title: Expression, regulation, and function of P2X(4) purinergic receptor in human cervical epithelial cells.
abstract: Micromolar concentrations of ATP stimulate biphasic change in transepithelial conductance across CaSki cultures on filters, an acute transient increase (phase I response; triggered by P2Y(2) receptor and mediated by calcium mobilization-dependent cell volume decrease) followed by a slower decrease in permeability (phase II response). Phase II response is mediated by augmented calcium influx and protein kinase C-dependent increase in tight junctional resistance. The objective of the study was to determine the role of P2X(4) receptor as a mediator of phase II response. Human cervical epithelial cells express P2X(4) receptor mRNA (1.4-, 2.2-, and 4.4-kb isoforms by Northern blot analysis) and P2X(4) protein. Depletion of vitamin A reversibly downregulated P2X(4) receptor mRNA and protein and ATP-induced calcium influx. Depletion of vitamin A abrogated phase II response, and the effect could be partially reversed only with retinoic acid receptor (RAR)-selective retinoids but not retinoid X receptor (RXR) agonists. Depletion of vitamin A also abrogated protein kinase C increase in tight junctional resistance, and the effect could not be reversed with retinoids. Depletion of vitamin A also abrogated phase I increase in permeability and reversibly downregulated P2Y(2) receptor mRNA and ATP-induced calcium mobilization. However, in contrast to phase II response, both RAR and RXR agonists could fully reverse those effects. These results suggest that phase II response is mediated by a P2X(4) receptor mechanism.
authors.affiliation: Department of Obstetrics and Gynecology, University MacDonald Women's Hospital, University Hospitals of Cleveland, Ohio 44106, USA. gig@po.cwru.edu
authors.forename: George I
authors.initials: GI
authors.lastname: Gorodeski
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D002132:Calcium Radioisotopes / Q000493:pharmacokinetics; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002584:Cervix Uteri / Q000166:cytology*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005260:Female; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis; D018048:Receptors, Purinergic P2 / Q000235:genetics* / Q000378:metabolism*; D058848:Receptors, Purinergic P2X4; D058473:Receptors, Purinergic P2Y2; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D047488:Retinoid X Receptors; D012176:Retinoids / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D002132:Calcium Radioisotopes; C548226:P2RX4 protein, human; C546385:P2RY2 protein, human; D012333:RNA, Messenger; D018048:Receptors, Purinergic P2; D058848:Receptors, Purinergic P2X4; D058473:Receptors, Purinergic P2Y2; D018168:Receptors, Retinoic Acid; D047488:Retinoid X Receptors; D012176:Retinoids; D014157:Transcription Factors; D000255:Adenosine Triphosphate