A NOVEL CHLORIDE-DEPENDENT GTP-UTILIZING PROTEIN-KINASE IN PLASMA-MEMBRANES FROM HUMAN RESPIRATORY EPITHELIUM

The protein kinases that stimulate ion flux across airway epithelium a re believed to utilize ATP as phosphate donor. Here we show that a chl oride-sensitive protein kinase (in an apically enriched plasma membran e fraction from human nasal respiratory epithelium) uses guanosine 5'- triphosphate in preference to ATP as phosphate donor and is not inhibi ted by the protein kinase inhibitors staurosporine, 1-(5-isoquinolinyl sulfonyl)-2-methylpiperazine, and N-(2-guanodinoethyl)-5-isoquinoline sulfonamide. This kinase phosphorylates a 37-kDa membrane protein (p37 ), which exhibits a 4,4'diisothiocyanostilbene-2,2'-disulfonic acid (D IDS)-sensitive phosphorylation peak at 40 mM Cl- (DIDS inhibition cons tant = 8 mu M). p37 is additionally phosphorylated by an N-(2-guanodin oethyl)-5-isoquinoline sulfonamide-inhibitable protein kinase that use s ATP and shows a similar chloride sensitivity. The profile of membran e phosphoproteins generated by both kinases is also dependent on the s ource of P-i, the species of anion, and the concentration of anion. We propose a molecular mechanism for the transduction of Cl- concentrati on into a guanosine 5'-triphosphate-selective protein kinase signal an d show that anion substitution alters the intensity of phosphorylation of membrane proteins in the absence of exogenously added protein kina ses.