title: A P2X7 receptor stimulates plasma membrane trafficking in the FRTL rat thyrocyte cell line.
abstract: Thyroid cells express a variety of P2Y and P2X purinergic receptor subtypes. G protein-coupled P2Y receptors influence a wide variety of thyrocyte-specific functions; however, functional P2X receptor-gated channels have not been observed. In this study, we used whole cell patch-clamp recording and fluorescence imaging of the plasma membrane marker FM1-43 to examine the effects of extracellular ATP on membrane permeability and trafficking in the Fisher rat thyroid cell line FRTL. We found a cation-selective current that was gated by ATP and 2',3'-O-(4-benzoylbenzoyl)-ATP but not by UTP. The ATP-evoked currents were inhibited by pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid, adenosine 5'-triphosphate-2',3'-dialdehyde, 100 microM Zn(2+), and 50 microM Cu(2+). Fluorescence imaging revealed pronounced, temperature-sensitive stimulation of exocytosis and membrane internalization by ATP with the same pharmacological profile as observed for activation of current. The EC(50) for ATP stimulation of internalization was 440 microM in saline containing 2 mM Ca(2+) and 2 mM Mg(2+), and 33 microM in low-Mg(2+), nominally Ca(2+)-free saline. Overall, the results are most consistent with activation of a P2X(7) receptor by ATP(4-). However, low permeability to N-methyl-d-glucamine(+) and the propidium cation YO-PRO-1 indicates absence of the cytolytic pore that often accompanies P2X(7) receptor activation. ATP stimulation of internalization occurs in Na(+)-free, Ca(2+)-free, or low-Mg(2+) saline and therefore does not depend on cation influx through the ATP-gated channel. We conclude that ATP activation of a P2X(7) receptor stimulates membrane internalization in FRTL cells via a transduction pathway that does not depend on cation influx.
authors.affiliation: Department of Physiology and Biophysics, University of Texas Medical Branch, 301 Univ. Boulevard, Galveston, TX 77555-0641, USA.
authors.forename: M Y
authors.initials: MY
authors.lastname: Kochukov
authors.forename: A K
authors.initials: AK
authors.lastname: Ritchie
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D019169:Jurkat Cells; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018613:Microscopy, Confocal; D018408:Patch-Clamp Techniques; D010539:Permeability / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology*; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D013961:Thyroid Gland / Q000166:cytology / Q000378:metabolism
chemical_list: C073804:FM1 43; C546468:P2RX7 protein, human; C546470:P2rx7 protein, rat; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; D000255:Adenosine Triphosphate