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The Journal of Neuroscience, July 23, 2008, 28(30):7648-7658; doi:10.1523/JNEUROSCI.0744-08.2008

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Cellular/Molecular
Lysosomes Are the Major Vesicular Compartment Undergoing Ca²⁺-Regulated Exocytosis from Cortical Astrocytes

Dongdong Li,^1,2,3 Nicole Ropert,^1,2,3 Annette Koulakoff,^4,5 Christian Giaume,^4,5 and Martin Oheim^1,2,3

¹Institut National de la Santé et de la Recherche Médicale (INSERM), Unité 603, and ²Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8154, and ³Université Paris Descartes, Laboratory of Neurophysiology and New Microscopies, F-75006 Paris, France, and ⁴INSERM, Unité 840, and ⁵Collège de France, F-75005 Paris, France

Correspondence should be addressed to Martin Oheim, Université Paris Descartes, Laboratory of Neurophysiology and New Microscopies, 45 rue des Saints Pères, F-75006 Paris, France. Email: martin.oheim{at}univ-paris5.fr

Although Ca²⁺-dependent exocytosis is considered to be a pathway for gliotransmitter release from astrocytes, the structural and functional bases of this process remain controversial. We studied the relationship between near-membrane Ca²⁺ elevations and the dynamics of single astroglial vesicles with styryl (FM) dyes. We show that cultured astrocytes, unlike neurons, spontaneously internalize FM dyes, resulting in the labeling of the entire acidic vesicle population within minutes. Interestingly, metabotropic glutamate receptor activation did not affect the FM labeling. Most FM-stained vesicles expressed sialin, CD63/LAMP3, and VAMP7, three markers for lysosomes and late endosomes. A subset of lysosomes underwent asynchronous exocytosis that required both Ca²⁺ mobilization from intracellular stores and Ca²⁺ influx across the plasma membrane. Lysosomal fusion occurred within seconds and was complete with no evidence for kiss and run. Our experiments suggest that astroglial Ca²⁺-regulated exocytosis is carried by lysosomes and operates on a timescale orders of magnitude slower than synaptic transmission.

Key words: glia; vesicle release; intracellular signaling; total internal reflection fluorescence microscopy; TIRF; kiss and run; readily releasable pool

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Received Feb. 18, 2008; revised May 14, 2008; accepted June 12, 2008.

Correspondence should be addressed to Martin Oheim, Université Paris Descartes, Laboratory of Neurophysiology and New Microscopies, 45 rue des Saints Pères, F-75006 Paris, France. Email: martin.oheim{at}univ-paris5.fr

This article has been cited by other articles:

				M. Jiang and G. Chen Ca2+ Regulation of Dynamin-Independent Endocytosis in Cortical Astrocytes J. Neurosci., June 24, 2009; 29(25): 8063 - 8074. [Abstract] [Full Text] [PDF]

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