Ángel Santiago

Evidence is accumulating linking prenatal fluoride exposure with adverse neurodevelopment. Maternal urinary fluoride (MUF) is a well-established biomarker of fluoride exposure. Because most fluoride is stored in calcified tissues, pregnancy-associated changes in bone metabolism may contribute to fetal fluoride exposure. We evaluated whether maternal bone resorption, indexed by urinary N-telopeptide of type I collagen (NTX), is associated with MUF across pregnancy. Participants were drawn from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) birth cohorts. Each woman contributed one paired MUF–NTX measurement per trimester. Both biomarkers were creatinine-normalized to account for urine dilution. Trimester-specific generalized linear models with a Gamma distribution estimated associations between NTX and MUF, adjusting for maternal age, birth order, infant birthweight, and cohort. Across the trimesters, MUF was relatively stable (0.89 ± 0.37, 0.91 ± 0.41, and 0.83 ± 0.42 mg/L), whereas NTX increased with gestation (68.0 ± 33.5, 99.0 ± 50.3, and 132.4 ± 65.4 nmol BCE/mM creatinine). Higher NTX was consistently associated with higher MUF: β = 0.00315 (p < 0.0001) in Trimester 1, β = 0.00207 (p = 0.001) in Trimester 2, and β = 0.00253 (p < 0.0001) in Trimester 3, corresponding to 11%, 11%, and 18% higher MUF per 1-SD increase in NTX. Results were unchanged after adjustment for estimated fluoride intake, with no evidence of non-linearity. Maternal bone resorption was independently associated with MUF, consistent with a skeletal contribution to urinary fluoride. Research may be needed on measures that can blunt bone mobilization of fluoride during pregnancy.

γ-Secretase (GS) is a key therapeutic target in Alzheimer’s disease because it catalyzes amyloid-β production. To reduce toxic amyloid-β species, several γ-secretase modulators (GSMs) have been developed. Among these, GSM-1, a piperidine carboxylic acid-based modulator, has shown potent activity in preclinical studies; however, its binding site and molecular mechanism remain unclear. Here, a molecular dynamics protocol inspired by the Wrap-‘N’-Shake approach was used to investigate how the axial and equatorial conformations of the piperidine nitrogen in GSM-1 interact with GS’s presenilin subunit. Both conformations formed stable interactions with presenilin TM1 and TM5. The carboxylate group established persistent interactions with R220 in TM5, while the trifluoromethylphenyl group engaged residues K76, K80, V87, and L91 in TM1. These findings provide the first model of GSM-1 engagement with GS, identify the key GSM-1 chemical groups involved in recognition, and establish a mechanistic foundation for the rational design of next-generation GSM analogs.

The Gpn1, Gpn2, and Gpn3 proteins are members of the GTPase GPN family; yeast Npa3 is an orthologue of the human Gpn1 protein. These proteins play a crucial role in the nuclear accumulation of RNA polymerase II, functioning as molecular chaperones. The crystallographic structures of Npa3 reveal open and closed conformations, which are dependent on the bound guanine nucleotide (GMPPCP or GDP, respectively). The open conformation of Npa3 exhibits a hydrophobic pocket proposed to be essential for the recognition and binding of specific peptides of RNA polymerase II, contributing to its biogenesis; however, structural data on these complexes remain unavailable. In this work, we present in silico models of the interactions between the crystallographic structure of monomeric Npa3 in its open conformation and yeast RNA polymerase II peptides, generated through flexible computational docking. To identify inhibitors of these interactions, potentially useful in understanding the molecular and cellular functions of these proteins, we performed molecular docking experiments using a designed library of FDA-approved compounds on both the Npa3 structure and a homology model of human Gpn1. Our analysis identified potential inhibitors, including atovaquone for both Npa3 and Gpn1 (docking scores: −14.4 and −13.5 kcal/mol, respectively) and tibolone for Npa3 (−13.6 kcal/mol), following flexible docking optimization. Additionally, our docking models suggest key residues in Npa3 such as F143 and W179, which may be critical for recognizing RNA polymerase II subunits and drug-like molecules. These findings can be further explored through biochemical and mutagenesis studies to assess their roles in RNA polymerase II recognition.

γ-Secretase (GS) is one of the most attractive molecular targets for the treatment of Alzheimer’s disease (AD). Its key role in the final step of amyloid-β peptides generation and its relationship in the cascade of events for disease development have caught the attention of many pharmaceutical groups. Over the past years, different inhibitors and modulators have been evaluated as promising therapeutics against AD. However, despite the great chemical diversity of the reported compounds, a global classification and visual representation of the chemical space for GS inhibitors and modulators remain unavailable. In the present work, we carried out a two-dimensional (2D) chemical space analysis from different classes and subclasses of GS inhibitors and modulators based on their structural similarity. Along with the novel structural information available for GS complexes, our analysis opens the possibility to identify compounds with high molecular similarity, critical to finding new chemical structures through the optimization of existing compounds and relating them with a potential binding site.

