Pourhamzeh, M. | bioRxiv Science

bioRxiv2026

Reduced phosphatases and hyperphosphorylated glutamatergic receptors persist from early to late stages of prion disease

Synapse loss occurs early in prion disease, yet the intracellular signaling driving this dysregulation remains poorly understood. Evidence of neuronal hyperactivity was reported in humans with sporadic and familial CJD as well as in the early stages of prion disease in mice (strain 22L). Here we perform a longitudinal study of prion-infected mice (strain RML) and show an increase in the immediate-early gene, Arc, suggesting this is a conserved response to prions. We also observed a persistent decrease in phosphatase abundance (PP1 and PP2B) starting at the earliest timepoint (preclinical) in the cerebral cortex. At this stage, mGluR5 dimers and phosphorylated AMPA receptors were increased. By clinical disease onset, mGluR5 dimers declined, and activity shifted toward NMDA receptor activation, marked by GluN2B hyperphosphorylation. Together, these findings suggest that early phosphatase reduction accompanies neuronal hyperactivity and precedes substantial inflammation. Elucidating the mechanisms driving this early phosphatase loss and its role in neuronal hyperactivity may reveal novel therapeutic targets for prion disease.

neuroscience↗

bioRxiv2026

ESCRT-0 regulates AMPA receptor currents and Ca2+- dependent signaling

Membrane protein trafficking is essential for synaptic growth, maintenance, function, and plasticity, and involves the regulated exocytosis and endocytosis of proteins to and from the pre-and post-synaptic membranes. Defects in the clearance of membrane proteins can lead to the accumulation of ubiquitinated membrane proteins and contribute to neurodegenerative disease. The ESCRT (endosomal sorting complexes required for transport) machinery binds and sorts ubiquitinated membrane proteins into lysosomes for degradation, yet the presence and function of ESCRTs in sorting ubiquitinated AMPA and other receptors at the post-synapse remain unclear. Here we show that the ubiquitin-binding ESCRT-0 protein, Hrs, localizes to both pre- and post-synapses, and levels are modulated by neuronal activity, increasing and decreasing with higher and lower neuronal activity, respectively. Phosphoproteomic profiling of Hrs-depleted post-synaptic membranes revealed a role for Hrs in glutamatergic synaptic transmission, including long-term potentiation. In addition, Hrs-depleted neurons showed faster AMPAR current kinetics and reduced amplitude in whole-cell patch-clamp recordings. Genetic deletion of neuronal Hgs in mice led to reductions in phosphorylated CaMKII- and -{beta} (T286/T287) and structural proteins, PSD-95 and gephyrin, suggestive of LTD (long-term depression)-like synaptic depression. In contrast, Hrs overexpression led to increases in Ca2+-dependent signaling, including protein kinase C (PKC) and PKC substrate, AMPAR subunit GluA1-S831, a site which increases conductance. Together, these findings identify a dynamic, bidirectional role for Hrs at the post-synapse as it both senses and is modulated by neuronal activity, ultimately impacting excitatory synaptic strength. Significance StatementSynaptic plasticity relies on dynamic trafficking and turnover of membrane proteins, including AMPA-type glutamate receptors (AMPARs), yet how receptor trafficking intersects with ubiquitin-mediated sorting pathways at synapses remains unclear. We show that the ubiquitin-binding ESCRT-0 protein, Hrs, localizes to both pre- and post-synapses, and its abundance is bidirectionally regulated by neuronal activity. Genetic depletion of Hrs in mice reduces CaMKII phosphorylation and impacts AMPAR channel surface localization. In contrast, neuronal-specific Hrs overexpression led to enhanced GluA1 and protein kinase C substrate phosphorylation, suggesting altered AMPAR trafficking, subunit composition, and/or function. Thus, Hrs emerges as a modulator of glutamatergic signaling, coupling ubiquitin-mediated receptor sorting to the fine-tuning of synaptic transmission, with direct implications for learning and memory in health and disease.

neuroscience↗