Axo-axonic Innervation of Neocortical Pyramidal Neurons by GABAergic Chandelier Cells Requires AnkyrinG-Associated L1CAM

Chandelier Cells Swipe Right for L1CAM

Establishing a functional neuronal circuit requires not only synapsing with the right cell type, but also targeting the right subcellular compartment. In this issue of Neuron, Tai et al. (2019) identify the cell adhesion molecule L1CAM as integral to the mechanism by which chandelier cells establish subcellular compartment-specific innervation of pyramidal neurons in the mammalian cerebral cortex.

Cellular Mechanisms Contributing to the Functional Heterogeneity of GABAergic Synapses

GABAergic inhibitory neurotransmission contributes to diverse aspects of brain development and adult plasticity, including the expression of complex cognitive processes. This is afforded for in part by the dynamic adaptations occurring at inhibitory synapses, which show great heterogeneity both in terms of upstream signaling and downstream effector mechanisms. Single-particle tracking and live imaging have revealed that complex receptor-scaffold interactions critically determine adaptations at GABAergic synapses. Super-resolution imaging studies have shown that protein interactions at synaptic sites contribute to nano-scale scaffold re-arrangements through post-translational modifications (PTMs), facilitating receptor and scaffold recruitment to synaptic sites. Additionally, plasticity mechanisms may be affected by the protein composition at individual synapses and the type of pre-synaptic input. This mini-review article examines recent discoveries of plasticity mechanisms that are operational within GABAergic synapses and discusses their contribution towards functional heterogeneity in inhibitory neurotransmission.