Structural basis of astrocytic Ca2+ signals at tripartite synapses

Misa Arizono, V. V. G. Krishna Inavalli, Aude Panatier, Thomas Pfeiffer, Julie Angibaud, Florian Levet, Mirelle J. T. Ter Veer, Jillian Stobart, Luigi Bellocchio, Katsuhiko Mikoshiba, Giovanni Marsicano, Bruno Weber, Stéphane H. R. Oliet, U. Valentin Nägerl
Nat Commun. 2020-04-20; 11(1):
DOI: 10.1038/s41467-020-15648-4

PubMed
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Arizono M(1)(2), Inavalli VVGK(1)(2), Panatier A(1)(3), Pfeiffer T(1)(2), Angibaud J(1)(2), Levet F(1)(2)(4)(5)(6), Ter Veer MJT(1)(2), Stobart J(7), Bellocchio L(1)(3), Mikoshiba K(8), Marsicano G(1)(3), Weber B(7), Oliet SHR(1)(3), Nägerl UV(9)(10).

Author information:
(1)Interdisciplinary Institute for Neuroscience, University of Bordeaux,Bordeaux, France.
(2)Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France.
(3)NeuroCentre Magendie, Inserm U1215, Bordeaux, France.
(4)Bordeaux Imaging Center, University of Bordeaux, Bordeaux, France.
(5)Bordeaux Imaging Center, CNRS UMS 3420, Bordeaux, France.
(6)Bordeaux Imaging Center, INSERM US04, Bordeaux, France.
(7)University of Zurich, Institute of Pharmacology & Toxicology, Zürich,Switzerland.
(8)ShanghaiTech University, Shanghai, 201210, China.
(9)Interdisciplinary Institute for Neuroscience, University of Bordeaux,Bordeaux, France. .
(10)Interdisciplinary Institute for Neuroscience, CNRS UMR 5297, Bordeaux, France. .

Astrocytic Ca2+ signals can be fast and local, supporting the idea that astrocytes have the ability to regulate single synapses. However, the anatomical basis of such specific signaling remains unclear, owing to difficulties in resolving the spongiform domain of astrocytes where most tripartite synapses are
located. Using 3D-STED microscopy in living organotypic brain slices, we imaged the spongiform domain of astrocytes and observed a reticular meshwork of nodes and shafts that often formed loop-like structures. These anatomical features were also observed in acute hippocampal slices and in barrel cortex in vivo. The majority of dendritic spines were contacted by nodes and their sizes were correlated. FRAP experiments and Ca2+ imaging showed that nodes were biochemical compartments and Ca2+ microdomains. Mapping astrocytic Ca2+ signals onto STED images of nodes and dendritic spines showed they were associated with individual synapses. Here, we report on the nanoscale organization of astrocytes, identifying nodes as a functional astrocytic component of tripartite synapses that may enable synapse-specific communication between neurons and astrocytes.

 


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