We report the synthesis of a new series of γ‐aminobutyric acid (GABA) analogues where the nitrogen at the ɣ‐position is contained in a 1,4‐disubstituted‐1,2,3‐triazole ring system. The triazole ring system was assembled by the Cu(I)‐catalyzed alkyne‐azide 1,3‐dipolar cycloaddition (CuACC) protocol. We have identified two active compounds with 43 and 59 % inhibition respectively. A descriptive quantum QSAR study was carried out to correlate this activity with the structural changes in the GABA scaffold. The inhibitory activity of the compounds is related to the electronic properties of the triazole ring and substituents. The interaction with P. fluorescens GABA‐aminotransferase (GABA‐AT) was evaluated by molecular docking, using a homology model of the biological target. One compound showed the best interaction energy, the thiophene‐ substituted triazole 26 c , with a value that correlates well with the experimental inhibition results. The triazole ring is determinant for a proper orientation for interaction with the GABA‐AT enzyme. In addition, the molecular docking revealed the importance of a hydrophobic pocket near the PLP prosthetic group and how this pocket can be used to improve the inhibitory activity of GABA analogues. Human GABA‐AT molecular docking studies of these analogues showed their great potential as competitive inhibitors of this enzyme.

The TATA-box binding protein (TBP) is an important element of the transcription machinery in archaea and eukaryotic organisms. TBP is expressed in organisms adapted to different temperatures, indicating a robust structure, and experimental studies have shown that the mid-unfolding temperature (Tm) of TBP is directly correlated with the optimal growth temperature (OGT) of the organism. To understand which are the relevant structural requirements for its stability, we present the first structural and dynamic computational study of TBPs, combining molecular dynamics (MD) simulations and a quantitative structure-property relationship (QSPR) over a set of TBPs of organisms adapted to different temperatures. We found that the main structural properties of TBP used to adapt to high temperature are: an increase in the ease of desolvation of charged residues at the surface, an increase in the local resiliency, the presence of Leu clusters in the protein core, and an increase in the loss of hydrophobic packing in the N-terminal subdomain. In view of our results, we consider that TBP is a good model to study thermal adaptation and our analysis opens the possibility of performing protein engineering on TBPs to study transcription at high or low temperatures.

The TATA‐binding protein (TBP) is a central transcription factor in eukaryotes that interacts with a large number of different transcription factors; thus, affecting these interactions will be lethal for any living being. In this work, we present the first structural and dynamic computational study of the surface properties of the TBP DNA‐binding domain for a set of parasites involved in diseases of worldwide interest. The sequence and structural differences of these TBPs, as compared with human TBP, were proposed to select representative ensembles generated from molecular dynamics simulations and to evaluate their druggability by molecular ensemble‐based docking of drug‐like molecules. We found that potential druggable sites correspond to the NC2‐binding site, N‐terminal tail, H2 helix, and the interdomain region, with good selectivity for Plasmodium falciparum, Necator americanus, Entamoeba histolytica, Candida albicans, and Taenia solium TBPs. The best hit compounds share structural similarity among themselves and have predicted dissociation constants ranging from nM to μM. These can be proposed as initial scaffolds for experimental testing and further optimization. In light of the obtained results, we propose TBP as an attractive therapeutic target for treatment of parasitic diseases.

GPN‐loop GTPases 1 and 3 are required for RNA polymerase II (RNAPII) nuclear import. Gpn1 and Gpn3 display some sequence similarity, physically associate, and their protein expression levels are mutually dependent in human cells. We performed here Fluorescence Resonance Energy Transfer (FRET), molecular modeling, and cell biology experiments to understand, and eventually disrupt, human Gpn1–Gpn3 interaction in live HEK293‐AD cells. Transiently expressed EYFP‐Gpn1 and Gpn3‐CFP generated a strong FRET signal, indicative of a very close proximity, in the cytoplasm of HEK293‐AD cells. Molecular modeling of the human Gpn1–Gpn3 heterodimer based on the crystallographic structure of Npa3, the Saccharomyces cerevisiae Gpn1 ortholog, revealed that human Gpn1 and Gpn3 associate through a large interaction surface formed by internal α‐helix 7, insertion 2, and the GPN‐loop from each protein. In site‐directed mutagenesis experiments of interface residues, we identified the W132D and M227D EYFP‐Gpn1 mutants as defective to produce a FRET signal when coexpressed with Gpn3‐CFP. Simultaneous but not individual expression of Gpn1 and Gpn3, with either or both proteins fused to EYFP, retained RNAPII in the cytoplasm and markedly inhibited global transcription in HEK293‐AD cells. Interestingly, the W132D and M227D Gpn1 mutants that showed an impaired ability to interact with Gpn3 by FRET were also unable to delocalize RNAPII in this assay, indicating that an intact Gpn1–Gpn3 interaction is required to display the dominant‐negative effect on endogenous Gpn1/Gpn3 function we described here. Altogether, our results suggest that a Gpn1–Gpn3 strong interaction is critical for their cellular function.