Structural principles that enable oligomeric small heat-shock protein paralogs to evolve distinct functions

Hochberg, Georg K. A.; Shepherd, Dale A.; Marklund, Erik; Santhanagoplan, Indu; Degiacomi, Matteo T.; Laganowsky, Arthur; Allison, Timothy M.; Basha, Eman; Marty, Michael T.; Galpin, Martin R.; Struwe, Weston B.; Baldwin, Andrew J.; Vierling, Elizabeth; Benesch, Justin L. P.

doi:10.1126/science.aam7229

Cited by 55 publications

(82 citation statements)

References 81 publications

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“…This tetrahedral architecture is equivalent to that observed for the sHSP Acr1 from Mycobacterium tuberculosis (48). Native MS of Ps18.1 CT-ACD (49), and overlapping small angle x-ray scattering (SAXS) profiles for Ta16.9 and Ps18.1 provide evidence that Ps18.1 also has tetrahedral geometry ( Fig. S3).…”

Section: A New Geometry For the Shsp Dodecamersupporting

confidence: 54%

It takes a dimer to tango: Oligomeric small heat-shock proteins dissociate to capture substrate

Santhanagopalan

Degiacomi

Shepherd

et al. 2018

Preprint

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Small heat-shock proteins (sHsps) are ubiquitous molecular chaperones, and their mutations or altered expression are linked to multiple human disease states. sHsp monomers assemble into large oligomers with dimeric substructure, and the dynamics of sHsp oligomers has led to major questions about the form that captures substrate, a critical aspect of their mechanism of action. We show that substructural dimers of plant dodecameric sHsps, Ta16.9 and homologous Ps18.1, are functional units in the initial encounter with unfolding substrate. We introduced inter-polypeptide disulfide bonds at the two dodecameric interfaces, dimeric and non-dimeric, to restrict how their assemblies can dissociate. When disulfide bonded at the non-dimeric interface, mutants of Ta16.9 and Ps18.1 (TaCT-ACD and PsCT-ACD) were inactive, but when reduced had wild-type-like chaperone activity, demonstrating that dissociation at non-dimeric interfaces is essential for activity. In addition, the size of the TaCT-ACD and PsCT-ACD covalent unit defined a new tetrahedral geometry for these sHsps, different than the Ta16.9 x-ray structure. Importantly, oxidized Tadimer (disulfide bonded at the dimeric interface) showed greatly enhanced ability to protect substrate, indicating that strengthening the dimeric interface increases chaperone efficiency. Size and secondary structure changes with temperature revealed that folded sHsp dimers interact with substrate, and support dimer stability as a determinant of chaperone efficiency. These data yield a model in which sHsp dimers capture substrate prior to assembly into larger, heterogeneous sHSP-substrate complexes for subsequent substrate refolding or degradation, and suggest that tuning the strength of the dimer interface can be used to engineer sHsp chaperone efficiency.

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Section: A New Geometry For the Shsp Dodecamersupporting

confidence: 54%

It takes a dimer to tango: Oligomeric small heat-shock proteins dissociate to capture substrate

Santhanagopalan

Degiacomi

Shepherd

et al. 2018

Preprint

Self Cite

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“…Similar heterogeneity of N-terminal residues has been observed in other sHsps and shown to regulate assembly (75), including in HspB5 and HspB6, both of which co-assemble with HspB1 in vivo (76). The HspB5 β2 strand and residues immediately preceding it exist in multiple conformations (77), including bound to β3 both intra- (45, 71) and inter-monomer (77).…”

Section: Discussionsupporting

confidence: 60%

Phosphorylation of HspB1 regulates its mechanosensitive molecular chaperone interaction with native filamin C

Collier

Alderson

et al. 2018

Preprint

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Small heat-shock proteins (sHsps; HspBs) are molecular chaperones involved in the cellular stress response and a range of basal functions. Despite a multitude of targets, sHsp interactions are not well understood due their heterogeneous structures and weak binding affinities. The most widely expressed human sHsp, HspB1, is prevalent in striated muscle, where the actin cross-linker filamin C (FLNC, γ-filamin, ABP-L) is a putative binding partner. Musculoskeletal HspB1 is phosphorylated in response to a variety of cues, including mechanical stress, which promotes oligomer disassembly and association with myoarchitectural elements. Here, we report the up-regulation and interaction of both proteins in the hearts of a mouse model of heart failure, with HspB1 being phosphorylated and FLNC increasingly associated with the sarcomeric Z-disc. We used a combination of structural approaches to reveal that phosphorylation of HspB1 results in increased availability of the residues surrounding the phosphosite, facilitating their interaction with folded FLNC domains equivalent to a force-sensing region in the paralog filamin A. By employing native mass spectrometry, we show that domains 18 to 21 of FLNC are extensible under conditions mimicking force, with phosphorylated HspB1 stabilising an intermediate from further unfolding. These findings report on conformations accessible during the cycles of mechanical extension central to filamin function, and are consistent with an interaction between the chaperone and a native target that is strengthened upon the application of force. This may represent a new mode of molecular chaperone activity, allowing HspB1 to protect FLNC from over-extension during mechanical stress.

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“…However, the simulations only consider the evolution of binding interfaces, which limits the 431 modification of interactions to a subset of all mutations that can ultimately affect PPIs 432 (Hochberg et al, 2018). Other mechanisms responsible for the loss of paralog interactions 433 could involve transcriptional regulation or cell compartment localization such that paralogs 434…”

Section: 427mentioning

confidence: 99%

“…Since nascent paralogs are by definition identical after duplication, they would also have a high propensity to assemble with each other. Hence, the maintenance of HETs could be the default state until specific mutations accumulate (Ashenberg et al, 2011;Hochberg et al, 2018). Here, our hypothesis is that the association of paralogs forming HETs acts as a constraint that may slow paralog functional divergence because it keeps gene products physically associated.…”

Section: Introductionmentioning

confidence: 98%

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The role of structural pleiotropy and regulatory evolution in the retention of heteromers of paralogs

Marchant

Cisneros

Dubé

et al. 2019

Preprint

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Many paralogs derive from the duplication of genes encoding homomeric proteins. Such duplication events lead to the formation of homomers and heteromers, thus creating new structures from a single event. We exhaustively characterize this phenomenon using the budding yeast protein-protein interaction network. We observe that paralogs that heteromerize are very frequent and less functionally diverged than those that lost this property, raising the possibility that heteromerization prevents functional divergence. Using in silico evolution, we show that for homomers and heteromers that share binding interfaces, mutations on one complex have pleiotropic effects on the other complex, resulting in highly correlated responses to selection. As a result, heteromerization could be preserved indirectly due to selection for the maintenance of homomers. By integrating data on gene expression and protein localization, we find that regulatory evolution could play a role in overcoming these structural pleiotropic effects and in allowing paralog functional divergence.

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Structural principles that enable oligomeric small heat-shock protein paralogs to evolve distinct functions

Cited by 55 publications

References 81 publications

It takes a dimer to tango: Oligomeric small heat-shock proteins dissociate to capture substrate

It takes a dimer to tango: Oligomeric small heat-shock proteins dissociate to capture substrate

Phosphorylation of HspB1 regulates its mechanosensitive molecular chaperone interaction with native filamin C

The role of structural pleiotropy and regulatory evolution in the retention of heteromers of paralogs

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