A selective epsilon-protein kinase C antagonist inhibits protection of cardiac myocytes from hypoxia-induced cell death

Cold ischemic injury of transplanted kidneys: new insights from experimental studies

Kidney transplantation is the preferred and definitive treatment for end-stage renal disease (ESRD), and kidneys from deceased donors are a major source for it. These kidneys are routinely cold stored to prolong viability, which, however, when prolonged can cause injury, resulting in reduced graft function and survival. Recent experimental studies have identified the release of iron and free radicals, activation of calpain, and formation of F2-isoprostanes as important components of cold ischemic injury, as are the swelling of mitochondria and activation of mitochondrial apoptotic pathways. Moreover, studies have also suggested that fortifying the storage solution with deferoxamine or preconditioning the donor kidneys with hemeoxygenase-1 may prove viable clinical strategies to limit cold ischemic injury. This review will summarize these and other new experimental data that have implications for reducing cold ischemic transplant injury, a step necessary to improve deceased-donor allograft survival.

Role for PKC-ε in neuronal death induced by oxidative stress

We investigated which isoforms of PKCs can be modulated and what their roles are during l-buthionine-S,R-sulfoximine (BSO)-induced neuronal death. We observed the isoform specific translocation of PKC-epsilon from the soluble fraction to the particulate in cortical neurons treated with 10 mM BSO. The translocation of PKC-epsilon by BSO was blocked by antioxidant trolox, suggesting the PKC-epsilon as a downstream of reactive oxygen species (ROS) elevated by BSO. Trolox inhibited the ROS elevation and the neuronal death in BSO-treated cortical cells. The BSO-induced neuronal death was remarkably inhibited by both the pharmacological inhibition of PKC-epsilon with epsilonV1-2 and the functional blockade for PKC-epsilon through overexpression of PKC-epsilon V1 region, suggesting the detrimental role of PKC-epsilon. These results suggest that PKC-epsilon is the major PKC isoform involved in the pathways triggered by ROS, leading to neuronal death in BSO-treated cortical neurons.

Exaggerated nociceptive responses on morphine withdrawal: roles of protein kinase C ε and γ

On withdrawal from opioids many patients experience a heightened sensitivity to stimuli and an exaggerated pain response. The phenomenon has been little studied in infants. We present evidence that in postnatal day 7 rats an exaggerated nociceptive ventral root response of spinal cords in vitro and withdrawal-associated thermal hyperalgesia in vivo are dependent on protein kinase C (PKC), and we document the roles of PKC and gamma isozymes. In vitro, the slow ventral root potential (sVRP) is a nociceptive-related response in spinal cord that is depressed by morphine and recovers to levels significantly above control on administration of naloxone. A broad-spectrum PKC antagonist, GF109213X, blocked withdrawal hyperresponsiveness of the sVRP whereas an antagonist specific to Ca(++)-dependent isozymes, Go69076, did not. Consistent with this finding, a specific peptide inhibitor of calcium-independent PKC, but not an inhibitor of calcium-dependent PKC gamma, blocked withdrawal hyperresponsiveness of the sVRP. Similarly, in vivo in 7-day-old rat pups, inhibition of PKC, but not PKC gamma, prevented thermal hyperalgesia precipitated by naloxone at 30 min post-morphine. In contrast, thermal hyperalgesia during spontaneous withdrawal was inhibited by both PKC and gamma inhibitors. The consistency between the in vivo and in vitro findings with respect to naloxone-precipitated withdrawal provides further evidence that the sVRP reflects nociceptive neurotransmission. In addition the difference between naloxone-precipitated and spontaneous withdrawal in vivo suggests that in postnatal day 7 rats, morphine exposure produces an early phase of primary afferent sensitization dependent upon PKC translocation, followed by a later phase involving spinal sensitization mediated by PKC gamma.

Salmonella typhimurium SipA-induced neutrophil transepithelial migration: involvement of a PKC-alpha-dependent signal transduction pathway

Salmonella typhimurium elicits an intense proinflammatory response characterized by movement of polymorphonuclear neutrophils (PMN) across the epithelial barrier to the intestinal lumen. We previously showed that S. typhimurium, via the type III secretion system effector protein SipA, initiates an ADP-ribosylation factor-6- and phospholipase D-dependent lipid-signaling cascade that directs activation of protein kinase C (PKC) and subsequent transepithelial movement of PMN. Here we sought to determine the specific PKC isoforms that are induced by the S. typhimurium effector SipA in model intestinal epithelia and to link the functional consequences of these isoforms in the promotion of PMN transepithelial migration. In vitro kinase PKC activation assays performed on polarized monolayers of T84 cells revealed that S. typhimurium and recombinant SipA induced activation of PKC-alpha, -delta, and -epsilon. To elucidate which of these isoforms play a key role in mediating epithelial cell responses that lead to the observed PMN transepithelial migration, we used a variety of PKC inhibitors with different isoform selectivity profiles. Inhibitors selective for PKC-alpha (Gö-6976 and 2,2',3,3',4,4'-hexahydroxyl-1,1'-biphenyl-6,6'-dimethanoldimethyl ether) markedly reduced S. typhimurium- and recombinant SipA-induced PMN transepithelial migration, whereas inhibitors to PKC-delta (rottlerin) or PKC-epsilon (V1-2) failed to exhibit a significant decrease in transepithelial movement of PMN. These results were confirmed biochemically and by immunofluorescence coupled to confocal microscopy. Our results are the first to show that the S. typhimurium effector protein SipA can activate multiple PKC isoforms, but only PKC-alpha is involved in the signal transduction cascade leading to PMN transepithelial migration.

Epsilon protein kinase C mediated ischemic tolerance requires activation of the extracellular regulated kinase pathway in the organotypic hippocampal slice

Ischemic preconditioning (IPC) promotes brain tolerance against subsequent ischemic insults. Using the organotypic hippocampal slice culture, we conducted the present study to investigate (1) the role of adenosine A1 receptor (A1AR) activation in IPC induction, (2) whether epsilon protein kinase C (epsilonPKC) activation after IPC is mediated by the phosphoinositol pathway, and (3) whether epsilonPKC protection is mediated by the extracellular signal-regulated kinase (ERK) pathway. Our results demonstrate that activation of A1AR emulated IPC, whereas blockade of the A1AR during IPC diminished neuroprotection. The neuroprotection promoted by the A1AR was also reduced by the epsilonPKC antagonist. To determine whether epsilonPKC activation in IPC and A1AR preconditioning is mediated by activation of the phosphoinositol pathway, we incubated slices undergoing IPC or adenosine treatment with a phosphoinositol phospholipase C inhibitor. In both cases, preconditioning neuroprotection was significantly attenuated. To further characterize the subsequent signal transduction pathway that ensues after epsilonPKC activation, mitogen-activated protein kinase kinase was blocked during IPC and pharmacologic preconditioning (PPC) (with epsilonPKC, NMDA, or A1AR agonists). This treatment significantly attenuated IPC- and PPC-induced neuroprotection. In conclusion, we demonstrate that epsilonPKC activation after IPC/PPC is essential for neuroprotection against oxygen/glucose deprivation in organotypic slice cultures and that the ERK pathway is downstream to epsilonPKC.

Differential inhibition by alpha and epsilonPKC pseudosubstrate sequences: a putative mechanism for preferential PKC activation in neonatal cardiac myocytes

The aims of the current study were: 1) to determine if the epsilonPKC pseudosubstrate peptide (epsilonphi) (NH(2)-RKRQGAVRRRVHQVNG-COOH) could be used as an epsilonPKC-selective inhibitor in neonatal cardiac myocytes (NCMs) and 2) to determine if differences in the alpha and epsilonPKC autoinhibitory pseudosubstrate mechanisms could play roles in alpha and epsilonPKC-selective functions. Introduction of the epsilonphi into NCMs by transient permeabilization modestly attenuated 3 nM 4-beta PMA-induced slowing of contraction rate, an epsilonPKC mediated response (Circ Res. 76:654-663; J. Biol. Chem. 271:24962-24966). In contrast, the alphaPKC pseudosubstrate peptide (alphaphi) (NH(2)-RFARKGALRQKNVHEVK-COOH) was 6- to 10-fold more potent at antagonizing the 3 nM 4-beta PMA-induced slowing of contraction rate. Addition of purified PKC to the particulate cell fraction of NCMs promoted (32)P incorporation into 3 proteins of approximately 18, approximately 46 and approximately 97 kDa. The alphaphi antagonized these phosphorylations with IC(50) values of 1 - 5 microM. These IC(50) values were 1.8 - 4.7-fold lower than those observed for the epsilonphi. In in vitro phosphorylation assays with recombinant alpha or epsilon PKC isozymes the phi failed to inhibit the PKC isozyme as potently as the alphaphi peptide but both the alphaphi and the epsilonphi were equally effective inhibitors of the recombinant alphaPKC isozyme. In addition, in vitro cleavage of the epsilonphi by the protease Arg-C in lysates from NCMs treated with 3 nM 4-beta PMA was greatly enhanced when compared to that of the alphaPKC isozyme. Our studies suggest that the epsilonphi cannot be used as a selective inhibitor of the epsilonPKC isozyme in NCMs and that there are differences in the epsilonPKC and alphaPKC autoinhibitory pseudosubstrate mechanisms.

