title: RNA interference targeted to multiple P2X receptor subtypes attenuates zinc-induced calcium entry.
abstract: A postulated therapeutic avenue in cystic fibrosis (CF) is activation of Ca(2+)-dependent Cl(-) channels via stimulation of Ca(2+) entry from extracellular solutions independent of CFTR functional status. We have shown that extracellular zinc and ATP induce a sustained increase in cytosolic Ca(2+) in human airway epithelial cells that translates into stimulation of sustained secretory Cl(-) transport in non-CF and CF human and mouse airway epithelial cells, cell monolayers, and nasal mucosa. On the basis of these studies, the Ca(2+) entry channels most likely involved were P2X purinergic receptor channels. In the present study, molecular and biochemical data show coexpression of P2X(4), P2X(5), and P2X(6) subtypes in non-CF (16HBE14o(-)) and CF (IB3-1) human bronchial epithelial cells. Other P2X receptor Ca(2+) entry channel subtypes are expressed rarely or not at all in airway epithelia, epithelial cell models from other CF-relevant tissues, or vascular endothelia. Novel transient lipid transfection-mediated delivery of small interference RNA fragments specific to P2X(4) and P2X(6) (but not P2X(5)) into IB3-1 CF human airway epithelial cells inhibited extracellular zinc- and ATP-induced Ca(2+) entry markedly in fura-2 Ca(2+) measurements and "knocked down" protein by >65%. These data suggest that multiple P2X receptor Ca(2+) entry channel subtypes are expressed in airway epithelia. P2X(4) and P2X(6) may coassemble on the airway surface as targets for possible therapeutics for CF independent of CFTR genotype.
authors.affiliation: Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, AL 35294-0005, USA.
authors.forename: Lihua
authors.initials: L
authors.lastname: Liang
authors.forename: Akos
authors.initials: A
authors.lastname: Zsembery
authors.forename: Erik M
authors.initials: EM
authors.lastname: Schwiebert
mesh_terms: D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003550:Cystic Fibrosis / Q000378:metabolism / Q000503:physiopathology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000502:physiology; D034622:RNA Interference; D012333:RNA, Messenger / Q000032:analysis; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058469:Receptors, Purinergic P2X; D020545:Respiratory Mucosa / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015032:Zinc / Q000378:metabolism*
chemical_list: C505032:CFTR protein, human; D020033:Protein Isoforms; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D015032:Zinc; D002118:Calcium