Hydrogen sulfide targets EGFR Cys797/Cys798 residues to induce Na(+)/K(+)-ATPase endocytosis and inhibition in renal tubular epithelial cells and increase sodium excretion in chronic salt-loaded rats.

AIMS: The role of hydrogen sulfide (H2S) in renal sodium and water homeostasis is unknown. We investigated whether H2S promoted Na(+)/K(+)-ATPase endocytosis via the H2S/EGFR/gab1/PI3K/Akt pathway in renal tubular epithelial cells.
RESULTS: H2S decreased Na(+)/K(+)-ATPase activity and induced its endocytosis in renal tubular epithelial cells, which was abrogated by small interfering RNA (siRNA) knockdown of epidermal growth factor receptor (EGFR) and gab1, a dominant-negative mutant of Akt and PI3K inhibitors. H2S increased EGFR, gab1, PI3K, and Akt phosphorylation in both renal tubular epithelial cells and kidneys of chronic salt-loaded rats. These increases were abrogated by siRNA knockdown of EGFR, but not of c-Src. Radiolabeled H2S exhibited transient, direct binding to EGFR and directly activated EGFR. Some disulfide bonds in EGFR intracellular kinase domain were susceptible to H2S-induced cleavage. Mutations of EGFR Cys797 (human) or Cys798 (rat) residues increased EGFR activity and prevented H2S-induced Na(+)/K(+)-ATPase endocytosis. H2S also inhibited sodium hydrogen exchanger-3 (NHE3) activity in renal tubular epithelial cells. H2S treatment increased sodium excretion in chronic and acute salt-loaded rats and decreased blood pressure in chronic salt-loaded rats. INNOVATION AND
CONCLUSION: H2S directly targets some disulfide bonds in EGFR, which activates the EGFR/gab1/PI3K/Akt pathway and subsequent Na(+)/K(+)-ATPase endocytosis and inhibition in renal tubular epithelial cells. EGFR Cys797/Cys798 residues are essential for an intrinsic inhibitory mechanism and for H2S actions in renal tubular epithelial cells. Other pathways, including NHE3, may be involved in mediating the renal effects of H2S. Our results reveal a new renal sodium homeostasis mechanism, which may provide for novel treatment approaches for diseases related to renal sodium homeostasis dysfunction.