Sodium-calcium Exchanger 1 Regulates Epithelial Cell Migration via Calcium-Dependent Extracellular-Signal-Regulated Kinase Signaling [Cell Biology]
March 13th, 2015 by Balasubramaniam, S. L., Gopalakrishnapillai, A., Gangadharan, V., Duncan, R. L., Barwe, S. P.
Na+/Ca2+ exchanger-1 (NCX1) is a major calcium extrusion mechanism in renal epithelial cells enabling the efflux of one Ca2+ ion and the influx of three Na+ ions. The gradient for this exchange activity is provided by Na,K-ATPase, a hetero-oligomer consisting of a catalytic α-subunit and a regulatory β-subunit (Na,K-β) that also functions as a motility and tumor suppressor. We showed earlier that mice with heart-specific ablation (KO) of Na,K-β had a specific reduction in NCX1 protein and were ouabain-insensitive. Here, we demonstrate that Na,K-β associates with NCX1 and regulates its localization to the cell surface. MDCK cells with Na,K-β knockdown (β-KD) have reduced NCX1 protein and function accompanied by 2.1-fold increase in free intracellular calcium and a corresponding increase in the rate of cell migration. Increased intracellular calcium upregulated ERK1/2 via calmodulin-dependent activation of PI3K. Both myosin light chain (MLC) kinase and Rho-associated kinase acted as mediators of ERK1/2-dependent migration. Restoring NCX1 expression in β-KD cells reduced migration rate and ERK1/2 activation, suggesting that NCX1 functions downstream of Na,K-β in regulating cell migration. In parallel, inhibition of NCX1 by KB-R7943 in MDCK, LLC-PK1 and human primary renal epithelial cells (HREpiC) increased ERK1/2 activation and cell migration. This increased migration was associated with high MLC phosphorylation by PI3K/ERK dependent mechanism in HREpiC cells. These data confirm the role of NCX1 activity in regulating renal epithelial cell migration.