Abstract: TH-PO395

Osmotic Pressure Increases TGFβ1-Mediated Loss of SGLT2 Expression in Human Proximal Tubule Cells

Session Information

Category: Cell Biology

  • 203 Growth Factors, Chemokines, Autacoids

Authors

  • Pan, Xinlu, St Helier Hospital, London, United Kingdom
  • Baines, Deborah L., St George's, University of London, London, United Kingdom
  • Phanish, Mysore Keshavmurthy, SW Thames renal and transplantation unit, London, United Kingdom
  • Dockrell, Mark E., South West Thames Institute for Renal Research, London, United Kingdom
Background

Approximately 90% of glucose is reabsorbed by the low affinity Na+/glucose co-transporter SGLT2, predominantly expressed in the early proximal tubule. This transporter has received renewed interest in the light of anti-diabetic drugs targeting its activity. Although reports suggest an increase in SGLT2 expression in diabetic nephropathy (DN), we hypothesised that the loss of phenotype of proximal tubule epithelial cells (PTEC) observed in DN may result in a decrease in SGLT2 expression.

Methods

Primary human PTEC were cultured on plain or collagen IV coated plastic-ware in supplemented medium. Cells at 80% confluence were treated with: 5mM D-Glucose (normoglycaemia), 25mM D-Glucose (hyperglycaemia), or 5 mM D-Glucose + 20mM L-Glucose (osmotic control) +/-TGFβ1(0.75ng/ml). After 24h, medium was collected and cells lysed. Western blot was used to detect protein expression; membranes were probed with antibodies against: SGLT2, SGLT1, K-Cadherin and tubulin.

Results

Primary PTEC expressed mature SGLT2, molecular weight of ~ 73KDa, indicating appropriate post-translational processing and membrane localisation. Probing with the SGLT1 antibody only identified bands of 60 KDa or lower, indicating an immature protein not expressed at the membrane. TGFβ1 treatment (24h) resulted in a decrease in SGLT2 expression in all treatments; this effect was more pronounced in cells grown on collagen and in osmotic control containing non-transported/non-metabolised L-glucose. K-Cadherin protein expression was not reduced by TGFβ1 at this time point; in fact there was a tendency to increased expression in cells treated with D-Glucose + TGFβ1.

Conclusion

Our data demonstrates that TGFβ1 reduced the expression of mature SGLT2 protein in human primary PTEC. This is not consistent with recent reports of a TGFβ1-induced increase in SGLT2 expression using transformed cells grown on plastic, less representative of the in vivo situation. SGLT2 was decreased prior to any measurable loss of K-Cadherin, suggesting that SGLT2 could be a more sensitive phenotypic marker than cadherin in PTEC. An increase in K-Cadherin expression in response to D-Glucose + TGFβ1 may be secondary to cellular hypertrophy observed in DN. In the other presentation from our group on this topic we investigate whether there is a metabolic interaction between TGFβ1 and SGLT2 activity.

Funding

  • Private Foundation Support