Differential expression of KCNQ1 K+ channel in tubular cells of frog kidney

Abstract

The aim of this study was to evaluate KCNQ1 K+ channel expression in the frog kidney of Rana esculenta. KCNQ1 K+ channel, also known as KvLQT1, is the pore forming a-subunit of the IKs K+ channel, a delayed rectifier voltage-gated K+ channel, which has an important role in water and salt transport in the kidney and gastrointestinal tract. The expression of KCNQ1 K+ channel along tubular epithelium differs from species to species. In the present study the expression of KCNQ1 K+ channel in the frog kidney has been demonstrated by immunohistochemistry. The presence of KCNQ1 K+ channel was demonstrated in the epithelial cells of distal convoluted tubule and collecting duct. However, the pattern of expression of KCNQ1 K+ channel differs between distal convoluted tubules and collecting duct. All epithelial cells of distal convoluted tubules revealed basolateral expression of KCNQ1 K+ channel. On the contrary, only the single cells of collecting duct, probably intercalated cells, showed diffuse cell surface staining with antibodies against KCNQ1 K+ channel. These findings suggest that KCNQ1 K+ channel has cell-specific roles in renal potassium ion transport.

Figure 1

(a) Lack of KCNQ1 expression in proximal tubules (Immunoperoxidase staining, scale bar 500 µm); (b) KCNQ1 expression in distal convoluted tubular epithelial cells (Immunoperoxidase staining, scale bar 100 µm); (c) Basolateral expression of KCNQ1 channels protein in distal tubular cells (arrows) (Immunoperoxidase staining, scale bar 50 µm); (d) Membrane expression of KCNQ1 on intercalated cells (arrowhead) of medullar collecting ducts (Immunoperoxidase staining, scale bar 50 µm).