The adenosine transporter, mENT1, is a target for adenosine receptor signaling and protein kinase Cepsilon in hypoxic and pharmacological preconditioning in the mouse cardiomyocyte cell line, HL-1

Brief exposure of the heart to hypoxia results in less cellular damage after subsequent hypoxia, an effect known as preconditioning (PC). PC has been widely studied but is still not fully understood. Adenosine (Ado), adenosine receptors, and protein kinase C (PKC) have been implicated as integral components of PC. Adenosine (nucleoside) transporters (NTs) facilitate flux of Ado across cell membranes, but their role in PC is unknown. Therefore, we used the murine cardiomyocyte cell line, HL-1, and asked if there was feedback regulation of NTs by Ado, Ado receptors, and PKC following either hypoxic or pharmacological PC. Activation (by specific agonists) of A1 or A3 Ado receptors or PKC resulted in PC in HL-1. The A1 (but not A3) receptor is coupled to PKCepsilon, and activation of PKCepsilon (by specific peptide agonist) resulted in PC. Moreover, PKCepsilon stimulates Ado uptake via the predominant NT in HL-1, mouse equilibrative nucleoside transporter 1 (mENT1). Studies in primary neonatal mouse cardiomyocytes confirmed our observations in HL-1 cells. Hypoxic challenge led to a rapid increase in, and efflux of, intracellular Ado from cells, which was blocked by NT inhibitors (dipyridamole/nitrobenzylthioinosine). Moreover, NT inhibition during hypoxia or PC was highly protective, suggesting that Ado loss contributes to decreased cell viability. Our data suggest that hypoxic challenge causes an efflux of Ado via ENTs, activation of A1 and/or A3 receptors, signaling through PKCepsilon, and activation of ENT1. Since Ado is required for ATP synthesis on reperfusion, this feedback regulation of mENT1 would promote reuptake of Ado.

ANTI-APOPTOTIC EFFECT OF ATORVASTATIN, A 3-HYDROXY-3-METHYLGLUTARYL COENZYME A REDUCTASE INHIBITOR, ON CARDIAC MYOCYTES THROUGH PROTEIN KINASE C ACTIVATION

Pleiotropic effects of statins, which are independent of lipid lowering, have been reported. In the present study, we examined the effect of a statin on apoptosis of adult rat cultured cardiac myocytes. We used the protein kinase C (PKC) inhibitors staurosporine (1 micro mol/L), chelerythrine (10 micro mol/L) and rottlerin (5 micro mol/L) to induce myocyte apoptosis. The effect of atorvastatin (10(-7) g/mL), a statin, on myocyte apoptosis induced by these PKC inhibitors was examined. All these PKC inhibitors markedly increased the percentage of terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labeling (TUNEL)-positive myocytes. This increase was significantly suppressed by atorvastatin treatment. Both chelerythrine and rottlerin induced subcellular translocation of PKCdelta and elevated caspase-3 activity in myocytes. The changes in the subcellular distribution of PKCdelta and caspase-3 activity induced by these PKC inhibitors were suppressed by atorvastatin treatment. The results of the present study suggest that the inhibitory effect of atorvastatin on apoptosis of adult rat cardiac myocytes induced by the PKC inhibitors is through activation of PKCdelta pathway.

Protein kinase C plays an essential role in sildenafil-induced cardioprotection in rabbits

Sildenafil citrate (Viagra) is the most widely used pharmacological drug for treating erectile dysfunction in men. It has potent cardioprotective effects against ischemia-reperfusion injury via nitric oxide and opening of mitochondrial ATP-sensitive K(+) channels. We further investigated the role of protein kinase C (PKC)-dependent signaling pathway in sildenafil-induced cardioprotection. Rabbits were treated (orally) with sildenafil citrate (1.4 mg/kg) 30 min before index ischemia for 30 min and reperfusion for 3 h. The PKC inhibitor chelerythrine (5 mg/kg i.v.) was given 5 min before sildenafil. Infarct size (% of risk area) reduced from 33.65 +/- 2.17 in the vehicle (saline) group to 15.07 +/- 0.63 in sildenafil-treated groups, a 45% reduction compared with vehicle (mean +/- SE, P < 0.05). Chelerythrine abolished sildenafil-induced protection, as demonstrated by increase in infarct size to 31.14 +/- 2.4 (P < 0.05). Chelerythrine alone had an infarct size of 33.5 +/- 2.5, which was not significantly different compared with DMSO-treated group (36.8 +/- 1.7, P > 0.05). Western blot analysis demonstrated translocation of PKC-alpha, -, and -delta isoforms from cytosol to membrane after treatment with sildenafil. However, no change in the PKC-beta and -epsilon isoforms was observed. These data provide direct evidence of an essential role of PKC, and potentially PKC-alpha, -, and -delta, in sildenafil-induced cardioprotection in the rabbit heart.

Gene Expression Analysis Points to Hemostasis in Livers of Rats Cotreated with Lipopolysaccharide and Ranitidine

Studies in rats have demonstrated that modest underlying inflammation can precipitate idiosyncratic-like liver injury from the histamine 2-receptor antagonist, ranitidine (RAN). Coadministration to rats of nonhepatotoxic doses of RAN and the inflammagen, bacterial lipopolysaccharide (LPS), results in hepatocellular injury. We tested the hypothesis that hepatic gene expression changes could be distinguished among vehicle-, LPS-, RAN- and LPS/RAN-treated rats before the onset of significant liver injury in the LPS/RAN-treated rats (i.e., 3 h post-treatment). Rats were treated with LPS (44 x 10(6) EU/kg, i.v.) or its vehicle, then two hours later with RAN (30 mg/kg, i.v.) or its vehicle. They were killed 3 h after RAN treatment, and liver samples were taken for evaluation of liver injury and RNA isolation. Hepatic parenchymal cell injury, as estimated by increases in serum alanine aminotransferase (ALT) activity, was not significant at this time. Hierarchal clustering of gene expression data from Affymetrix U34A rat genome array grouped animals according to treatment. Relative to treatment with vehicle alone, treatment with RAN and/or LPS altered hepatic expression of numerous genes, including ones encoding products involved in inflammation, hypoxia, and cell death. Some were enhanced synergistically by LPS/RAN cotreatment. Real-time PCR confirmed robust changes in expression of B-cell translocation gene 2, early growth response-1, and plasminogen-activator inhibitor-1 (PAI-1) in cotreated rats. The increase in PAI-1 mRNA was reflected in an increase in serum PAI-1 protein concentration in LPS/RAN-treated rats. Consistent with the antifibrinolytic activity of PAI-1, significant fibrin deposition occurred only in livers of LPS/RAN-treated rats. The results suggest the possibility that expression of PAI-1 promotes fibrin deposition in liver sinusoids of LPS/RAN-treated rats and are consistent with the development of local ischemia and consequent tissue hypoxia.

Mechanisms of myocardial protection produced by chronic ethanol consumption

Recent evidence suggests that chronic ingestion of small quantities of ethanol may protect myocardium from ischemic injury by activating many of the endogenous signal transduction elements that have been implicated during other forms of preconditioning. Studies conducted in a variety of animal models in vitro and in vivo have indicated that chronic ethanol consumption improves functional recovery after global ischemia, reduces biochemical markers of ischemic injury, and decreases myocardial infarct size. Many of these beneficial actions appear to occur independent of alterations in systemic and coronary hemodynamics and transmural myocardial perfusion. To date, adenosine type 1 (A(1)) receptors, alpha(1)-adrenoceptors, the epsilon isoform of protein kinase C (PKC), and adenosine triphosphate-dependent potassium (K(ATP)) channels have been shown to mediate cardioprotection associated with chronic ethanol ingestion. These data suggest another mechanism by which chronic, intermittent consumption of ethanol may reduce overall cardiovascular mortality, decrease the incidence of coronary artery disease, and improve survival after myocardial infarction in humans. In this brief review, we discuss current evidence supporting a role for endogenous signaling in chronic ethanol-induced myocardial protection against ischemic injury.

State-specific monoclonal antibodies identify an intermediate state in epsilon protein kinase C activation

Evaluation of the activation state of protein kinase C (PKC) isozymes relies on analysis of subcellular translocation. A monoclonal antibody, 14E6, specific for the activated conformation of epsilonPKC, was raised using the first variable (V1) domain of epsilonPKC as the immunogen. 14E6 binding is specific for epsilonPKC and is greatly increased in the presence of PKC activators. Immunofluorescence staining by 14E6 of neonatal rat primary cardiac myocytes and the NG108-15 neuroblastoma glioma cell line, NG108-15/D2, increases rapidly following cell activation and is localized to new subcellular sites. However, staining of translocated epsilonPKC with 14E6 is transient, and the epitope disappears 30 min after activation of NG-108/15 cells by a D2 receptor agonist. In contrast, subcellular localization associated with activation, as determined by commercially available polyclonal antibodies, persists for at least 30 min. In vitro, epsilonRACK, the receptor for activated epsilonPKC, inhibits 14E6 binding to epsilonPKC, suggesting that the 14E6 epitope is lost or hidden when active epsilonPKC binds to its RACK. Therefore, the 14E6 antibody appears to identify a transient state of activated but non-anchored epsilonPKC. Moreover, binding of 14E6 to epsilonPKC only after activation suggests that lipid-dependent conformational changes associated with epsilonPKC activation precede binding of the activated isozyme to its specific RACK, epsilonRACK. Further, monoclonal antibody 14E6 should be a powerful tool to study the pathways that control rapid translocation of epsilonPKC from cytosolic to membrane localization on activation.

