scholarly journals The Pathogenic R5L Mutation Disrupts Formation of Tau Complexes on the Microtubule by Altering Local N-Terminal Structure

2021 ◽  
Author(s):  
Alisa Cario ◽  
Adriana Savastano ◽  
Neil B. Wood ◽  
Zhu Liu ◽  
Michael J. Previs ◽  
...  
Keyword(s):  
Point Mutations ◽  
Intrinsically Disordered Protein ◽  
State Theory ◽  
Disease State ◽  
Missense Mutations ◽  
Microtubule Binding ◽  
Intrinsically Disordered ◽  
Projection Domain ◽  
Terminal Structure

The microtubule-associated protein (MAP) Tau is an intrinsically disordered protein (IDP) primarily expressed in axons, where it functions to regulate microtubule dynamics, modulate motor protein motility, and participate in signaling cascades. Tau misregulation and point mutations are linked to neurodegenerative diseases, including Progressive Supranuclear Palsy (PSP), Pick's Disease and Alzheimer's disease. Many disease-associated mutations in Tau occur in the C-terminal microtubule-binding domain of the protein. Effects of C-terminal mutations in Tau have led to the widely accepted disease-state theory that missense mutations in Tau reduce microtubule-binding affinity or increase Tau propensity to aggregate. Here, we investigate the effect of an N-terminal disease-associated mutation in Tau, R5L, on Tau-microtubule interactions using an in vitro reconstituted system. Contrary to the canonical disease-state theory, we determine the R5L mutation does not reduce Tau affinity for the microtubule using Total Internal Reflection Fluorescence (TIRF) Microscopy. Rather, the R5L mutation decreases the ability of Tau to form larger order complexes, or Tau patches, at high concentrations of Tau. Using Nuclear Magnetic Resonance (NMR), we show that the R5L mutation results in a local structural change that reduces interactions of the projection domain in the presence of microtubules. Altogether, these results challenge both the current paradigm of how mutations in Tau lead to disease and the role of the projection domain in modulating Tau behavior on the microtubule surface.

scholarly journals A functional role for intrinsic disorder in the tau-tubulin complex

2016 ◽  
Vol 113 (50) ◽  
pp. 14336-14341 ◽  
Author(s):  
Ana M. Melo ◽  
Juliana Coraor ◽  
Garrett Alpha-Cobb ◽  
Shana Elbaum-Garfinkle ◽  
Abhinav Nath ◽  
...  
Keyword(s):  
Single Molecule ◽  
Solution Structure ◽  
Dynamic Instability ◽  
Resonance Energy ◽  
Intrinsically Disordered Protein ◽  
Conformational Ensemble ◽  
Binding Region ◽  
Global Features ◽  
Microtubule Binding ◽  
Intrinsically Disordered

Tau is an intrinsically disordered protein with an important role in maintaining the dynamic instability of neuronal microtubules. Despite intensive study, a detailed understanding of the functional mechanism of tau is lacking. Here, we address this deficiency by using intramolecular single-molecule Förster Resonance Energy Transfer (smFRET) to characterize the conformational ensemble of tau bound to soluble tubulin heterodimers. Tau adopts an open conformation on binding tubulin, in which the long-range contacts between both termini and the microtubule binding region that characterize its compact solution structure are diminished. Moreover, the individual repeats within the microtubule binding region that directly interface with tubulin expand to accommodate tubulin binding, despite a lack of extension in the overall dimensions of this region. These results suggest that the disordered nature of tau provides the significant flexibility required to allow for local changes in conformation while preserving global features. The tubulin-associated conformational ensemble is distinct from its aggregation-prone one, highlighting differences between functional and dysfunctional states of tau. Using constraints derived from our measurements, we construct a model of tubulin-bound tau, which draws attention to the importance of the role of tau’s conformational plasticity in function.

