Rebuilding essential active zone functions within a synapse.

Presynaptic active zones are molecular machines that control neurotransmitter secretion. They form sites for vesicle docking and priming and couple vesicles to Ca entry for release triggering. The complexity of active zone machinery has made it challenging to determine its mechanisms in release.

PKC-phosphorylation of Liprin-α3 triggers phase separation and controls presynaptic active zone structure.

The active zone of a presynaptic nerve terminal defines sites for neurotransmitter release. Its protein machinery may be organized through liquid-liquid phase separation, a mechanism for the formation of membrane-less subcellular compartments. Here, we show that the active zone protein Liprin-α3 rapidly and reversibly undergoes phase separation in transfected HEK293T cells.

Synapse and Active Zone Assembly in the Absence of Presynaptic Ca Channels and Ca Entry.

Presynaptic Ca2 channels are essential for Ca-triggered exocytosis. In addition, there are two competing models for their roles in synapse structure. First, Ca channels or Ca entry may control synapse assembly.

ELKS1 Captures Rab6-Marked Vesicular Cargo in Presynaptic Nerve Terminals.

Neurons face unique transport challenges. They need to deliver cargo over long axonal distances and to many presynaptic nerve terminals. Rab GTPases are master regulators of vesicular traffic, but essential presynaptic Rabs have not been identified.

A Presynaptic Liquid Phase Unlocks the Vesicle Cluster.

How are synaptic vesicles tied together in a nerve terminal? A recent study by Milovanovic and colleagues offers a new mechanism for this old and important problem: synapsin proteins establish a liquid phase that clusters vesicles. Liquid-liquid phase separation provides a fluid-like state that accommodates the dynamic demands of presynaptic vesicle traffic.

Liprin-α3 controls vesicle docking and exocytosis at the active zone of hippocampal synapses.

The presynaptic active zone provides sites for vesicle docking and release at central nervous synapses and is essential for speed and accuracy of synaptic transmission. Liprin-α binds to several active zone proteins, and loss-of-function studies in invertebrates established important roles for Liprin-α in neurodevelopment and active zone assembly. However, Liprin-α localization and functions in vertebrates have remained unclear.

Rapid Sequential in Situ Multiplexing with DNA Exchange Imaging in Neuronal Cells and Tissues.

To decipher the molecular mechanisms of biological function, it is critical to map the molecular composition of individual cells or even more importantly tissue samples in the context of their biological environment in situ. Immunofluorescence (IF) provides specific labeling for molecular profiling. However, conventional IF methods have finite multiplexing capabilities due to spectral overlap of the fluorophores.

Fusion Competent Synaptic Vesicles Persist upon Active Zone Disruption and Loss of Vesicle Docking.

In a nerve terminal, synaptic vesicle docking and release are restricted to an active zone. The active zone is a protein scaffold that is attached to the presynaptic plasma membrane and opposed to postsynaptic receptors. Here, we generated conditional knockout mice removing the active zone proteins RIM and ELKS, which additionally led to loss of Munc13, Bassoon, Piccolo, and RIM-BP, indicating disassembly of the active zone.