Ion transport regulated by protease-activated receptor 2 in human airway Calu-3 epithelia.
We examined the mechanisms underlying anion secretion mediated by protease-activated receptor 2 (PAR2) and its role in the regulation of ion transport, using polarized human airway Calu-3 cells. PAR2 stimulation by trypsin and a PAR2-activating peptide (PAR2AP), especially from the basolateral aspect, caused transient Cl(-) secretion due to cytosolic Ca(2+) mobilization. Antagonists of PI-PLC (U73122, ET-18-OCH(3)) and inositol 1,4,5-triphosphate (xestospongin C (Xest C)) were without effect on the PAR2AP-mediated Cl(-) secretion, whereas it was attenuated by D609 (a PC-PLC inhibitor) and phorbol 12-myristate 13 acetate (PMA, a PKC activator). Even 30 min after removal of PAR2AP after a 10-min-exposure, cells were still poorly responsive to PAR2 stimulation, but the reduced responsiveness was upregulated by a PKC inhibitor, GF109203X (GFX). Pretreatment with PAR2AP did not affect responses to anion secretagogues, such as isoproterenol, forskolin, thapsigargin, 1-ethyl-2-benzimdazolinone, and adenosine, but ATP-induced responses were significantly reduced. Nystatin permeabilization studies revealed that the presence of PAR2AP prevented ATP-induced increments in basolateral membrane K(+) conductance without affecting apical membrane Cl(-) conductance. ATP-elicited Ca(2+) mobilization, which was sensitive to D609 and PMA, was inhibited by the pretreatment with PAR2AP, and this inhibition was blunted by the presence of GFX. Collectively, stimulation of PAR2 generates a brief response of Cl(-) secretion through PC-PLC-mediated pathway, followed by not only auto-desensitization of PAR2 itself but also cross-desensitization of a PC-PLC-coupled purinoceptor. The two types of desensitization seem likely to have PKC-mediated downregulation of PC-PLC in common.
Sato
Shinji
S
Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Showa-ku, Aichi, Japan.
Ito
Yasushi
Y
Kondo
Masashi
M
Ohashi
Takamasa
T
Ito
Satoru
S
Nakayama
Shinsuke
S
Shimokata
Kaoru
K
Kume
Hiroaki
H
D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002712:Chlorides / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D017136:Ion Transport; D008168:Lung / Q000187:drug effects / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D044464:Receptor, PAR-2 / Q000235:genetics / Q000378:metabolism*; D014357:Trypsin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism*
D002712:Chlorides; D010446:Peptide Fragments; D012333:RNA, Messenger; D044464:Receptor, PAR-2; D011493:Protein Kinase C; D010738:Type C Phospholipases; C105598:phosphatidylcholine-specific phospholipase C; D014357:Trypsin; D011188:Potassium; D002118:Calcium