Phosphoinositide binding differentially regulates NHE1 Na+/H+ exchanger-dependent proximal tubule cell survival.
Tubular atrophy predicts chronic kidney disease progression, and is caused by proximal tubular epithelial cellcaused by proximal tubular epithelial cell (PTC) apoptosis. The normally quiescent Na(+)/H(+) exchanger-1 (NHE1) defends against PTC apoptosis, and is regulated by PI(4,5)P(2) binding. Because of the vast array of plasma membrane lipids, we hypothesized that NHE1-mediated cell survival is dynamically regulated by multiple anionic inner leaflet phospholipids. In membrane overlay and surface plasmon resonance assays, the NHE1 C terminus bound phospholipids with low affinity and according to valence (PIP(3) > PIP(2) > PIP = PA > PS). NHE1-phosphoinositide binding was enhanced by acidic pH, and abolished by NHE1 Arg/Lys to Ala mutations within two juxtamembrane domains, consistent with electrostatic interactions. PI(4,5)P(2)-incorporated vesicles were distributed to apical and lateral PTC domains, increased NHE1-regulated Na(+)/H(+) exchange, and blunted apoptosis, whereas NHE1 activity was decreased in cells enriched with PI(3,4,5)P(3), which localized to basolateral membranes. Divergent PI(4,5)P(2) and PI(3,4,5)P(3) effects on NHE1-dependent Na(+)/H(+) exchange and apoptosis were confirmed by selective phosphoinositide sequestration with pleckstrin homology domain-containing phospholipase Cδ and Akt peptides, PI 3-kinase, and Akt inhibition in wild-type and NHE1-null PTCs. The results reveal an on-off switch model, whereby NHE1 toggles between weak interactions with PI(4,5)P(2) and PI(3,4,5)P(3). In response to apoptotic stress, NHE1 is stimulated by PI(4,5)P(2), which leads to PI 3-kinase activation, and PI(4,5)P(2) phosphorylation. The resulting PI(3,4,5)P(3) dually stimulates sustained, downstream Akt survival signaling, and dampens NHE1 activity through competitive inhibition and depletion of PI(4,5)P(2).
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109.
Bassam G
BG
Abu Jawdeh
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109.
Shenaz
S
Khan
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109; Departments of Physiology and Biophysics, Lerner Research Institute, Case Western Reserve University, Cleveland, Ohio 44109.
Isabelle
I
Deschênes
Departments of Physiology and Biophysics, Lerner Research Institute, Case Western Reserve University, Cleveland, Ohio 44109.
Malcolm
M
Hoshi
Departments of Physiology and Biophysics, Lerner Research Institute, Case Western Reserve University, Cleveland, Ohio 44109.
Monu
M
Goel
Departments of Physiology and Biophysics, Lerner Research Institute, Case Western Reserve University, Cleveland, Ohio 44109.
Jeffrey T
JT
Lock
Departments of Physiology and Biophysics, Lerner Research Institute, Case Western Reserve University, Cleveland, Ohio 44109.
Krekwit
K
Shinlapawittayatorn
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109; Departments of Physiology and Biophysics, Lerner Research Institute, Case Western Reserve University, Cleveland, Ohio 44109.
Gerald
G
Babcock
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109.
Sujata
S
Lakhe-Reddy
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109.
Garren
G
DeCaro
Department of Cleveland Clinic Foundation, Case Western Reserve University, Cleveland, Ohio 44109.
Satya P
SP
Yadav
Department of Cleveland Clinic Foundation, Case Western Reserve University, Cleveland, Ohio 44109.
Maradumane L
ML
Mohan
Department of Cleveland Clinic Foundation, Case Western Reserve University, Cleveland, Ohio 44109.
Sathyamangla V
SV
Naga Prasad
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109; Departments of Physiology and Biophysics, Lerner Research Institute, Case Western Reserve University, Cleveland, Ohio 44109.
William P
WP
Schilling
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109.
Eckhard
E
Ficker
Department of Medicine, Case Western Reserve University, Cleveland, Ohio 44109. Electronic address: jeffrey.schelling@case.edu.
Jeffrey R
JR
Schelling
D000818:Animals; D017209:Apoptosis; D027682:Cation Transport Proteins / Q000378:metabolism*; D002470:Cell Survival; D003600:Cytosol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007295:Inositol Phosphates / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D010455:Peptides / Q000737:chemistry; D018129:Phosphatidylinositol Phosphates / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry; D017434:Protein Structure, Tertiary; D011522:Protons; D012964:Sodium / Q000737:chemistry; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D020349:Surface Plasmon Resonance; D013552:Swine
D027682:Cation Transport Proteins; D007295:Inositol Phosphates; D010455:Peptides; D018129:Phosphatidylinositol Phosphates; D010743:Phospholipids; D011522:Protons; C490997:Slc9a1 protein, mouse; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; C060974:phosphatidylinositol 3,4,5-triphosphate; C066454:inositol 4,5-bisphosphate; D012964:Sodium