Biology subjects

Kurshan, P. T.

Publications and source records attributed to Kurshan, P. T..

5 recordsLinked to original sources

bioRxiv2026

Cell-intrinsic regulation of presynaptic release site patterning

Functional neuronal connectivity depends not only on synaptic partner choice but also on the number, strength, and spatial distribution of release sites between partners. How these features are regulated remains poorly understood. Here, using the C. elegans DA9 motor neuron, we identify the immunoglobulin superfamily cell adhesion molecules SYG-1 and SYG-2 as cell-autonomous regulators of presynaptic release-site patterning. SYG-2 regulates presynapse number, size, and spacing, whereas SYG-1 primarily regulates spacing. Endogenous localization and cell-specific knockout analyses reveal that SYG-2 recruits SYG-1 to the presynaptic domain through previously unrecognized cis interactions. Endogenous structure-function studies further demonstrate that the SYG-2 intracellular domain is required for presynaptic organization and can promote presynapse formation independently of its extracellular domain. Genetic and targeted actin-disruption experiments implicate the adaptor protein NCK-1 and local actin remodeling in SYG-2 intracellular signaling. Together, these findings reveal how cell adhesion molecules can act cell-intrinsically to pattern presynaptic release sites after synaptic partners have been established.

neuroscience↗

bioRxiv2026

Patient CACNA1A variant uncouples calcium channel conductance from synaptic output

Channelopathies are a class of neurodevelopmental disorders with often devastating consequences, and effective therapies depend on understanding how patient variants alter channel function. These effects are typically assessed by biophysical characterization in heterologous expression systems. Mutations in CACNA1A, which encodes the P/Q-type calcium channel CaV2.1, underlie a spectrum of neurological disorders in which symptoms are generally classified as loss-of-function (LoF) or gain-of-function (GoF). However, some patients present with overlapping phenotypes that defy this binary framework. Here we describe a CACNA1A variant for which heterologous assays fail to capture a key in vivo functional effect. We characterize a de novo variant of a highly conserved residue, D1634N, identified in a patient with a mixed clinical presentation that includes both LoF- and GoF-associated symptoms. Biophysical characterization in HEK293T cells supports a classic and severe LoF effect, including reduced current density and a right-shifted current-voltage relationship. In contrast, in vivo analysis of the corresponding endogenous variant in the C. elegans homolog reveals a paradoxical increase in spontaneous synaptic vesicle release, despite reduced channel expression. Molecular dynamics simulations predict that the mutation prolongs dwell time in a partially open state, potentially increasing calcium influx at rest. This model is supported by biophysical recordings of the human channel showing increased current at hyperpolarized potentials and by rescue of the C. elegans phenotype through genetic elevation of resting membrane potential. Together, these findings reconcile the patients clinical presentation by describing a complex, mixed-function variant, highlight the importance of cellular context in variant interpretation and therapeutic development, and establish C. elegans as a powerful in vivo platform for evaluating the functional consequences of pathogenic ion channel variants.

neuroscience↗

bioRxiv2025

WormSNAP: A software for fast, accurate, and unbiased detection of fluorescent puncta in C. elegans

The detection and characterization of fluorescent puncta are critical tasks in image analysis pipelines for fluorescence imaging. Existing methods for quantitative characterization of such puncta often suffer from biases and limitations, compromising the reliability and reproducibility of results. Moreover, the widespread adoption of many available analysis scripts is often hampered by over-optimization for specific samples, requiring extensive coding knowledge to repurpose for other datasets. We present WormSNAP (Worm SyNapse Analysis Program), a freely available, stand-alone, no-code approach to automated unbiased detection and characterization of 2D fluorescent puncta, originally developed to characterize images of the synapses residing in C. elegans nerve cords but suitable for broader 2D fluorescence image analysis. WormSNAP incorporates a local means thresholding algorithm and a user-friendly Graphical User Interface (GUI) for efficient and accurate analysis of large datasets, with user control of thresholding and restriction parameters and visualization options for further refinement. WormSNAP also calculates three types of correlation metrics for 2-channel images, enabling users to select the ideal metric for their dataset. WormSNAP provides robust and accurate fluorescent puncta detection in a variety of conditions, accelerating the image analysis workflow from data acquisition to figure generation.

neuroscience↗

bioRxiv2023

Protein-lipid interactions drive presynaptic assembly upstream of cell adhesion molecules

Textbook models of synaptogenesis position cell adhesion molecules such as neurexin as initiators of synapse assembly. Here we discover a mechanism for presynaptic assembly that occurs prior to neurexin recruitment, while supporting a role for neurexin in synapse maintenance. We find that the cytosolic active zone scaffold SYD-1 interacts with membrane phospholipids to promote active zone protein clustering at the plasma membrane, and subsequently recruits neurexin to stabilize those clusters. Employing molecular dynamics simulations to model intrinsic interactions between SYD-1 and lipid bilayers followed by in vivo tests of these predictions, we find that PIP2-interacting residues in SYD-1s C2 and PDZ domains are redundantly necessary for proper active zone assembly. Finally, we propose that the uncharacterized yet evolutionarily conserved short {gamma} isoform of neurexin represents a minimal neurexin sequence that can stabilize previously assembled presynaptic clusters, potentially a core function of this critical protein.

neuroscience↗

bioRxiv2017

Clarinet (CLA-1), a novel active zone protein required for synaptic vesicle clustering and release

Active zone proteins cluster synaptic vesicles at presynaptic terminals and coordinate their release. In forward genetic screens we isolated a novel C. elegans active zone gene, clarinet (cla-1). cla-1 mutants exhibit defects in synaptic vesicle clustering, reduced spontaneous neurotransmitter release, increased synaptic depression and reduced synapse number. Ultrastructurally, cla-1 mutants have fewer synaptic vesicles adjacent to the dense projection and an increased number of docked vesicles. Cla-1 encodes 3 isoforms containing common C-terminal PDZ and C2 domains with homology to vertebrate active zone proteins Piccolo and RIM. The short isoform localizes exclusively to the active zone while a longer ~9000 amino acid isoform colocalizes with synaptic vesicles. Specific loss of CLA-1L results in synaptic vesicle clustering defects and increased synaptic depression, but not in reduced synapse number or mini frequency. Together our data indicate that specific isoforms of clarinet serve distinct functions, regulating synapse development, synaptic vesicle clustering and release.

neuroscience↗