Biology subjects

Alvarez-Castelao, B.

Publications and source records attributed to Alvarez-Castelao, B..

4 recordsLinked to original sources

bioRxiv2025

The proteasome maturation factor POMP moonlights as a stress-induced transcriptional regulator

Proteostasis - the maintenance of proteins at proper concentrations, conformations, and subcellular locations - is essential for cellular function and is governed by tightly regulated protein synthesis and degradation pathways. The Proteasome Maturation Protein (POMP) is a key chaperone involved in assembling the proteasome, the primary complex responsible for protein degradation. Despite the conserved role of POMP, its loss produces contrasting proteostatic effects in yeast and mammalian cells, pointing to additional, unexplored functions. In this study, we investigated the possibility that POMP plays a moonlighting role in proteostasis regulation. We discovered that upon proteasome disruption, POMP rapidly accumulates in the nucleolus in a manner dependent on HSF1 and reactive oxygen species (ROS). Proteomic analysis of POMP interactors revealed RNA processing factors and transcriptomic profiling showed that nucleolar POMP orchestrates a protective transcriptional program. Our findings indicate POMP is a built-in sensor and effector within the proteasome assembly pathway, capable of buffering disturbances in proteasome function through a novel, non-canonical role. Notably, this mechanism is developmentally controlled and active in neurodegenerative disease contexts. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=163 SRC="FIGDIR/small/650603v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@196cd2borg.highwire.dtl.DTLVardef@177d240org.highwire.dtl.DTLVardef@18c9bcborg.highwire.dtl.DTLVardef@483b94_HPS_FORMAT_FIGEXP M_FIG C_FIG

biochemistry↗

bioRxiv2024

Cell type-Specific In Vivo Proteomes with a Multi-copy Mutant Methionyl t-RNA Synthetase Mouse Line

The functional diversity of cells is driven by the different proteins they express. While improvements in protein labeling techniques have allowed for the measurement of proteomes with increased sensitivity, measuring cell type-specific proteomes in vivo remains challenging. One of the most useful pipelines is bioorthogonal non-canonical amino acid tagging (BONCAT) with the MetRS* system, consisting of a transgenic mouse line expressing a mutant methionyl-tRNA synthetase (MetRS*) controlled by Cre recombinase expression. This system allows for cell type-specific labeling of proteins with a non-canonical amino acid (azidonorleucine, ANL), which can be subsequently conjugated to affinity or fluorescent tags using click chemistry. Click-modified proteins can then be visualized, purified and identified. The reduction in sample complexity allows for the detection of small changes in protein composition. Here we describe a multicopy MetRS* mouse line (3xMetRS* mouse line), which exhibits markedly enhanced ANL protein labeling, boosting the sensitivity and temporal resolution of the system and eliminating the need for working under methionine depletion conditions. Cell type-specific in vivo labeling is possible even in heterozygous animals, thus offering an enormous advantage for crossing the line into mutation and disease-specific backgrounds. Using the 3xMetRS* line we identified the in vivo proteome of a sparse cell population - the dopaminergic neurons of the olfactory bulb and furthermore determined newly synthesized proteins after short labeling durations following a single intraperitoneal ANL injection.

cell biology↗

bioRxiv2023

Trazodone rescues dysregulated synaptic and mitochondrial nascent translatomes in neurodegeneration

The unfolded protein response (UPR) is rapidly gaining momentum as a therapeutic target for protein misfolding neurodegenerative diseases, in which its overactivation results in sustained translational repression leading to synapse loss and neurodegeneration. In mouse models of these disorders, from Alzheimers to prion disease, modulation of the pathway - including by the licensed drug, trazodone - restores global protein synthesis rates with profound neuroprotective effects. However, the precise nature of the translational impairment, in particular the specific proteins affected in disease, and their response to therapeutic UPR modulation are poorly understood. We used non-canonical amino acid tagging (NCAT) to measure de novo protein synthesis in the brains of prion-diseased mice with and without trazodone treatment, in both whole hippocampus and cell-specifically. During disease the predominant translatome changes occur in synaptic, cytoskeletal and mitochondrial proteins in both hippocampal neurons and astrocytes. Remarkably, trazodone treatment for just two weeks largely restored the whole disease translatome in the hippocampus to that of healthy, uninfected mice, predominantly with recovery of proteins involved in synaptic and mitochondrial function. In parallel, trazodone treatment restored the disease-associated decline in synapses and mitochondria and their function to wildtype levels. In conclusion, this study increases our understanding of how translational repression contributes to neurodegeneration through synaptic and mitochondrial toxicity via depletion of key proteins essential for their function. Further, it provides new insights into the neuroprotective mechanisms of trazodone through reversal of this toxicity, relevant for the treatment of neurodegenerative diseases via translational modulation.

neuroscience↗

bioRxiv2019

Neuronal Proteostasis is mediated by the switch-like expression of Heme-regulated Kinase 1, acting as both a sensor and effector

All cells, including neurons, have regulatory feedback mechanisms that couple protein synthesis and degradation to maintain and optimize protein concentrations in the face of intra- and extracellular perturbations. We examined the feedback between the major protein degradation pathway, the ubiquitin-proteasome system (UPS), and protein synthesis in neurons. When protein degradation by the UPS was inhibited we observed a coordinate dramatic reduction in nascent protein synthesis in both neuronal cell bodies and dendrites. The mechanism for translation inhibition involved the phosphorylation of eIF2a, surprisingly mediated by eIF2a kinase 1, or heme-regulated kinase inhibitor (HRI), known for its sensitivity to heme levels in erythrocyte precursors (Han et al., 2001). Under basal conditions, neuronal expression of HRI is barely detectable. Following proteasome inhibition, HRI protein levels increase owing to stabilization of the short-lived HRI protein and enhanced translation via the increased availability of tRNAs for rare codons. Once expressed, HRI is constitutively active in neurons because endogenous heme levels are so low; HRI activity results in eIF2a phosphorylation and the resulting inhibition of translation. These data demonstrate a novel role for HRI in neurons, acting as an \"immediate early protein\" that senses and responds to compromised function of the proteasome to restore proteostasis.\n\nOne sentence summaryProteasome inhibition leads to a compensatory reduction in neuronal protein synthesis via the stabilization and enhanced translation of short-lived HRI kinase, which is constitutively active upon expression owing to low neuronal heme levels.

neuroscience↗