Cell- and stimulus-dependent heterogeneity of synaptic vesicle endocytic recycling mechanisms revealed by studies of dynamin 1-null neurons.
Mice lacking expression of dynamin 1, a GTPase implicated in the fission reaction of synaptic vesicle endocytosis, fail to thrive and exhibit severe activity-dependent endocytic defects at their synapses. Here, we have used electron tomography to investigate the massive increase in clathrin-coated pit abundance that is selectively observed at a subset of synapses in dynamin 1 KO primary neuron cultures under conditions of spontaneous network activity. This increase, leading to branched tubular plasma membrane invaginations capped by clathrin-coated buds, occurs selectively at inhibitory synapses. A similar massive increase of clathrin-coated profiles (in this case, of clathrin-coated vesicles) is observed at inhibitory synapses of neurons that lack expression of synaptojanin 1, a phosphoinositide phosphatase involved in clathrin-coated vesicle uncoating. Thus, although excitatory synapses are largely spared under these conditions, inhibitory synapses are uniquely sensitive to perturbation of endocytic proteins, probably as a result of their higher levels of tonic activity leading to a buildup of clathrin-coated intermediates in these synapses. In contrast, the predominant endocytic structures observed at the majority of dynamin 1 KO synapses after acute stimulation are endosome-like intermediates that originate by a dynamin 1-independent form of endocytosis. These findings reveal a striking heterogeneity in the mode of synaptic vesicle recycling in different synapses and functional states.
Hayashi
Mitsuko
M
Department of Cell Biology, Program in Cellular Neuroscience, Neurodegeneration and Repair, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA.
Raimondi
Andrea
A
O'Toole
Eileen
E
Paradise
Summer
S
Collesi
Chiara
C
Cremona
Ottavio
O
Ferguson
Shawn M
SM
De Camilli
Pietro
P
D000818:Animals; D034284:Dynamin I / Q000235:genetics / Q000502:physiology*; D004705:Endocytosis; D051379:Mice; D018345:Mice, Knockout; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000502:physiology; D009474:Neurons / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000502:physiology; D013572:Synaptic Vesicles / Q000378:metabolism*
D009419:Nerve Tissue Proteins; C097702:synaptojanin; D010744:Phosphoric Monoester Hydrolases; D034284:Dynamin I