Rapid, nongenomic effects of aldosterone in the heart mediated by epsilon protein kinase C

Aldosterone elevates Na+/K+/2Cl- cotransporter activity in rabbit cardiomyocytes within 15 min, an effect blocked by K-canrenoate and thus putatively mineralocorticoid receptor mediated. Increased cotransporter activity raises intracellular [Na+] sufficient to produce a secondary increase in Na+-K+ pump activity; when this increase in intracellular [Na+] is prevented, a rapid effect of aldosterone to lower pump activity is seen. Addition of transcription inhibitor actinomycin D did not change basal or aldosterone-induced lowered pump activity, indicating a direct, nongenomic action of aldosterone. We examined a possible role for protein kinase C (PKC) in the rapid nongenomic effects of aldosterone. Single ventricular myocytes and pipette solutions containing 10 mm intracellular [Na+] were used in patch clamp studies to measure Na+-K+ pump activity. Aldosterone lowered pump current, an effect abolished by epsilon PKC (epsilonPKC) inhibition but neither alphaPKC nor scrambled epsilonPKC; addition of epsilonPKC activator peptide mimicked the rapid aldosterone effect. In rabbits chronically infused with aldosterone, the lowered pump current in cardiomyocytes was acutely (< or =15 min) restored by epsilonPKC inhibition. These studies show that rapid effects of aldosterone on Na+-K+ pump activity are nongenomic and specifically epsilonPKC mediated; in addition, such effects may be prolonged (7 d) and long-lived ( approximately 4 h isolated cardiomyocyte preparation time). The rapid, prolonged, long-lived effects can be rapidly (< or =15 min) reversed by epsilonPKC blockade, suggesting a hitherto unrecognized complexity of aldosterone action in the heart and perhaps by extension other tissues.

Cardio-protective determinants are conserved in aged human myocardium after ischemic preconditioning

Ischemic preconditioning (IPrec) improves post-ischemic dysfunctions of the myocardium along with activation of protein kinase C isozymes including PKCdelta. Moreover, expression of cardio-protective determinants can reduce ischemic damages. Because IPrec is limited in aged hearts, we assessed in an experimental model the impact of aging on PKCdelta and selected protective proteins in the preconditioned myocardium from adult (< or =55) and older (> or =70 years) humans. Adult myocardium showed PKCdelta up-regulation after IPrec along with improved post-ischemic contractility. Although there was no functional benefit, PKCdelta increased in older myocardium as well. Subsequent mRNA analyses demonstrated that IPrec stabilizes the mRNA expression of protective proteins (Hsp70, Bcl-2/-xL, IAPs) in both aging groups. Moreover, older hearts revealed increase in post-ischemic Hsp90beta. Our study indicates, that IPrec conserves the expression of cardio-protective determinants in aged hearts despite limited functional recovery.

Insulin-induced improvement of postischemic recovery is abolished by inhibition of protein kinase C in rat heart

OBJECTIVE

We demonstrated earlier that postischemic addition of insulin improves recovery of function in isolated rat heart by phosphatidylinositol 3-kinase. Activation of phosphatidylinositol 3-kinase before ischemia improves recovery of the heart after ischemia through protein kinase C. We tested whether protein kinase C activation is required for the positive inotropic effect of insulin during reperfusion.

METHODS

Isolated working rat hearts were perfused with Krebs-Henseleit buffer containing [2-(3)H]glucose (5 mmol/L, 0.05 microCi/mL) plus oleate (0.4 mmol/L) and were subjected to 15 minutes of global ischemia followed by 35 minutes of reperfusion with or without insulin (1 mU/mL). We measured cardiac power, glucose uptake, and tissue metabolites. The protein kinase C inhibitor chelerythrine (5 micromol/L) was added either at the beginning of the experiment or together with insulin. Experiments were repeated under normoxic conditions.

RESULTS

Cardiac power before ischemia was 9.63 to 12.4 mW. Insulin improved recovery of power after ischemia (96.3% +/- 10.8% versus 65.7% +/- 3.79%, P <.05). This effect was abolished by chelerythrine (55.3% +/- 6.49%). However, chelerythrine given at reperfusion did not block insulin's effect on recovery (101.0% +/- 4.25%, P <.05). Postischemic glucose uptake was not increased by insulin (3.07 +/- 0.32 before, 3.45 +/- 0.34 micromol/min/gdw after ischemia, not significant) and was not affected by chelerythrine (3.01 +/- 0.26 before, 3.29 +/- 0.32 micromol/min/gdw after ischemia, not significant). Under normoxic conditions, chelerythrine did not influence insulin's effects on glucose uptake or power.

CONCLUSION

The results suggest that (1) insulin's effect on recovery is dependent on ischemia-induced protein kinase C activation, (2) the activity of protein kinase C during reperfusion may not be important for this effect of insulin, and (3) protein kinase C plays no role in insulin's effect on glucose uptake under normoxic or postischemic conditions.

Opposing roles of δ and εPKC in cardiac ischemia and reperfusion: targeting the apoptotic machinery

Heart attacks, or acute myocardial infarctions (AMI), affect more than one million people in the US every year. The damage that occurs to the heart by AMI is often permanent and as a result, the morbidity and mortality rates of patients that experience AMIs continue to be high. Consequently, AMI patients are at significantly increased risks for future myocardial infarctions, decreased heart function, heart failure, and death [Heart and Stroke statistical update. In American Heart Association (2002) 4]. In this review, we discuss the events that lead to cardiac damage by AMI. Specifically, we discuss the current understanding of the role of ischemic damage vs. reperfusion damage, which is induced by the return of blood, oxygen, and nutrients to the organ. We also discuss the role of apoptosis and necrosis in cardiac damage, the means to protect the heart from damage by ischemia and reperfusion, and the role of protein kinase C in these processes.

Inhibition of δ-Protein Kinase C Protects Against Reperfusion Injury of the Ischemic Heart In Vivo

Background— Current treatment for acute myocardial infarction (AMI) focuses on reestablishing blood flow (reperfusion). Paradoxically, reperfusion itself may cause additional injury to the heart. We previously found that δ-protein kinase C (δPKC) inhibition during simulated ischemia/reperfusion in isolated rat hearts is cardioprotective. We focus here on the role for δPKC during reperfusion only, using an in vivo porcine model of AMI.

Methods and Results— An intracoronary application of a selective δPKC inhibitor to the heart at the time of reperfusion reduced infarct size, improved cardiac function, inhibited troponin T release, and reduced apoptosis. Using 31 P NMR in isolated perfused mouse hearts, we found a faster recovery of ATP levels in hearts treated with the δPKC inhibitor during reperfusion only.

Conclusions— Reperfusion injury after cardiac ischemia is mediated, at least in part, by δPKC activation. This study suggests that including a δPKC inhibitor at reperfusion may improve the outcome for patients with AMI.

Preservation of base-line hemodynamic function and loss of inducible cardioprotection in adult mice lacking protein kinase C epsilon

Signaling pathways involving protein kinase C isozymes are modulators of cardiovascular development and response to injury. Protein kinase C epsilon activation in cardiac myocytes reduces necrosis caused by coronary artery disease. However, it is unclear whether protein kinase C epsilon function is required for normal cardiac development or inducible protection against oxidative stress. Protein kinase C delta activation is also observed during cardiac preconditioning. However, its role as a promoter or inhibitor of injury is controversial. We examined hearts from protein kinase C epsilon knock-out mice under physiological conditions and during acute ischemia reperfusion. Null-mutant and wild-type mice displayed equivalent base-line morphology and hemodynamic function. Targeted disruption of the protein kinase C epsilon gene blocked cardioprotection caused by ischemic preconditioning and alpha(1)-adrenergic receptor stimulation. Protein kinase C delta activation increased in protein kinase C epsilon knock-out myocytes without altering resistance to injury. These observations support protein kinase C epsilon activation as an essential component of cardioprotective signaling. Our results favor protein kinase C delta activation as a mediator of normal growth. This study advances the understanding of cellular mechanisms responsible for preservation of myocardial integrity as potential targets for prevention and treatment of ischemic heart disease.

Protein kinase C-epsilon modulates mitochondrial function and active Na+ transport after oxidant injury in renal cells

The aim of this study was to determine whether protein kinase C-epsilon (PKC-epsilon) is involved in the repair of mitochondrial function and/or active Na+ transport after oxidant injury in renal proximal tubular cells (RPTC). Sublethal injury was produced in primary cultures of RPTC using tert-butylhydroperoxide (TBHP), and the recovery of functions was examined. PKC-epsilon was activated three- to fivefold after injury. Active PKC-epsilon translocated to the mitochondria. Basal oxygen consumption (Qo2), uncoupled Qo2, and ATP production decreased 58, 60, and 41%, respectively, at 4 h and recovered by day 4 after injury. At 4 h, complex I-coupled respiration decreased 50% but complex II- and IV-coupled respirations were unchanged. Inhibition of PKC-epsilon translocation using a peptide selective inhibitor, PKC-epsilonV1-2, reduced decreases in basal and uncoupled Qo2 values and increased complex I-linked respiration in TBHP-injured RPTC at 4 h of recovery. Furthermore, PKC-epsilonV1-2 prevented decreases in ATP production in injured RPTC. Na+-K+-ATPase activity and ouabain-sensitive 86Rb+ uptake were decreased by 60 and 53%, respectively, at 4 h of recovery. Inhibition of PKC-epsilon activation prevented a decline in Na+-K+-ATPase activity and reduced decreases in ouabain-sensitive 86Rb+ uptake. We conclude that during early repair after oxidant injury in RPTC 1) PKC-epsilon is activated and translocated to mitochondria; 2) PKC-epsilon activation decreases mitochondrial respiration, electron transport rate, and ATP production by reducing complex I-linked respiration; and 3) PKC-epsilon mediates decreases in active Na+ transport and Na+-K+-ATPase activity. These data show that PKC-epsilon activation after oxidant injury in RPTC is involved in the decreases in mitochondrial function and active Na+ transport and that inhibition of PKC-epsilon activation promotes the repair of these functions.

