Biology subjects

Vieira, S. I.

Publications and source records attributed to Vieira, S. I..

3 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↗

bioRxiv2023

Unexpected Kif4a functions in adult regeneration encompass a dual role in neurons and in proliferative repair Schwann cells.

Contrary to the adult central nervous system (CNS), the peripheral nervous system (PNS) has an intrinsic ability to regenerate that, among others, passes by expressing regeneration-associated genes such as kinesin family members. We here show that Kinesin family motor protein 4a (KIF4A), associated to neurodevelopmental disorders and thought for long to be only embryonically expressed, is highly abundant in axons and Schwann cells of adult rat CNS and rat and human PNS. Moreover, Kif4a is up-regulated in injured PNS neurons, being detected in their nuclei and regrowing axons, consistent with its functions as a chromokinesin and in the axonal transport of e.g. {beta}1-integrin and L1CAM. Interestingly, Kif4a is also highly up-regulated in Schwann cells transdifferentiating into a proliferative repair phenotype at the injured distal nerve stumps. A role for Kif4a in cultured Schwann cells proliferation was confirmed, with Kif4a mRNA expression being [~]6-fold higher in proliferating versus growth-arrested Schwann cells, and Kif4a knockdown impairing Schwann cells proliferation. To our knowledge, this is the first description of KIF4A expression in adult nervous systems, up-regulation in neuroregeneration and pro-neuroregenerative roles, including promoting Schwann cells proliferation. KIF4A dual role in axonal regeneration, through neurons and glia, places as an attractive target for future neuroregeneration therapies.

neuroscience↗

bioRxiv2020

APP binds to the EGFR ligands HB-EGF and EGF, acting synergistically with EGF to promote ERK signaling and neuritogenesis

The amyloid precursor protein (APP) is a transmembrane glycoprotein central to Alzheimers disease (AD) with functions in brain development and plasticity, including in neurogenesis and neurite outgrowth. Epidermal growth factor (EGF) and heparin-binding EGF-like growth factor (HB-EGF) are well described neurotrophic and neuromodulator EGFR ligands, both implicated in neurological disorders like Schizophrenia and AD. Here we show that APP interacts with these two EGFR ligands and characterize the effects of APP-EGF interaction in ERK activation and neuritogenesis. HB-EGF was identified as a novel APP interactor in a yeast two-hybrid screen of a human brain cDNA library. Yeast co-transformation and co-immunoprecipitation assays confirmed APP interaction with HB-EGF. Moreover, co-immunoprecipitation also revealed that APP binds to cellular pro-EGF. Overexpression of HB-EGF in HeLa cells, or exposure of SH-SY5Y cells to EGF, both resulted in increased APP protein levels. EGF and APP were also observed to synergistically activate the ERK signaling pathway, crucial for early neuronal differentiation. Immunofluorescence analysis of cellular neuritogenesis in conditions of APP overexpression and EGF exposure, confirmed a synergistic effect in promoting the number and the mean length of neurite-like processes per cell. Synergistic ERK activation and neuritogenic effects were completely blocked by the EGFR inhibitor PD 168393, implying EGF-induced activation of EGFR as part of the mechanism. This work shows novel APP protein interactors and provides a major insight into the APP-driven mechanisms underlying neurite outgrowth and neuronal differentiation, with potential relevance for AD and for adult neuroregeneration.

neuroscience↗