Biology subjects

Zoidl, G.

Publications and source records attributed to Zoidl, G..

4 recordsLinked to original sources

bioRxiv2025

Molecular determinants of low affinity complexes formed by the electrical synapse proteins Connexin36 (Cx36) and ZO-1

Although chemical and electrical synapses function fundamentally differently, they evidently share common design principles. Like neurotransmitter receptors, Connexin 36 (Cx36) containing gap junction channels, key constituents of electrical synapses, are anchored to scaffolding proteins that stabilize the connexin at the synapse. One of the most prominent proteins that has been described in this context is the Zonula occludens protein 1 (ZO-1). ZO-1 interacts with Cx36 via one of its three PDZ domains. This interaction is inherently weak and was suggested to facilitate the dynamic regulation of electrical synapses. In the present study, we have combined Gaussian accelerated molecular dynamics simulations and binding assays to identify the exact residues in the PDZ binding motif of Cx36 that are necessary to sustain these low affinity interactions. Among the different Cx36 mutations we have generated, we discovered a single substitution at position 319 within the PDZ binding motif that massively increases binding in different experimental settings. In addition to this site, we found that acidic residues adjacent to the PDZ binding motif (PBM) in Cx36 and its fish orthologues are evolutionarily tuned to weaken PDZ interactions as well. We were able to enhance PDZ1 binding drastically by substituting these residues with hydrophobic or positively charged amino acids. Finally, we demonstrate that the weak PDZ1/Cx36 interaction is sensitive to CaMKII mediated phosphorylation of Cx36, suggesting that ZO-1 unbinding may be a necessary event to potentiate electrical synapses. In summary, our study provides a detailed analysis of different mechanisms that can be exploited to modify the interaction between two key components of an electrical synapse: Cx36 and ZO-1.

biochemistry↗

bioRxiv2024

Panx1 deletion promotes synaptic reconfiguration and recruitment of cell death pathways in the Zebrafish MPTP model

Pannexin-1 channels have garnered attention for their implications in neurodevelopment, potentially having a dual role in mediating a delicate balance between cell death and survival. However, a comprehensive understanding of the underlying molecular and cellular mechanisms and Panx1s potential protective functions throughout neurodevelopment remains to be determined. Zebrafish larvae with loss of Pannexin-1a function were subjected to an acute exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Early-life changes in larvae induced by uncoupling of oxidative phosphorylation were investigated by a computational Gene Set Expression Analysis of RNA-seq data and experimental testing of light-stimulated locomotor behavior, cell death, and bioelectrical properties of local field potentials in the ascending visual pathway. A KEGG pathway analysis underscored Panx1as regulatory influence on neurodevelopment. Targeting Panx1a caused a deregulation of oxidative phosphorylation, glycolysis, reactive oxygen production, hypoxia, unfolded protein response pathways, and reduced extracellular ATP. Further, Panx1a ablation enhanced the transcriptional activation of 5 AMP-activated protein kinase (AMPK) kinase, a cellular energy sensor activated by falling energy status, largely to activate glucose and fatty acid uptake and oxidation when cellular energy is low. The activation of the AMPK pathway in Panx1a knock-out larvae correlated with the stimulation of the mammalian target of rapamycin (mTORC1) pathway that controls cellular metabolism, catabolism, immune responses, autophagy, survival, proliferation, and migration, to maintain cellular homeostasis. The differential expression of mTORC1 pathway genes associated with autophagy, and apoptosis signaling pathways. The resultant cell death was pronounced in the pallium and tectum regions. The loss of cells interrelated with a trans-synaptic a loss of synaptic neurotransmitter receptor and ion channel/transporter expression. Local field potential recordings in the optic tectum and pallium demonstrated that Panx1as involvement in modulating local neuronal networks was altered. Collectively, the results shed light on the impacts of acute MPTP treatment on locomotor behavior, transcriptomic shifts, metabolic disturbances, and the pivotal role of Panx1a in cell death. These insights enhance our comprehension of the intricate molecular and cellular mechanisms underpinning neurodevelopment, with implications for potential therapeutic strategies targeting Panx1 channels in autism and Alzheimers disease. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=172 HEIGHT=200 SRC="FIGDIR/small/590821v2_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1a8688eorg.highwire.dtl.DTLVardef@16849a3org.highwire.dtl.DTLVardef@1ba8298org.highwire.dtl.DTLVardef@1d3efff_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIA genetic model was combined with the neurotoxin MPTP to explore the roles of zebrafish Pannexin-1 channels in neurodevelopment under oxidative stress conditions. C_LIO_LIA potential beneficial impact of targeting Panx1a is superseded by synaptic plasticity loss, dysfunctional mitochondrial metabolism, and cell death pathway activation. C_LIO_LILoss of Panx1a amplifies AMPK/mTORC1 pathway activation of cell death pathways. C_LIO_LIA role of Panx1a as a regulator of energy and synaptic homeostasis was identified. C_LI

neuroscience↗

bioRxiv2022

Intralumenal docking of Cx36 channels in the ER isolates mis-trafficked protein

The intracellular domains of connexins are essential for the assembly of gap junctions. For connexin 36 (Cx36), the major neuronal connexin, it has been shown that a dysfunctional PDZ binding motif interferes with electrical synapse formation. However, it is still unknown how this motif coordinates the transport of Cx36. In the present study, we characterize a phenotype of Cx36 mutants that lack a functional PDZ binding motif using HEK293T cells as an expression system. We provide evidence that an intact PDZ binding motif is critical for proper ER export of Cx36. Removing the PDZ binding motif of Cx36 results in ER retention and the formation of multi-membrane vesicles containing gap junction-like connexin aggregates. Using a combination of site directed mutagenesis and electron micrographs we reveal that these vesicles consist of Cx36 channels that docked prematurely in the ER. Our data suggest a model in which ER-retained Cx36 channels reshape the ER membrane into concentric whorls that are released into the cytoplasm.

cell biology↗

bioRxiv2021

Panx1b modulates the luminance response and direction of motion in the zebrafish

Pannexin1 (Panx1) can form ATP-permeable integral membrane channels that play roles in the physiology of the visual system. Two independent gene copies of Panx1, panx1a and panx1b, have been identified in the zebrafish with unique and shared properties and tissue expression patterns. Panx1a channels, located in horizontal cells of the outer retina, modulate light decrement detection through an ATP/pH-dependent mechanisms and adenosine/dopamine signaling. Here, we decipher how the strategic localization of Panx1b channels in the inner retina and ganglion cell layer modulates visually evoked motor behavior. We describe a panx1b knockout model generated by TALEN technology. The RNA-seq analysis of 6 days post-fertilization larvae is confirmed by Real-Time PCR and paired with testing of visual-motor behaviors. The Panx1b protein emerges as a modulator of the circadian clock system. The loss of panx1b also disrupts the retinal response to the abrupt loss of illumination and decreases the larval ability to follow leftward direction of motion in the dark. The evidence suggests that in the retina Panx1b contributes to the OFF pathways function, like Panx1a, though through different signaling mechanisms. In this process, the loss of Panx1b channels compromises the final output of luminance as well as direction of motion detector RGCs. In addition, the disruption of the circadian clock system in mutants suggests that Panx1b could participate in non-image forming processes in the inner retina.

neuroscience↗