Biology subjects

Hogg, P.

Publications and source records attributed to Hogg, P..

3 recordsLinked to original sources

bioRxiv2022

Dynamic Disulfide Bond Topologies in von-Willebrand-Factor's C4-Domain Undermine Platelet Binding

BackgroundThe von Willebrand Factor (vWF) is a key player in regulating hemostasis through adhesion of platelets to sites of vascular injury. It is a large multi-domain mechano-sensitive protein stabilized by a net of disulfide bridges. Binding to platelet integrin is achieved by the vWF-C4 domain which exhibits a fixed fold, even under conditions of severe mechanical stress, but only if critical internal disulfide bonds are closed. ObjectiveTo quantitatively determine C4s disulfide topologies and their implication in vWFs platelet-binding function via integrin. MethodsWe employed a combination of classical Molecular Dynamics and quantum mechanical simulations, mass spectrometry, site-directed mutagenesis, and platelet binding assays. ResultsWe quantitatively show that two disulfide bonds in the vWF-C4 domain, namely the two major force-bearing ones, are partially reduced in human blood. Reduction leads to pronounced conformational changes within C4 that considerably affect the accessibility of the RGD-integrin binding motif, and thereby impair integrin-mediated platelet binding. Our combined approach also reveals that reduced species in the C4 domain undergo specific thiol/disulfide exchanges with the remaining disulfide bridges, in a process in which mechanical force may increase the proximity of specific reactant cysteines, further trapping C4 in a state of low integrin-binding propensity. We identify a multitude of redox states in all six vWF-C domains, suggesting disulfide bond reduction and swapping to be a general theme. ConclusionOverall, our data put forward a mechanism in which disulfide bonds dynamically swap cysteine partners and control the interaction of vWF with integrin and potentially other partners, thereby critically influencing its hemostatic function. EssentialsO_LIPlatelet integrins interact with the disulfide-bonded C4 domain of von Willebrand Factor C_LIO_LIThe redox state of vWF-C4s disulfide bonds is studied by molecular simulations and experiments C_LIO_LITwo bonds are reduced causing C4 unfolding and disulfide swapping C_LIO_LIOpening of disulfide bonds impairs integrin-mediated platelet binding C_LI

biophysics↗

bioRxiv2021

BrainPalmSeq: A curated RNA-seq database of palmitoylating and de-palmitoylating enzyme expression in the mouse brain

Protein S-palmitoylation is a reversible post-translational lipid modification that plays a critical role in neuronal development and plasticity, while dysregulated S-palmitoylation underlies a number of severe neurological disorders. Dynamic S-palmitoylation is regulated by a large family of ZDHHC palmitoylating enzymes, their accessory proteins, and a small number of known de-palmitoylating enzymes. Here, we curated and analyzed expression data for the proteins that mediate S-palmitoylation from publicly available RNAseq datasets, providing a comprehensive overview of their distribution in the mouse nervous system. We developed a web-tool that enables interactive visualization of the expression patterns for these proteins in the nervous system (http://brainpalmseq.med.ubc.ca/), and explored this resource to find region and cell-type specific expression patterns that give insight into the function of palmitoylating and de-palmitoylating enzymes in the brain and neurological disorders. We found coordinated expression of ZDHHC enzymes with their accessory proteins, de-palmitoylating enzymes and other brain-expressed genes that included an enrichment of S-palmitoylation substrates. Finally, we utilized ZDHHC expression patterns to predict and validate palmitoylating enzyme-substrate interactions.

neuroscience↗

bioRxiv2021

Comprehensive imaging of synaptic activity reveals dendritic growth rules that cluster inputs

The distribution of synapses across dendritic arbors determines their contribution to neural computations since nonlinear conductances amplify co-active clustered inputs. To determine whether, and how patterned synaptic topography arises during development we developed a random-access microscope capable of full-neuron calcium imaging of activity and structural plasticity of developing neurons in awake Xenopus tadpoles. By imaging growing brain neurons in response to plasticity-inducing visual training, we show coordinated growth and synaptogenesis specific to each neurons spike tuning. High evoked activity in neurons tuned to the trained stimulus induced pruning of non-driven inputs across the dendritic arbor as these neurons strengthened their responses to this stimulus. In stark contrast, initially unresponsive neurons that shifted their spike tuning toward the trained stimulus exhibited localized growth and new responsive synapses near existing active inputs. These information-driven growth rules promote clustering of synapses tuned to a developing neurons emerging receptive field. One-Sentence SummarySensory input directs brain neuronal growth and connectivity promoting clustering of synaptic inputs tuned to a neurons encoding properties.

neuroscience↗