Biology subjects

Frade, J. M.

Publications and source records attributed to Frade, J. M..

4 recordsLinked to original sources

bioRxiv2024

Neuronal expression of E2F4DN restores adult neurogenesis in homozygous 5xFAD mice via TrkB signaling

The etiology of Alzheimers disease (AD) has been associated with impaired neurogenesis in the adult subventricular zone (SVZ), but the molecular mechanism leading to this impairment remains poorly understood. Neuronal dysfunction in the AD-affected brain might lead to reduced production of neuron-derived paracrine factors acting through receptors necessary for adult SVZ neurogenesis (ASN). To test this hypothesis, we focused on the TrkB receptor, which can transduce signals from the neurotrophins BDNF and NT4/5, since TrkB is known to regulate the ASN process and its function becomes altered in AD. Here we show that ASN is impaired in the SVZ of homozygous 5xFAD (h5xFAD) mice. This impairment is prevented by administering an AAV.PHP.eB vector that expresses in neurons the transcription factor E2F4 carrying the Thr249Ala/Th251Ala mutation (E2F4DN), a gene therapeutic approach previously demonstrated to exert multifactorial effects in this mouse model of AD. The use of culture media conditioned by primary cortical neurons expressing E2F4DN was able to recover the proliferative and differentiative capacity of neural stem cells (NSCs) isolated from h5xFAD mice. This effect was blocked by inhibiting the TrkB receptor. Accordingly, TrkB activation mimicked the effect of the E2F4DN-conditioned medium on the proliferative and differentiative capacity of h5xFAD NSCs, a finding consistent with the upregulation of NT4/5 expression in the E2F4DN-transduced neurons. We conclude that the activation of TrkB by neurotrophins released by E2F4DN-expressing neurons can recover the ASN phenotype in 5xFAD mice. Therefore, the multifactorial therapeutic capacity of E2F4DN includes the recovery of impaired ASN through the upregulation of TrkB signaling in NSCs.

neuroscience↗

bioRxiv2024

Resistance of E2F4DN to p38MAPK phosphorylation attenuates DNA damage-induced neuronal death via Cited2

E2F4 is a transcription factor that supports cellular homeostasis and serves as a substrate for the stress-activated kinase p38MAPK, which phosphorylates it at a conserved Thr248/Thr250 motif. A non-phosphorylatable mutant, E2F4DN (Thr248Ala/Thr250Ala), has shown therapeutic efficacy in a murine model of Alzheimers disease (AD). We hypothesized that phosphorylation of E2F4 disrupts its protective function, whereas E2F4DN retains this activity during cellular stress. To test this hypothesis, we treated N2a-derived neurons with camptothecin (CPT) to induce genotoxic stress. CPT activated p38MAPK within 8 hours, leading to E2F4 phosphorylation at the Thr248/Thr250 site. We then overexpressed E2F4DN or a phosphomimetic variant, E2F4CA (Thr248Glu/Thr250Glu), and assessed apoptosis by procaspase-3 cleavage. E2F1, used as a pro-apoptotic control, strongly induced caspase-3 activation. This effect was partially mimicked by E2F4CA, whereas E2F4DN markedly suppressed caspase-3 cleavage. Notably, E2F4DN but not E2F4CA upregulated the antiapoptotic factor Cited2, and Cited2 knockdown abolished the protective effect of E2F4DN. These findings suggest that p38MAPK-mediated phosphorylation of E2F4 promotes neuronal apoptosis, while E2F4DN maintains homeostatic function via Cited2, offering mechanistic insight into its neuroprotective role in AD.

neuroscience↗

bioRxiv2020

E2F4 as a single multifactorial target against Alzheimer's disease

Alzheimers disease (AD) has a multifactorial etiology, which requires a single multi-target approach for an efficient treatment. We have focused on E2F4, a transcription factor that regulates cell quiescence and tissue homeostasis, controls gene networks affected in AD, and is upregulated in the brain of Alzheimers patients and of APPswe/PS1dE9 and 5xFAD transgenic mice. E2F4 contains an evolutionarily-conserved Thr-motif that, when phosphorylated, modulates its activity, thus constituting a potential target for intervention. Here we show that neuronal expression in 5xFAD mice of a dominant negative form of E2F4 lacking this Thr-motif (E2F4DN) potentiates a transcriptional program consistent with the attenuation of the immune response and global brain homeostasis. This correlates with reduced microgliosis and astrogliosis, modulation of A{beta} proteostasis, and blockade of neuronal tetraploidization. Moreover, E2F4DN prevents cognitive impairment and body weight loss, a known somatic alteration associated with AD. Our finding is relevant for AD, since E2F4 is expressed in cortical neurons from Alzheimer patients in association with Thr-specific phosphorylation, as evidenced by an anti-E2F4/anti-phosphoThr proximity ligation assay. We propose E2F4DN-based gene therapy as a promising multifactorial approach against AD.

pathology↗

bioRxiv2018

Checkpoint signaling abrogation after cell cycle reentry reveals that differentiated neurons are mitotic cells

Mitotic activity associated to neuron cell-death instead of cell-division is reported in neurodegenerative diseases. However, why mitotic activity can take place in supposedly postmitotic neurons and how it is associated to cell-death remains largely unexplained. To address these questions, we have studied the response of primary neurons to oncogenic deregulation using a fusion protein based on truncated Cyclin E and Cdk2. Oncogenic Cyclin E/Cdk2 elicits mitotic checkpoint signaling, resulting in cell-cycle arrest and cell-death. However, as in mitotic cells, checkpoint suppression enables oncogenic cell-cycle progression and neuronal division. Further, neurons actively adapt to the cell-cycle by losing and reforming the axon initial segment, which integrates synaptic inputs to sustain action potentials. We conclude that neurons are mitotic cells in a reversible quiescent-like state, which is falsely portrayed as irreversible by mitotic checkpoints. In extension, neuronal death in lieu of cell-division reflects oncosuppressive checkpoint signaling.

neuroscience↗