Biology subjects

Vargas, C.

Publications and source records attributed to Vargas, C..

4 recordsLinked to original sources

bioRxiv2023

Effects of Polyphosphate metabolism Mutations on Biofilm, Capsule Formation and Virulence Traits in Hypervirulent ST23 Klebsiella pneumoniae SGH10

The emergence of hypervirulent Klebsiella pneumoniae (hvKP) strains poses a significant threat to public health due to their high mortality rates and propensity to cause severe community-acquired infections in otherwise healthy individuals. The ability of hvKP to form biofilms and produce a protective capsule contributes to its enhanced virulence and is a significant challenge to effective antibiotic treatment. Therefore, understanding the molecular mechanisms underlying hvKP virulence and biofilm formation is crucial for developing new therapeutic strategies. Polyphosphate Kinase 1 (PPK1) is an enzyme responsible for inorganic polyphosphate synthesis and plays a vital role in regulating various physiological processes in bacteria. In this study, we investigated the impact of polyP metabolism on the biofilm and capsule formation and virulence traits in hvKP using Dictyostelium discoideum amoeba as a model host. We found that the PPK1 null-mutant was impaired in biofilm and capsule formation and showed attenuated virulence in D. discoideum compared to the wild-type strain. We performed a shotgun proteomic analysis of the PPK1 mutant and wild-type strain to gain further insight into the underlying molecular mechanism. The results revealed that the PPK1 mutant had a differential expression of proteins (DEP) involved in capsule synthesis (Wzi - Ugd), biofilm formation (MrkC-D-H), synthesis of the colibactin genotoxin precursor (ClbB), as well as proteins associated with the synthesis and modification of lipid A (ArnB -LpxC - PagP). These proteomic findings corroborate the phenotypic observations and indicate that the PPK1 mutation is associated with impaired biofilm and capsule formation and attenuated virulence in hypervirulent K. pneumoniae. Overall, our study highlights the importance of polyP synthesis in regulating extracellular biomolecules and virulence in K. pneumoniae and provides insights into potential therapeutic targets for treating K. pneumoniae infections.

microbiology↗

bioRxiv2023

The intrinsically disordered region of the E3 ubiquitin ligase TRIP12 induces the formation of chromatin condensates and interferes with DNA damage response.

Chromatin compaction is crucial for the faithful expression and integrity of the genome. Although largely studied, proteins and mechanisms that control the chromatin compaction are not entirely discovered. We previously showed that the nuclear HECT-type E3 ubiquitin ligase Thyroid hormone Receptor Interacting Protein 12 (TRIP12) is tightly associated to chromatin. As TRIP12 is overexpressed in several types of cancers, we explored herein the consequences of a TRIP12 overexpression on chromatin homeostasis. First, we established the TRIP12 proxisome and unveiled its pleiotropic role in chromatin regulation. Second, we demonstrated that TRIP12 overexpression leads to the formation of chromatin condensates enriched in heterochromatin marks via its intrinsically disordered region (IDR). We further discovered that the formation of TRIP12-mediated chromatin condensates is highly dynamic and driven by a mechanism of phase separation. Chromatin condensate formation depends on the TRIP12 concentration, the length of the TRIP12-IDR and relies on electrostatic interactions. We found that the formation of TRIP12 mediated-condensates alters cell cycle progression, genome accessibility, transcription as well as DNA damage response by inhibiting the accumulation of Mediator of DNA Damage Checkpoint 1 (MDC1). Altogether, this study reveals a novel dynamic role for TRIP12 in chromatin compaction independently of its ubiquitin ligase activity with important consequences on cellular homeostasis. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/556486v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@13b3d90org.highwire.dtl.DTLVardef@46b991org.highwire.dtl.DTLVardef@1410bdeorg.highwire.dtl.DTLVardef@1722197_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

The Loss of the E3 ubiquitin ligase TRIP12 inhibits Pancreatic Acinar Cell Plasticity and Tumor Cell Metastatic Capacity

Background & AimsAlthough specialized and dedicated to the production of digestive enzymes, pancreatic acinar cells harbor a high plasticity and are able to modify their identity. They undergo reversible acinar-to-ductal cell metaplasia (ADM) through epigenetic silencing of the acinar lineage gene program mainly controlled by PTF1a (Pancreas Transcription Factor 1a). ADM becomes irreversible in the presence of oncogenic Kras mutations and leads to the formation of preneoplastic lesions. We investigated the role of the E3 ubiquitin ligase Thyroid hormone Receptor Interacting Protein 12 (TRIP12), involved in PTF1a degradation, in pancreatic carcinogenesis. MethodsWe used genetically engineered mouse models of pancreas-selective Trip12 deletion, mutant Kras (G12D) and mutant Trp53 (R172H). We performed RNA sequencing analysis from acinar cells and cell lines derived from mice models tumors. We investigated the impact of TRIP12 deficiency on acute pancreatitis, tumor formation and metastasis development. ResultsTRIP12 is overexpressed in human pancreatic preneoplastic lesions and tumors. We show that a conditional deletion of TRIP12 in the pancreas during murine embryogenesis alters pancreas homeostasis and acinar cell genes expression patterns in adults. EGF induced-ADM is suppressed in TRIP12-depleted pancreatic acini. In vivo, a loss of TRIP12 prevents acini to develop ADM in response to pancreatic injury, the formation of Kras-induced pancreatic preneoplastic lesions, and impairs tumors and metastasis formation in the presence of mutated Trp53. TRIP12 is required for Claudin18.2 isoform expression in pancreatic tumors cells. ConclusionsOur study identifies TRIP12 as a novel regulator of acinar fate in the adult pancreas with an important dual role in pancreatic carcinogenesis, in initiation steps and in metastatic behavior of tumor cells. SynopsisThis study shows that Thyroid hormone Receptor Interacting Protein 12 plays an important dual role in the initiation steps and invasion of pancreatic carcinogenesis. Moreover, expression of TRIP12 switches on the expression of Claudin-18, a targetable biomarker of pancreatic tumors.

cancer biology↗

bioRxiv2021

A Bioinspired Glycopolymer for Capturing Membrane Proteins in Native-Like Lipid-Bilayer Nanodiscs

Amphiphilic copolymers that directly extract membrane proteins and lipids from cellular membranes to form nanodiscs combine the advantages of harsher membrane mimics with those of a native-like membrane environment. Among the few commercial polymers that are capable of forming nanodiscs, alternating diisobutylene/maleic acid (DIBMA) copolymers have gained considerable popularity as gentle and UV-transparent alternatives to aromatic polymers. However, their moderate hydrophobicities and high electric charge densities render all existing aliphatic copolymers rather inefficient under near-physiological conditions. Here, we introduce Glyco-DIBMA, a bioinspired glycopolymer that possesses increased hydrophobicity and reduced charge density but nevertheless retains excellent solubility in aqueous solutions. Glyco-DIBMA outperforms established aliphatic copolymers in that it solubilizes lipid vesicles of various compositions much more efficiently, thereby furnishing smaller, more narrowly distributed nanodiscs that preserve a bilayer architecture and exhibit rapid lipid exchange. We demonstrate the superior performance of Glyco-DIBMA in preparative and analytical applications by extracting a broad range of integral membrane proteins from cellular membranes and further by purifying a membrane-embedded voltage-gated K+ channel, which was fluorescently labeled and analyzed with the aid of microfluidic diffusional sizing (MDS) directly within native-like lipid-bilayer nano-discs.

biochemistry↗