Biology subjects

Almeida, D. L.

Publications and source records attributed to Almeida, D. L..

2 recordsLinked to original sources

bioRxiv2026

The phosphoS655 Alzheimer's Amyloid Precursor Protein (APP) interactome in neuronal differentiation

The Alzheimers Amyloid Precursor Protein (APP) has determinant roles in neuronal development and function, both in its full-length conformation and as some of its proteolytic peptides, particularly secreted (s)APPa. Given that APP phosphorylation tightly regulates its trafficking, proteolysis, and protein-protein binding, it consequently affects several APP functions. The S655 residue, located in the basolateral sorting motif YTSI at APP C-terminus has been observed to be phosphorylated in mature full-length APP and its C-terminal fragments. Previously observed to modify APPs protein interactions, resulting in altered endolysosomal trafficking, andincreased half-life and sAPPa generation, phosphoS655 APP has potential to modulate APP-mediated neuronal differentiation. To study the phosphoS655 differential interactome relevant for neuronal differentiation, SH-SY5Y cells expressing Wt or S655 phosphomutants APP-GFP were differentiated at two time points. APP-GFP and their respective interacting partners were immunoprecipitated using GFP-trap, and interactors identified by mass spectrometry. Both dephospho and phosphoS655 interactomes were generally enriched in similar processes, primarily RNA processing and translation, as well as signal transduction, metabolism, and cytoskeleton remodeling. The smaller phosphoS655 interactome contributes for functional specialization via binding to e.g. FUBP3, ELAVL4, ATXN2, Tubulin, INA. Several of these specific binding partners are known to promote neurite outgrowth and likely underlie our experimental observation that phosphoS655 APP promotes neuritogenesis, particularly the formation of longer neuritic extensions. These results are not only important for the body of knowledge on this Alzheimers disease core protein, but may also aid in future therapies against this disease.

neuroscience↗

bioRxiv2022

ApoE isoforms differentially regulate neuronal membrane proteasomes to shift the threshold for pathological aggregation of endogenous Tau

Neuroproteasomes are a subset of 20S proteasomes that are localized to the neuronal plasma membrane and degrade newly synthesized proteins. To date, the molecular composition of neuroproteasomes is undefined, and moreover, whether neuroproteasomes can influence protein aggregation with relevance to neurodegenerative disorders remains unexplored. Using a Cre-dependent conditional knock-in mouse line to endogenously tag the proteasome, we find that neuroproteasomes co-purify with ApoE, the most significant risk factor for late-onset Alzheimers Disease (AD). We discover that neuroproteasome membrane localization is differentially modulated by ApoE isoforms (E4<E3<E2) in vitro, in vivo, and in human postmortem samples. We synthesized selective, neuroproteasome-specific inhibitors and discovered that neuroproteasome inhibition induces aggregation of endogenous mouse and human Tau, without the need for seeding or pathogenic mutations. Using hApoE-KI/hTau-KI crosses, we find that ApoE isoforms differentially shift the aggregation threshold for Tau. Neuroproteasome inhibition in vivo is sufficient to induce sarkosyl-insoluble and Thioflavin-S positive endogenous Tau aggregates in only three days, which are completely abrogated by co-application of cycloheximide. Newly synthesized Tau levels increase threefold after neuroproteasome inhibition, leading us to posit that newly synthesized Tau is uniquely susceptible to aggregation due to neuroproteasome dysfunction. Overall, our data define neuroproteasomes as a pivotal proteostasis mechanism underlying the formation of endogenous Tau aggregates, which is directly regulated by the largest genetic risk factor for late-onset Alzheimers Disease.

neuroscience↗