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Santa-María, Ismael

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Ismael

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Santa-María

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Ciencias Experimentales

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Editorial Special Issue Neuroscience “Tauopathies”.
(Neuroscience, 2023) Ávila, Jesús; Santa-María, Ismael; Sotiropulos, Ioannis
The role of the VQIVYK peptide in tau protein phosphorylation.
(Journal of Neurochemistry, 2007) Perez, Mar; Santa-María, Ismael; Tortosa, Elena; Cuadros, Raquel; Del Valle, Mercedes; Hernandez, Felix; Moreno, Francisco J.; Avila, Jesús
Although it remains unclear whether they are related to one another, tau aggregation and phosphorylation are the main pathological hallmarks of the neuronal disorders known as tauopathies. The capacity to aggregate is impaired in a variant of the tau 3R isoform that lacks residues 306–311 (nomenclature for the largest CNS tau isoform) and hence, we have taken advantage of this feature to study how phosphorylation and aggregation may be related as well as the role of this six amino acid peptide (VQIVYK). Through these analyses, we found that the phosphorylation of the tau variant was higher than that of the complete tau protein and that not only the deletion of these residues, but also the interaction of these residues, in tau 3R, with thioflavin-S augmented tau phosphorylation by glycogen synthase kinase 3. In addition, the binding of the peptide containing the residues 306–311 to the whole tau protein provoked an increase in tau phosphorylation. This observation could be physiologically relevant as may suggest that tau–tau interactions, through those residues, facilitate tau phosphorylation. In summary, our data indicate that deletion of residues VQIVYK, in tau protein produces an increase in tau phosphorylation, without tau aggregation, because the VQIVYK peptide, that favors aggregation, is missing. On the other hand, when the whole tau protein interacts with thioflavin-S or the peptide VQIVYK, an increase in both aggregation and phosphorylation occurs.
Queuosine Formation in Eukaryotic tRNA Occurs via a Mitochondria-localized Heteromeric Transglycosylase.
(Journal of Biological Chemistry, 2009) Boland, Coilin; Hayes, Patti; Santa-María, Ismael; Nishimura, Susumu; Kelly, Vincent P.
tRNA guanine transglycosylase (TGT) enzymes are responsible for the formation of queuosine in the anticodon loop (position 34) of tRNAAsp, tRNAAsn, tRNAHis, and tRNATyr; an almost universal event in eubacterial and eukaryotic species. Despite extensive characterization of the eubacterial TGT the eukaryotic activity has remained undefined. Our search of mouse EST and cDNA data bases identified a homologue of the Escherichia coli TGT and three spliced variants of the queuine tRNA guanine transglycosylase domain containing 1 (QTRTD1) gene. QTRTD1 variant_1 (Qv1) was found to be the predominant adult form. Functional cooperativity of TGT and Qv1 was suggested by their coordinate mRNA expression in Northern blots and from their association in vivo by immunoprecipitation. Neither TGT nor Qv1 alone could complement a tgt mutation in E. coli. However, transglycosylase activity could be obtained when the proteins were combined in vitro. Confocal and immunoblot analysis suggest that TGT weakly interacts with the outer mitochondrial membrane possibly through association with Qv1, which was found to be stably associated with the organelle.
Tridimensional Structural Analysis of Tau Isoforms Generated by Intronic Retention.
(Journal of Alzheimer's Disease Reports, 2023) Domene-Serrano, Indalo; Cuadros, Raquel; Hernández, Félix; Ávila, Jesús; Santa-María, Ismael
Background: Tauopathies are a subset of neurodegenerative diseases characterized by abnormal tau inclusions. Recently, we have discovered a new, human specific, tau isoform termedW-tau that originates by intron 12 retention. Our preliminary data suggests this newly discovered W-tau isoform might prevent aberrant aggregation of other tau isoforms but is significantly downregulated in tauopathies such as Alzheimer´s disease. Objective: To accurately predict, examine, and understand tau protein structure and the conformational basis for the neuroprotective role of W-tau. Methods: A tridimensional deep learning-based approach and in vitro polymerization assay was included to accurately predict, analyze, and understand tau protein structure and the conformational basis for the neuroprotective role of W-tau. Results: Our findings demonstrate: a) the predicted protein tridimensionality structure of the tau isoforms raised by intron retention and their comparison with the other tau isoforms; b) the interaction of W-tau peptide (from W-tau isoform) with other tau isoforms; c) the effect of W-tau peptide in the polymerization of those tau isoforms. Conclusions: This study supports the importance of the structure-function relationship on the neuroprotective behavior of W-tau inhibiting tau fibrillization in vitro.
