Biology subjects

Mesa, H.

Publications and source records attributed to Mesa, H..

3 recordsLinked to original sources

bioRxiv2025

Synaptic Toxicity of OGA Inhibitors and the Failure of Ceperognastat

O-GlcNAcase inhibitors (OGAi) have been proposed as therapeutics for Alzheimers disease due to their ability to increase O-GlcNAcylation of tau and reduce its aggregation. However, the recent failure of ceperognastat in a Phase II trial--marked by accelerated cognitive decline in the treatment arm--has raised concerns about the safety of this therapeutic class. Here, we evaluated the acute synaptic effects of three structurally distinct OGAi (ceperognastat, ASN90, and MK8719) in mouse hippocampal slices. Electrophysiological recordings revealed that all three compounds impaired both short- and long-term synaptic plasticity, as evidenced by reduced paired-pulse facilitation/depression and suppressed long-term potentiation. Immunohistochemistry showed altered synaptic protein levels, with increased PSD-95 and reduced Synaptophysin 1 in neurons, alongside a biphasic shift in Tau phosphorylation. These findings indicate that OGAi produce rapid and convergent synaptotoxic effects across pre- and postsynaptic compartments, likely reflecting a class-wide mechanism. We argue that electrophysiological screening should be standard in CNS drug development and caution against targeting essential synaptic processes in chronic neurodegenerative conditions.

pharmacology and toxicology↗

bioRxiv2024

Modular Fluorescent Cholesterol Naphthalimide Probes And Their Application For Cholesterol Trafficking Studies In Cells

Development of fluorescent cholesterol analogs to better understand subcellular cholesterol trafficking is of great interest for cell biology and medicine. Our approach utilizes a bifunctional 1,8-naphthalimide scaffold with a push-pull character, modified on one side with a head group and a linker on the other side connecting it to cholesterol via an ester bond. Through structure-function studies, weve explored how different substituents--linkers and head groups--affect the ability of these fluorescent cholesterol naphthalimide analogs (CNDs) to mimic natural cholesterol behavior at both molecular and cellular levels. We categorized the resulting analogs into three groups: neutral, charged, and those featuring a hydroxyl group. Each compound was assessed for its solvatochromic behavior in organic solvents and model membranes. Extensive all-atom molecular dynamics simulations helped us examine how these analogs perform in model membranes compared to cholesterol. Additionally, we investigated the partitioning of these fluorescent probes in phase-separated giant unilamellar vesicles. We evaluated the uptake and distribution of these probes within mouse fibroblast cells and astrocytes, for their subcellular distributions in lysosomes and compared that to BODIPY-cholesterol, a well-regarded fluorescent cholesterol analog. The internalization efficiency of the fluorescent probes varies in different cell types and is affected mainly by the head groups. Our results demonstrate that the modular design significantly simplifies the creation of fluorescent cholesterol probes bearing distinct spectral, biophysical, and cellular targeting features, which makes it a valuable toolkit for the investigation of subcellular distribution and trafficking of cholesterol and its derivatives.

biochemistry↗

bioRxiv2022

Human neurons lacking amyloid precursor protein exhibit cholesterol-associated developmental and presynaptic deficits

Amyloid precursor protein (APP) produces aggregable {beta}-amyloid peptides and its mutations are associated with familial Alzheimers disease, which makes it one of the most studied proteins. However, APPs role in the human brain remains unclear despite years of investigation. One problem is that most studies on APP have been carried out in cell lines or model organisms, which are physiologically different from human neurons in the brain. Recently, human induced neurons (hiNs) derived from induced pluripotent stem cells provide a practical platform for studying the human brain in vitro. Here, we generated APP-null iPSCs using CRISPR/Cas9 genome editing technology and differentiate them to matured human neurons with functional synapses using a two-step procedure. During hiN differentiation and maturation, APP-null cells exhibited less neurite growth and reduced synaptogenesis in serum-free but not serum-containing media. We have found that cholesterol (Chol) remedies those developmental defects in APP-null cells, consistent with Chols role in neurodevelopment and synaptogenesis. Phenotypic rescue was also achieved by co-culturing those cells with wildtype mouse astrocytes, suggesting that APPs developmental role is likely astrocytic. Next, we examined matured hiNs using patch-clamp recording and detected reduced synaptic transmission in APP-null cells. This change was largely due to decreased synaptic vesicle (SV) release and retrieval, which was confirmed by live-cell imaging using two SV-specific fluorescent reporters. Adding Chol shortly before stimulation mitigated the SV deficits in APP-null iNs, indicating that APP facilitates presynaptic membrane Chol turnover during SV exo-/endocytosis cycle. Taken together, our study in hiNs supports the notion that APP contributes to neurodevelopment, synaptogenesis and neurotransmission via maintaining brain Chol homeostasis. Given the vital role of Chol in the central nervous system, the functional connection between APP and Chol bears important implication in the pathogenesis of Alzheimers disease.

neuroscience↗