Biology subjects

Weesner, J. A.

Publications and source records attributed to Weesner, J. A..

4 recordsLinked to original sources

bioRxiv2025

Targeting Lysosomal Dysfunction to Alleviate Plaque Deposition in an Alzheimer Disease Model

Alzheimer disease (AD) is characterized by aberrant amyloid precursor protein (APP) processing and lysosomal dysfunction. This study identifies two members of the lysosomal multi-enzyme complex (LMC), neuraminidase 1 (Neu1) and protective protein/cathepsin A (PPCA), as a critical regulators of APP metabolism. Neu1 deficiency in human AD brains and 5xFAD/Neu1-/- mice leads to sialic acid retention on APP and its secretases, enhancing amyloidogenic cleavage and A{beta}42 production. Additionally, Neu1 deficiency increases lysosomal exocytosis, contributing to extracellular A{beta} release and neuroinflammation. Conversely, overexpression of PPCA in neurons or co-expression of PPCA and NEU1 normalizes sialylation patterns, reduces secretase activity, and mitigates plaque burden. These findings reveal a novel bidirectional dependency between Neu1 and PPCA, underscoring their cooperative role in maintaining lysosomal homeostasis. Additionally, AAV-mediated co-expression of NEU1 and PPCA in 5XFAD brains demonstrates therapeutic potential by reducing amyloid pathology. These findings position lysosomal dysfunction and the Neu1-PPCA axis as promising targets for therapeutic intervention in AD.

neuroscience↗

bioRxiv2024

Neuraminidase 1 regulates the cellular state of microglia by modulating the sialylation of Trem2

Neuraminidase 1 (Neu1) cleaves terminal sialic acids from sialoglycoproteins in endolysosomes and at the plasma membrane. As such, Neu1 regulates immune cells, primarily those of the monocytic lineage. Here we examined how Neu1 influences microglia by modulating the sialylation of full-length Trem2 (Trem2-FL), a multifunctional receptor that regulates microglial survival, phagocytosis, and cytokine production. When Neu1 was deficient/downregulated, Trem2-FL remained sialylated, accumulated intracellularly, and was excessively cleaved into a C-terminal fragment (Trem2-CTF) and an extracellular soluble domain (sTrem2), enhancing their signaling capacities. Sialylated Trem2-FL (Sia-Trem2-FL) did not hinder Trem2-FL-DAP12-Syk complex assembly but impaired signal transduction through Syk, ultimately abolishing Trem2-dependent phagocytosis. Concurrently, Trem2-CTF-DAP12 complexes dampened NF{kappa}B signaling, while sTrem2 propagated Akt-dependent cell survival and NFAT1-mediated production of TNF and CCL3. Because Neu1 and Trem2 are implicated in neurodegenerative/neuroinflammatory diseases, including Alzheimer disease (AD) and sialidosis, modulating Neu1 activity represents a therapeutic approach to broadly regulate microglia-mediated neuroinflammation.

neuroscience↗

bioRxiv2023

AAV-mediated gene therapy for Sialidosis

Sialidosis is a glycoprotein storage disease caused by deficiency of the lysosomal sialidase NEU1, which leads to pathogenic accumulation of sialylated glycoproteins and oligosaccharides in tissues and body fluids. The disease belongs to the group of orphan disorders with no therapy currently available. Here, we have tested the therapeutic potential of AAV-mediated gene therapy for the treatment of sialidosis in a mouse model of the disease. One-month-old Neu1-/- mice were co-injected with two scAAV2/8 vectors, expressing NEU1 and its chaperone PPCA, and sacrificed at 3 months post-injection. Treated mice were phenotypically indistinguishable from their WT controls. Histopathologically, they showed diminished or absent vacuolization in cells of visceral organs, including the kidney, as well as the choroid plexus and other areas of the brain. This was accompanied by restoration of NEU1 activity in most tissues, reversal of sialyl-oligosacchariduria, and normalization of lysosomal exocytosis in the CSF and serum of treated mice. AAV injection prevented the occurrence of generalized fibrosis, which is a prominent contributor of disease pathogenesis in Neu1-/- mice and likely in patients. Overall, this therapeutic strategy holds promise for the treatment of sialidosis and may be applicable to adult forms of human idiopathic fibrosis with low NEU1 expression.

genetics↗

bioRxiv2023

Altered GM1 catabolism affects NMDAR-mediated Ca2+ signaling at ER-PM junctions and increases synaptic spineformation

Endoplasmic reticulum-plasma membrane (ER-PM) junctions mediate Ca2+ flux across neuronal membranes. The properties of these membrane contact sites are defined by their lipid content, but little attention has been given to glycosphingolipids (GSLs). Here, we show that GM1-ganglioside, an abundant GSL in neuronal membranes, is integral to ER-PM junctions; it interacts with synaptic proteins/receptors and regulates Ca2+ signaling. In a model of the neurodegenerative lysosomal storage disease, GM1-gangliosidosis, pathogenic accumulation of GM1 at ER-PM junctions due to {beta}-galactosidase deficiency drastically alters neuronal Ca2+ homeostasis. Mechanistically, we show that GM1 interacts with the phosphorylated NMDAR Ca2+ channel, thereby increasing Ca2+ flux, activating ERK signaling, and increasing the number of synaptic spines without increasing synaptic connectivity. Thus, GM1 clustering at ER-PM junctions alters synaptic plasticity and exacerbates the generalized neuronal cell death characteristic of GM1-gangliosidosis.

neuroscience↗