The structural plasticity of polyglutamine repeats

Pereira, Pedro José Barbosa; Manso, José A.; Macedo-Ribeiro, Sandra

doi:10.1016/j.sbi.2023.102607

Cited by 7 publications

(3 citation statements)

References 112 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1A ), in line with the predictions from AlphaFold2 ( 19 ). This is expected since there is extensive evidence in the literature supporting the idea that polyQ and Q-rich sequences have the ability to form α-helical and coiled-coil structures ( 20 - 24 ). This tendency is especially pronounced when these sequences are preceded by a region with high propensity for forming helical structures.…”

Section: Resultsmentioning

confidence: 93%

Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets

Manso

Carabias

Sárkány

et al. 2023

mBio

Self Cite

View full text Add to dashboard Cite

An important feature associated with Candida albicans pathogenicity is its ability to switch between yeast and hyphal forms, a process in which CaRas1 plays a key role. CaRas1 is activated by the guanine nucleotide exchange factor (GEF) CaCdc25, triggering hyphal growth-related signaling pathways through its conserved GTP-binding (G)-domain. An important function in hyphal growth has also been proposed for the long hypervariable region downstream the G-domain, whose unusual content of polyglutamine stretches and Q/N repeats make CaRas1 unique within Ras proteins. Despite its biological importance, both the structure of CaRas1 and the molecular basis of its activation by CaCdc25 remain unexplored. Here, we show that CaRas1 has an elongated shape and limited conformational flexibility and that its hypervariable region contains helical structural elements, likely forming an intramolecular coiled-coil. Functional assays disclosed that CaRas1-activation by CaCdc25 is highly efficient, with activities up to 2,000-fold higher than reported for human GEFs. The crystal structure of the CaCdc25 catalytic region revealed an active conformation for the α-helical hairpin, critical for CaRas1-activation, unveiling a specific region exclusive to CTG-clade species. Structural studies on CaRas1/CaCdc25 complexes also revealed an interaction surface clearly distinct from that of homologous human complexes. Furthermore, we identified an inhibitory synthetic peptide, prompting the proposal of a key regulatory mechanism for CaCdc25. To our knowledge, this is the first report of specific inhibition of the CaRas1-activation via targeting its GEF. This, together with their unique pathogen-structural features, disclose a set of novel strategies to specifically block this important virulence-related mechanism. IMPORTANCE Candida albicans is the main causative agent of candidiasis, the commonest fungal infection in humans. The eukaryotic nature of C. albicans and the rapid emergence of antifungal resistance raise the challenge of identifying novel drug targets to battle this prevalent and life-threatening disease. CaRas1 and CaCdc25 are key players in the activation of signaling pathways triggering multiple virulence traits, including the yeast-to-hypha interconversion. The structural similarity of the conserved G-domain of CaRas1 to those of human homologs and the lack of structural information on CaCdc25 has impeded progress in targeting these proteins. The unique structural and functional features for CaRas1 and CaCdc25 presented here, together with the identification of a synthetic peptide capable of specifically inhibiting the GEF activity of CaCdc25, open new possibilities to uncover new antifungal drug targets against C. albicans virulence.

show abstract

Section: Resultsmentioning

confidence: 93%

Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets

Manso

Carabias

Sárkány

et al. 2023

mBio

Self Cite

View full text Add to dashboard Cite

show abstract

“…This is in agreement with a representation of htt aggregates as a fibrillar core, rich in β-sheet, surrounded by a more dynamic and liquid shell, where proteins tend to acquire a more ɑ-helical structure. Given the polymorphic nature of polyQs (101, 102) and the relatively high helical content of htt exon 1 (103, 104), it is conceivable that htt fibrils maturate from within the condensate, giving rise to the partition of structures we observed (81, 105). In this process, the amyloid form of the yeast Rnq1 protein ([ RNQ + ] prion state) has been proposed to facilitate nucleation of htt aggregates (55), and htt aggregates formed in the absence of this Rnq1-nucleating effect are not toxic and tend to be less liquid-like (47).…”

Section: Discussionmentioning

confidence: 96%

Nanoscale Structural Mapping of Protein Aggregates in Live Cells Modeling Huntington’s Disease

