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Berka, K.

Publications and source records attributed to Berka, K..

8 recordsLinked to original sources

Mapping pathogenic patterns in membrane transporters from the GLUT transporter family

Significance Missense mutations can lead to pathological effects in human cells. Predictive methods that account for structural context, such as AlphaMissense, can provide pathogenicity scores. The accumulation of pathogenicity hotspots can reveal important structural features within individual proteins of protein families, such as GLUT transporters. Mapping pathogenicity scores onto the structure can thus provide a mechanistic explanation of the protein function necessary for its role in the cell. Abstract Non-synonymous amino acid substitutions (missense mutations) are common in the general population; some are causative of serious disease. Depending on their structural context, they can disrupt protein function, folding, or dynamics. Computational predictive methods developed in recent years, such as AlphaMissense, provide new insights into how missense mutations affect protein structure by predicting and mapping their pathogenicity across each amino acid in the human proteome. In this study, we identify recurring patterns of pathogenicity prediction across the GLUT family membrane transporters encoded by genes SLC2A1-14. Within the GLUT transporter family, we observe higher pathogenicity profiles in the transmembrane domains, particularly in pore-lining and binding-site residues. Predicted missense pathogenicity is elevated throughout residues assigned to the central cavity, suggesting sensitivity of the transport pathway. Another finding shows higher pathogenicity in specific transmembrane helices of the protein, with the same pattern across all proteins. On the other hand, we observed lower pathogenicity values in some representatives of the GLUT family. We validated these predictions against clinically observed missense variants from ClinVar and benchmarked three prediction methods. AlphaMissense showed the strongest concordance with clinical classifications (AUC = 0.88), and the structural distribution of clinically reported pathogenic variants broadly recapitulated the predicted pathogenicity landscape. On the other hand, we observed lower pathogenicity values in some representatives of the GLUT family, and in select cases, clinical and predicted data diverged, suggesting more localized functional constraint than genome-wide prediction alone would indicate. These findings show that the pathogenicity of glucose transport within the GLUT family may be shaped by functional redundancy and physiological essentiality across GLUT groups, supported by convergent evidence from structural, computational, and clinical variant data.

bioinformatics↗

AlphaFind v2: Similarity Search in AlphaFold DB and TED Domains across Structural Contexts

The availability of large-scale protein structure collections enables structure-based analysis of their function and evolution beyond what is possible from sequence alone. However, applying three-dimensional structure comparison at scale remains computationally demanding and limits practical exploration of large experimental and predicted collections. This creates a need for fast, structure-based search methods that retain biological relevance while enabling large-scale exploration. In this paper, we present AlphaFind v2, an application for finding structurally similar proteins in the AlphaFold Database (https://alphafold.ebi.ac.uk/) of predicted structures. AlphaFind v2 uses fast pre-filtering via state-of-the-art protein embeddings that preserve structural information, followed by refinement with US-align. The application presents multiple complementary search modes, including (i) search over full protein chains, (ii) search aware of the AlphaFold pLDDT metric, restricting similarity computation to the most stable and structurally relevant regions, (iii) search over protein domains from the TED database (https://ted.cathdb.info/), and (iv) a multidomain search mode, combining multiple chain-level domain matches within a single score and alignment. The application accepts protein identifiers and returns similar proteins with metrics, rich metadata, and interactive superpositions. AlphaFind v2 additionally allows searching within an organism or CATH label and matches the proteins with experimental structures. AlphaFind v2 is accessible at https://alphafind.ics.muni.cz/. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=79 SRC="FIGDIR/small/710735v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@5e7ce7org.highwire.dtl.DTLVardef@15a3458org.highwire.dtl.DTLVardef@12299ccorg.highwire.dtl.DTLVardef@9f21af_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

