Biology subjects

MacGillavry, H. D.

Publications and source records attributed to MacGillavry, H. D..

5 recordsLinked to original sources

bioRxiv2021

Dynamics and nanoscale organization of the postsynaptic endocytic zone at excitatory synapses

At postsynaptic sites of neurons, a prominent clathrin-coated structure, the endocytic zone (EZ), controls the trafficking of glutamate receptors and is essential for synaptic plasticity. Despite its importance, little is known about how this clathrin structure is organized to mediate endocytosis. We used live-cell and super-resolution microscopy techniques to reveal the dynamic organization of this poorly understood clathrin structure. We found that a subset of endocytic proteins only transiently appeared at postsynaptic sites. In contrast, other proteins, including Eps15, intersectin1L, and {beta}2-adaptin, were persistently enriched and partitioned at the edge of the EZ. We found that uncoupling the EZ from the synapse led to the loss of most of these components, while disrupting the actin cytoskeleton or AP2-membrane interactions did not alter EZ positioning. We conclude that the EZ is a stable, highly organized molecular platform where components are differentially recruited and positioned to orchestrate the endocytosis of synaptic receptors.

cell biology↗

bioRxiv2020

Distinct mechanisms underlie the subsynaptic mobility of presynaptic metabotropic glutamate receptor types to tune receptor activation

Presynaptic metabotropic glutamate receptors (mGluRs) are essential for activity-dependent modulation of synaptic transmission. However, the mechanisms that control the subsynaptic dynamics of these receptors and their contribution to synaptic signaling are poorly understood. Here, using complementary super-resolution microscopy and single-molecule tracking techniques, we provide novel insights into the molecular mechanisms that control the nanoscale distribution and mobility of presynaptic mGluRs in hippocampal neurons. We demonstrate that the group II receptor mGluR2 localizes diffusely along the axon and boutons, and is highly mobile, while the group III receptor mGluR7 is stably anchored at the active zone, indicating that distinct mechanisms underlie the dynamic distribution of these receptor types. Surprisingly, using domain swapping experiments we found that intracellular interactions modulate surface diffusion of mGluR2, but not mGluR7. Instead, we found that immobilization of mGluR7 at the active zone relies on its extracellular domain. Importantly, receptor activation or increase in synaptic activity did not alter the surface mobility of presynaptic mGluRs. Finally, computational modeling of presynaptic mGluR activity revealed that the precise subsynaptic distribution of mGluRs controls their activation probability and thus directly impacts their ability to modulate neurotransmitter release. Altogether, this study demonstrates that distinct mechanisms control surface mobility of presynaptic mGluRs to differentially contribute to the regulation of glutamatergic synaptic transmission.

neuroscience↗

bioRxiv2020

Quantitative mapping of transcriptome and proteome dynamics during polarization of human iPSC-derived neurons

Early neuronal development is a well-coordinated process in which neuronal stem cells differentiate into polarized neurons. This process has been well studied in classical non-human model systems, but to what extent this is recapitulated in human neurons remains unclear. To study neuronal polarization in human neurons, we cultured human iPSC-derived neurons, characterized early developmental stages, measured electrophysiological responses, and systematically profiled transcriptomic and proteomic dynamics during these steps. We found extensive remodeling of the neuron transcriptome and proteome, with altered mRNA expression of ~1,100 genes and different expression profiles of ~1,500 proteins during neuronal differentiation and polarization. We also identified a distinct stage in axon development marked by an increase in microtubule remodeling and apparent relocation of the axon initial segment from the distal to proximal axon. Our comprehensive characterization and quantitative map of transcriptome and proteome dynamics provides a solid framework for studying polarization in human neurons.

neuroscience↗

bioRxiv2019

ORANGE: A CRISPR/Cas9-based genome editing toolbox for epitope tagging of endogenous proteins in neurons

The correct subcellular distribution of protein complexes establishes the complex morphology of neurons and is fundamental to their functioning. Thus, determining the dynamic distribution of proteins is essential to understand neuronal processes. Fluorescence imaging, in particular super-resolution microscopy, has become invaluable to investigate subcellular protein distribution. However, these approaches suffer from the limited ability to efficiently and reliably label endogenous proteins. We developed ORANGE: an Open Resource for the Application of Neuronal Genome Editing, that mediates targeted genomic integration of fluorescent tags in neurons. This toolbox includes a knock-in library for in-depth investigation of endogenous protein distribution, and a detailed protocol explaining how knock-in can be developed for novel targets. In combination with super-resolution microscopy, ORANGE revealed the dynamic nanoscale organization of endogenous neuronal signaling molecules, synaptic scaffolding proteins, and neurotransmitter receptors. Thus, ORANGE enables quantitation of expression and distribution for virtually any protein in neurons at high resolution and will significantly further our understanding of neuronal cell biology.

neuroscience↗

bioRxiv2019

Temporal quantitative proteomics of protein translation and phosphorylation in synaptic plasticity

At neuronal synapses, activation of metabotropic glutamate receptors (mGluR1/5) triggers a form of long-term depression (mGluR-LTD) that relies on new protein synthesis and the internalization of AMPA-type glutamate receptors. Dysregulation of these processes has been implicated in the development of mental disorders such as autism spectrum disorders and therefore merit a better understanding on a molecular level. Here, to study mGluR-LTD, we integrated quantitative high-resolution phosphoproteomics with the analyses of newly synthesized proteins via bio-orthogonal amino acids (azidohomoalanine) in a pulsed labeling strategy combined with tandem mass tag label-based quantification in cultured hippocampal neurons stimulated with DHPG. We identified several kinases with important roles in DHPG-mGluR-LTD, which we confirmed using small molecule kinase inhibitors. Furthermore, changes in the AMPA receptor endocytosis pathway in both protein synthesis and protein phosphorylation upon LTD were identified, whereby Intersectin-1 was validated as a vital player in this pathway. This study revealed several novel insights into the molecular mechanisms underlying mGluR-LTD and provides a broad view on its molecular basis, which serves as a rich resource for further analyses.

neuroscience↗