Emerging fields in chaperone proteins: A French workshop.

The "Bioénergétique et Ingénierie des Protéines (BIP)" laboratory, CNRS (France), organized its first French workshop on molecular chaperone proteins and protein folding in November 2017. The goal of this workshop was to gather scientists working in France on chaperone proteins and protein folding. This initiative was a great success with excellent talks and fruitful discussions.

VLITL is a major cross-β-sheet signal for fibrinogen Aα-chain frameshift variants.

The first case of hereditary fibrinogen Aα-chain amyloidosis was recognized >20 years ago, but disease mechanisms still remain unknown. Here we report detailed clinical and proteomics studies of a French kindred with a novel amyloidogenic fibrinogen Aα-chain frameshift variant, Phe521Leufs, causing a severe familial form of renal amyloidosis. Next, we focused our investigations to elucidate the molecular basis that render this Aα-chain variant amyloidogenic.

Zinc binding to RNA recognition motif of TDP-43 induces the formation of amyloid-like aggregates.

Aggregation of TDP-43 (transactive response DNA binding protein 43 kDa) is a hallmark of certain forms of amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). Moreover, intracellular TDP-43-positive inclusions are often found in other neurodegenerative diseases. Recently it was shown that zinc ions can provoke the aggregation of endogenous TDP-43 in cells, allowing to assume a direct interaction of TDP-43 with zinc ions.

Hsp90 directly interacts, in vitro, with amyloid structures and modulates their assembly and disassembly.

Background: The 90kDa heat shock protein (Hsp90) participates in regulating the homeostasis of cellular proteins and was considered one of the key chaperones involved in the control and regulation of amyloid deposits. Hsp90 interacts with the amyloid protein tau through tau aggregation-prone regions, including the VQIVYK hexapeptide motif. This hexapeptide, which self-aggregates, forming amyloid fibrils, is widely used to model amyloid formation mechanisms.

Hsp90 oligomerization process: How can p23 drive the chaperone machineries?

The 90-kDa heat shock protein (Hsp90) is a highly flexible dimer that is able to self-associate in the presence of divalent cations or under heat shock. In a previous work, we focused on the Mg2+-induced oligomerization process of Hsp90, and characterized the oligomers. Combining analytical ultracentrifugation, size-exclusion chromatography coupled to multi-angle laser light scattering and high-mass matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, we studied the interaction of p23 with both Hsp90 dimer and oligomers.

Hsp90 Oligomers Interacting with the Aha1 Cochaperone: An Outlook for the Hsp90 Chaperone Machineries.

The 90-kDa heat shock protein (Hsp90) is a highly flexible dimer able to self-associate in the presence of divalent cations or under heat shock. This study investigated the relationship between Hsp90 oligomers and the Hsp90 cochaperone Aha1 (activator of Hsp90 ATPase). The interactions of Aha1 with Hsp90 dimers and oligomers were evaluated by ultracentrifugation, size-exclusion chromatography coupled to multiangle laser light scattering and high-mass matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Optimized protocol for protein macrocomplexes stabilization using the EDC, 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide, zero-length cross-linker.

Since noncovalent protein macrocomplexes are implicated in many cellular functions, their characterization is essential to understand how they drive several biological processes. Over the past 20 years, because of its high sensitivity, mass spectrometry has been described as a powerful tool for both the protein identification in macrocomplexes and the understanding of the macrocomplexes organization. Nonetheless, stabilizing these protein macrocomplexes, by introducing covalent bonds, is a prerequisite before their analysis by the denaturing mass spectrometry technique.

Biochemical and biophysical characterization of the Mg2+-induced 90-kDa heat shock protein oligomers.

The 90-kDa heat shock protein (Hsp90) is involved in the regulation and activation of numerous client proteins essential for diverse functions such as cell growth and differentiation. Although the function of cytosolic Hsp90 is dependent on a battery of cochaperone proteins regulating both its ATPase activity and its interaction with client proteins, little is known about the real Hsp90 molecular mechanism. Besides its highly flexible dimeric state, Hsp90 is able to self-oligomerize in the presence of divalent cations or under heat shock.

The 90-kDa heat shock protein Hsp90 protects tubulin against thermal denaturation.

Hsp90 and tubulin are among the most abundant proteins in the cytosol of eukaryotic cells. Although Hsp90 plays key roles in maintaining its client proteins in their active state, tubulin is essential for fundamental processes such as cell morphogenesis and division. Several studies have suggested a possible connection between Hsp90 and the microtubule cytoskeleton.

EB1 regulates microtubule dynamics and tubulin sheet closure in vitro.

End binding 1 (EB1) is a plus-end-tracking protein (+TIP) that localizes to microtubule plus ends where it modulates their dynamics and interactions with intracellular organelles. Although the regulating activity of EB1 on microtubule dynamics has been studied in cells and purified systems, the molecular mechanisms involved in its specific activity are still unclear. Here, we describe how EB1 regulates the dynamics and structure of microtubules assembled from pure tubulin.

Apo-Hsp90 coexists in two open conformational states in solution.

Background Information: Hsp90 (90 kDa heat-shock protein) plays a key role in the folding and activation of many client proteins involved in signal transduction and cell cycle control. The cycle of Hsp90 has been intimately associated with large conformational rearrangements, which are nucleotide-binding-dependent. However, up to now, our understanding of Hsp90 conformational changes derives from structural information, which refers to the crystal states of either recombinant Hsp90 constructs or the prokaryotic homologue HtpG (Hsp90 prokaryotic homologue).

Hydrodynamic properties and quaternary structure of the 90 kDa heat-shock protein: effects of divalent cations.

The 90 kDa heat-shock protein (Hsp90) is one of the major stress proteins whose overall structure remains unknown. In this study, we investigated the influence of divalent cations Mg(2+) and Ca(2+) on the hydrodynamic properties and quaternary structure of Hsp90. Using analytical ultracentrifugation, size-exclusion chromatography, and polyacrylamide gel electrophoresis, we showed that native Hsp90 was mostly dimeric.

Binding of ATP to heat shock protein 90: evidence for an ATP-binding site in the C-terminal domain.

The presence of a nucleotide binding site on hsp90 was very controversial until x-ray structure of the hsp90 N-terminal domain, showing a nonconventional nucleotide binding site, appeared. A recent study suggested that the hsp90 C-terminal domain also binds ATP (Marcu, M. G.