Phospho-dependent phase separation of FMRP and CAPRIN1 recapitulates regulation of translation and deadenylation

Science ◽  
2019 ◽  
Vol 365 (6455) ◽  
pp. 825-829 ◽  
Author(s):  
Tae Hun Kim ◽  
Brian Tsang ◽  
Robert M. Vernon ◽  
Nahum Sonenberg ◽  
Lewis E. Kay ◽  
...  
Keyword(s):  
Phase Separation ◽  
Rna Processing ◽  
Intrinsically Disordered Protein ◽  
Resonance Spectroscopy ◽  
Specific Interactions ◽  
Intrinsically Disordered ◽  
Functional Consequences ◽  
Translational Regulators

Membraneless organelles involved in RNA processing are biomolecular condensates assembled by phase separation. Despite the important role of intrinsically disordered protein regions (IDRs), the specific interactions underlying IDR phase separation and its functional consequences remain elusive. To address these questions, we used minimal condensates formed from the C-terminal disordered regions of two interacting translational regulators, FMRP and CAPRIN1. Nuclear magnetic resonance spectroscopy of FMRP-CAPRIN1 condensates revealed interactions involving arginine-rich and aromatic-rich regions. We found that different FMRP serine/threonine and CAPRIN1 tyrosine phosphorylation patterns control phase separation propensity with RNA, including subcompartmentalization, and tune deadenylation and translation rates in vitro. The resulting evidence for residue-specific interactions underlying co–phase separation, phosphorylation-modulated condensate architecture, and enzymatic activity within condensates has implications for how the integration of signaling pathways controls RNA processing and translation.

scholarly journals Synergism between a simple sugar and a small intrinsically disordered protein mitigate the lethal stresses of severe water loss

2017 ◽  
Author(s):  
Skylar X. Kim ◽  
Gamze Çamdere ◽  
Xuchen Hu ◽  
Douglas Koshland ◽  
Hugo Tapia
Keyword(s):  
Water Loss ◽  
Molecular Basis ◽  
Intrinsically Disordered Protein ◽  
Biological Functions ◽  
Intrinsically Disordered ◽  
Disordered Protein ◽  
Drought Tolerant ◽  
Simple Sugar

ABSTRACTAnhydrobiotes are rare microbes, plants and animals that tolerate severe water loss. Understanding the molecular basis for their desiccation tolerance may provide novel insights into stress biology and critical tools for engineering drought-tolerant crops. Using the anhydrobiote, budding yeast, we show that trehalose and Hsp12, a small intrinsically disordered protein (sIDP) of the hydrophilin family, synergize to mitigate completely the inviability caused by the lethal stresses of desiccation. We show that these two molecules help to stabilize the activity and prevent aggregation of model proteins both in vivo and in vitro. We also identify a novel role for Hsp12 as a membrane remodeler, a protective feature not shared by another yeast hydrophilin, suggesting that sIDPs have distinct biological functions.

scholarly journals Hidden structure in disordered proteins is adaptive to intracellular changes

2021 ◽  
Author(s):  
David Moses ◽  
Karina Guadalupe ◽  
Feng Yu ◽  
Eduardo Flores ◽  
Anthony Perez ◽  
...  
Keyword(s):  
Intrinsically Disordered Protein ◽  
Disordered Proteins ◽  
Physicochemical Composition ◽  
Intrinsically Disordered ◽  
Structural Preferences ◽  
Live Cell Microscopy ◽  
Sense And Respond ◽  
Intracellular Changes ◽  
Structural Methods

Intrinsically disordered protein regions (IDRs) are ubiquitous in all proteomes and essential to cellular function. Unlike folded domains, IDRs exist in an ensemble of rapidly changing conformations. The sequence-encoded structural biases in IDR ensembles are important for function, but are difficult to resolve. Here, we reveal hidden structural preferences in IDR ensembles in vitro with two orthogonal structural methods (SAXS and FRET), and demonstrate that these structural preferences persist in cells using live cell microscopy. Importantly, we demonstrate that some IDRs have structural preferences that can adaptively respond to even mild intracellular environment changes, while other IDRs may display a remarkable structural resilience. We propose that the ability to sense and respond to changes in cellular physicochemical composition, or to resist such changes, is a sequence-dependent property of IDRs in organisms across all kingdoms of life.

scholarly journals Laminin Polymerization and Inherited Disease: Lessons From Genetics

2021 ◽  
Vol 12 ◽  
Author(s):  
Liam Shaw ◽  
Conor J. Sugden ◽  
Kevin J. Hamill
Keyword(s):  
Point Mutations ◽  
Basement Membranes ◽  
Missense Mutations ◽  
Inherited Disease ◽  
Stem Cell Maintenance ◽  
Physiological Importance ◽  
Membrane Structure And Function ◽  
Assembly Kinetics ◽  
And Function