Binding of Tau Protein to the Ends of ex vivo Paired Helical Filaments.
(Journal of Alzheimer's Disease, 2008) Santa-María, Ismael; Cuadros, Raquel; Moreno, Francisco J.; Muñoz, Victor; Avila, Jesús; Hernandez, Felix
Human recombinant tau can bind to the end of isolated human paired helical filaments (PHF). The sequential binding of tau protein to PHF could result in an elongation of the previously polymerized PHF. However, we have observed that the elongation takes place in a different way on different types of PHF. We have found that there are at least three populations of PHF. For one population, tau protein is able to bind to the ends of the filament and to elongate that filament. In the second PHF population, tau protein binds but does not elongates the filament. In the third, neither tau binding nor elongation was observed.
Mechanisms linking cerebrovascular dysfunction and tauopathy: Adding a layer of epiregulatory complexity.
(British Journal of Pharmacology, 2023) Kim, Yoon A.; Mellen Rodriguez, Marian; Kizil, Caghan; Santa-María, Ismael
Intracellular accumulation of hyperphosphorylated misfolded tau proteins are found in many neurodegenerative tauopathies, including Alzheimer's disease (AD). Tau pathology can impact cerebrovascular physiology and function through multiple mechanisms. In vitro and in vivo studies have shown that alterations in the blood–brain barrier (BBB) integrity and function can result in synaptic abnormalities and neuronal damage. In the present review, we will summarize how tau proteostasis dysregulation contributes to vascular dysfunction and, conversely, we will examine the factors and pathways leading to tau pathological alterations triggered by cerebrovascular dysfunction. Finally, we will highlight the role epigenetic and epitranscriptomic factors play in regulating the integrity of the cerebrovascular system and the progression of tauopathy including a few observartions on potential therapeutic interventions.
Coenzyme Q Induces Tau Aggregation, Tau Filaments, and Hirano Bodies.
(Journal of Neuropathology & Experimental Neurology, 2008) Santa-María, Ismael; Santpere, Gabriel; MacDonald, Michael J.; Gomez de Barreda, Elena; Hernandez, Felix; Moreno, Francisco J.; Ferrer, Isidro; Avila, Jesús
Tau aggregation is a common feature of tauopathies such as Alzheimer disease (AD). In AD, tau assembles into fibrillar polymers; it may also be present in other aberrant aggregates, including Hirano bodies. The mechanisms leading to tau polymer- ization in vivo are not understood. In this study, we found that coenzyme Q (ubiquinone) facilitates tau aggregation after binding to tau molecules at the region of the tau molecule involved in self- assembly. Consequently, after tau-tau interactions, this region is masked in fibrillar tau polymers. Further in vitro studies showed that ubiquinone facilitates the interaction of tau protein with actin to form structures that are morphologically similar to Hirano bodies. Finally, studies in AD brains show that Hirano bodies react with an antibody raised against ubiquinone, indicating that ubiquinone is a component of Hirano bodies. Taken together, the in vitro models and findings in AD suggest that in the presence of ubiquinone, Hirano bodies may result from the interaction of actin and other proteins, including tau.
Retromer deficiency in Tauopathy models enhances the truncation and toxicity of Tau.
(Nature Communications volume, 2022) Asadzadeh, Jamshid; Ruchti, Evelyne; Jiao, Wei; Limoni, Greta; MacLachlan, Catherine; Small, Scott A.; Knott, Graham; Santa-María, Ismael; McCabe, Brian D.
Alteration of the levels, localization or post-translational processing of the microtubule associated protein Tau is associated with many neurodegenerative disorders. Here we develop adult-onset models for human Tau (hTau) toxicity in Drosophila that enable age-dependent quantitative measurement of central nervous system synapse loss and axonal degeneration, in addition to effects upon lifespan, to facilitate evaluation of factors that may contribute to Tau-dependent neurodegeneration. Using these models, we interrogate the interaction of hTau with the retromer complex, an evolutionarily conserved cargo-sorting protein assembly, whose reduced activity has been associated with both Parkinson’s and late onset Alzheimer’s disease. We reveal that reduction of retromer activity induces a potent enhancement of hTau toxicity upon synapse loss, axon retraction and lifespan through a specific increase in the production of a C-terminal truncated isoform of hTau. Our data establish a molecular and subcellular mechanism necessary and sufficient for the depletion of retromer activity to exacerbate Tau-dependent neurodegeneration.
