Biology subjects

Hansen, L. A.

Publications and source records attributed to Hansen, L. A..

3 recordsLinked to original sources

bioRxiv2024

Negative Charges, Not Necessary Phosphorylation, are Required for Ligand Recognition by 14-3-3 Proteins

Protein-protein interactions involving 14-3-3 proteins regulate various cellular activities in normal and pathological conditions. These interactions have mostly been reported to be phosphorylation-dependent, but the 14-3-3 proteins also interact with unphosphorylated proteins. In this work, we investigated whether phosphorylation is required, or, alternatively, whether negative charges are sufficient for 14-3-3{varepsilon} binding. We substituted the pThr residue of pT(502-510) peptide by residues with varying number of negative charges, and investigated binding of the peptides to 14-3-3{varepsilon} using MD simulations and biophysical methods. We demonstrated that at least one negative charge is required for the peptides to bind 14-3-3{varepsilon} while phosphorylation is not necessary, and that two negative charges are preferable for high affinity binding.

biophysics↗

bioRxiv2024

Commensal-derived short-chain fatty acids disrupt lipid membrane homeostasis in Staphylococcus aureus

The role of commensal anaerobic bacteria in chronic respiratory infections is unclear, yet they can exist in abundances comparable to canonical pathogens in vivo. Their contributions to the metabolic landscape of the host environment may influence pathogen behavior by competing for nutrients and creating inhospitable conditions via toxic metabolites. Here, we reveal a mechanism by which the anaerobe-derived short chain fatty acids (SCFAs) propionate and butyrate negatively affect Staphylococcus aureus physiology by disrupting branched chain fatty acid (BCFA) metabolism. In turn, BCFA impairment results in impaired growth, diminished expression of the agr quorum sensing system, as well as increased sensitivity to membrane-targeting antimicrobials. Altered BCFA metabolism also reduces S. aureus fitness in competition with Pseudomonas aeruginosa, suggesting that airway microbiome composition and the metabolites they produce and exchange directly impact pathogen succession over time. The pleiotropic effects of these SCFAs on S. aureus fitness and their ubiquity as metabolites in animals also suggests that they may be effective as sensitizers to traditional antimicrobial agents when used in combination.

microbiology↗

bioRxiv2023

Optimizing Phosphopeptide Structures That Target 14-3-3ϵ in Cutaneous Squamous Cell Carcinoma

14-3-3{varepsilon} is involved in various types of malignancies by increasing cell proliferation, promoting cell invasion or inhibiting apoptosis. In cutaneous squamous cell carcinoma (cSCC), 14-3-3{varepsilon} is over expressed and mislocalized from the nucleus to the cytoplasm where it interacts with the cell division cycle 25 A (CDC25A) and suppresses apoptosis. Hence inhibition of the 14-3-3{varepsilon} - CDC25A interaction is an attractive target for promoting apoptosis in cSCC. In this work, we optimized the structure of our previously designed inhibitor of 14-3-3{varepsilon} - CDC25A interaction, pT, a phosphopeptide fragment corresponding to one of the two binding regions of CDC25A to 14-3-3{varepsilon}. Starting from pT, we developed peptide analogs that bind 14-3-3{varepsilon} with nanomolar affinities. Peptide analogs were designed by shortening the pT peptide, and introducing modifications at position 510 of the pT(502-510) analog. Both molecular dynamics (MD) simulations and biophysical methods were used to determine peptides binding to 14-3-3{varepsilon}. Shortening the pT peptide from 14 to 9 amino acid residues resulted in a peptide (pT(502-510)) that binds 14-3-3{varepsilon} with a KD value of 45.2 nM. Gly to Phe substitution in position 510 of pT(502-510) led to further improvement in affinity (KD: 22.0 nM) of the peptide for 14-3-3{varepsilon}. Our results suggest that the designed peptide analogs are potential candidates for inhibiting 14-3-3{varepsilon} -CDC25A interactions in cSCC cells; thus, inducing their apoptosis.

biochemistry↗