Simultaneous Activation of p38 MAPK and p42/44 MAPK by ATP Stimulates the K+ Current ITREK in Cardiomyocytes

Abstract

Living cells exhibit multiple K(+) channel proteins; among these is the recently reported atypical two-pore domain K(+) channel protein TREK-1. Most K(+) currents are modulated by neurohormones and under various pathological conditions. Here, in rat ventricular cardiomyocytes using the whole-cell patch-clamp technique, we characterize for the first time a native TREK-1-like current (I(TREK)) that is activated by ATP, a purine agonist applied at a micromolar range. This current is sensitive to arachidonic acid, intracellular acidosis, and various K(+) current inhibitors. Reverse transcription-polymerase chain reaction reveals the presence of a TREK-1-like mRNA in rat cardiomyocytes that shows 93% identity with mouse TREK-1. ATP effects are greatly attenuated in the presence of arachidonic acid or HCO(-)(3)-induced intracellular acidosis. Using a series of inhibitors, we further demonstrate that the ATP-induced stimulation of I(TREK) implies the activation of cytosolic phospholipase A(2) and the release of arachidonic acid. These events require the simultaneous involvement of p38 MAPK and p42/44 MAPK, respectively, via a cAMP-dependent protein kinase and a tyrosine kinase pathway, whereas the two MAPKs conjugate to activate a mitogen- and stress-activated protein kinase (MSK-1). Our results thus demonstrate the occurrence of a TREK-1-like current in cardiac cells whose activation by purine agonists implies a dual-MAPK cytosolic pathway.

Concomitant Recruitment of ERK1/2 and p38 MAPK Signalling Pathway Is Required for Activation of Cytoplasmic Phospholipase A2via ATP in Articular Chondrocytes

“…Influence of ERK1/2 and p38 MAPKs on the ATP-dependent Activation of cPLA 2 and PGE 2 Release-The activation of p38 MAPK by ATP in two different cell types has been reported recently (34,35). We have now demonstrated the ATP-dependent activation of p38 MAPK in chondrocytes.…”

“…Because giving PD98059 and SB203580 separately or in combination caused no difference in the released amount of PGE 2 or AA, and because overexpression of DN-MEK and DN-p38 separately or in combination inhibited in the same range the PGE 2 release, we can infer that ERK1/2 and p38 act concomitantly rather than cooperatively to mediate the ATP-dependent activation of cPLA 2 and release of PGE 2 , as in macrophages (42) and platelets (43). These effects might be due to each MAPK phosphorylating a different site among the several consensus sites on cPLA 2 or to the integration of the phosphorylation of both MAPK by an upstream enzyme, which then activates cPLA 2 , as in cardiomyocytes (34). Finally, calcium chelation did not prevent the activation of ERK1/2 and p38 MAPKs by ATP; therefore, the activation of the MAPKs is not due to increased intracellular calcium, as in HEK-293 cells (44) or in response to ATP in PC12 cells (45).…”

Two‐Pore K + Channel TREK‐1 Regulates Sinoatrial Node Membrane Excitability

“…A, Simulated and experimentally measured37 TREK ‐1 current‐voltage relationship. Current was normalized to 1.2 μA/μF at +30 mV in agreement with difference in background K + current measured between WT and Kcnk2 −/− sinoatrial node cells.…”

Mitogen-Activated Protein Kinases Inhibit the ROMK (Kir 1.1)-Like Small Conductance K Channels in the Cortical Collecting Duct

“…Therefore, it was conceivable that P38 and ERK are two molecules of the PTK-dependent pathway, which regulates the SK channels in the CCD. Moreover, MAPK have been shown to regulate ion channels by a PTK-independent pathway (17,22,23). Therefore, we carried out the patch-clamp experiments to determine whether inhibition of P38, ERK, or JNK could increase the SK channel activity in the CCD.…”

“…It is well established that ERK and P38 also can regulate membrane proteins, including receptors and ion channels, in addition to the traditional role of regulating signal molecules in the nucleus and cytosol (15)(16)(17)22,23). It has been shown that P38 inhibits epithelial Na channels in alveolar epithelial cells by changing membrane expression or trafficking (16).…”