Complexin1

Complexin-1 (CPLX1) is a small, soluble presynaptic protein that binds to SNARE complexes and regulates neurotransmitter release. In humans, the CPLX1 gene encodes the Complexin-1 protein, one member of the Complexin family that is expressed in the nervous system.

Complexin-1 participates in the regulation of neurotransmitter release at chemical synapses. It binds to the core SNARE complex formed by syntaxin-1, SNAP-25, and synaptobrevin (VAMP2). By stabilizing a partially assembled SNARE complex, Complexin-1 promotes rapid, calcium-triggered vesicle fusion while also suppressing spontaneous, calcium-independent release in many synapses. Its action is thought to involve cooperation with synaptotagmin-1, the principal calcium sensor for evoked release.

Expression of CPLX1 is primarily neuronal, with high levels in brain regions involved in fast synaptic transmission. Complexin-1 localizes to presynaptic terminals and coexists with other SNARE components. The Complexin family also includes CPLX2, CPLX3, and CPLX4, which display distinct tissue- and cell-type-specific expression patterns.

Functional studies in model organisms indicate that loss or disruption of CPLX1 impairs synaptic transmission and alters neurotransmitter release probability, underscoring its role in maintaining proper synaptic communication and plasticity. Overall, Complexin-1 acts as a regulator that fine-tunes exocytosis and contributes to the precision of neural signaling.