Biology subjects

Di Leva, F. S.

Publications and source records attributed to Di Leva, F. S..

3 recordsLinked to original sources

bioRxiv2026

Sephin1 rewires proteostasis through actin-dependent signaling

The maintenance of protein homeostasis is vital for all cells. Alteration in protein handling underlies several diseases. The small molecule sephin1 is a promising clinical candidate against proteostasis disruption, but its mechanism of action is still uncertain. Our experimental evidence shows that sephin1 binds G-actin and drives actin cytoskeleton misfolding, and eventually, Golgi disintegration. At first, sephin1 impairs the autophagic flux and elicits the phosphorylation of the subunit of eIF2 and the ER-stress independent expression of CHOP via GCN2 kinase. Sephin1 also inhibits the mammalian target of rapamycin (mTORC1), activates the transcription Factor EB (TFEB), drives the expression of TFEB-direct target genes, and eventually stimulates the autophagy lysosomal pathway. Our results reveal that the actin cytoskeleton may regulate autophagy via mTORC1-TFEB complemented with the GCN2-eIF2-CHOP signaling pathway.

cell biology↗

bioRxiv2026

From Structure to Dynamics: Activation Mechanism of the G Protein-Coupled Bile Acid Receptor 1-Gs Complex

The G protein-coupled bile acid receptor 1 (GPBAR1, also known as TGR5) is a key mediator of bile acid signaling, exerting its physiological effects through coupling with the stimulatory G protein (Gs). This interaction is essential for stabilizing the receptors active conformation and triggering downstream signaling. Among endogenous ligands, lithocholic acid (LCA) is the most potent natural agonist. However, the dynamic features underlying its binding and activation mechanisms remain poorly defined. In this study, we investigated the molecular basis of the interaction between LCA and GPBAR1, as well as the functional consequences of this interaction on receptor activation by integrating homology modelling, molecular docking, and molecular dynamics (MD) simulations. Our calculations reveal that LCA binding stabilizes the active state of GPBAR1, biasing the conformational ensemble of TM5 and TM6, as well as the main microswitches. These ligand-induced rearrangements enhance the coupling interface with the 5 helix of Gs and facilitate allosteric communication between the orthosteric and intracellular sites. Overall, our findings provide dynamic insight into how LCA modulates GPBAR1 activation and G protein engagement, highlighting its role as a molecular effector in bile acid signaling, and furnishing molecular detail relevant to ongoing efforts in GPBAR1-targeted compound development.

bioinformatics↗

bioRxiv2025

Ligand-Induced Structural Dynamics Drive Allosteric Regulation of Translation Initiation Factor eIF4E

The eukaryotic initiation factor 4E (eIF4E) governs cap-dependent translation, and its dysregulation contributes both to cancer and neurological disorders, making it an attractive target for therapeutic intervention. Among the few small-molecule inhibitors developed, 4EGI-1 and its analogue i4EG-BiP have shown promise in cellular and preclinical models. These compounds disrupt eIF4Es interaction with its partner eIF4G while enhancing binding to its negative regulators, the 4E-binding proteins (4E-BPs). Despite their chemical similarity and overlapping functional effects, structural data suggest the two ligands engage different regions of eIF4E, lateral for 4EGI-1 and frontal for i4EG-BiP, raising questions about the basis of their shared activity. Here, we integrate molecular simulations, site-directed mutagenesis, and fluorescence binding assays to elucidate the mechanism of action of both ligands. Funnel metadynamics free-energy calculations reveal that the frontal binding mode is thermodynamically preferred for both compounds. Furthermore, we demonstrate that the conformational rearrangement induced by frontal binding selectively promotes 4E-BP1 over eIF4G association, explaining their common allosteric regulatory effect. These findings reconcile divergent structural observations and highlight how ligand-induced dynamics can be exploited to reprogram eIF4E interactions, offering a framework for next-generation therapeutics targeting dysregulated translation.

molecular biology↗