title: Functional interdependence of NHE1 and merlin in human melanoma cells.
abstract: Upregulation of the Na(+)/H(+) exchanger isoform 1 (NHE1) has been correlated with tumor malignancy. In contrast, moesin-radixin-ezrin-like protein (merlin) is a tumor suppressor that protects from cancerogenesis. Merlin is highly related to the members of the ezrin, radixin, and moesin (ERM) protein family that are directly attached to and functionally linked with NHE1. In addition, merlin inhibits the MAPK cascade and the Rho-GTPases known to activate NHE1 activity. The present study investigates whether NHE1 expression and activity affect merlin or, conversely, whether merlin has an impact on NHE1 in human melanoma (MV3) cells. Indeed, features of merlin-deficient MV3 cells point to a functional link: merlin-deficient cells showed a decreased NHE1 expression and, paradoxically, an increase in NHE1 activity as measured upon cytosolic acidification (NH4Cl prepulse method). Loss of merlin also led to an elevated cell motility that could be further increased by NHE1 overexpression, whereas NHE1 overexpression alone had no effect on migration. In contrast, neither NHE1 expression nor its activity had an impact on merlin expression. These results suggest a novel tumor suppressor function of merlin in melanoma cells: the inhibition of the proto-oncogenic NHE1 activity, possibly including its downstream signaling pathways.
authors.affiliation: Institute of Physiology II, University of Münster, Robert-Koch-Str. 27b, D-48149 Münster, Germany.
authors.forename: Fabian
authors.initials: F
authors.lastname: Frontzek
authors.forename: Svenja
authors.initials: S
authors.lastname: Nitzlaff
authors.forename: Malte
authors.initials: M
authors.lastname: Horstmann
authors.forename: Albrecht
authors.initials: A
authors.lastname: Schwab
authors.forename: Christian
authors.initials: C
authors.lastname: Stock
mesh_terms: D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020935:MAP Kinase Signaling System; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D025581:Neurofibromin 2 / Q000235:genetics / Q000378:metabolism*; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D025581:Neurofibromin 2; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers
keywords: NHE1; cell motility; melanoma; merlin; motilité cellulaire; mélanome; neurofibromatosis type 2 tumor suppressor; suppresseur de tumeur responsable de la neurofibromatose de type 2