Biology subjects

Rinaldi, D.

Publications and source records attributed to Rinaldi, D..

5 recordsLinked to original sources

bioRxiv2025

Organelle distribution and protein translation defects in radial glia cells with mutations in Eml1

Cerebral cortical development is a finely regulated process, depending on key neuronal progenitors, giving rise to post-mitotic neurons that migrate to superficial regions in the developing brain. Disruptions can give rise to severe cortical malformations that are associated with intellectual disability and intractable epilepsy. Mutations in EML1/Eml1, coding for a microtubule (MT)-associated protein, lead to subcortical heterotopia (SH) in both humans and mice. In developing mutant mouse brains, ectopic apical radial glia (aRG) progenitors were found outside the normal proliferative ventricular zone (VZ). The normal role of Eml1 in these cells remains to be precisely determined. Using proteomics and imaging approaches, we compared brain tissue from control and mutant mice and identified microtubule and organelle dysregulation. Eml1 influences the trafficking of organelles to different compartments of aRG, where they may be involved in local functions. Thus, we find that mitochondrial and polysome distribution are altered in mutant conditions. Indeed, Eml1 interacts with translational machinery, and an overall downregulation of translation is observed when analysing the translatome of Eml1 mutant aRG. Paradoxically, an upregulation of translation-related mRNAs is also observed. These new data uncover an unprecedented function of Eml1, as well as associating novel subcellular patho-mechanisms with severe heterotopia formation.

neuroscience↗

bioRxiv2025

Translatome and translation dynamics analysis of a RiboCancer cell line panel reveals that leukemia-associated Rps15 mutations rewire translation through codon-specific tRNA accommodation defects.

Deletions and point mutations targeting ribosomal proteins (RPs) have been identified in cancer. Yet, their role in translational dysregulation remains poorly understood. We performed an integrated genome-wide translatome analysis (proteome, Ribo-seq and total RNA-seq) as well as RiboMethSeq on an isogenic cell line library modeling the most recurrent RP defects in cancer (Rpl5+/-, Rpl11+/-, Rpl22+/-, Rpl22-/-, Rpl10 R98S, Rps15 P131S and Rps15 H137Y). RP knock-out had minimal effects on translation, whereas RP point mutations induced a significant number of translation efficiency changes, affecting up to 10% of expressed genes in Rps15 mutants associated with Chronic Lymphocytic Leukemia (CLL). Cryo-electron microscopy and biochemical analyses revealed that the Rps15 mutations destabilize the C-terminal Rps15 domain, affecting the translation elongation cycle dynamics, and deregulating accommodation of aminoacylated tRNAs at the ribosomal A-site. Using Ribo-seq and translation reporter assays, we show that this accommodation defect shows codon specificity, explaining the reduced translation efficiency of genes enriched for these codons in Rps15 mutant cells, such as histones. Notably, genes with reduced translation efficiency in Rps15 mutated cells were enriched for transcriptional regulators such as transcription factor Runx3, resulting in downregulation of Runx3 target genes involved in immune regulation. Altogether, this study provides a comparative map of the translational rewiring driven by the most frequent somatic RP mutations. We provide unprecedented mechanistic insights in the translation defects induced by CLL-associated Rps15 mutations, and reveal an unappreciated cross-talk between translational and transcriptional dysregulation in these RP mutant cells. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=102 SRC="FIGDIR/small/687986v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@cd2846org.highwire.dtl.DTLVardef@10f3c49org.highwire.dtl.DTLVardef@13f1595org.highwire.dtl.DTLVardef@a212df_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

SURF2 is a MDM2 antagonist in triggering the nucleolar stress response

Cancer cells are addicted to strong ribosome production to sustain their proliferation rate. Many chemotherapies impede ribosome production which is perceived by cells as "nucleolar stress" (NS), triggering p53-dependent and independent response pathways leading to cell cycle arrest and/or apoptosis. The 5S RNP particle, a sub-ribosomal particle, is instrumental to NS response. Upon ribosome assembly defects, the 5S RNP accumulate as free form. This free form is able to sequester and inhibit MDM2, thus promoting p53 stabilization. To investigate how cancer cells can resist to NS, we purified free-5S RNP and uncovered a new interaction partner, SURF2. Functional characterization of SURF2 shows that its depletion increases cellular sensitivity to NS, while its overexpression promotes their resistance to it. Consistently, SURF2 expression level negatively correlates with the overall survival in adrenocortical and head and neck squamous cell carcinomas. Our data demonstrate that SURF2 buffers free-5S RNP particles, and can modulate their activity. SURF2 regulates NS responses, and is a key player in both ribosomopathies and oncogenic mechanisms.

cell biology↗

bioRxiv2021

Integrin activation is an essential component of SARS-CoV-2 infection

Cellular entry of coronaviruses depends on binding of the viral spike (S) protein to a specific cellular receptor, the angiotensin-converting enzyme 2 (ACE2). Furthermore, the viral spike protein expresses an RGD motif, suggesting that cell surface integrins may be attachment co-receptors. However, using infectious SARS-CoV-2 requires a biosafety level 3 laboratory (BSL-3), which limits the techniques that can be used to study the mechanism of cell entry. Here, we UV-inactivated SARS-CoV-2 and fluorescently labeled the envelope membrane with octadecyl rhodamine B (R18) to explore the role of integrin activation in mediating both cell entry and productive infection. We used flow cytometry and confocal fluorescence microscopy to show that fluorescently labeled SARS-CoV-2R18 particles engage basal-state integrins. Furthermore, we demonstrate that Mn2+, which activates integrins and induces integrin extension, enhances cell binding and entry of SARS-CoV-2R18 in proportion to the fraction of integrins activated. We also show that one class of integrin antagonist, which binds to the I MIDAS site and stabilizes the inactive, closed conformation, selectively inhibits the engagement of SARS-CoV-2R18 with basal state integrins, but is ineffective against Mn2+-activated integrins. At the same time, RGD-integrin antagonists inhibited SARS-CoV-2R18 binding regardless of integrin activity state. Integrins transmit signals bidirectionally: inside-out signaling primes the ligand binding function of integrins via a talin dependent mechanism and outside-in signaling occurs downstream of integrin binding to macromolecular ligands. Outside-in signaling is mediated by G13 and induces cell spreading, retraction, migration, and proliferation. Using cell-permeable peptide inhibitors of talin, and G13 binding to the cytoplasmic tail of an integrins {beta} subunit, we further demonstrate that talin-mediated signaling is essential for productive infection by SARS-CoV-2.

cell biology↗

bioRxiv2020

The final step of 40S ribosomal subunit maturation is controlled by a dual key lock

Preventing premature interaction of preribosomes with the translation apparatus is essential to translation accuracy. Hence, the final maturation step releasing functional 40S ribosomal subunits, namely processing of the 18S ribosomal RNA 3 end, is safeguarded by protein DIM2, which both interacts with the endoribonuclease NOB1 and masks the rRNA cleavage site. To elucidate the control mechanism that unlocks NOB1 activity, we performed cryo-EM analysis of late human pre-40S particles purified using a catalytically-inactive form of ATPase RIO1. These structures, together with in vivo and in vitro functional analyses, support a model in which ATP-loaded RIO1 cooperates with ribosomal protein RPS26/eS26 to displace DIM2 from the 18S rRNA 3 end, thereby triggering final cleavage by NOB1; release of ADP then leads to RIO1 dissociation from the 40S subunit. This dual key lock mechanism requiring RIO1 and RPS26 guarantees the precise timing of pre-40S particle conversion into translation-competent ribosomal subunits.

molecular biology↗