Inhibition of serine/threonine phosphatase enhances arachidonic acid-induced [Ca2+]i via protein kinase A.
Arachidonic acid (AA) regulates intracellular calcium concentration ([Ca2+]i) in a variety of cell types including salivary cells. In the present study, the effects of serine/threonine phosphatases on AA-induced Ca(2+) signaling in mouse parotid acini were determined. Mice were euthanized with CO2. Treatment of acini with the serine/threonine phosphatase inhibitor calyculin A blocked both thapsigargin- and carbachol-induced Ca2+ entry but resulted in an enhancement of AA-induced Ca2+ release and entry. Effects were mimicked by the protein phosphatase-1 (PP1) inhibitor tautomycin but were inhibited by the PP2A inhibitor okadaic acid. The protein kinase A (PKA) inhibitor PKI(14-22) significantly attenuated AA-induced enhancement of Ca2+ release and entry in the presence of calyculin A, whereas it had no effect on calyculin A-induced inhibition of thapsigargin-induced Ca2+ responses. The ryanodine receptor (RyR) inhibitor, tetracaine, and StHt-31, a peptide known to competitively inhibit type II PKA regulatory subunit binding to PKA-anchoring protein (AKAP), abolished calyculin A enhancement of AA-induced Ca2+ release and entry. StHt-31 also abolished forskolin potentiation of 4-chloro-3-ethylphenol (4-CEP) and AA on Ca2+ release but had no effect on 8-(4-methoxyphenylthio)-2'-O-methyladenosine-3',5'-cAMP potentiation of 4-CEP responses. Results suggest that inhibition of PP1 results in an enhancement of AA-induced [Ca2+]i via PKA, AKAP, and RyRs.
Saino
Tomoyuki
T
Department of Oral Biology, Box 357132, University of Washington, Seattle, WA 98195, USA.
Watson
Eileen L
EL
D054758:A Kinase Anchor Proteins / Q000378:metabolism; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018679:Cholinergic Agonists / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D008387:Marine Toxins; D051379:Mice; D010080:Oxazoles / Q000494:pharmacology*; D010306:Parotid Gland / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D010446:Peptide Fragments / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors* / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
D054758:A Kinase Anchor Proteins; D002121:Calcium Channel Blockers; D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D010080:Oxazoles; D010446:Peptide Fragments; D047428:Protein Kinase Inhibitors; D019837:Ryanodine Receptor Calcium Release Channel; D016718:Arachidonic Acid; C059041:calyculin A; D017868:Cyclic AMP-Dependent Protein Kinases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D000252:Calcium-Transporting ATPases