Identification of Novel Signaling Complexes by Functional Proteomics

The rapid development of proteomic technologies, combined with the completion of the Human Genome Map, has enabled the compiling of an unprecedented inventory of cellular proteins. Functional proteomics is an emerging field that aims to utilize the enormous amount of information provided by these proteomic technologies to understand the functions of cellular proteins. The utility of functional proteomics has been recently exploited to elucidate cellular mechanisms in numerous fields, of particular salience in the area of signal transduction. This review presents a functional proteomic approach for the study of cardiac cell signaling. It illustrates the strategies by which the subproteome of a targeted signaling system is characterized in an unbiased fashion, the manner in which the biochemical functions of this subproteome are assessed using established molecular and protein chemistry methods, and the challenges associated with these studies.

Transient attenuation of protein kinase Cepsilon can terminate a chronic hyperalgesic state in the rat

Recently we demonstrated that a single 3-day episode of carrageenan-induced acute cutaneous inflammation can create a chronic state of increased susceptibility to inflammatory hyperalgesia. In this latent "primed" state, although there is no ongoing hyperalgesia, the hyperalgesic response to subsequent challenges with inflammatory agent (prostaglandin E2; PGE2) is greatly enhanced. Furthermore, the PGE2-induced hyperalgesia in primed skin was found to require activity of the epsilon isozyme of protein kinase C (PKCepsilon), a second messenger that is not required for PGE2-induced hyperalgesia in control animals. In the present study we tested the hypothesis that activity of PKCepsilon not only plays a critical role in the expression of primed PGE2-induced hyperalgesia, but also in the development and maintenance of the primed state itself. Antisense oligodeoxynucleotide was employed to produce a decrease in PKCepsilon in the nerve, verified by Western blot analysis. PKCepsilon was found to be essential both for the development of carrageenan-induced hyperalgesic priming, as well as for the maintenance of the primed state. Furthermore, hyperalgesic priming could be induced by an agonist of PKCepsilon (pseudo-receptor octapeptide for activated PKCepsilon) at a dose that itself causes no hyperalgesia. The finding that transient inhibition of PKCepsilon can not only prevent the development of priming, but can also terminate a fully developed state of priming suggests the possibility that selective targeting PKCepsilon might be an effective new strategy in the treatment of chronic inflammatory pain.

Preconditioning the Myocardium: From Cellular Physiology to Clinical Cardiology

Yellon, Derek M., and James M. Downey. Preconditioning the Myocardium: From Cellular Physiology to Clinical Cardiology. Physiol Rev 83: 1113-1151, 2003; 10.1152/physrev.00009.2003.—The phenomenon of ischemic preconditioning, in which a period of sublethal ischemia can profoundly protect the cell from infarction during a subsequent ischemic insult, has been responsible for an enormous amount of research over the last 15 years. Ischemic preconditioning is associated with two forms of protection: a classical form lasting ∼2 h after the preconditioning ischemia followed a day later by a second window of protection lasting ∼3 days. Both types of preconditioning share similarities in that the preconditioning ischemia provokes the release of several autacoids that trigger protection by occupying cell surface receptors. Receptor occupancy activates complex signaling cascades which during the lethal ischemia converge on one or more end-effectors to mediate the protection. The end-effectors so far have eluded identification, although a number have been proposed. A range of different pharmacological agents that activate the signaling cascades at the various levels can mimic ischemic preconditioning leading to the hope that specific therapeutic agents can be designed to exploit the profound protection seen with ischemic preconditioning. This review examines, in detail, the complex mechanisms associated with both forms of preconditioning as well as discusses the possibility to exploit this phenomenon in the clinical setting. As our understanding of the mechanisms associated with preconditioning are unravelled, we believe we can look forward to the development of new therapeutic agents with novel mechanisms of action that can supplement current treatment options for patients threatened with acute myocardial infarction.

Cardioprotection involves activation of NF-kappa B via PKC-dependent tyrosine and serine phosphorylation of I kappa B-alpha

Previous studies indicated that activation of PKC and Src tyrosine kinases by ischemic preconditioning (PC) may participate in the activation of NF-kappa B. However, the molecular mechanisms underlying activation of NF-kappa B during ischemic PC remain unknown. In the hearts of conscious rabbits, it was found that ischemic PC (6 cycles of 4-min coronary occlusion and 4-min reperfusion) significantly induced both tyrosine (+226.9 +/- 42%) and serine (+137.0 +/- 36%) phosphorylation of the NF-kappa B inhibitory protein I kappa B-alpha, concomitant with increased activation of the I kappa B-alpha kinases IKK alpha (+255.0 +/- 46%) and IKK beta (+173.1 +/- 35%). Furthermore, both tyrosine and serine phosphorylation of I kappa B-alpha were blocked by pretreatment with either the nonreceptor tyrosine kinase inhibitor lavendustin-A (LD-A) or the PKC inhibitor chelerythrine (Che) (both given at doses previously shown to block ischemic PC). Interestingly, Che completely abolished PC-induced activation of IKK alpha/beta, whereas LD-A had no effect. In addition, I kappa B-alpha protein level did not change during ischemic PC. Together, these data indicate that ischemic PC-induced activation of NF-kappa B occurs through both tyrosine and serine phosphorylation of I kappa B-alpha and is regulated by nonreceptor tyrosine kinases and PKC.

Isoform-specific induction of PKC-epsilon by high glucose protects heart-derived H9c2 cells against hypoxic injury

We investigated which PKC isoforms are involved in high glucose-induced protection against hypoxic injury. Treatment for 48 h with high glucose (22 mM) markedly increased the expression of PKC- epsilon in the particulate fraction (213+/-22.1% of the control) but had no effect on other types of PKC isoforms, suggesting that the high glucose-induced increase in PKC expression is isoform-specific. The mRNA level for PKC- epsilon was also substantially increased, reaching its peak after 4h of high glucose treatment. The high glucose increased PKC-epsilon activity in the particulate fraction up to 183+/-32.2% of the control. During hypoxia, the amount of PKC-epsilon in the particulate fraction was remarkably diminished in the low glucose-treated cells, but remained at a higher level in high glucose-treated cells. The treatment with epsilon V1-2 (10 microM), a specific inhibitor of PKC epsilon, abolished the protective effect of high glucose against hypoxia. These results suggest that isoform-specific induction of PKC-epsilon is involved in high glucose-induced protection against hypoxic injury in heart-derived H9c2 cells.

Combined pharmacological preconditioning with a G-protein-coupled receptor agonist, a mitochondrial KATP channel opener and a nitric oxide donor mimics ischaemic preconditioning

1. Although pharmacological preconditioning (PPC) has emerged as an alternative to ischaemic preconditioning (IPC) in cardioprotection, the efficacy of PPC compared with IPC has not been investigated. Because IPC is mediated by complex signalling cascades arising from multiple triggers, we have hypothesized that combined PPC is necessary to mimic IPC. 2. Isolated and perfused rat hearts underwent IPC by three cycles of 5 min ischaemia and 5 min reperfusion before 30 min global ischaemia followed by 120 min reperfusion. Adenosine (30 micromol/L), diazoxide (50 micromol/L) and s-nitroso-N-acetylpenicillamine (SNAP; 50 micromol/L) were added for 25 min just before (pretreatment modality) or 45 min before (PPC modality) the index ischaemia. 3. Ischaemic preconditioning significantly improved isovolumic left ventricular (LV) function and reduced infarct size. Although pretreatment with adenosine, diazoxide or SNAP alone was capable of reducing infarct size, PPC with each drug alone or in a combination of two drugs except for diazoxide plus SNAP failed to reduce infarct size. In contrast, PPC in combination with adenosine, diazoxide and SNAP (triple combination PPC) conferred significant improvement of LV function and reduction of infarct size that was as effective as IPC. 4. Cardioprotection afforded by triple combination PPC was abolished by the Gi/o-protein inhibitor pertussis toxin, the mitochondiral KATP channel inhibitor 5-hydroxydecanoate or the nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethyl imidazoline-1-oxyl 3-oxide (carboxy-PTIO). 5. Protein kinase C (PKC)-epsilon in the particulate fraction was activated throughout preconditioning ischaemia and reperfusion. Although PKC-epsilon was activated during treatment with adenosine, diazoxide or SNAP alone, it was inactivated after washout. In contrast, PKC-epsilon remained activated after triple combination PPC. The PKC inhibitor chelerythrine abolished activation of PKC-epsilon and cardioprotection afforded by IPC and triple combination PPC. 6. These results demonstrate that combined PPC with a G-protein-coupled receptor agonist, a mitochondrial KATP channel opener and an NO donor is necessary to mimic IPC and such synergistic cardioprotection is associated with enhanced and sustained activation of PKC-epsilon.

