Lysosomes are the major vesicular compartment undergoing Ca2+-regulated exocytosis from cortical astrocytes.
Although Ca(2+)-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 Ca(2+) 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 Ca(2+) mobilization from intracellular stores and Ca(2+) 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 Ca(2+)-regulated exocytosis is carried by lysosomes and operates on a timescale orders of magnitude slower than synaptic transmission.
Li
Dongdong
D
Institut National de la Santé et de la Recherche Médicale, Unité 603, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8154, Laboratory of Neurophysiology and New Microscopies, Université Paris Descartes, Paris, France.
Ropert
Nicole
N
Koulakoff
Annette
A
Giaume
Christian
C
Oheim
Martin
M
D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects* / Q000502:physiology; D018955:CD36 Antigens / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D003078:Colchicine / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects* / Q000502:physiology; D005456:Fluorescent Dyes; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008247:Lysosomes / Q000502:physiology*; D051379:Mice; D050683:R-SNARE Proteins / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection / Q000379:methods; D050257:Tubulin Modulators / Q000494:pharmacology
D018955:CD36 Antigens; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D050683:R-SNARE Proteins; D050257:Tubulin Modulators; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D004533:Egtazic Acid; D019284:Thapsigargin; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D003078:Colchicine; D002118:Calcium