Tissue expression of mRNA of chloride channel from MDCK cells and its regulation by protein kinases.

A new chloride channel has recently been identified by expression cloning (Paulmichl, M., et al. Nature 356: 238). To date there is no information available on the distribution of this channel in mammalian tissues. We cloned rat homologue of this Cl channel and found 92% identity in deduced amino-acid sequence. We studied the tissue distribution of its mRNA and regulation by protein kinases. Its mRNA was expressed in all 17 bovine tissues we studied, most abundantly in the brain. In the kidney, it was expressed more in the medulla than cortex. Dehydration up to 5 days did not change its mRNA level in the rat kidney. Both phorbol myristate acetate (PMA) and forskolin down regulated its expression in MDCK cells, suggesting that both PKC and PKA modulated its expression. The physiological role of this chloride channel remains to be clarified.