Cardioprotection through a PKC-dependent decrease in myofilament ATPase

Activation of myocardial kappa-opioid receptor-protein kinase C (PKC) pathways may improve postischemic contractile function through a myofilament reduction in ATP utilization. To test this, we first examined the effects of PKC inhibitors on kappa-opioid receptor-dependent cardioprotection. The kappa-opioid receptor agonist U50,488H (U50) increased postischemic left ventricular developed pressure and reduced postischemic end-diastolic pressure compared with controls. PKC inhibitors abolished the cardioprotective effects of U50. To determine whether kappa-opioid-PKC-dependent decreases in Ca2+-dependent actomyosin Mg2+-ATPase could account for cardioprotection, we subjected hearts to three separate actomyosin ATPase-lowering protocols. We observed that moderate decreases in myofibrillar ATPase were equally cardioprotective as kappa-opioid receptor stimulation. Immunoblot analysis and confocal microscopy revealed a kappa-opioid-induced increase in myofilament-associated PKC-epsilon, and myofibrillar Ca2+-independent PKC activity was increased after kappa-opioid stimulation. This PKC-myofilament association led to an increase in troponin I and C-protein phosphorylation. Thus we propose PKC-epsilon activation and translocation to the myofilaments causes a decrease in actomyosin ATPase, which contributes to the kappa-opioid receptor-dependent cardioprotective mechanism.

Additive protection of the ischemic heart ex vivo by combined treatment with delta-protein kinase C inhibitor and epsilon-protein kinase C activator

BACKGROUND

Protein kinase C (PKC) plays a major role in cardioprotection from ischemia/reperfusion injury. Using an HIV-1 Tat protein-derived peptide to mediate rapid and efficient transmembrane delivery of peptide regulators of PKC translocation and function, we examined the cardioprotective effect of selective delta-PKC inhibitor (deltaV1-1) and epsilon-PKC activator (psi(epsilon)RACK) peptides for ischemia/reperfusion damage in isolated perfused rat hearts. Furthermore, we examined the protective effects of these PKC isozymes in isolated perfused hearts subjected to ischemia/reperfusion damage using transgenic mice expressing these peptides specifically in their cardiomyocytes.

METHODS AND RESULTS

In isolated perfused rat hearts, administration of deltaV1-1 but not psi(epsilon)RACK during reperfusion improved cardiac function and decreased creatine phosphokinase release. In contrast, pretreatment with psi(epsilon)RACK but not deltaV1-1, followed by a 10-minute washout before ischemia/reperfusion, also improved cardiac function and decreased creatine phosphokinase release. Furthermore, administration of psi(epsilon)RACK before ischemia followed by deltaV1-1 during reperfusion only conferred greater cardioprotective effects than that obtained by each peptide treatment alone. Both the delta-PKC inhibitor and epsilon-PKC activator conferred cardioprotection against ischemia/reperfusion injury in transgenic mice expressing these peptides in the heart, and coexpression of both peptides conferred greater cardioprotective effects than that obtained by the expression of each peptide alone.

CONCLUSIONS

delta-PKC inhibitor prevents reperfusion injury, and epsilon-PKC activator mimics ischemic preconditioning. Furthermore, treatment with both peptides confers additive cardioprotective effects. Therefore, these peptides mediate cardioprotection by regulating ischemia/reperfusion damage at distinct time points.

Integrated pharmacological preconditioning in combination with adenosine, a mitochondrial KATP channel opener and a nitric oxide donor

BACKGROUND

Mitochondrial K(ATP) channel activation is an essential component of ischemic preconditioning. These channels are selectively opened by diazoxide and may be up-regulated by adenosine and nitric oxide. Therefore, pharmacological preconditioning with diazoxide in combination with adenosine and a nitric oxide donor (triple-combination pharmacological preconditioning) may enhance cardioprotection.

METHODS AND RESULTS

Isolated and perfused rat hearts underwent ischemic preconditioning with 3 cycles of 5 minutes of ischemia and 5 minutes of reperfusion before 5 minutes of oxygenated potassium cardioplegia and 35 minutes of ischemia. Pharmacological preconditioning was performed by adding adenosine, diazoxide, and a nitric oxide donor S-nitroso-N-acetyl-penicillamine each alone or in combinations for 25 minutes followed by 10 minutes washout before cardioplegic arrest. Only triple-combination pharmacological preconditioning conferred significant cardioprotection as documented by highly improved left ventricular function and limited creatine kinase release during reperfusion that was comparable to that afforded by ischemic preconditioning. Mitochondrial K(ATP) channel activity assessed by flavoprotein oxidation was increased by diazoxide, but no further increase in flavoprotein oxidation was obtained by ischemic preconditioning and triple-combination pharmacological preconditioning. Significant activation of protein kinase C-epsilon was observed in only ischemic preconditioning and triple-combination pharmacological preconditioning. Pretreatment with the mitochondrial K(ATP) channel inhibitor 5-hydroxydecanoate or the protein kinase C inhibitor chelerythrine abrogated activation of protein kinase C-epsilon and cardioprotection afforded by ischemic preconditioning and triple-combination pharmacological preconditioning.

CONCLUSIONS

Integrated pharmacological preconditioning is not simply mediated by enhanced mitochondrial K(ATP) channel activation, but is presumably mediated through amplified protein kinase C signaling promoted by coordinated interaction of adenosine, mitochondrial K(ATP) channel activation, and nitric oxide.

Dose-dependent effects of acute exercise on PKC levels in rat heart: is PKC the heart's prophylactic?

Epidemiological studies have demonstrated that chronic exercise is cardioprotective, and recent evidence from our laboratory suggests a key role for protein kinase C (PKC)-dependent pathways, at least in part, as a cellular basis for this response. However, the dose-response relationship linking exercise volume and the time course of isoform-specific PKC activation are poorly understood.

AIM

The purpose of this investigation was to determine the effects of acute exercise of varying durations on PKC subcellular distribution and phosphorylation in the rat left ventricle.

METHODS

Adult (5 months) male Fischer-344 more rats were subjected to a single bout (OB) or 7 days (SB) of treadmill running (n = 6/group; 23 m min-1, 20 min), and compared with sedentary controls (SED; n = 8). Hearts were isolated immediately after [early window (EW); n = 3/group] or 24 h after the last exercise bout [late window (LW); n = 3/group] in OB and SD, respectively. Total PKC and subcellular distribution for the alpha, delta, epsilon, betaI, and betaII isoforms, as well as phosphorylated (phospho-) PKC epsilon (pSer729), PKC alpha (pSer657) and PKCdelta (pThr507) levels were assessed by western blotting. Protein kinase C epsilon and PKC alpha mRNA levels were assessed by real time polymerase chain reaction.

RESULTS

Following OB, PKCbetaI protein levels were reduced, while total phospho-PKC epsilon (pSer729), PKC alpha (pSer657) and PKC delta (pThr507) levels were increased during EW (P < 0.05). Interestingly, total PKC delta (31%) and membrane-associated PKC alpha (24%) levels decreased from EW to LW (P < 0.05). In contrast, SB yielded chronic increases in total PKC epsilon (80.5%) levels and PKC delta (20.0%) levels (P < 0.03), with reversal of effects on phospho-PKC epsilon (Ser729), phospho-PKC alpha (Ser657) and phospho-PKC delta (Thr507) levels observed with OB. Reductions in total phospho-PKC alpha (Ser657) persisted at SB (26.1%; P < 0.02). Interestingly, mRNA levels for PKC epsilon were significantly increased following SB while PKC alpha mRNA levels were reduced, respectively.

CONCLUSION

These data suggest that divergent patterns of PKC activation occur following OB and SB at both the transcriptional and translational levels. That similar patterns of PKC translocation are observed in experimental models of ischaemic preconditioning and genetic PKC manipulation provide evidence for a dose-dependent cardioprotective phenotype induced by physical activity.

KR-31466, a benzopyranylindol analog, attenuates hypoxic injury through mitochondrial K(ATP) channel and protein kinase C activation in heart-derived H9c2 cells

In the present study, we investigated whether a novel benzopyranylindol analogue, KR-31466 (KR466) (1-[(2S,3R,4S)-3,4-dihydro-2-dimethoxymethyl-3-hydroxy-2-methyl-6-nitro-2H-1-benzopyran-4-yl]-1H-indole-2-carboxylic acid ethyl ester) can attenuate hypoxic injury in heart-derived H9c2 cells and, if so, whether the protective effect of KR466 is mediated through mitochondrial ATP-sensitive potassium (mtK(ATP)) opening. The treatment of H9c2 cells with KR466 (3 - 30 microM) significantly reduced hypoxia-induced cell death in a concentration-dependent manner, as shown by lactate dehydrogenase release and propidium iodide-uptake. In addition, KR466 (10 microM) significantly reduced the increase in hypoxia-induced TUNEL-positive cells, suggesting its anti-apoptotic potential in H9c2 cells. The protective effects of KR466 were abolished by 5-hydroxydecanoate, a specific blocker of the mtK(ATP) channel, suggesting the involvement of the mtK(ATP) channel in the protective effect of KR466. A specific inhibitor of protein kinase C (PKC), chelerythrine (3 microM), significantly attenuated the protective effect of KR466 against hypoxia-induced cardiac cell death. In conclusion, our results suggest that KR466 can protect H9c2 cells from hypoxia-induced death through mtK(ATP) channel opening and PKC activation.

