chaperone that specifically interacts with slowly aggregating proteins on their off‐folding pathway

FEBS Letters

Treweek, Teresa M¹  Carver, John A¹  Poon, Stephen¹  Easterbrook-Smith, Simon B²  Wilson, Mark R³ 

[1] Department of Chemistry, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia;School of Molecular and Microbial Biosciences, The University of Sydney, Sydney, NSW 2006, Australia;Department of Biological Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia

关键词: Molecular chaperone;    Protein unfolding;    Aggregation;    Clusterin;    Small heat-shock protein;    3SS-α-lactalbumin;    α-lactalbumin with Cys6–Cys120 selectively reduced and carboxymethylated;    DTT;    dithiothreitol;    GuHCl;    guanidinium hydrochloride;    HDC;    1% heat-denatured casein dissolved in phosphate-buffered saline;    HMW;    high molecular weight;    PBS;    phosphate-buffered saline;    R-cam-α-lactalbumin;    reduced and carboxyamidated α-lactalbumin;    R-cm-α-lactalbumin;    reduced and carboxymethylated α-lactalbumin;    sHsp;    small heat-shock protein;   

DOI  :  10.1016/S0014-5793(02)02326-8

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

Clusterin is an extracellular mammalian chaperone protein which inhibits stress-induced precipitation of many different proteins. The conformational state(s) of proteins that interact with clusterin and the stage(s) along the folding and off-folding (precipitation-bound) pathways where this interaction occurs were previously unknown. We investigated this by examining the interactions of clusterin with different structural forms of α-lactalbumin, γ-crystallin and lysozyme. When assessed by ELISA and native gel electrophoresis, clusterin did not bind to various stable, intermediately folded states of α-lactalbumin nor to the native form of this protein, but did bind to and inhibit the slow precipitation of reduced α-lactalbumin. Reduction-induced changes in the conformation of α-lactalbumin, in the absence and presence of clusterin, were monitored by real-time ¹H NMR spectroscopy. In the absence of clusterin, an intermediately folded form of α-lactalbumin, with some secondary structure but lacking tertiary structure, aggregated and precipitated. In the presence of clusterin, this form of α-lactalbumin was stabilised in a non-aggregated state, possibly via transient interactions with clusterin prior to complexation. Additional experiments demonstrated that clusterin potently inhibited the slow precipitation, but did not inhibit the rapid precipitation, of lysozyme and γ-crystallin induced by different stresses. These results suggest that clusterin interacts with and stabilises slowly aggregating proteins but is unable to stabilise rapidly aggregating proteins. Collectively, our results suggest that during its chaperone action, clusterin preferentially recognises partly folded protein intermediates that are slowly aggregating whilst venturing along their irreversible off-folding pathway towards a precipitated protein.

【 授权许可】

Unknown