The laminins (LM) are a family of basement membranes glycoproteins with essential structural roles in supporting epithelia, endothelia, nerves and muscle adhesion, and signaling roles in regulating cell migration, proliferation, stem cell maintenance and differentiation. Laminins are obligate heterotrimers comprised of α, β and γ chains that assemble intracellularly. However, extracellularly these heterotrimers then assemble into higher-order networks via interaction between their laminin N-terminal (LN) domains. In vitro protein studies have identified assembly kinetics and the structural motifs involved in binding of adjacent LN domains. The physiological importance of these interactions has been identified through the study of pathogenic point mutations in LN domains that lead to syndromic disorders presenting with phenotypes dependent on which laminin gene is mutated. Genotype-phenotype comparison between knockout and LN domain missense mutations of the same laminin allows inferences to be drawn about the roles of laminin network assembly in terms of tissue function. In this review, we will discuss these comparisons in terms of laminin disorders, and the therapeutic options that understanding these processes have allowed. We will also discuss recent findings of non-laminin mediators of laminin network assembly and their implications in terms of basement membrane structure and function.

The intracellular hyaluronan receptor RHAMM/IHABP interacts with microtubules and actin filaments

1999 ◽  
Vol 112 (22) ◽  
pp. 3943-3954 ◽  
Author(s):  
V. Assmann ◽  
D. Jenkinson ◽  
J.F. Marshall ◽  
I.R. Hart
Keyword(s):  
Actin Filaments ◽  
Human Cancer ◽  
Cell Surface Receptor ◽  
Dependent Manner ◽  
Interaction Domain ◽  
Microtubule Binding ◽  
Projection Domain ◽  
Hyaluronan Receptor

We reported recently on the intracellular localisation of the hyaluronan receptor RHAMM/IHABP in human cancer cells. Here we describe the colocalisation of RHAMM/IHABP proteins with microtubules, both in interphase and dividing cells, suggesting that RHAMM/IHABP represents a novel member of the family of microtubule-associated proteins (MAPs). We have identified four different splice variants of RHAMM/IHABP, all of which colocalise, at least transiently, with microtubules when expressed as GFP fusion proteins in HeLa cells. Using microtubule-binding assays and transient transfection experiments of deletion-bearing RHAMM/IHABP mutants, we localised the microtubule-binding region to the extreme N terminus of RHAMM/IHABP. This interaction domain is composed of two distinct subdomains, one of which is sufficient to mediate binding to the mitotic spindle while both domains are required for binding of RHAMM/IHABP proteins to interphase microtubules. Sequence analysis revealed that the projection domain of RHAMM/IHABP is predicted to form coiled-coils, implying that RHAMM/IHABP represents a filamentous protein capable of interacting with other proteins and we found that RHAMM/IHABP interacts with actin filaments in vivo and in vitro. Moreover, in vitro translated RHAMM/IHABP isoforms efficiently bind to immobilised calmodulin in a Ca(2+)-dependent manner via a calmodulin-binding site within the projection domain of RHAMM/IHABP (residues 574–602). Taken together, our results strongly suggest that RHAMM/IHABP is a ubiquitously expressed, filamentous protein capable of interacting with microtubules and microfilaments and not, as numerous previous reports suggest, a cell surface receptor for the extracellular matrix component hyaluronan.

scholarly journals Evolutionary Analysis of Rett Syndrome-Causing Proteins and Their Pathogenic Missense Point Mutations: Structural Order–Disorder, Post-Translational Modifications, Evolutionary Rates, and Interacting Proteins

2019 ◽  
Author(s):  
Muhamad Fahmi ◽  
Gen Yasui ◽  
Kaito Seki ◽  
Syouichi Katayama ◽  
Takako Kaneko-Kawano ◽  
...  
Keyword(s):  
Rett Syndrome ◽  
Evolutionary Dynamics ◽  
Point Mutations ◽  
Evolutionary Rates ◽  
Molecular Networks ◽  
Evolutionary Analysis ◽  
Missense Mutations ◽  
Intrinsically Disordered ◽  
Structural Order ◽  
Phylogenetic Profiles