Nerve growth factor receptor (Ngfr) induces neurogenic plasticity by suppressing reactive astroglial Lcn2/Slc22a17 signaling in Alzheimer’s disease.
(Regenerative Medicine, 2023) Siddiqui, Tohid; Ilyas Cosacak, Mehmet; Popova, Stanislava; Santa-María, Ismael; Kizil, Caghan
Neurogenesis, crucial for brain resilience, is reduced in Alzheimer’s disease (AD) that induces astroglial reactivity at the expense of the pro-neurogenic potential, and restoring neurogenesis could counteract neurodegenerative pathology. However, the molecular mechanisms promoting pro-neurogenic astroglial fate despite AD pathology are unknown. In this study, we used APP/PS1dE9 mouse model and induced Nerve growth factor receptor (Ngfr) expression in the hippocampus. Ngfr, which promotes neurogenic fate of astroglia during the amyloid pathology-induced neuroregeneration in zebrafish brain, stimulated proliferative and neurogenic outcomes. Histological analyses of the changes in proliferation and neurogenesis, single-cell transcriptomics, spatial proteomics, and functional knockdown studies showed that the induced expression of Ngfr reduced the reactive astrocyte marker Lipocalin-2 (Lcn2), which we found was sufficient to reduce neurogenesis in astroglia. Anti-neurogenic effects of Lcn2 was mediated by Slc22a17, blockage of which recapitulated the pro-neurogenicity by Ngfr. Long-term Ngfr expression reduced amyloid plaques and Tau phosphorylation. Postmortem human AD hippocampi and 3D human astroglial cultures showed elevated LCN2 levels correlate with reactive gliosis and reduced neurogenesis. Comparing transcriptional changes in mouse, zebrafish, and human AD brains for cell intrinsic differential gene expression and weighted gene co-expression networks revealed common altered downstream effectors of NGFR signaling, such as PFKP, which can enhance proliferation and neurogenesis in vitro when blocked. Our study suggests that the reactive non-neurogenic astroglia in AD can be coaxed to a pro-neurogenic fate and AD pathology can be alleviated with Ngfr. We suggest that enhancing pro-neurogenic astroglial fate may have therapeutic ramifications in AD.
RNA methyltransferase NSun2 deficiency promotes neurodegeneration through epitranscriptomic regulation of tau phosphorylation.
(Acta Neuropathologica, 2022) Kim, Yoon A.; Siddiqui, Tohid; Blaze, Jennifer; Ilyas Cosacak, Mehmet; Winters, Tristan; Kumar, Atul; Tein, Ellen; Sproul, Andrew A.; Teich, Andrew F.; Bartolini, Francesca; Akbarian, Schahram; Kizil, Caghan; Hargus, Gunnar; Santa-María, Ismael
Epitranscriptomic regulation adds a layer of post-transcriptional control to brain function during development and adulthood. The identification of RNA-modifying enzymes has opened the possibility of investigating the role epitranscriptomic changes play in the disease process. NOP2/Sun RNA methyltransferase 2 (NSun2) is one of the few known brain-enriched methyltransferases able to methylate mammalian non-coding RNAs. NSun2 loss of function due to autosomal-recessive mutations has been associated with neurological abnormalities in humans. Here, we show NSun2 is expressed in adult human neurons in the hippocampal formation and prefrontal cortex. Strikingly, we unravel decreased NSun2 protein expression and an increased ratio of pTau/NSun2 in the brains of patients with Alzheimer’s disease (AD) as demonstrated by Western blotting and immunostaining, respectively. In a well-established Drosophila melanogaster model of tau-induced toxicity, reduction of NSun2 exacerbated tau toxicity, while overexpression of NSun2 partially abrogated the toxic effects. Conditional ablation of NSun2 in the mouse brain promoted a decrease in the miR-125b m6A levels and tau hyperphosphorylation. Utilizing human induced pluripotent stem cell (iPSC)-derived neuronal cultures, we confirmed NSun2 deficiency results in tau hyperphosphorylation. We also found that neuronal NSun2 levels decrease in response to amyloid-beta oligomers (AβO). Notably, AβO-induced tau phosphorylation and cell toxicity in human neurons could be rescued by overexpression of NSun2. Altogether, these results indicate that neuronal NSun2 deficiency promotes dysregulation of miR-125b and tau phosphorylation in AD and highlights a novel avenue for therapeutic targeting.