Differentiation of nonbeating embryonic stem cells into beating cardiomyocytes is dependent on downregulation of PKC beta and zeta in concert with upregulation of PKC epsilon

Cardiomyocyte differentiation overall has been analyzed in vivo and in vitro at the molecular level by homologous recombination, gene mutation studies, and by transgenics; however, the roles of many signal transduction mechanisms that drive this differentiation process are still not fully understood. One set of signal transduction components that has been studied in detail in mature, differentiated cardiomyocytes is the PKC isotype superfamily. However, while the function of each isotype is slowly being uncovered in adult cardiomyocytes, limited information persists concerning their function in the differentiation process of cardiomyocytes. To begin analyzing the function of specific PKC isotypes in the differentiation process, we employed an established model for differentiating ES cells into cardiomyocyte-positive embryoid bodies (EBs) in vitro. RT-PCR, Western analyses, and confocal microscopy all showed that the expression of specific PKC isotypes was significantly changed as ES cells differentiated into cardiomyocytes. More importantly, by using antagonists specific for each isotype we found that this change was a final step in the differentiation process. PKC beta and zeta downregulation served to promote differentiation (beating), while upregulation of PKC epsilon appeared to amplify differentiation (beating). Finally, melding classical tools (i.e., ionic exchange glass beads) with recently developed methods for differentiating ES cells creates a possible novel technique for investigating differentiation of ES cells into cardiomyocytes as well as other cell types.

Amlodipine inhibits doxorubicin-induced apoptosis in neonatal rat cardiac myocytes

OBJECTIVES

We examined whether amlodipine, a calcium channel antagonist with potent antioxidant activity, inhibits doxorubicin-induced apoptosis in cultured neonatal rat cardiac myocytes.

BACKGROUND

Recent studies have shown that doxorubicin induces apoptosis as well as necrosis in myocytes through generation of reactive oxygen species.

METHODS

The effects of amlodipine and several other antioxidants on doxorubicin-induced oxidative stress and mitochondria-mediated apoptosis were examined.

RESULTS

Treatment of myocytes with doxorubicin (10(-6) mol/l) for 14 h increased the number of cells with elevated peroxides, as histochemically estimated by 2',7'-dichlorofluorescin (DCF) diacetate, and the percentage of apoptotic myocytes, as estimated by Hoechst 33258 nuclear staining, compared with control myocytes (25.0 +/- 1.6% vs. 5.2 +/- 1.2%). Moreover, doxorubicin-induced myocyte apoptosis was also confirmed by annexin V-fluorescein isothiocyanate binding assay. Doxorubicin induced a reduction in myocyte adenosine 5'-triphosphate content, a loss of mitochondrial membrane potential, cytochrome c release from the mitochondria into the cytosol, and caspase-3 activation to 1.9-fold of control. Amlodipine significantly attenuated increased DCF fluorescence, inhibited the mitochondria-mediated apoptotic responses described earlier, and decreased apoptosis in the doxorubicin-treated myocytes in a dose-dependent fashion. Amlodipine at 10(-6) mol/l significantly decreased apoptosis to 15.4 +/- 0.7%, and this antiapoptotic action was more effective than that seen with other antioxidants, including probucol, ascorbic acid, and alpha-tocopherol. In contrast, the calcium channel antagonist nifedipine (10(-6) mol/l) did not inhibit apoptosis. Catalase, glutathione, and N-acetylcysteine, but not mannitol or superoxide dismutase, significantly decreased DCF fluorescence and attenuated myocyte apoptosis induced by doxorubicin to 18.7 +/- 1.2%, 19.1 +/- 1.7%, and 18.7 +/- 0.6%, respectively.

CONCLUSIONS

Amlodipine significantly inhibits doxorubicin-induced myocyte apoptosis by suppressing the mitochondrial apoptotic pathway. This effect is attributed to the antioxidant properties of amlodipine, affecting mainly hydrogen peroxide.

Epsilon PKC is required for the induction of tolerance by ischemic and NMDA-mediated preconditioning in the organotypic hippocampal slice

Glutamate receptors and calcium have been implicated as triggering factors in the induction of tolerance by ischemic preconditioning (IPC) in the brain. However, little is known about the signal transduction pathway that ensues after the IPC induction pathway. The main goals of the present study were to determine whether NMDA induces preconditioning via a calcium pathway and promotes translocation of the protein kinase C epsilon (epsilonPKC) isozyme and whether this PKC isozyme is key in the IPC signal transduction pathway. We corroborate here that IPC and a sublethal dose of NMDA were neuroprotective, whereas blockade of NMDA receptors during IPC diminished IPC-induced neuroprotection. Calcium chelation blocked the protection afforded by both NMDA and ischemic preconditioning significantly, suggesting a significant role of calcium. Pharmacological preconditioning with the nonselective PKC isozyme activator phorbol myristate acetate could not emulate IPC, but blockade of PKC activation with chelerythrine during IPC blocked its neuroprotection. These results suggested that there might be a dual involvement of PKC isozymes during IPC. This was corroborated when neuroprotection was blocked when we inhibited epsilonPKC during IPC and NMDA preconditioning, and IPC neuroprotection was emulated with the activator of epsilonPKC. The possible correlation between NMDA, Ca2+, and epsilonPKC was found when we emulated IPC with the diacylglycerol analog oleoylacetyl glycerol, suggesting an indirect pathway by which Ca2+ could activate the calcium-insensitive epsilonPKC isozyme. These results demonstrated that the epsilonPKC isozyme played a key role in both IPC- and NMDA-induced tolerance.

An epsilonPKC-selective inhibitor attenuates back phosphorylation of a low molecular weight protein in cardiac myocytes

We have studied epsilon PKC-mediated phosphorylation events in neonatal cardiac myocytes using back phosphorylation. 3 nM 4-beta 12-myristate-13-acetate (PMA)-intact cell treatment preferentially activates epsilon PKC in these cells (Circ. Res. 76 (1995) 654) and caused decreased 32P incorporation (back phosphorylation) into an approximately 18-kDa protein. This response required physiological levels of free Mg(2+) and short (3-5 min) incubation periods in back phosphorylation assays. Introduction of a selective epsilon PKC translocation inhibitor (epsilon V1) into these cells attenuated the 3 nM PMA-induced back phosphorylation response while translocation inhibitors to the classical PKC or deltaPKC isozymes were without effect. Pretreatment of our cells with endothelin-1 (ET1) had similar effects to 3 nM PMA albeit the magnitude of the ET1 back phosphorylation response was about one-half that of 3 nM PMA. Our results suggest that epsilon PKC phosphorylates an approximately 18-kDa protein found in the particulate cell fraction of neonatal cardiac myocytes. Epsilon PKC modulates diverse cardiac responses including contraction, ion channel functions, hypertrophy, and ischemic preconditioning. Characterization of epsilon PKC-selective phosphotransferase events may reveal novel regulatory mechanisms for this enzyme in neonatal cardiac myocytes.

Effects of pharmacological preconditioning with U50488H on calcium homeostasis in rat ventricular myocytes subjected to metabolic inhibition and anoxia

1. The effects of pharmacological preconditioning with U50488H (U(50)), a selective kappa-opioid receptor agonist, on Ca(2+) homeostasis in rat ventricular myocytes subjected for 9 min to metabolic inhibition (MI) and anoxia (A), consequences of ischaemia, were studied and compared with those of preconditioning with brief periods of MI/A. 2. Precondition with 30 micro M of U(50) for three cycles of 1 min each cycle separated by 3 min of recovery (UP) significantly increased the percentage of non-blue cells following MI/A. The effect of UP is the same as that of preconditioning with an inhibitor of glycolysis and an oxygen scavenger for three 1-min cycles separated by three-minute recovery (MI/AP). The results indicate that like MI/AP, UP also confers cardioprotection. 3. MI/A increased intracellular Ca(2+) ([Ca(2+)](i)) and reduced the amplitude of caffeine-induced [Ca(2+)](i) transients, an indication of Ca(2+) content in the sarcoplasmic reticulum (SR). MI/A also reduced the electrically-induced [Ca(2+)](i) transient, that indicates Ca(2+)-release during excitation-contraction coupling, and Ca(2+) sparks in unstimulated myocytes, that indicates spontaneous Ca(2+)-release from SR. It also prolonged the decline of the electrically-induced [Ca(2+)](i) transient and slowed down the recovery of the electrically-induced [Ca(2+)](i) transient after administration of caffeine. In addition, MI/A prolonged the decline of caffeine induced [Ca(2+)](i) transient, an indication of Na(+)-Ca(2+) exchange activity, and UP prevented it. So UP, that confers cardioprotection, prevented the changes induced by MI/A. With the exception of Ca(2+)-spark, which was not studied, the effects of MI/AP are the same as those of UP. 4. It is concluded that pharmacological preconditioning with U(50), that confers immediate cardioprotection, prevents changes of Ca(2+) homeostasis altered by MI/A in the rat heart. This may be responsible, at least partly, for the cardioprotective action. 5. The study also provided evidence that MI/A causes mobilization of Ca(2+) from SR to cytoplasm causing Ca(2+)-overload which may be due to reduced Ca(2+)-uptake by SR. MI/A also reduces spontaneous and electrically induced Ca(2+) release from SR.