Rett syndrome (RTT) is mainly caused by mutations in methyl CpG-binding protein 2, cyclin-dependent kinase-like 5, or forkhead box protein G1. These RTT-causing proteins harbor an intrinsically disordered region (IDR) whose conformation exhibits spatiotemporal heterogeneity, which not only confer versatility to the protein, but also implicates them in diseases. The IDR generally evolves more rapidly than an ordered structure. In this study, we examined the relationship between pathogenic RTT-associated point mutations in RTT-causing proteins and the evolutionary dynamics of sequence features including structural order–disorder, phosphorylation sites, and evolutionary rates. We also analyzed the molecular properties and evolution of proteins that interact with RTT-causing proteins in terms of phylogenetic profiles, tissue specificity, subcellular localization, expression level, and functions. The results indicate that constrained IDRs may function by forming contacts with other regions in the protein sequence causing pathogenic missense mutations likely to arise in the rapidly evolving IDR and affect molecular networks, leading to disease. The results also provide novel insights into the genetic basis for RTT and the evolution of the neocortex in higher vertebrates.

scholarly journals Coordination of RNA and protein condensation by the P granule protein MEG-3

2020 ◽  
Author(s):  
Helen Schmidt ◽  
Andrea Putnam ◽  
Dominique Rasoloson ◽  
Geraldine Seydoux
Keyword(s):  
Protein Interactions ◽  
Intrinsically Disordered Protein ◽  
Protein Protein Interactions ◽  
C Elegans ◽  
Intrinsically Disordered ◽  
Disordered Protein ◽  
C Terminus ◽  
Necessary And Sufficient

ABSTRACTGerm granules are RNA-protein condensates in germ cells. The mechanisms that drive germ granule assembly are not fully understood. MEG-3 is an intrinsically-disordered protein required for germ (P) granule assembly in C. elegans. MEG-3 forms gel-like condensates on liquid condensates assembled by PGL proteins. MEG-3 is related to the GCNA family and contains an N-terminal disordered region (IDR) and a predicted ordered C-terminus featuring an HMG-like motif (HMGL). Using in vitro and in vivo experiments, we find the MEG-3 C-terminus is necessary and sufficient to build MEG-3/PGL co-condensates independent of RNA. The HMGL domain is required for high affinity MEG-3/PGL binding in vitro and for assembly of MEG-3/PGL co-condensates in vivo. The MEG-3 IDR binds RNA in vitro and is required but not sufficient to recruit RNA to P granules. Our findings suggest that P granule assembly depends in part on protein-protein interactions that drive condensation independent of RNA.

scholarly journals Conserved tau microtubule-binding repeat histidines confer pH-dependent tau-microtubule association

2018 ◽  
Author(s):  
Rabab A. Charafeddine ◽  
Wilian A. Cortopassi ◽  
Parnian Lak ◽  
Matthew P. Jacobson ◽  
Diane L. Barber ◽  
...  
Keyword(s):  
Intracellular Ph ◽  
Electrostatic Interactions ◽  
Cell Model ◽  
Interaction Strength ◽  
Microtubule Binding ◽  
Intrinsically Disordered ◽  
C Terminus ◽  
Decreasing Ph ◽  
Positively Charged

ABSTRACTTau, a member of the MAP2/tau family of microtubule-associated proteins, functions to stabilize and organize axonal microtubules in healthy neurons. In contrast, tau dissociates from microtubules and forms neurotoxic extracellular aggregates in neurodegenerative tauopathies. MAP2/tau family proteins are characterized by three to five conserved, intrinsically disordered repeat regions that mediate electrostatic interactions with the microtubule surface. We use molecular dynamics, microtubule-binding experiments and live cell microscopy to show that highly conserved histidine residues near the C terminus of each MT-binding repeat are pH sensors that can modulate tau-MT interaction strength within the physiological intracellular pH range. At lower pH, these histidines are positively charged and form cation-π interactions with phenylalanine residues in a hydrophobic cleft between adjacent tubulin dimers. At higher pH, tau deprotonation decreases microtubule-binding both in vitro and in cells. However, electrostatic and hydrophobic characteristics of histidine are required for tau-MT-binding as substitution with constitutively positively charged, non-aromatic lysine or uncharged alanine greatly reduces or abolishes tau-MT binding. Consistent with these findings, tau-MT binding is reduced in a cancer cell model with increased intracellular pH but is rapidly rescued by decreasing pH to normal levels. Thus, these data add a new dimension to the intracellular regulation of tau activity and could be relevant in normal and pathological conditions.

Sign in / Sign up

Export Citation Format

Share Document