Ouabain and Insulin Induce Sodium Pump Endocytosis in Renal Epithelium

Abstract

Cardiotonic steroids signaling through the basolateral sodium pump (Na/KATPase) have been shown to alter renal salt handling in intact animals. As the relationship between renal salt handling and blood pressure is a key determinant of hypertension, and patients with insulin resistance are frequently hypertensive, we chose to examine whether there might be competition for resources necessary for receptor mediated endocytosis. In LLC-PK1 cells, the Na/K-ATPase-α1 and carcinoembryonic antigen cell adhesion molecule (CEACAM1), a plasma membrane protein that promotes receptor-mediated endocytosis, co-localized in the plasma membranes and translocated to the intracellular region in response to ouabain. Either ouabain or insulin alone caused accumulation of CEACAM1 as well as IRβ, and EGFR in early endosomes, but no synergy was demonstrable. Like ouabain, insulin also caused c-Src activation. When caveolin or Na/K-ATPase-α1 expression was knocked down with siRNA, insulin but not ouabain induced CEACAM1, IRβ, and EGFR endocytosis. To determine whether this might be relevant to salt handling in vivo, we examined salt loading in mice with null renal CEACAM2 expression (Cc2−/−). The Cc2−/− animals demonstrated greater increases in blood pressure with increases in dietary salt than control animals. These data demonstrate that cardiotonic steroids and insulin compete for cellular endocytosis resources and suggest that under conditions where circulating insulin concentrations are high, cardiotonic steroid mediated natriuresis could be impaired.

Cardiac glycosides induced toxicity in human cells expressing α1-, α2-, or α3-isoforms of Na-K-ATPase

“…The knockdown of ␣1 in the work by Xie et al was correlated with an increase in basal Src activity and activation of consequent signal transduction pathways. Although our present work does not address this issue directly, our previously published study (4) showed no relationship between Src/phosphoinositide-3-kinase signaling pathways to ouabain-induced inhibition and subsequent internalization of Na ϩ -K ϩ -ATPase in our cellular system, as opposed to results described previously by Xie et al (11,(22)(23)(24).…”

ATP1A1-Mediated Src Signaling Inhibits Coronavirus Entry into Host Cells

“…CoV and VSV replication was not affected, as revealed by the addition of the CTSs after inoculation. Inhibition of MHV was found to be independent of the particular virus receptor being used by the virus, despite the reported interaction between CEACAM1 and ATP1A1 (41). This is in line with FIPV and MERS-CoV being similarly inhibited although they use entirely different entry receptors (54,55).…”

“…CEACAM1 has been reported to interact with ATP1A1 in porcine cells (41). Since murine CEACAM1a, the natural receptor of MHV, is a homologue thereof, we investigated whether the positive effect of ATP1A1 on MHV infection is somehow linked to MHV binding to CEACAM1a.…”

Effect of Insulin on Proximal Tubules Handling of Glucose: A Systematic Review

“…In the same way, in a culture complex model, insulin exposition raised renal NKA activity in the first 30 minutes, but it returned to the baseline levels after 2 hours and was even lower at 48-hour measurements [166]. This reduction was likewise observed after one hour of insulin exposition in another study [167]. Taken together, these results suggest a dual temporal insulin action on NKA activity.…”