Guo,

Chiesa,

Yin

et al. 2023

Preprint

View full text Add to dashboard Cite

Protein aggregation, in the form of amyloid fibrils, is intimately correlated with many neurodegenerative diseases. Despite recent advances in structural biology, it remains challenging to acquire structural information of proteins in live cells. Tagging with fluorescent proteins, like green fluorescent protein (GFP), is routinely used for protein visualization. Yet, this method alone cannot provide detailed structural information on the protein system of interest, and tagging proteins has the potential to perturb native structure and function. Here, by fluorescence-detected as well as label-free scattering-based mid-infrared photothermal (MIP) microscopy, we demonstrate nanoscale mapping of secondary structure of protein aggregates in a yeast model of Huntington’s disease. We first used GFP as a highly sensitive photothermal reporter to validate β-sheet enrichment in huntingtin (htt) protein aggregates. We then obtained label-free structural maps of protein aggregates. Our data showed that the fluorescent protein tag indeed perturbed the secondary structure of the aggregate, evident by a spectral shift. Live cell MIP spectroscopy further revealed the fine spatial distribution of structurally distinct components in protein aggregates, featuring a 246-nm diameter core highly enriched in β-sheet surrounded by a ɑ-helix-rich shell. Interestingly, this structural partition exists only in presence of the [RNQ+] prion, a prion that acts to facilitate the formation of other amyloid prions. Indeed, when htt is induced to aggregate in the absence of this prion ([rnq-] state), it forms non-toxic amyloid aggregates exclusively. These results showcase the potential of MIP for unveiling detailed and subtle structural information on protein systems in live cells.SignificanceProtein aggregation is a hallmark of neurodegenerative diseases, such as Huntington’s Disease. Understanding the nature of neurotoxic aggregates could lead to better therapeutic approaches. The limited progress in this direction is partly due to the lack of tools for extracting structural information in the physiological context of the aggregates. Here, we report a photothermally detected mid-infrared micro-spectroscopy technique able to dissect the secondary structure of aggregates of the huntingtin protein in live cells. We describe for the first time a nanoscale partition of secondary structures between β-rich core and ɑ-rich shell of the aggregates. This work demonstrates the potential of mid-infrared photothermal microscopy for structural and functional mapping of proteins in live cells.

show abstract

“…Most knowledge of the molecular mechanisms, the mutant proteins, and the aggregates is available for the most common polyQ disorder: HD [ 5 ]. This review will focus on HD, with readers referred to other literature for more information on other polyQ disorders [ 2 , 6 , 7 ].…”

Section: Polyq Diseasesmentioning

confidence: 99%

Solid-state nuclear magnetic resonance in the structural study of polyglutamine aggregation

van der Wel

2024

Biochemical Society Transactions

View full text Add to dashboard Cite

The aggregation of proteins into amyloid-like fibrils is seen in many neurodegenerative diseases. Recent years have seen much progress in our understanding of these misfolded protein inclusions, thanks to advances in techniques such as solid-state nuclear magnetic resonance (ssNMR) spectroscopy and cryogenic electron microscopy (cryo-EM). However, multiple repeat-expansion-related disorders have presented special challenges to structural elucidation. This review discusses the special role of ssNMR analysis in the study of protein aggregates associated with CAG repeat expansion disorders. In these diseases, the misfolding and aggregation affect mutant proteins with expanded polyglutamine segments. The most common disorder, Huntington's disease (HD), is connected to the mutation of the huntingtin protein. Since the discovery of the genetic causes for HD in the 1990s, steady progress in our understanding of the role of protein aggregation has depended on the integrative and interdisciplinary use of multiple types of structural techniques. The heterogeneous and dynamic features of polyQ protein fibrils, and in particular those formed by huntingtin N-terminal fragments, have made these aggregates into challenging targets for structural analysis. ssNMR has offered unique insights into many aspects of these amyloid-like aggregates. These include the atomic-level structure of the polyglutamine core, but also measurements of dynamics and solvent accessibility of the non-core flanking domains of these fibrils' fuzzy coats. The obtained structural insights shed new light on pathogenic mechanisms behind this and other protein misfolding diseases.

show abstract

The structural plasticity of polyglutamine repeats

Cited by 7 publications

References 112 publications

Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets

Pathogen-specific structural features of Candida albicans Ras1 activation complex: uncovering new antifungal drug targets

Nanoscale Structural Mapping of Protein Aggregates in Live Cells Modeling Huntington’s Disease

Solid-state nuclear magnetic resonance in the structural study of polyglutamine aggregation

Contact Info

Product

Resources

About