Assessment of the cytoprotective role of adenosine in an in vitro cellular model of myocardial ischemia

This work aimed to detect functional adenosine receptors in isolated rat cardiomyocytes and to study the influence of stimulation of these receptors in an in vitro model of ischemia. Cultures of cardiomyocytes were prepared from newborn rat ventricles. The contractions were photometrically monitored. In this preparation, adenosine induced a positive chronotropic response. This effect was reproduced by CGS 21680 (2-(4-[2-carboxyethyl]-phen-ethyl-amino) adenosine-5'N-ethylunosamide), a specific adenosine A(2) receptor agonist, and antagonized by DMPX (3,7-dimethyl-1-propargylxanthine), an adenosine A(2) receptor antagonist. However, R-PIA (R-N(6)-(2-phenylisopropyl)-adenosine; a specific adenosine A(1) receptor agonist) induced a negative chronotropic effect that was abolished by its corresponding adenosine A(1) antagonist DPCPX (1,3-dipropyl-8-cyclo-pentyl-adenosine). Substrate-free hypoxia, as simulation of ischemia, induced a progressive decrease and then arrest of spontaneous cell contractions. The spontaneous rhythmic contractile activity was restored during reoxygenation following simulated ischemia. Adenosine A(1) receptor stimulation with R-PIA induced a decrease of hypoxia-induced damage. This effect was antagonized by DPCPX, an adenosine A(1) receptor antagonist. Conversely, the cells treated with CGS 21680 did not display complete recovery after reoxygenation. In addition, this effect was abolished by DMPX, since the cells recovered normal function after reoxygenation. To conclude, it appeared that cardiomyocytes possess both functional adenosine A(1) and A(2) receptors and that only the activation of adenosine A(1) receptor had a cytoprotective effect against simulated ischemia-induced cardiac cell injury.

Protein kinase C-epsilon promotes survival of lung cancer cells by suppressing apoptosis through dysregulation of the mitochondrial caspase pathway

The serine/threonine protein kinase C (PKC) has been implicated in the regulation of drug resistance and cell survival in many types of cancer cells. However, the one or more precise mechanisms remain elusive. In this study, we have identified and determined the mechanism by which PKC-epsilon, a novel PKC isoform, modulates drug resistance in lung cancer cells. Western blot analysis demonstrates that expression of PKC-epsilon, but not other PKC isoforms, is associated with the chemo-resistant phenotype of non-small cell lung cancer (NSCLC) cell lines. Northern blotting and nuclear run-on transcription analysis further reveals that the failure of expression of PKC-epsilon in the chemo-sensitive phenotype of small cell lung cancer (SCLC) cells results from transcriptional inactivation of the gene. Importantly, forced expression of PKC-epsilon in NCI-H82 human SCLC cells confers a significant resistance to the chemotherapeutic drugs, etoposide and doxorubicin. Resistance is characterized by a significant reduction in apoptosis in PKC-epsilon-expressing cells. Treatment of NCI-H82 cells with etoposide induces a series of time-dependent events, including the release of cytochrome c from the mitochondria to the cytosol, activation of caspase-9 and caspase-3, and cleavage of poly(ADP-ribose) polymerase (PARP). All of these events are blocked by PKC-epsilon expression. Furthermore, caspase-specific inhibitors, z-VAD-fmk and z-DEVD-fmk, significantly attenuate the accumulation of sub-G(1) population and block the PARP cleavage in response to etoposide. These results suggest that PKC-epsilon prevents cells from undergoing apoptosis through inhibition of the mitochondrial-dependent caspase activation, thereby leading to cell survival. Finally, down-regulation of PKC-epsilon expression by the antisense cDNA in NSCLC cells results in increased sensitivity to etoposide. Taken together, our findings suggest an important role for PKC-epsilon in regulating survival of lung cancer cells.

Role of protein phosphatases in hypoxic preconditioning

To find a protein kinase C (PKC)-independent preconditioning mechanism, hypoxic preconditioning (HP; i.e., 10-min anoxia and 10-min reoxygenation) was applied to isolated rat hearts before 60-min global ischemia. HP led to improved recovery of developed pressure and reduced end-diastolic pressure in the left ventricle during reperfusion. Protection was unaffected by the PKC inhibitor bisindolylmaleimide (BIM; 1 micromol/l). It was abolished by the inhibitor of protein phosphatases 1 and 2A cantharidin (20 or 5 micromol/l) and partially enhanced by the inhibitor of protein phosphatase 2A okadaic acid (5 nmol/l). In adult rat cardiomyocytes treated with BIM and exposed to 60-min simulated ischemia (anoxia, extracellular pH 6.4), HP led to attenuation of anoxic Na(+)/Ca(2+) overload and of hypercontracture, which developed on reoxygenation. This protection was prevented by treatment with cantharidin but not with okadaic acid. In conclusion, HP exerts PKC-independent protection on ischemic-reperfused rat hearts and cardiomyocytes. Protein phosphatase 1 seems a mediator of this protective mechanism.

The protective effect of phorbol esters on Fas-mediated apoptosis in T cells. Transcriptional and postranscriptional regulation

Phorbol esters are tumor promoters that bind and activate both conventional and new Protein kinase C (PKC) isoforms. In various circumstances, PKC-dependent signaling pathways can promote cell survival and protect against cell death. This was first analysed in Jurkat T cells where Phorbol Myristate Acetate (PMA) was found to inhibit Fas-mediated apoptosis as judged by DiOC6(3) staining, caspase activation and DNA fragmentation, indicating that PMA exerts its protective effect upstream or at the mitochondrial level in these cells. PMA activated most of the main kinase pathways in T cells such as PKCs, p42/44MAPK, p38MAPK and p90Rsk but not JNK and Akt. A pharmacological approach allowed us to identify that nPKCs are both necessary and likely sufficient to promote T cell survival. Besides this post-transcriptional regulation, nPKCs may also regulate apoptosis at the transcriptional level. cDNA arrays were used to identify a set of genes whose expression was modulated in death versus survival conditions. Following PMA treatment, expression of Mcl-1 and Bcl-x increased while that of c-Myc was significantly reduced. Moreover, survivin expression decreased upon CH11 or PMA treatment. c-Myc, survivin and Bcl-x modulation seems to be regulated at the transcriptional level while decrease in Mcl-1 protein in CH11-treated cells resulted especially from a caspase-dependent proteolysis. Taken together, our data demonstrate that PMA-mediated inhibition of apoptosis is a complex process that is integrated at both the transcriptional and post-transcriptional level and point out to the potential role of Mcl-1, Bcl-x, c-Myc and survivin in this process.

Activation of protein kinases in chronically hypoxic infant human and rabbit hearts: role in cardioprotection

BACKGROUND

Many infants who undergo heart surgery have a congenital cyanotic defect in which the heart is chronically perfused with hypoxic blood. However, the signaling pathways by which infant hearts adapt to chronic hypoxia and resist subsequent surgical ischemia is unknown.

METHODS AND RESULTS

We determined the activation and translocation of protein kinase C (PKC) isoforms and mitogen activated protein kinases (MAP kinases) in 15 infants with cyanotic (SaO2<85%) or acyanotic (SaO2>95%) heart defects undergoing surgical repair and in 80 rabbits raised from birth in a hypoxic (SaO2<85%) or normoxic (SaO2>95%) environment. Tissues from infant human and rabbit hearts were processed for Western and in vitro kinase analysis. In human infants with cyanotic heart defects, PKCepsilon, p38 MAP kinase, and JUN kinase but not p42/44 MAP kinase were activated and translocated from the cytosolic to the particulate fraction compared with acyanotic heart defects. In rabbit infants there was a parallel response for PKCepsilon, p38 MAP kinase, and JUN kinase similar to humans. In infant rabbit hearts inhibition of PKCepsilon with chelerythrine, p38 MAP kinase, with SB203580 and JUN kinase with curcumin abolished the cardioprotective effects of chronic hypoxia but had no effects on normoxic hearts.

CONCLUSIONS

Infant human and rabbit hearts adapt to chronic hypoxia through activation of PKCepsilon, p38 MAP kinase, and JUN kinase signal transduction pathways. These pathways may be responsible for cardioprotection in the chronically hypoxic infant rabbit heart.

Activation and phosphatidylinositol 3-kinase-dependent phosphorylation of protein kinase C-epsilon by the B cell antigen receptor

Protein kinase C (PKC) enzymes play an important role in B cell antigen receptor (BCR) signaling, linking the BCR to the activation of mitogen-activated protein kinases as well as the NF-kappa B, and AP-1 transcription factors. There are eleven different PKC isoforms, each of which is likely to have a unique set of substrates and hence a unique role in signal transduction. Although PKC-alpha, PKC-beta, PKC-delta, and PKC-zeta have been shown to be targets of BCR signaling, the full spectrum of PKC enzymes that are activated by the BCR remains to be determined. In this report, we show that PKC-epsilon is a target of BCR signaling. We found that PKC-epsilon is highly expressed in B cells and that BCR engagement causes PKC-epsilon to translocate from the cytosol to cellular membranes. This presumably reflects the binding of PKC-epsilon to its membrane-associated lipid activator, diacylglycerol. We also found that BCR engagement resulted in the phosphatidylinositol 3-kinase-dependent phosphorylation of PKC-epsilon. This modification may promote the full activation of PKC-epsilon. Activation of PKC-epsilon could be a key event in BCR signaling since PKC-epsilon has been strongly linked to cell survival and proliferation in other cell types.

