Purinergic stimulation of K+-dependent Na+/Ca2+ exchanger isoform 4 requires dual activation by PKC and CaMKII.

K + -dependent Na + /Ca 2+ -exchanger isoform 4 (NCXK4) is one of the most broadly expressed members of the NCKX (K + -dependent Na + /Ca 2+ -exchanger) family. Recent data indicate that NCKX4 plays a critical role in controlling normal Ca 2+ signal dynamics in olfactory and other neurons. Synaptic Ca 2+ dynamics are modulated by purinergic regulation, mediated by ATP released from synaptic vesicles or from neighbouring glial cells. Previous studies have focused on modulation of Ca 2+ entry pathways that initiate signalling. Here we have investigated purinergic regulation of NCKX4, a powerful extrusion pathway that assists in terminating Ca 2+ signals. NCKX4 activity was stimulated by ATP through activation of the P2Y receptor signalling pathway. Stimulation required dual activation of PKC (protein kinase C) and CaMKII (Ca 2+ /calmodulin-dependent protein kinase II). Mutating T312, a putative PKC phosphorylation site on NCKX4, partially prevented purinergic stimulation. These data illustrate how purinergic regulation can shape the dynamics of Ca 2+ signalling by activating a signal damping and termination pathway.