| First Author | Zacchia M | Year | 2018 |
| Journal | J Am Soc Nephrol | Volume | 29 |
| Issue | 6 | Pages | 1720-1730 |
| PubMed ID | 29678998 | Mgi Jnum | J:291015 |
| Mgi Id | MGI:6436005 | Doi | 10.1681/ASN.2017121268 |
| Citation | Zacchia M, et al. (2018) Acid Stimulation of the Citrate Transporter NaDC-1 Requires Pyk2 and ERK1/2 Signaling Pathways. J Am Soc Nephrol 29(6):1720-1730 |
| abstractText | Background Urine citrate is reabsorbed exclusively along the renal proximal tubule via the apical Na(+)-dicarboxylate cotransporter NaDC-1. We previously showed that an acid load in vivo and media acidification in vitro increase NaDC-1 activity through endothelin-1 (ET-1)/endothelin B (ETB) signaling. Here, we further examined the signaling pathway mediating acid-induced NaDC-1 activity.Methods We transiently transfected cultured opossum kidney cells, a model of the proximal tubule, with NaDC-1 and ETB and measured [(14)C]-citrate uptake after media acidification under various experimental conditions, including inactivation of Pyk2 and c-Src, which were previously shown to be activated by media acidification. Wild-type (Pyk2(+/+)) and Pyk2-null (Pyk2(-/-)) mice were exposed to NH4Cl loading and euthanized after various end points, at which time we harvested the kidneys for immunoblotting and brush border membrane NaDC-1 activity studies.Results Inhibition of Pyk2 or c-Src prevented acid stimulation but not ET-1 stimulation of NaDC-1 in vitro Consistent with these results, NH4Cl loading stimulated NaDC-1 activity in kidneys of wild-type but not Pyk2(-/-) mice. In cultured cells and in mice, ERK1/2 was rapidly phosphorylated by acid loading, even after Pyk2 knockdown, and it was required for acid but not ET-1/ETB stimulation of NaDC-1 in vitro Media acidification also induced the phosphorylation of Raf1 and p90RSK, components of the ERK1/2 pathway, and inhibition of these proteins blocked acid stimulation of NaDC-1 activity.Conclusions Acid stimulation of NaDC-1 activity involves Pyk2/c-Src and Raf1-ERK1/2-p90RSK signaling pathways, but these pathways are not downstream of ET-1/ETB in this process. |
