Biology subjects

Kuropka, B.

Publications and source records attributed to Kuropka, B..

22 records · Page 2Linked to original sources

bioRxiv2020

Antimicrobial peptide induced-stress renders Staphylococcus aureus susceptible to toxic nucleoside analogues

Cationic antimicrobial peptides (AMPs) are active immune effectors of multicellular organisms and also considered as new antimicrobial drug candidates. One of the problems encountered when developing AMPs as drugs is the difficulty to reach sufficient killing concentrations under physiological conditions. Here, using pexiganan, a cationic peptide derived from a host defence peptide of the African clawed frog and the first AMP developed into an antibacterial drug, we studied if sub-lethal effects of AMPs can be harnessed to devise treatment combinations. We studied the pexiganan stress response of Staphylococcus aureus at sub-lethal concentrations using quantitative proteomics. Several proteins involved in nucleotide metabolism were elevated, suggesting a metabolic demand. We then show that S. aureus is highly susceptible to antimetabolite nucleoside analogues when exposed to pexiganan, even at sub-inhibitory concentrations. These findings could be used to enhance pexiganan potency while decreasing the risk of resistance emergence, and our findings can likely be extended to other antimicrobial peptides.

microbiology↗

bioRxiv2019

Positive and negative intra-molecular modulation in a dual-cassette RNA helicase

RNA helicase Brr2 is required for the activation of the spliceosome prior to the first catalytic step of splicing. Brr2 represents a distinct subgroup of Ski2-like nucleic acid helicases whose members comprise tandem helicase cassettes. Only the N-terminal cassette of Brr2 is an active ATPase and can unwind substrate RNAs. The C-terminal cassette represents a pseudo-enzyme that can stimulate RNA-related activities of the N-terminal cassette. However, the molecular mechanisms, by which the C-terminal cassette modulates the activities of the N-terminal unit remain elusive. Here, we show that N- and C-terminal cassettes adopt vastly different relative orientations in a crystal structure of Brr2 in complex with an activating domain of the spliceosomal Prp8 protein as compared to the crystal structure of isolated Brr2. Likewise, the cassettes occupy different relative positions and engage in different inter-cassette contacts during different stages of splicing. Engineered disulfide bridges that lock the cassettes in two different relative orientations have opposite effects on RNA-related activities of the N-terminal cassette compared to the unrestrained protein. Moreover, different relative positioning of the cassettes strongly influences ATP hydrolysis by the N-terminal cassette. Our results demonstrate that the inactive C-terminal cassette of Brr2 can exert both positive and negative influence on the active N-terminal helicase unit from a distance.

biochemistry↗

bioRxiv2019

Eating in a losing cause: anorexia and macronutrient manipulation by a cockroach fails to boost immunity

BackgroundHost-pathogen interactions can lead to dramatic changes in host feeding behaviour. One aspect of this includes self-medication, where infected individuals consume substances such as toxins or alter their macronutrient consumption to enhance immune competence. Another widely adopted animal response to infection is illness-induced anorexia, which is thought to assist host immunity directly or by limiting the nutritional resources available to pathogens. Here, we recorded macronutrient preferences of the global pest cockroach, Blatta orientalis to investigate how shifts in host macronutrient dietary preference and quantity of carbohydrate (C) and protein (P) interact with immunity following bacterial infection. ResultsWe find that B. orientalis avoids diets enriched for P under normal conditions, and that high P diets reduce cockroach survival in the long term. However, following bacterial challenge, cockroaches significantly reduced their overall nutrient intake, particularly of carbohydrates, and increased the relative ratio of protein (P:C) consumed. Surprisingly, these behavioural shifts had a limited effect on cockroach immunity and survival, with minor changes to immune protein abundance and antimicrobial activity between individuals placed on different diets, regardless of infection status. ConclusionsWe show that cockroach feeding behaviour can be modulated by a pathogen, resulting in an illness-induced anorexia-like feeding response and a shift from a C-enriched to a more P:C equal diet. However, our results also indicate that such responses do not provide significant immune protection in B. orientalis, suggesting that the hosts dietary shift might also result from random rather than directed behaviour. The lack of an apparent benefit of the shift in feeding behaviour highlights a possible reduced importance for diet in immune regulation in these invasive animals, although further investigations employing pathogens with alternative infection strategies are warranted.

ecology↗

bioRxiv2018

Intramolecular domain dynamics regulate synaptic MAGUK protein interactions

PSD-95 MAGUK family scaffold proteins are multi-domain organisers of synaptic transmission that contain three PDZ domains followed by an SH3-GK domain tandem. This domain architecture allows coordinated assembly of protein complexes composed of neurotransmitter receptors, synaptic adhesion molecules, cytoskeletal proteins and downstream signalling effectors. Here we show that binding of monomeric PDZ3 ligands to the third PDZ domain of PSD-95 induces functional changes in the intramolecular SH3-GK domain assembly that influence subsequent homotypic and heterotypic complex formation. We identify PSD-95 interactors that differentially bind to the SH3-GK domain tandem depending on its conformational state. Among these interactors we further establish the heterotrimeric G protein subunit Gnb5 as a PSD-95 complex partner at dendritic spines. The PSD-95 GK domain binds to Gnb5 and this interaction is triggered by PDZ3 ligands binding to the third PDZ domain of PSD-95, unraveling a hierarchical binding mechanism of PSD-95 complex formation.

molecular biology↗