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Abstract: TH-PO921

K-Cadherin Expression Regulates Activation State of Transcription Factors in the Presence and Absence of TGF-β1

Session Information

Category: CKD (Non-Dialysis)

  • 1903 CKD (Non-Dialysis): Mechanisms

Authors

  • Kalsi, Kameljit Kaur, South West Thames Institute for Renal Research, Carshalton, United Kingdom
  • Jain, Seema, South West Thames Institute for Renal Research, Carshalton, United Kingdom
  • Phanish, Mysore K., South West Thames Institute for Renal Research, Carshalton, United Kingdom
  • Dockrell, Mark E., South West Thames Institute for Renal Research, Carshalton, United Kingdom
Background

K-cadherin (Cadherin 6) is an atypical type I cadherin with high expression in the kidney where it is exclusively expressed in the proximal tubule. Unlike other cadherins in the tubule K-cadherin is expressed basally directly adjacent to the basement membrane. Disruption and loss of renal K-cadherin expression is associated with progressive diabetic nephropathy. Disruption of the precise cellular localisation has been reported in Renal Cell Carcinoma. Recently we have reported a similar disruption in biopsies from renal transplants. The alteration of K-cadherin expression in cancer and fibrosis suggests a potential role in regulating gene expression.

Methods

HKC clone 8 cells, a transformed human PTEC line which do not have detectable K-cadherin protein, were transfected with human K-cadherin pcDNA3.1 expression vector (1µg). Cells were fixed and stained for K-cadherin and visualized by using a 3D deconvolution microscope. Primary human PTECs (K-cadherin positive), control HKC8 (HKC8 K-) and transfected HKC8 cells (HKC8 K+) were grown on non-coated plastic and collagen IV coated dishes and exposed to 2.5 ng/ml TGF-β1 for 5 min before cells were lysed and analysed by western blot.

Results

HKC8 K+ cells showed K-cadherin expression similar to that expected in primary cells, localised in vesicular Golgi-type structures as well as at the cell periphery and was predominantly found in the basal layer. Regulation of important transcription factors Elk1, Erk5a & Erk5b were investigated. TGF-β1 induced an increase of phospho-Elk1 in HKC8 K- cells grown on collagen IV but a reduction in phospho-Elk1 in HKC8 K+ cells. The expression of K-cadherin had no effect on TGFβ-induced phospho-Elk1 in cells grown on plastic. In primary PTECs grown on collagen IV TGFβ1 reduced phospho-Elk1 levels. Although TGFβ1 induces phosphorylation of Erk5a it has no effect on the levels of activated (phosphorylated) Erk5b. However, the expression of K-cadherin alone significantly increased phospho-Erk5b.

Conclusion

The basal expression of K-cadherin appears to be critical in regulating transcription factor activation in human primary proximal tubule cells due, at least in part, to its interaction with collagen IV. Disrupted expression seen in cancer and during renal injury will result in alteration of gene activation and cellular responses.