G-protein-gated inwardly rectifying potassium channels regulate ADP-induced cPLA2 activity in platelets through Src family kinases.
ADP-induced TXA2 generation requires the costimulation of P2Y1, P2Y12, and the GPIIb/IIIa receptors. Signaling events downstream of the P2Y receptors that contribute to ADP-induced TXA2 generation have not been clearly delineated. In this study, we have investigated the role of G-protein-gated inwardly rectifying potassium channels (GIRKs), a recently identified functional effector for the P2Y12 receptor, in the regulation of ADP-induced TXA2 generation. At 10-microM concentrations, the 2 structurally distinct GIRK channel blockers, SCH23390 and U50488H, caused complete inhibition of ADP-induced cPLA2 phosphorylation and TXA2 generation, without affecting the conversion of AA to TXA2 or ADP-induced primary platelet aggregation in aspirin-treated platelets. In addition, Src family kinase selective inhibitors abolished 2MeSADP-mediated cPLA2 phosphorylation and TXA2 generation. Furthermore, these GIRK channel blockers completely blocked Gi-mediated Src kinase activation, suggesting that GIRK channels are upstream of Src family tyrosine kinase activation. In weaver mouse platelets, which have dysfunctional GIRK2 subunits, ADP-induced TXA2 generation was impaired. However, we did not observe any defect in 2MeSADP-induced platelet functional responses in GIRK2-null mouse platelets, suggesting that functional channels composed of other GIRK subunits contribute to ADP-induced TXA2 generation, via the regulation of the Src and cPLA2 activity.
Shankar
Haripriya
H
Department of Physiology, Sol Sherry Thrombosis Research Center, Temple University, Rm 224OMS, 3420 N Broad St, Philadelphia, PA 19140, USA.
Kahner
Bryan N
BN
Prabhakar
Janani
J
Lakhani
Parth
P
Kim
Soochong
S
Kunapuli
Satya P
SP
D000244:Adenosine Diphosphate / Q000494:pharmacology*; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology*; D003594:Cytoplasmic Granules / Q000187:drug effects / Q000378:metabolism; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000502:physiology*; D006801:Humans; D051379:Mice; D010741:Phospholipases A / Q000097:blood*; D010974:Platelet Aggregation / Q000187:drug effects; D026902:Potassium Channel Blockers / Q000494:pharmacology; D012016:Reference Values; D013928:Thromboxane A2 / Q000097:blood; D019061:src-Family Kinases / Q000097:blood*
D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D026902:Potassium Channel Blockers; D013928:Thromboxane A2; D000244:Adenosine Diphosphate; D019061:src-Family Kinases; D010741:Phospholipases A