Biology subjects

Briza, P.

Publications and source records attributed to Briza, P..

3 recordsLinked to original sources

bioRxiv2025

Conformational and Functional Regulation of SET by Legumain Cleavage

The cysteine protease legumain typically localizes to the endolysosomal system, where it is an important player in the immune system. However, in the context of Alzheimers disease (AD), legumain has been shown to be translocated to the cytosol, where it cleaves SET, synonymously termed TAF-1 or I2PP2A, an inhibitor of protein phosphatase 2A. SET is primarily found in the nucleus, where it regulates gene transcription, cell cycle progression, and histone acetylation, but can also translocate to the cytoplasm where it regulates cell migration and is implicated in neuronal apoptosis in AD. In this study, we demonstrate that legumain cleaves SET at two major sites: Asn16 at the N-terminal end and Asn175 at the earmuff domain. Contrary to previous findings, our biochemical and crystallographic experiments reveal that the corresponding N- and C-terminal cleavage products remain bound in a stable complex, rather than dissociating. Additionally, we show that the C-terminal acidic stretch of SET is essential for its binding to histone 1, and that cleavage impairs this interaction. Finally, we demonstrate that SET positively modulates PP2A activity. This effect is however abolished upon cleavage by legumain.

molecular biology↗

bioRxiv2023

Phytocystatin 6 is a context-dependent, tight-binding inhibitor of Arabidopsis thaliana legumain isoform β

Plant legumains are crucial for processing seed storage proteins and are critical regulators of plant programmed cell death. Although research on legumains boosted recently, little is known about their activity regulation. In our study, we used pull-down experiments to identify AtCYT6 as a natural inhibitor of legumain isoform {beta} (AtLEG{beta}) in Arabidopsis thaliana. Biochemical analysis revealed that AtCYT6 inhibits both AtLEG{beta} and papain-like cysteine proteases through two cystatin domains. The N-terminal domain inhibits papain-like proteases, while the C-terminal domain inhibits AtLEG{beta}. Furthermore, we showed that AtCYT6 interacts with legumain in a substrate-like manner, facilitated by a conserved asparagine residue in its reactive center loop. Complex formation was additionally stabilized by charged exosite interactions, contributing to pH-dependent inhibition. Processing of AtCYT6 by AtLEG{beta} suggests a context-specific regulatory mechanism with implications for plant physiology, development, and programmed cell death. These findings enhance our understanding of AtLEG{beta} regulation and its broader physiological significance.

biochemistry↗

bioRxiv2020

Effect of structural stability on endolysosomal degradation and T-cell reactivity of major shrimp allergen tropomyosin

BackgroundTropomyosins are highly conserved proteins, an attribute that forms the molecular basis for their IgE antibody cross-reactivity. Despite structural similarities, their allergenicity varies greatly between ingested and inhaled invertebrate sources. In this study, we investigated the relationship between the structural stability of different tropomyosins, their endolysosomal degradation patterns and T-cell reactivity. MethodsWe investigated the differences between four tropomyosins - the major shrimp allergen Pen m 1 and the minor allergens Der p 10 (dust mite), Bla g 7 (cockroach) and Ani s 3 (fish parasite) - in terms of IgE binding, structural stability, endolysosomal degradation and subsequent peptide generation, and T-cell cross-reactivity in a BALB/c murine model. ResultsDespite their conserved primary structure and consequent IgE co-reactivity, the invertebrate tropomyosins displayed different protein stabilities. Pen m 1 and Ani s 3, but not Der p 10 and Bla g 7 elicited differential melting temperatures that were pH-dependent. Endolysosomal experiments demonstrated differential degradation, as a function of stability, generating different peptide repertoires. Pen m 1 T-cell clones, with specificity for sequences highly conserved in all four tropomyosins, did not proliferate with Der p 10, Bla g 7 and Ani s 3, indicating that these peptides were not naturally produced for other invertebrate tropomyosins. ConclusionsOur data suggest that, although invertebrate tropomyosins exhibit a high degree of IgE cross-reactivity due to conserved B-cell epitopes, they do not necessarily share identical cross-reactive T-cell epitopes. This is likely due to differential endolysosomal processing as a function of different structural stabilities.

immunology↗