Pharmacologic and functional differences among p2x₇ nucleotide receptor expressing cell types

The pharmacologic and functional responses of the membrane permealmliz ing ATP receptor P2X₇ were characterised in murine BAri.2f5 macrophages, miirine BW5147 lymphocytes, human THP-1 rnonocytes treated wiih Intel ferun and iipopnlysaccharide and HEK-293 cells stably transfected with 1 Jurat P2X7 cDXA (HKK-P2X₇). All P2X7-expressing cell types except BWM-17 displayed significant ethidiurn⁺ uptake in response to the P2X₇ agonist 2′3′(4 benzoyl)-benloyl-ATP (BzATP) reflecting P2X ₇-mediated membrane per meabilixation. Although the lymphocytes failed to take up ethidium⁺, they express plasma membrane P2X ⁷ receptors because BzATP trisfierod a rapid and sustained calcium influx in all four P2X₇-exprossing cell lines. The data suggest tiiat P2X₇ receptor expression does not confer BzATP dependent pere formation in all cell types. The calcium calmodulin-dppendent. protein kinase inhibitor KN-62 inhibited ethidium⁺ and calcium influx in all cell types except HEK-P2X₇. This inhibition did not involve CaM-kinases because 1 ) inhibition was not calcium dependent, 2) ethidium⁺ influx was rapidly inhibited by KX 62 and 3) another CaM-kinase inhibitor, KX-93, was without effect- KN 62 is a novel P2X₇ inhibitor whose effects appear to be direct and limited to human and murine mil types which natively express the P2X₇ reccplor.