AJP - Lung Cellular and Molecular Physiology, Vol 267, Issue 5 592-L601, Copyright © 1994 by American Physiological Society
A novel chloride-dependent GTP-utilizing protein kinase in plasma membranes from human respiratory epithelium
K. J. Treharne, L. J. Marshall and A. Mehta
Department of Child Health, Ninewells Hospital Medical School, Dundee, Scotland, United Kingdom.
The protein kinases that stimulate ion flux across airway epithelium are
believed to utilize ATP as phosphate donor. Here we show that a
chloride-sensitive protein kinase (in an apically enriched plasma membrane
fraction from human nasal respiratory epithelium) uses guanosine
5'-triphosphate in preference to ATP as phosphate donor and is not
inhibited by the protein kinase inhibitors staurosporine,
1-(5-isoquinolinylsulfonyl)-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 (DIDS)-sensitive
phosphorylation peak at 40 mM Cl- (DIDS inhibition constant = 8 microM).
p37 is additionally phosphorylated by an
N-(2-guanodinoethyl)-5-isoquinoline sulfonamide-inhibitable protein kinase
that uses ATP and shows a similar chloride sensitivity. The profile of
membrane phosphoproteins generated by both kinases is also dependent on the
source of Pi, the species of anion, and the concentration of anion. We
propose a molecular mechanism for the transduction of Cl- concentration
into a guanosine 5'-triphosphate-selective protein kinase signal and show
that anion substitution alters the intensity of phosphorylation of membrane
proteins in the absence of exogenously added protein kinases.
