ATP-induced mucin release from cultured airway goblet cells involves, in part, activation of protein kinase C.
Extracellular nucleotides stimulate mucin release by binding to the P2u receptor coupled to phospholipase C via G proteins (Br. J. Pharmacol. 103:1053-1056, 1991; Am. J. Respir. Cell Mol. Biol. 8:121-125, 1993). In the present study, we intended to investigate pathways downstream to the phospholipase C activation which is responsible for adenosine triphosphate (ATP)-induced mucin release in hamster tracheal epithelial cells in primary culture. We have found that: (1) Ca2+ ionophores (A23187 and ionomycin) did not affect mucin release even at 1 microM; (2) thapsigargin (10 microM), either alone or in combination with ATP (20 microM), did not enhance mucin release over its respective control group; (3) pretreatment of hamster tracheal surface epithelial (HTSE) cells with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA-AM) (50 microM) did not inhibit ATP-induced mucin release; (4) 4beta-phorbol 12alpha-myristate 13-acetate (PMA, 1 microM) stimulated mucin release and its effect was completely blocked by protein kinase C inhibitors such as sphingosine (10 microM) and calphostin C (0.1 microM), whereas ATP-induced mucin release was blocked, only in part, by these inhibitors; (5) desensitization of protein kinase C by pretreatment with PMA inhibited the PMA-induced mucin release completely, however, ATP-induced mucin release was inhibited only partially. We conclude that mucin release by ATP does not require an increase in the intracellular Ca2+ level but involves the activation of protein kinase C. The results also suggest the presence of another mechanism separate from the phospholipase C-protein kinase C pathway for the ATP-induced mucin release.
Ko
K H
KH
Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore 21201, USA.
Jo
M
M
McCracken
K
K
Kim
K C
KC
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D004789:Enzyme Activation; D008297:Male; D008647:Mesocricetus; D009077:Mucins / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D014132:Trachea / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism*
D009077:Mucins; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D010738:Type C Phospholipases; D002118:Calcium