Biology subjects

Hervas, R.

Publications and source records attributed to Hervas, R..

4 recordsLinked to original sources

bioRxiv2020

Tau amyloidogenesis begins with a loss of its conformational polymorphism

Knowledge on the molecular bases of early amyloid assembly is fundamental to understand its structure-dysfunction relationship during disease progression. Tauopathies, a well-defined set of neurodegenerative disorders that includes Alzheimers disease, are characterized by the pathological amyloid aggregation of tau. However, the underlying molecular mechanisms that trigger tau aggregation and toxicity are poorly understood. Here, using a single-molecule approach, AFM-based single molecule-force spectroscopy (AFM-SMFS), combined with a protein-engineering mechanical protection strategy, we have analyzed the fluctuations of the conformational space of tau during the start of its pathological amyloid assembly. Specifically, we have analyzed the region that includes the four tau microtubule-binding repeats, known to play a key role on tau aggregation. We find that, unlike other amyloid-forming proteins, tau aggregation is accompanied by a decrease of conformational polymorphism, which is driven by amyloid-promoting factors, such as the {Delta}280K and P301L mutations, linked to Frontotemporal Dementia-17, or by specific chemical conditions. Such perturbations have distinct effects and lead to different tau (aggregate) structures. In addition to providing insight into how tau aggregates in a context dependent manner, these findings may help delve into how protein aggregation-based diseases, like Alzheimers, might be treated using monomer fluctuations as a pharmacological target. O_FIG O_LINKSMALLFIG WIDTH=157 HEIGHT=200 SRC="FIGDIR/small/158923v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@951f1borg.highwire.dtl.DTLVardef@2d5f5borg.highwire.dtl.DTLVardef@cf7776org.highwire.dtl.DTLVardef@abe671_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2020

Molecular determinants of liquid demixing and amyloidogenesis in human CPEB3

The cytoplasmic polyadenylation element-binding protein 3 (CPEB3), is an RNA-binding protein which in its soluble state is localized in membraneless neuronal RNA granules keeping target mRNAs in a repressed state. The stimulus-dependent aggregation of CPEB3 activates target mRNAs translation, a central event for the maintenance of long-term memory-related synaptic plasticity in mammals. To date, the molecular determinants that govern both connected events remain unclear. Here, to gain insight into these processes, the biophysical properties of the human CPEB3 (hCPEB3) are characterized. We found that hCPEB3 homotypic condensation is mainly driven by hydrophobic interactions and occurs under physiological conditions. Moreover, hCPEB3 biomolecular condensates are dynamic inside living cells, whose localization and stabilization are mediated by its RNA-recognition domains. In contrast, the hCPEB3 polar N-terminal region is crucial for hCPEB3 amyloid-like aggregation in vitro, which is disrupted by the polyglutamine binding peptide 1 (QBP1), A{beta}42 seeds and Hsp70, highlighting the importance of the Q4RQ4 tract as well as the hydrophobic residues for hCPEB3 functional aggregation. Based on these findings, we postulate a model for hCPEB3s role in memory persistence that advances a rather sophisticated control for hCPEB3 condensate dissociation and amyloid-like formation to achieve its physiological function. HighlightsO_LIhCPEB3 forms toxic intermediates that persist longer than in other functional amyloids. C_LIO_LIRNA-recognition domains stabilize hCPEB3 granule formation and dynamics. C_LIO_LIDifferent segments within hCPEB3 promote amyloidogenesis and liquid demixing. C_LIO_LIhCPEB3 amyloid formation requires both hydrophobic and polyQ segments. C_LI Graphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

neuroscience↗

bioRxiv2020

Divergent CPEB prion-like domains reveal different assembly mechanisms for a generic amyloid-like fold

Functional amyloids are present in a wide variety of organisms ranging from bacteria to humans. Experience-dependent aggregation of the cytoplasmic polyadenylation element-binding (CPEB) prion-like protein to a translationally active state has emerged as a plausible biochemical substrate of long-lasting memories. CPEB aggregation is driven by prion-like domains (PLD) that are highly divergent in sequence across species. Here, we describe the amyloid-like features of the neuronal Aplysia CPEB (ApCPEB) PLD in vitro using single-molecule and bulk biophysical methods and compare them with those previously reported for neuronal Drosophila CPEB, Orb2 PLD. The existence of transient oligomers and mature filaments suggests similarities in the late stages of the assembly pathway for both PLDs. However, while prior to aggregation the Orb2 PLD monomer remains as a random coil in solution, ApCPEB PLD adopts a diversity of conformations comprising -helical structures that evolve to coiled-coil species, suggesting structural differences at the beginning of their amyloid assembly pathways. Our results show how divergent PLDs of CPEB proteins from different species retain the ability to form a generic amyloid-like fold through different assembly mechanisms.

neuroscience↗

bioRxiv2020

Preferred Conformations in the Intrinsically Disordered Region of Human CPEB3 Explain its Role in Memory Consolidation

While implicated in neurodegenerative diseases, amyloids are also essential to some physiological processes, including memory consolidation by neuronal-specific isoforms of the Cytoplasmic Polyadenylation Element Binding (CPEB) protein family. CPEB mediates memory persistence by the formation of self-sustaining amyloid assemblies through its intrinsically disordered region (IDR). Here, we characterize the atomic level conformation and ps-ns dynamics of the 426-residue IDR of human CPEB3 (hCPEB3), which has been associated with episodic memory in humans, by NMR spectroscopy. We found that the first 29 residues: M1QDDLLMDKSKTQPQPQQQQRQQQQPQP29, adopt a helical+disordered motif. Residues 86-93: P83QQPPPP93, and 166-175: P166PPPAPAPQP175 form polyproline II (PPII) helices. While the (VG)5 repeat motif is completely disordered, residues 200-250 adopt three partially populated -helices. Residues 345-355, which comprise the nuclear localization signal (NLS), form a modestly populated -helix and border a phosphoTyr which may mediate STAT5B binding. These findings allow us to suggest a model for nascent hCPEB3 structural transitions at single residue resolution, advancing that amyloid breaker residues, like proline, are a key difference between functional versus pathological amyloids. Besides revealing some aspects of the molecular basis of memory, these findings could aid the future development of treatments for post-traumatic stress disorder. Areas: Biophysics, Structural Biology, Biochemistry & Neurosciences.

biochemistry↗