Inhibitory and excitatory axon terminals share a common nano-architecture of their Cav2.1 (P/Q-type) Ca2+ channels

11.08.2015

Althof D, Baehrens D, Watanabe M, Suzuki N, Fakler B and Kulik A

Front Cell Neurosci. 2015;9:315

Front. Cell. Neurosci.            online article

Tuning of the time course and strength of transmitter release is fundamental for the precise operation of cortical network activity and is controlled by Ca2+ influx into terminals through Cav2.1 channels. Proper channel-mediated Ca2+ signaling depends on the topographical arrangement of the channels in the presynaptic membrane. We Used SDS-FRL immunoelectron microscopy together with automatized computational analysis of Cav2.1 immunogold labeling to determine the precise subcellular organization of Cav2.1 channels in inhibitory and excitatory terminals. Immunoparticles labeling Cav2.1 were enriched over the active zone of the boutons with the number of channels (3-62) correlated with the area of the synaptic membrane. Analysis showed that channels are non-uniformly distributed over the presynaptic membrane specialization where they are arranged in clusters of an average 5 channels per cluster covering a mmean area with a diamter of 70 nm. Clustered arrangement and cluster properties did not show any significant difference between GABAergic and glutamatergic terminals. Our data demonstrate a common nano-architecture of Cav2.1 channels in inhibitory and excitatory boutons in the hippocampus suggesting that the cluster arrangement is crucial for the precise release of neurotransmitters from the axonal boutons.