The sodium-hydrogen exchanger NHE1 is an Akt substrate necessary for actin filament reorganization by growth factors.
The kinase Akt mediates signals from growth factor receptors for increased cell proliferation, survival, and migration, which contribute to the positive effects of Akt in cancer progression. Substrates are generally inhibited when phosphorylated by Akt; however, we show phosphorylation of the plasma membrane sodium-hydrogen exchanger NHE1 by Akt increases exchanger activity (H(+) efflux). Our data fulfill criteria for NHE1 being a bona fide Akt substrate, including direct phosphorylation in vitro, using mass spectrometry and Akt phospho-substrate antibodies to identify Ser(648) as the Akt phosphorylation site and loss of increased exchanger phosphorylation and activity by insulin and platelet-derived growth factor in fibroblasts expressing a mutant NHE1-S648A. How Akt induces actin cytoskeleton remodeling to promote cell migration and tumor cell metastasis is unclear, but disassembly of actin stress fibers by platelet-derived growth factor and insulin and increased proliferation in growth medium are inhibited in fibroblasts expressing NHE1-S648A. We predict that other functions shared by Akt and NHE1, including cell growth and survival, might be regulated by increased H(+) efflux.
Meima
Marcel E
ME
Department of Cell and Tissue Biology, University of California, San Francisco, California 94143, USA.
Webb
Bradley A
BA
Witkowska
H Ewa
HE
Barber
Diane L
DL
D000199:Actins / Q000378:metabolism*; D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D013058:Mass Spectrometry; D018613:Microscopy, Confocal; D009154:Mutation; D010766:Phosphorylation / Q000187:drug effects; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012694:Serine / Q000378:metabolism; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*
D000199:Actins; D027682:Cation Transport Proteins; D007328:Insulin; D036341:Intercellular Signaling Peptides and Proteins; D010982:Platelet-Derived Growth Factor; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D012694:Serine; D051057:Proto-Oncogene Proteins c-akt