title: Intracellular pH regulation by Na⁺/H⁺ exchanger-1 (NHE1) is required for growth factor-induced mammary branching morphogenesis.
abstract: Regulation of intracellular pH (pHi) and protection against cytosolic acidification is primarily a function of the ubiquitous plasma membrane Na+/H+exchanger-1 (NHE1), which uses a highly conserved process to transfer cytosolic hydrogen ions (H+) across plasma membranes in exchange for extracellular sodium ions (Na+). Growth factors, which are essential regulators of morphogenesis, have also been found to be key activators of NHE1 exchanger activity; however, the crosstalk between both has not been fully evaluated during organ development. Here we report that mammary branching morphogenesis induced by transforming growth factor-alpha (TGFα) requires PI3K-dependent NHE1-activation and subsequent pHi alkalization. Inhibiting NHE1 activity after TGFα stimulation with 10 μM of the NHE1-specific inhibitor N-Methyl-N-isobutyl Amiloride (MIA) dramatically disrupted branching morphogenesis, induced extensive proliferation, ectopic expression of the epithelial hyper-proliferative marker Keratin-6 and sustained activation of MAPK. Together these findings indicate a novel developmental signaling cascade involving TGFα>PI3K>NHE1>pHi alkalization, which leads to a permissible environment for MAPK negative feedback inhibition and thus regulated mammary branching morphogenesis.
authors.affiliation: Department of Biology, College of Staten Island, 2800 Victory Blvd., Staten Island, NY 10314, USA.
authors.forename: Edmund C
authors.initials: EC
authors.lastname: Jenkins
authors.forename: Shawon
authors.initials: S
authors.lastname: Debnath
authors.forename: Stephen
authors.initials: S
authors.lastname: Gundry
authors.forename: Sajini
authors.initials: S
authors.lastname: Gundry
authors.forename: Umit
authors.initials: U
authors.lastname: Uyar
authors.forename: Jimmie E
authors.initials: JE
authors.lastname: Fata
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D027682:Cation Transport Proteins / Q000502:physiology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D053553:Keratin-6; D008321:Mammary Glands, Animal / Q000196:embryology* / Q000502:physiology; D051379:Mice; D009024:Morphogenesis / Q000187:drug effects / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D000081082:Phosphoinositide-3 Kinase Inhibitors; D015398:Signal Transduction; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000502:physiology*; D016211:Transforming Growth Factor alpha / Q000502:physiology
chemical_list: D000584:Amiloride; D027682:Cation Transport Proteins; D053553:Keratin-6; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D016211:Transforming Growth Factor alpha; C490997:Slc9a1 protein, mouse; C056369:5-(N-methyl-N-isobutyl)amiloride