BAG3 Is a Modular, Scaffolding Protein that physically Links Heat Shock Protein 70 (Hsp70) to the Small Heat Shock Proteins. Issue 1 (6th January 2017)

• Record Type: Journal Article
• Authors: Rauch, Jennifer N.; Tse, Eric; Freilich, Rebecca; Mok, Sue-Ann; Makley, Leah N.; Southworth, Daniel R.; Gestwicki, Jason E.
• Is Part Of: Journal of molecular biology. Volume 429:Issue 1(2017)
• Page Start: 128
• Page End: 141
• Publication Date: 2017-01-06
• Subjects: chaperones -- Hsp27 -- proteostasis -- intrinsically disordered proteins -- protein folding; sHsps small heat shock proteins -- Hsp heat shock protein -- BAG3 Bcl-2-associated anthanogene-3 -- NBD nucleotide-binding domain -- ITC isothermal titration calorimetry -- CSPs chemical shift perturbations -- FCPIA flow cytometry protein interaction assay -- SEC-MALS size exclusion chromatography with multi-angle light scattering -- EM electron microscopy; Molecular biology -- Periodicals; Biology -- Periodicals; Biochemistry -- Periodicals; Bacteriology -- Periodicals; Molecular Biology -- Periodicals; Biochemistry -- Periodicals; Biologie moléculaire -- Périodiques; Biologie -- Périodiques; Biochimie -- Périodiques; Moleculaire biologie; Biochemistry; Biology; Molecular biology; Periodicals; 572.805
• DOI: 10.1016/j.jmb.2016.11.013
• Languages: English
• ISSNs: 0022-2836

Abstract

Abstract: Small heat shock proteins (sHsps) are a family of ATP-independent molecular chaperones that are important for binding and stabilizing unfolded proteins. In this task, the sHsps have been proposed to coordinate with ATP-dependent chaperones, including heat shock protein 70 (Hsp70). However, it is not yet clear how these two important components of the chaperone network are linked. We report that the Hsp70 co-chaperone, BAG3, is a modular, scaffolding factor to bring together sHsps and Hsp70s. Using domain deletions and point mutations, we found that BAG3 uses both of its IPV motifs to interact with sHsps, including Hsp27 (HspB1), αB-crystallin (HspB5), Hsp22 (HspB8), and Hsp20 (HspB6). BAG3 does not appear to be a passive scaffolding factor; rather, its binding promoted de-oligomerization of Hsp27, likely by competing for the self-interactions that normally stabilize large oligomers. BAG3 bound to Hsp70 at the same time as Hsp22, Hsp27, or αB-crystallin, suggesting that it might physically bring the chaperone families together into a complex. Indeed, addition of BAG3 coordinated the ability of Hsp22 and Hsp70 to refold denatured luciferase in vitro . Together, these results suggest that BAG3 physically and functionally links Hsp70 and sHsps. Graphical abstract: Highlights: BAG3 binds small heat shock proteins and Hsp70 at the same time. BAG3 reduces the size of small heat shock protein oligomers. BAG3 coordinates the ability of sHsp and Hsp70 refold denatured luciferase.