Pathogenicity Patterns in Cytochrome P450 Family

MotivationCytochrome P450 proteins play a crucial role in human metabolism, from the production of hormones to drug metabolism. While multiple commonly known variants have known effects on the individual cytochrome P450 protein performance, the pathogenicity information is usually experimentally limited to only a few mutations. Current pathogenicity prediction software allows one to extend the scope to virtually mutate all amino acids with missense mutations. In this work, we do a comprehensive exploration that unveils pathogenicity patterns in the human cytochrome P450 family. Pathogenicity analysis was conducted across proteins using SIFT and AlphaMissense algorithms. ResultsOur findings indicate a progressive increase in pathogenicity along protein tunnels-identified via MOLE-toward the cofactor binding site, underscoring the essential role of cofactor interactions in enzymatic function. Notably, tunnel integrity emerges as a critical factor, with even single amino acid alterations potentially disrupting molecular guidance to active sites. These insights highlight the fundamental role of structural pathways in preserving cytochrome P450 functionality, with implications for understanding disease-associated variants and drug metabolism. AvailabilityData and source code can be found at https://github.com/annaspac/P450_pathogenicity_codes Contactanna.spackova@upol.cz, karel.berka@upol.cz O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=92 SRC="FIGDIR/small/646180v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@19f1b1aorg.highwire.dtl.DTLVardef@ac7f29org.highwire.dtl.DTLVardef@d06a6dorg.highwire.dtl.DTLVardef@fb342b_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

In-silico screening of drug candidates for thermoresponsive liposome formulations

Liposomal formulations can be advantageous in a number of scenarios such as targeted delivery to reduce the systemic toxicity of highly potent Active Pharmaceutical Ingredients (APIs), to increase drug bioavailability by prolonging systemic circulation, to protect labile APIs from degradation in the gastrointestinal tract, or to improve skin permeation in dermal delivery. However, not all APIs are suitable for encapsulation in liposomes. Some of the issues are too high permeability of the API across the lipid bilayer, which may lead to premature leakage, too low permeability, which may hinder the drug release process, or too strong membrane affinity, which may reduce the overall efficacy of drug release from liposomes. Since the most reliable way to test API encapsulation and release from liposomes so far has been experimental, an in silico model capable of predicting API transport across the lipid bilayer might accelerate formulation development. In this work, we demonstrate a new in silico approach to compute the temperature dependent permeability of a set of compounds across the bilayer of virtual liposomes constructed by molecular dynamics simulation. To validate this approach, we have conducted a series of experiments confirming the model predictions using a homologous series of fluorescent dyes. Based on the performance of individual molecules, we have defined a set of selection criteria for identifying compatible APIs for stable encapsulation and thermally controlled release from liposomes. To further demonstrate the in silico-based methodology, we have screened the DrugBank database, identified potent drugs suitable for liposome encapsulation and successfully carried out the loading and thermal release of one of them - an antimicrobial compound cycloserine.

pharmacology and toxicology↗

Uncovering of Cytochrome P450 Anatomy by SecStrAnnotator

Protein structural families are groups of homologous proteins defined by the organization of secondary structure elements (SSEs). Nowadays, many families contain vast numbers of structures, and the SSEs can help to orient within them. Communities around specific protein families have even developed specialized SSE annotations, always assigning the same name to the equivalent SSEs in homologous proteins. A detailed analysis of the groups of equivalent SSEs provides an overview of the studied family and enriches the analysis of any particular protein at hand. We developed a workflow for the analysis of the secondary structure anatomy of a protein family. We applied this analysis to the model family of cytochromes P450 (CYPs) - a family of important biotransformation enzymes with a community-wide used SSE annotation. We report the occurrence, typical length and amino acid sequence for the equivalent SSE groups, the conservation/variability of these properties and relationship to the substrate recognition sites. We also suggest a generic residue numbering scheme for the CYP family. Comparing the bacterial and eukaryotic part of the family highlights the significant differences and reveals an anomalous group of bacterial CYPs with some typically eukaryotic features. Application of our workflow to other families could produce equally surprising findings.

bioinformatics↗

Cytokinin fluoroprobe and receptor CRE1/AHK4 localize to both plasma membrane and endoplasmic reticulum

