CPLX1CPLX4

CPLX1CPLX4 refers to a proposed heteromeric complex formed by Complexin-1 (CPLX1) and Complexin-4 (CPLX4), members of the Complexin family of small SNARE-binding proteins. Complexins regulate synaptic vesicle exocytosis at chemical synapses by interacting with the SNARE complex, influencing both spontaneous and Ca2+-triggered neurotransmitter release. The CPLX family comprises four isoforms (CPLX1–CPLX4), which show distinct but overlapping expression patterns in the nervous system, including brain regions and retina. The idea of a CPLX1CPLX4 complex arises from observations suggesting physical association or co-localization of CPLX1 and CPLX4 in neuronal tissue, implying possible combinatorial roles beyond those of each isoform alone.

Functionally, complexins modulate vesicle fusion by stabilizing the SNARE complex and acting as a clamp to limit spontaneous release while promoting rapid release upon Ca2+ influx. A CPLX1CPLX4 complex could, in theory, provide nuanced regulation of release probability, vesicle priming, and synaptic plasticity at synapses expressing both isoforms. However, experimental evidence for a distinct, physiologically relevant CPLX1CPLX4 complex is still limited, and the precise stoichiometry, regulation, and functional significance remain to be fully established.

In research contexts, CPLX1CPLX4 serves as a framework for exploring how combinations of Complexin isoforms contribute to the diversity of synaptic transmission. Disruptions in complexin function have been linked to neurological disorders in some studies, underscoring the potential relevance of isoform interactions for synaptic health.