Munc131

Munc131 is not a standardly used term in genetics or neuroscience and may refer to Munc13-1, also known as UNC13A. The latter is a key presynaptic active-zone protein involved in neurotransmitter release and synaptic vesicle priming.

Munc13-1 belongs to the Munc13 family, which also includes UNC13B and UNC13C. It is predominantly expressed in neurons and localizes to presynaptic terminals where it prepares synaptic vesicles for fusion with the plasma membrane. Its activity is essential for efficient neurotransmitter release, particularly during fast synaptic transmission.

The protein promotes the priming of synaptic vesicles by facilitating the transition of syntaxin-1 from a closed to an open conformation, enabling the assembly of the SNARE complex required for membrane fusion. This priming step is tightly regulated by intracellular signals, including diacylglycerol (DAG) and calcium ions. The C1 domain binds DAG and phorbol esters, enhancing release, while the C2 domains contribute to calcium- and lipid-dependent regulation of membrane interactions.

Munc13-1 interacts with several other presynaptic proteins, notably RIM and Munc18-1, to position and stabilize the release machinery at active zones. Genetic and functional studies in model systems show that loss or disruption of Munc13-1 impairs synaptic vesicle priming and neurotransmission, underscoring its crucial role in synaptic function.

In summary, if encountered as Munc131, the term most plausibly points to Munc13-1 (UNC13A), a central regulator of synaptic vesicle priming in neurons.