Extracellular matrix remodeling through endocytosis and resurfacing of Tenascin-R

Tal M Dankovich,Alexander Dityatev,Hannah Abdul Hadi,Sabine Beuermann,Paola Agüi-Gonzalez,Benjamin H Cooper,Katharina Grewe,Philipp Emanuel Giro,Linda H M Olsthoorn,Gabriel Cassinelli Petersen,Jose Doeren,Rahul Kaushik,Silvio O Rizzoli,Verena Kluever,Simon Klöppner,Guobin Bao

doi:10.1038/s41467-021-27462-7

Abstract

The brain extracellular matrix (ECM) consists of extremely long-lived proteins that assemble around neurons and synapses, to stabilize them. The ECM is thought to change only rarely, in relation to neuronal plasticity, through ECM proteolysis and renewed protein synthesis. We report here an alternative ECM remodeling mechanism, based on the recycling of ECM molecules. Using multiple ECM labeling and imaging assays, from super-resolution optical imaging to nanoscale secondary ion mass spectrometry, both in culture and in brain slices, we find that a key ECM protein, Tenascin-R, is frequently endocytosed, and later resurfaces, preferentially near synapses. The TNR molecules complete this cycle within ~3 days, in an activity-dependent fashion. Interfering with the recycling process perturbs severely neuronal function, strongly reducing synaptic vesicle exo- and endocytosis. We conclude that the neuronal ECM can be remodeled frequently through mechanisms that involve endocytosis and recycling of ECM proteins.

Highlights

The brain extracellular matrix (ECM) consists of extremely long-lived proteins that assemble around neurons and synapses, to stabilize them
To test whether our observations extend to other ECM molecules, we used the ‘blocking-labeling’ assay to assess neurocan, chondroitin-sulfate (CS)-bearing proteoglycans labeled by Wisteria floribunda agglutin (WFA), and hyaluronic acid (HA)[10]
Numerous studies have demonstrated that synaptic plasticity events can induce the release of ECM-cleaving enzymes, and a Surface TNR β1-integrin

Summary

Introduction

The brain extracellular matrix (ECM) consists of extremely long-lived proteins that assemble around neurons and synapses, to stabilize them. Synapses were found to change shape and location continually, on a time scale of minutes, both in acute brain slices[6] and in the adult brain[7,8] These findings suggest that the ECM may be remodeled relatively frequently. The recycling TNR molecules were secreted mainly at synapses, in a process that was dependent on the overall network activity levels, and on the activity levels of the particular synapses These molecules were endocytosed by the neurons and were recycled back to the perisynaptic ECM, over ~3 days. We conclude that neurons maintain a pool of TNR that continually recycles in and out of perisynaptic ECM, allowing for frequent ECM remodeling without the need to synthesize new molecules, and thereby explaining how synaptic fluctuations could be dealt with without compromising the exceptionally long lifetime of ECM molecules

Methods

Results

Conclusion