Biology subjects

Scietti, L.

Publications and source records attributed to Scietti, L..

5 recordsLinked to original sources

bioRxiv2026

Targeting GL-Lect driven endocytosis to suppress cell plasticity in breast cancer

Aberrant endocytosis has long been associated with epithelial plasticity and tumorigenesis, but direct in vivo evidence of its causal role in tumor progression and metastasis has been lacking. Here, we identify and molecularly characterize a previously unrecognized form of E-cadherin (ECAD) internalization in mammary epithelial cells. This process is mediated by the endocytic adaptor Epsin 3 (EPN3) through glycolipid-lectin (GL-Lect) driven endocytosis requiring galectin-3 and Eps15-family adaptors. Leveraging an EPN3 knock-in mouse model, we show that dysregulation of GL-Lect driven endocytosis disrupts mammary gland morphogenesis and activates epithelial-to-mesenchymal plasticity (EMP), synergizing with the ERBB2/Neu breast oncogene to drive metastasis. Pharmacologic inhibition of the GL-Lect mechanism suppresses morphogenetic and invasive phenotypes ex vivo, providing proof-of-concept for therapeutic targeting. These findings establish the GL-Lect mechanism as a driver of metastatic plasticity and uncover a tractable vulnerability in BC.

cancer biology↗

bioRxiv2025

Endocytic control of cell-autonomous and non-cell-autonomous functions of p53

NUMB is an endocytic protein with tumor suppressor activity, largely mediated by its ability to inhibit p53 degradation. This function depends on the inclusion of a short alternatively spliced exon (Ex3) in NUMB, although the mechanistic link between endocytosis and p53 regulation remains unclear. Here, we show that the Ex3-encoded sequence directs NUMB to the plasma membrane, where it forms a complex with the endocytic adaptor SNX9. This complex recruits p53 in a SNX9-dependent manner and is internalized and trafficked to multivesicular bodies, culminating in exosomal secretion, in a process requiring both SNX9 and NUMB. Exosomal p53 is taken up by recipient cells and translocated to the nucleus, where it activates p53-dependent transcriptional and phenotypic programs. These findings suggest that exosome-mediated p53 transfer may contribute to the establishment of a tumor-suppressive microenvironment.

cancer biology↗

bioRxiv2024

Molecular Structure and Enzymatic Mechanism of the Human Collagen Hydroxylysine Galactosyltransferase GLT25D1/COLGALT1

During biosynthesis, collagen lysine residues undergo extensive post-translational modifications essential for the stability and functions of collagen supramolecular assemblies. In the endoplasmic reticulum, two distinct metal ion dependent enzyme families (i.e., multifunctional lysyl hydroxylases-glucosyltransferases LH/PLODs and galactosyltransferases GLT25D/COLGALT) alternatively operate on collagen lysine side chains ultimately generating the highly conserved -(1,2)-glucosyl-{beta}-(1,O)-galactosyl-5-hydroxylysine pattern. Malfunctions in the collagen lysine post-translational modification machinery is linked to multiple developmental pathologies as well as extracellular matrix alterations causing enhanced cellular proliferation and invasiveness of several solid tumors, prompting for an in-depth characterization of LH/PLOD and GLT25D/COLGALT enzyme families. Here, we present an integrative molecular study of GLT25D1/COLGALT, highlighting an elongated head-to-head homodimeric assembly characterized by an N-terminal segment of each monomer wrapping around its dimerization partner. Each monomer encompasses two Rossman fold-type domains (GT1 and GT2) separated by an extended linker. Both domains were found capable of binding Mn2+ cofactors and UDP--galactose donor substrates, resulting in four candidate catalytic sites per dimer. Site-directed mutagenesis and biochemical studies identify the C-terminal GT2 domain as the functional GLT25D1/COLGALT1 catalytic site, highlighting an unprecedented Glu-Asp-Asp motif critical for metal ion binding, and suggesting structural roles for the N-terminal GT1 essential for correct quaternary structure assembly. Conversely, dimerization was not a requirement for GLT25D1/COLGALT1 enzymatic activity in vitro, suggesting that the elongated enzyme homodimer assembly, resembling that of LH/PLOD binding partners, could represent a functional hallmark for correct recognition and successful processing of collagen lysine residues.

biochemistry↗

bioRxiv2021

SARS-CoV-2 Spike Affinity and Dynamics Exclude the Strict Requirement of an Intermediate Host

SARS-CoV-2 proximal origin is still unclear, limiting the possibility of foreseeing other spillover events with pandemic potential. Here we propose an evolutionary model based on the thorough dissection of SARS-CoV-2 and RaTG13 - the closest bat relative - spike dynamics, kinetics and binding to ACE2. Our results indicate that both spikes share nearly identical, high affinities for Rhinolophus affinis bat and human ACE2, pointing out to negligible species barriers directly related to receptor binding. Also, SARS-CoV-2 spike shows a higher degree of dynamics and kinetics optimization that favors ACE2 engagement. Therefore, we devise an affinity-independent evolutionary process that likely took place in R. affinis bats and limits the eventual involvement of other animal species in initiating the pandemic to the role of vector.

microbiology↗

bioRxiv2019

A cooperative network of molecular "hot spots" highlights the complexity of LH3 collagen glycosyltransferase activities

Hydroxylysine glycosylations are collagen-specific post-translational modifications essential for maturation and homeostasis of fibrillar as well as non-fibrillar collagen molecules. Lysyl hydroxylase 3 (LH3) is the only human enzyme capable of performing two chemically-distinct collagen glycosyltransferase reactions using the same catalytic site: inverting beta-1,O-galactosylation of hydroxylysines and retaining alpha-1,2-glycosylation of galactosyl hydroxylysines. Here, we used structure-based mutagenesis to show that both glycosyltransferase activities are strongly dependent on a broad cooperative network of amino acid side chains which includes the first-shell environment of the glycosyltransferase catalytic site and shares features with both retaining and inverting enzymes. We identified critical "hot spots" leading to selective loss of inverting activity without affecting the retaining reaction. Finally, we present molecular structures of LH3 in complex with UDP-sugar analogs which provide the first structural templates for LH3 glycosyltransferase inhibitor development. Collectively, our data provide a comprehensive overview of the complex network of shapes, charges and interactions that enable LH3 glycosyltransferase activities, expanding the molecular framework for the manipulation of glycosyltransferase functions in biomedical and biotechnological applications.

biochemistry↗