Protein kinase C stimulates the small-conductance K+ channel in the basolateral membrane of the CCD

Abstract

We have used the patch-clamp technique to study the regulation of the activity of the basolateral small-conductance K+ channel (SK) in the cortical collecting duct (CCD) of the rat kidney. Addition of 50-75 nM calphostin C, an agent which specifically inhibits protein kinase C (PKC), reduced channel activity by 90% in cell-attached patches. In contrast, addition of 1 microM phorbol 12-myristate 13-acetate, a stimulator of PKC, led to addition of "new" K+ channel currents in 9 of 20 patches in the basolateral membrane of the CCD, and the mean increase in NP0, a product of channel number (N) and open probability (Pzero), was 0.90 in these 9 patches. However, application of 1 nM exogenous PKC had no significant effect on channel activity in inside-out patches, suggesting that the PKC effect on the activity of the SK observed in cell-attached patches was not a result of a membrane-delimited action, such as a direct phosphorylation of the SK or closely associated proteins. The effect of calphostin C on the SK can be reversed by addition of either 10 microM S-nitroso-N-acetylpenicillamine, a donor of nitric oxide, or 100 microM 8-bromoguanosine 3',5'-cyclic monophosphate. In addition, the inhibitory effect of calphostin C on the SK was completely abolished by pretreatment of the cells with 1 microM okadaic acid, an inhibitor of protein phosphatase. However, 100 microM N omega-nitro-L-arginine methyl ester, an agent that inhibits nitric oxide synthases (NOS), blocked the SK in cell-attached patches in the presence of okadaic acid, suggesting that the effect of okadaic acid on calphostin C-induced inhibition of the SK was a step before formation of nitric oxide. We conclude that PKC is involved in the stimulation of the SK and that the effect of PKC on the SK may be mediated by regulation of NOS activity in the CCD of the rat kidney.

Human Bone Cell Hyperpolarization Response to Cyclical Mechanical Strain Is Mediated by an Interleukin-1β Autocrine/Paracrine Loop

“…EP1 receptor‐induced stimulation of calcium influx is independent of PLC activation, indicating that the EP1 receptor may activate a novel type of calcium permeable channel (40) . The increase in intracellular calcium, in association with PKC activation, acts to activate SK channel activity (43) …”

“…(40) The increase in intracellular calcium, in association with PKC activation, acts to activate SK channel activity. (43) Evidence is accumulating for a role for integrins and associated signaling pathways in the transduction of a mechanical signal to bone cells, as a result of strain deformation or fluid shear into a biochemical response. (16,44,45) Anti-␤1-integrin antibodies block direct membrane hyperpolarization by 0.33 Hz PIS and the production of transferable membrane hyperpolarization activity, suggesting a requirement for ␤1-integrins upstream of IL-1␤ release.…”

Regulation of Inwardly Rectifying K⁺ Channel in Cultured Opossum Proximal Tubule Cells by Protein Phosphatases 1 and 2A

“…In the renal K ϩ channels, the role of phosphorylation mediated by protein kinases in the regulation of channel activity has extensively been examined in the basolateral K ϩ channel of proximal tubule cells [4] and the basolateral and apical K ϩ channels in principal cells of CCD [8][9][10][11]. As for the dephosphorylation process, however, only a few papers have suggested that channel activities enhanced by PKA-mediated phosphorylation are inhibited by phosphatasemediated dephosphorylation in the apical K ϩ channel of rat CCD [13] or cloned renal K ϩ channels (ROMK) expressed in Xenopus oocyte [20].…”

“…[Japanese Journal of Physiology, 50, [249][250][251][252][253][254][255][256]2000] nase (PKG) in activation of the K ϩ channel in OKP cells [7]. In the principal cell of rat cortical collecting duct (CCD), the basolateral K ϩ channel is activated by PKC [8] and PKG [9], and the apical K ϩ channel, which is responsible for K ϩ secretion, is activated by PKA and inhibited by PKC [10] and Ca 2ϩ /calmodulin-dependent protein kinase II [11]. Apical K ϩ channels in the thick ascending limb of the rat were reported to be activated by PKA [12].…”

Inhibition of Ca2+‐dependent K+ channels in rat carotid body type I cells by protein kinase C

“…Inhibitory effects of PKC have been observed on inwardly rectifying K + channels in central neurones (Wu & Tang, 1995; Takano et al 1995) and recombinant expression systems (Henry et al 1996). In contrast, PKC has been shown to enhance K + channel activity in cortical collecting duct cells (Lu & Wang, 1996) and accelerate K + channel activation kinetics in pulmonary vascular smooth muscle cells (Smirnov & Aaronson, 1996). The responses of ATP‐sensitive K + channels (K ATP channels) to PKC activation appear to be tissue specific: in arterial smooth muscle cells, K ATP channels are inhibited by PKC (Bonev & Nelson, 1996), whereas in cardiac myocytes PKC causes K ATP activation (Hu et al 1996).…”