@phdthesis{Khayenko2023,
  author    = {Khayenko, Vladimir},
  title     = {Functional peptide-based probes for the visualization of inhibitory synapses},
  doi       = {10.25972/OPUS-32043},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-320438},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Short functional peptidic probes can maximize the potential of high-end microscopy techniques and multiplex imaging assays and provide new insights into normal and aberrant molecular, cellular and tissue function. Particularly, the visualization of inhibitory synapses requires protocol tailoring for different sample types and imaging techniques and relies either on genetic manipulation or on antibodies that underperform in tissue immunofluorescence. Starting from an endogenous activity-related ligand of gephyrin, a universal marker of the inhibitory post-synapse, I developed a short peptidic multivalent binder with exceptional affinity and selectivity to gephyrin. By tailoring fluorophores to the binder, I have obtained Sylite, a probe for the visualization of inhibitory synapses, with an outstanding signal-to-background ratio, that bests the "gold standard" gephyrin antibodies both in selectivity and in tissue immunofluorescence. In tissue Sylite benefits from simplified handling, provides robust synaptic labeling in record-short time and, unlike antibodies, is not affected by staining artefacts. In super-resolution microscopy Sylite precisely localizes the post-synapse and enables accurate pre- to post-synapse measurements. Combined with complimentary tracing techniques Sylite reveals inhibitory connectivity and profiles inhibitory inputs and synapse sizes of excitatory and inhibitory neurons in the periaqueductal gray brain region. Lastly, upon probe optimization for live cell application and with the help of novel thiol-reactive cell penetrating peptide I have visualized inhibitory synapses in living neurons. Taken together, my work provided a versatile probe for conventional and super-resolution microscopy and a workflow for the development and application of similar compact functional synthetic probes.},
  subject      = {Fluoreszenzsonde},
  language  = {en}
}
@article{MakbulKhayenkoMaricetal.2021,
  author    = {Makbul, Cihan and Khayenko, Vladimir and Maric, Hans Michael and B{\"o}ttcher, Bettina},
  title     = {Conformational Plasticity of Hepatitis B Core Protein Spikes Promotes Peptide Binding Independent of the Secretion Phenotype},
  series = {Microorganisms},
  volume    = {9},
  journal   = {Microorganisms},
  number    = {5},
  issn      = {2076-2607},
  doi       = {10.3390/microorganisms9050956},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-236720},
  year      = {2021},
  abstract  = {Hepatitis B virus is a major human pathogen, which forms enveloped virus particles. During viral maturation, membrane-bound hepatitis B surface proteins package hepatitis B core protein capsids. This process is intercepted by certain peptides with an "LLGRMKG" motif that binds to the capsids at the tips of dimeric spikes. With microcalorimetry, electron cryo microscopy and peptide microarray-based screens, we have characterized the structural and thermodynamic properties of peptide binding to hepatitis B core protein capsids with different secretion phenotypes. The peptide "GSLLGRMKGA" binds weakly to hepatitis B core protein capsids and mutant capsids with a premature (F97L) or low-secretion phenotype (L60V and P5T). With electron cryo microscopy, we provide novel structures for L60V and P5T and demonstrate that binding occurs at the tips of the spikes at the dimer interface, splaying the helices apart independent of the secretion phenotype. Peptide array screening identifies "SLLGRM" as the core binding motif. This shortened motif binds only to one of the two spikes in the asymmetric unit of the capsid and induces a much smaller conformational change. Altogether, these comprehensive studies suggest that the tips of the spikes act as an autonomous binding platform that is unaffected by mutations that affect secretion phenotypes.},
  language  = {en}
}
@article{KhayenkoMaric2021,
  author    = {Khayenko, Vladimir and Maric, Hans Michael},
  title     = {Innovative affinit{\"a}tsbasierte Markierungen f{\"u}r die High-End-Mikroskopie},
  series = {BIOspektrum},
  volume    = {27},
  journal   = {BIOspektrum},
  doi       = {10.1007/s12268-021-1672-7},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-287377},
  pages     = {709-712},
  year      = {2021},
  abstract  = {Advanced tissue imaging techniques and super resolution microscopy are opening new avenues of investigations in life sciences. These mainly instrumentation-driven innovations require the development of appropriate molecular labelling tools. Here, we discuss currently used and upcoming manipulation-free protein labelling strategies and their potential for the precise and interference-free visualization of endogenous proteins.},
  language  = {de}
}
@article{KhayenkoMaric2019,
  author    = {Khayenko, Vladimir and Maric, Hans Michael},
  title     = {Targeting GABA\(_A\)R-associated proteins: new modulators, labels and concepts},
  series = {Frontiers in Molecular Neuroscience},
  volume    = {12},
  journal   = {Frontiers in Molecular Neuroscience},
  number    = {162},
  doi       = {10.3389/fnmol.2019.00162},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201876},
  year      = {2019},
  abstract  = {γ-aminobutyric acid type A receptors (GABA\(_A\)Rs) are the major mediators of synaptic inhibition in the brain. Aberrant GABA\(_A\)R activity or regulation is observed in various neurodevelopmental disorders, neurodegenerative diseases and mental illnesses, including epilepsy, Alzheimer's and schizophrenia. Benzodiazepines, anesthetics and other pharmaceutics targeting these receptors find broad clinical use, but their inherent lack of receptor subtype specificity causes unavoidable side effects, raising a need for new or adjuvant medications. In this review article, we introduce a new strategy to modulate GABAeric signaling: targeting the intracellular protein interactors of GABA\(_A\)Rs. Of special interest are scaffolding, anchoring and supporting proteins that display high GABA\(_A\)R subtype specificity. Recent efforts to target gephyrin, the major intracellular integrator of GABAergic signaling, confirm that GABA\(_A\)R-associated proteins can be successfully targeted through diverse molecules, including recombinant proteins, intrabodies, peptide-based probes and small molecules. Small-molecule artemisinins and peptides derived from endogenous interactors, that specifically target the universal receptor binding site of gephyrin, acutely affect synaptic GABA\(_A\)R numbers and clustering, modifying neuronal transmission. Interference with GABA\(_A\)R trafficking provides another way to modulate inhibitory signaling. Peptides blocking the binding site of GABA\(_A\)R to AP2 increase the surface concentration of GABA\(_A\)R clusters and enhance GABAergic signaling. Engineering of gephyrin binding peptides delivered superior means to interrogate neuronal structure and function. Fluorescent peptides, designed from gephyrin binders, enable live neuronal staining and visualization of gephyrin in the post synaptic sites with submicron resolution. We anticipate that in the future, novel fluorescent probes, with improved size and binding efficiency, may find wide application in super resolution microscopy studies, enlightening the nanoscale architecture of the inhibitory synapse. Broader studies on GABA\(_A\)R accessory proteins and the identification of the exact molecular binding interfaces and affinities will advance the development of novel GABA\(_A\)R modulators and following in vivo studies will reveal their clinical potential as adjuvant or stand-alone drugs.},
  language  = {en}
}