| First Author | Thibodeau S | Year | 2020 |
| Journal | J Biol Chem | PubMed ID | 33199372 |
| Mgi Jnum | J:306604 | Mgi Id | MGI:6716978 |
| Doi | 10.1074/jbc.RA120.015037 | Citation | Thibodeau S, et al. (2020) Calmodulin binds and modulates K(+)-dependent Na(+)/Ca(2+)-exchanger isoform 4, NCKX4. J Biol Chem |
| abstractText | The family of K+-dependent Na+/Ca2+-exchangers, NCKX, are important mediators of cellular Ca2+ efflux, particularly in neurons associated with sensory transduction. The NCKX family comprises five proteins, NCKX1-5, each the product of a different SLC24 gene. NCKX4 (SLC24A4) has been found to have a critical role in termination and adaptation of visual and olfactory signals, melanocortin-dependent satiety signaling, and the maturation of dental enamel. To explore mechanisms that might influence the temporal control of NCKX4 activity, a yeast two-hybrid system was used to search for protein interaction partners. We identified calmodulin as a partner for NCKX4, and confirmed the interaction using glutathione-S-transferase-fusion-pulldown. Calmodulin binding to NCKX4 was demonstrated in extracts from mouse brain and in transfected HEK293 cells. Calmodulin bound in a Ca2+-dependent manner to a motif present in the central cytosolic loop of NCKX4, and was abolished by the double mutant I328D/F334D. When co-transfected in HEK293 cells, calmodulin bound to NCKX4 under basal conditions and induced a ~2.5-fold increase in NCKX4 abundance, but did not influence either cellular location or basal activity. When purinergic stimulation of NCKX4 was examined in these cells, co-expression of wild type calmodulin, but not a Ca(2+) binding-deficient calmodulin mutant, suppressed NCKX4 activation in a time-dependent manner. We propose that Ca2(+) binding to calmodulin pre-positioned on NCKX4 induces a slow conformational rearrangement that interferes with purinergic stimulation of the exchanger, possibly by obscuring T331, a previously identified potential protein kinase C site. |
