Biology subjects

de Marcos Lousa, C.

Publications and source records attributed to de Marcos Lousa, C..

2 recordsLinked to original sources

bioRxiv2026

Structural Basis for Activation of HRI by the DELE1 C-terminal domain

Haem-Regulated Inhibitor (HRI, aka EIF2AK1) is one of four stress-sensing kinases that phosphorylate eIF2 as part of the integrated stress response (ISR). HRI was first characterized as a haem-sensing kinase where it is inhibited when bound to haem. Recent studies have revealed another role for HRI in sensing mitochondrial stress via the mitochondrial protein DELE1. Upon stress, DELE1 is cleaved, and its C-terminal fragment (DELE1CTD) is released from the mitochondria to the cytoplasm, where it interacts with HRI, to trigger the ISR. This pathway is critical for mitochondrial quality control and neuronal health. Here, we perform biophysical analysis to demonstrate that purified recombinant DELE1CTD binds with high affinity to the N-terminal region of HRI, competing with and displacing haem to activate HRI and pointing to a shared binding site. Using Hydrogen Deuterium Exchange Mass Spectrometry (HDX-MS), we map the binding footprint of DELE1CTD on HRI and confirm that it overlaps with the haem-binding site. These findings support a simple activation mechanism: DELE1CTD activates HRI by excluding inhibitory haem from its binding site.

biochemistry↗

bioRxiv2024

The two crystal structures of unloaded and cargo-loaded Vacuolar Sorting Receptor 1 lumenal domain (VSR1-Nt) reveal two cargo binding sites and a mechanism of transport.

Vacuolar sorting receptors (VSRs) are type I membrane proteins crucial for seed germination and plant development. While VSR trafficking has been extensively studied, the mechanism of cargo binding and release by the N-terminal lumenal region is less understood. We have elucidated the crystal structures of unloaded and cargo-loaded forms of the lumenal region of VSR1 containing the protease-associated domain, the Central domain and epidermal growth factor-like repeats. Calcium coordination induces remodeling of the linkers between domains, triggering large conformational changes that expose two binding sites, one across the PA and Central domain and a second site in the Central domain. Our findings provide a mechanistic model for cargo binding in a calcium rich environment, where VSR is locked in a conformation exposing the cargo binding sites, while cargo release is favoured by lower calcium concentrations and trimer formation. These results advance our current knowledge on VSRs and will inform future studies on vacuolar trafficking and cargo binding/release.

plant biology↗