The plant hormone cytokinin regulates various cell and developmental processes, including cell division and differentiation, embryogenesis, activity of shoot and root apical meristems, formation of shoot and root lateral organs and others 1. Cytokinins are perceived by a subfamily of sensor histidine kinases (HKs), which via a two-component phosphorelay cascade activate transcriptional responses in the nucleus. Based on the subcellular localization of cytokinin receptors in various transient expression systems, such as tobacco leaf epidermal cells, and membrane fractionation experiments of Arabidopsis and maize, the endoplasmic reticulum (ER) membrane has been proposed as a principal hormone perception site 2-4. Intriguingly, recent study of the cytokinin transporter PUP14 has pointed out that the plasma membrane (PM)-mediated signalling might play an important role in establishment of cytokinin response gradients in various plant organs 5. However, localization of cytokinin HK receptors to the PM, although initially suggested 6, remains ambiguous. Here, by monitoring subcellular localizations of the fluorescently labelled natural cytokinin probe iP-NBD 7 and the cytokinin receptor ARABIDOPSIS HISTIDINE KINASE 4 (CRE1/AHK4) fused to GFP reporter, we show that pools of the ER-located cytokinin fluoroprobes and receptors can enter the secretory pathway and reach the PM. We demonstrate that in cells of the root apical meristem, CRE1/AHK4 localizes to the PM and the cell plate of dividing meristematic cells. Brefeldin A (BFA) experiments revealed vesicular recycling of the receptor and its accumulation in BFA compartments. Our results provide a new perspective on cytokinin signalling and the possibility of multiple sites of perception at PM and ER, which may determine specific outputs of cytokinin signalling.

plant biology↗

Testing the limits of in vitro sublingual macromolecular drug delivery: dextrans and albumin with nanofiber mats

Sublingual drug delivery allows systemic delivery of drug without difficulties connected with the gastrointestinal pathway. We developed a new simple protocol for easy-to-use processing and storage of porcine sublingual mucosal membrane for in vitro studies using \"flash freezing\" in liquid nitrogen. All the dextrans used as mucosal membrane integrity and permeability markers permeated only slowly through sublingual mucosa illustrating usability both the \"fresh\" and \"flash frozen\" sublingual membranes whereas conventional cold storage \"frozen\" membranes have shown significantly higher permeabilities for macromolecules due to the sustained damage. The permeability values were too low to expect dextrans to be potential carriers at this context. To test albumin as a drug carrier we compared FITC-albumin permeation from solutions vs. nanofiber mats donors. To increase the amounts and prolong the transport, we manufactured nanofiber mats loaded with fluorescently marked albumin using well-scalable electrospinning technology. Nanofiber mats have allowed albumin passage through the sublingual membrane in similar amounts as from the pure artificial saliva solution. Since salivary washout strictly limits the duration of liquid dosages, nanofiber mats may thus permit prolonged sublingual administration.\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=81 SRC=\"FIGDIR/small/690990v2_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (27K):\norg.highwire.dtl.DTLVardef@1045f19org.highwire.dtl.DTLVardef@1ff7f8dorg.highwire.dtl.DTLVardef@10f29fcorg.highwire.dtl.DTLVardef@8d80c2_HPS_FORMAT_FIGEXP M_FIG C_FIG

pharmacology and toxicology↗

MolMeDB: Molecules on Membranes Database

Biological membranes act as barriers or reservoirs for many compounds within the human body. As such, they play an important role in pharmacokinetics and pharmacodynamics of drugs and other molecular species. Until now, most membrane/drug interactions have been inferred from simple partitioning between octanol and water phases. However, the observed variability in membrane composition and among compounds themselves stretches beyond such simplification as there are multiple drug-membrane interactions. Numerous experimental and theoretical approaches are used to determine the molecule-membrane interactions with variable accuracy, but there is no open resource for their critical comparison. For this reason, we have built Molecules on Membranes Database (MolMeDB), which gathers data about over 3600 compound-membrane interactions including partitioning, penetration, and positioning. The data have been collected from scientific articles published in peer-reviewed journals and complemented by inhouse calculations from high-throughput COSMOmic approach to set up a baseline for further comparison. The data in MolMeDB are fully searchable and browsable by means of name, SMILES, membrane, method, or dataset and we offer the collected data openly for further reuse and we are open to further additions. MolMeDB can be a powerful tool that could help researchers better understand the role of membranes and to compare individual approaches used for the study of molecule/membrane interactions.\n\nDatabase URL: http://molmedb.upol.cz.

biophysics↗