Identification of complexin II in astrocytes: a possible regulator of glutamate release in these cells

Complexins are a family of SNARE complex-binding proteins which regulate neurotransmitter release by playing a crucial role in triggering fast exocytosis at the synapse. Current evidence indicates astrocytes can release glutamate via a vesicular mechanism similar to that at nerve terminals and thereby modulate synaptic activity. In addition, components of the biochemical machinery associated with synaptic release have been identified in these cells. However, whether complexins are also present in astrocytes and may therefore participate in the vesicular release of glutamate is a key issue that is yet to be determined. In the present study we therefore examined if astrocytes express complexin I (Cpx I) and/or complexin II (Cpx II). Our results indicate these cells contain Cpx II but not Cpx I in primary culture. In addition, serum deprivation for 24 h led to a 2.6-fold increase in Cpx II, suggesting this protein is responsive to insults. These findings point to Cpx II being a likely key modulator of synaptic activity at the level of these glial cells. Given the considered involvement of complexins in neurologic and psychiatric illness, astrocytic Cpx II represents a potentially important therapeutic target for the future treatment of such maladies.