Complexin-2 (CPLX2)

Complexin-2 (CPLX2) is a small soluble cytosolic protein that regulates vesicle fusion at synapses, critically modulating the timing and efficacy of neurotransmitter release by binding to the assembled neuronal SNARE (Soluble NSF Attachment Protein Receptor) complex[1][2][5][7]. Through dynamic interactions, complexin-2 both inhibits spontaneous ("clamps") and facilitates synchronous ("triggers") synaptic vesicle exocytosis in response to Ca²⁺ influx, ensuring precise and rapid synaptic transmission[2][5][7]. Its action involves binding to the groove between the synaptobrevin and syntaxin helices of the SNARE core complex, and its inhibitory clamp function is relieved upon Ca²⁺-activated synaptotagmin binding—thus coupling vesicle fusion tightly to action potential-induced Ca²⁺ signals[2][5][7]. Complexin-2 is predominantly expressed in neural tissue but is also found in B lymphocytes, where it inhibits spontaneous secretion of antibodies (IgM and IgG1)[4]. Reduced CPLX2 expression or genetic variants have been associated with synaptic deficits in neuropsychiatric and neurodegenerative disorders such as schizophrenia[1]. While of substantial mechanistic and pathophysiological interest, complexin-2 itself is not currently a direct therapeutic target of any drugs[1][2][4][5][7].

Other names

Complexin IICPX IICPX-2CPLX2Synaphin-1Synaphin 1921-LDKFZp547D155CPX2Hfb1complexin IIcomplexin-2complexin 2