Moderate alcohol consumption induces sustained cardiac protection by activating PKC-epsilon and Akt

C57BL/6 mice were fed 18% ethanol (vol/vol) in drinking water for 12 wk. Isovolumic hearts were subjected to 20 min of ischemia and 30 min of reperfusion on a Langendorff apparatus. There were no differences in baseline hemodynamic function between hearts from ethanol (EtOH)-fed mice and controls. However, prior alcohol consumption doubled recovery of left ventricular developed pressure (68 +/- 8 vs. 33 +/- 8 mmHg for controls; n = 10, P < 0.05) and reduced creatine kinase release by half (0.26 +/- 0.04 vs. 0.51 +/- 0.08 U x min(-1) x g wet wt(-1) for controls; n = 10, P < 0.05). EtOH feeding doubled expression of activated protein kinase C epsilon (PKC)epsilon (n = 6, P < 0.05); whereas PKC inhibition blocked protection during ischemia-reperfusion. EtOH feeding also increased expression of Akt three- to fivefold (n = 6, P < 0.05), whereas PKC inhibition prevented increases in Akt kinase activity. We conclude that signaling pathways involving PKC-epsilon are critical for sustained EtOH-mediated cardioprotection and that Akt may be a downstream effector of resistance to myocardial reperfusion injury.

Subtype specific roles of beta-adrenergic receptors in apoptosis of adult rat ventricular myocytes

We have previously reported that beta-adrenergic receptor (beta-AR) stimulation promotes apoptosis in adult ventricular myocytes through PKCepsilon-mediated suppression of ERK. In this study, we investigated differential effects of beta-AR subtypes on this signal pathway. The apoptosis induced by the non-specific beta-AR agonist isoproterenol was largely blocked by the beta(1)-selective antagonist CGP 20712A, but not by the beta(2)-selective antagonist ICI 118551. A pro-apoptotic effect of beta(1)-AR was also blocked by the PKA inhibitor H89, while the protein kinase A (PKA) activators forskolin and dibutyryl-cAMP both induced apoptosis. These results indicate that beta(1)-AR-mediated PKA activation is largely responsible for the apoptosis induced by beta-AR in adult rat cardiac myocytes. This conclusion was also supported by the finding that PKA was preferentially activated by beta(1)-AR over beta(2)-AR. beta(2)-AR selectively induced anti-apoptotic ERK activation in the presence of PKCepsilon suppression, and this ERK activation was sensitive to pertussis toxin. PKCepsilon itself as well as Akt, the other anti-apoptotic factor were activated by both beta-AR subtypes. Thus, beta(1)-AR induces pro-apoptotic signals mainly through PKA activation. In contrast, beta(2)-AR is linked to Gi-mediated ERK activation, which is involved in the anti-apoptotic pathway, and is regulated by PKCepsilon. Therefore, our findings suggest a rather complex role for beta-AR subtypes in the regulation of apoptosis in adult ventricular myocytes.

Adenosine A(1) receptor mediates late preconditioning via activation of PKC-delta signaling pathway

Protein kinase C (PKC) plays a central role in both early and late preconditioning (PC) but its association with inducible nitric oxide synthase (iNOS) is not clear in late PC. This study investigates the PKC signaling pathway in the late PC induced by activation of adenosine A(1) receptor (A(1)R) with adenosine agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA) and the effect on iNOS upregulation. Adult male mice were pretreated with saline or CCPA (100 microg/kg iv) or CCPA (100 microg/kg iv) with PKC-delta inhibitor rottlerin (50 microg/kg ip). Twenty-four hours later, the hearts were isolated and perfused in the Langendorff mode. Hearts were subjected to 40 min of ischemia, followed by 30 min reperfusion. After ischemia, the left ventricular end-diastolic pressure (LVEDP) was significantly improved and the rate-pressure product (RPP) was significantly higher in the CCPA group compared with the ischemia-reperfusion (I/R) control group. Creatine kinase release and infarct size were significantly lower in the CCPA group compared with the I/R control group. These salutary effects of CCPA were abolished in hearts pretreated with rottlerin. Immunoblotting of PKC showed that PKC-delta was upregulated (150.0 +/- 11.4% of control group) whereas other PKC isoforms remained unchanged, and iNOS was also significantly increased (146.2 +/- 9.0%, P < 0.05 vs. control group) after 24 h of treatment with CCPA. The data show that PKC is an important component of PC with adenosine agonist. It is concluded that activation of A(1)R induces late PC via PKC-delta and iNOS signaling pathways.

Actin capping protein: an essential element in protein kinase signaling to the myofilaments

Actin capping protein (CapZ) binds the barbed ends of actin at sarcomeric Z-lines. In addition to anchoring actin, Z-discs bind protein kinase C (PKC). Although CapZ is crucial for myofibrillogenesis, its role in muscle function and intracellular signaling is unknown. We hypothesized that CapZ downregulation would impair myocardial function and disrupt PKC-myofilament signaling by impairing PKC-Z-disc interaction. To test these hypotheses, we examined transgenic (TG) mice in which cardiac CapZ protein is reduced. Fiber bundles were dissected from papillary muscles and detergent extracted. Some fiber bundles were treated with PKC activators phenylephrine (PHE) or endothelin (ET) before detergent extraction. We simultaneously measured Ca2+-dependent tension and actomyosin MgATPase activity. CapZ downregulation increased myofilament Ca2+ sensitivity without affecting maximum tension or actomyosin MgATPase activity. Maximum tension and actomyosin MgATPase activity were decreased after PHE or ET treatment of wild-type (WT) muscle. Fiber bundles from TG hearts did not respond to PHE or ET. Immunoblot analysis revealed an increase in myofilament-associated PKC-epsilon after PHE or ET exposure of WT preparations. In contrast, myofilament-associated PKC-epsilon was decreased after PHE or ET treatment in TG myocardium. Protein levels of myofilament-associated PKC-beta were decreased in TG ventricle. C-protein and troponin I phosphorylation was increased after PHE or ET treatment in WT and TG hearts. Basal phosphorylation levels of C-protein and troponin I were higher in TG myocardium. These results indicate that downregulation of CapZ, or other changes associated with CapZ downregulation, increases cardiac myofilament Ca2+ sensitivity, inhibits PKC-mediated control of myofilament activation, and decreases myofilament-associated PKC-beta.

Protein kinase C epsilon-dependent regulation of cystic fibrosis transmembrane regulator involves binding to a receptor for activated C kinase (RACK1) and RACK1 binding to Na+/H+ exchange regulatory factor

Protein kinase C (PKC) regulation of cystic fibrosis transmembrane regulator (CFTR) chloride function has been demonstrated in several cell lines, including Calu-3 cells that express native, wild-type CFTR. We demonstrated previously that PKC epsilon was required for cAMP-dependent CFTR function. The goal of this study was to determine whether PKC epsilon interacts directly with CFTR. Using overlay assay, immunoprecipitation, pulldown and binding assays, we show that PKC epsilon does not bind to CFTR, but does bind to a receptor for activated C kinase (RACK1), a 37-kDa scaffold protein, and that RACK1 binds to Na(+)/H(+) exchange regulatory factor (NHERF1), a binding partner of CFTR. In vitro binding assays demonstrate dose-dependent binding of PKC epsilon to RACK1 which is inhibited by an 8-amino acid peptide based on the sequence of the sixth Trp-Asp repeat in RACK1 or by an 8-amino acid sequence in the V1 region of PKC epsilon, epsilon V1-2. A 4-amino acid sequence INAL (70-73) expressed in CFTR shares 50% homology to the RACK1 inhibitory peptide, but it does not bind PKC epsilon. NHERF1 and RACK1 bind in a dose-dependent manner. Immunofluorescence and confocal microscopy of RACK1 and CFTR revealed colocalization of the proteins to the apical and lateral regions of Calu-3 cells. The results indicate the RACK1 binds PKC epsilon and NHERF1, thus serving as a scaffold protein to anchor the enzyme in proximity to CFTR.

Cardioprotection mediated by sphingosine-1-phosphate and ganglioside GM-1 in wild-type and PKC epsilon knockout mouse hearts

Sphingosine-1-phosphate (S1P) protects neonatal rat cardiac myocytes from hypoxic damage through unknown signaling pathways. We tested the hypothesis that S1P-induced cardioprotection requires activation by the epsilon-isoform of protein kinase C (PKC epsilon) by subjecting hearts isolated from PKC epsilon knockout mice and wild-type mice to 20 min of global ischemia and 30 min of reperfusion. Pretreatment with a 2-min infusion of 10 nM S1P improved recovery of left ventricular developed pressure (LVDP) in both wild-type and PKC epsilon knockout hearts and reduced the rise in LV end-diastolic pressure (LVEDP) and creatine kinase (CK) release. Pretreatment for 2 min with 10 nM of the ganglioside GM-1 also improved recovery of LVDP and suppressed CK release in wild-type hearts but not in PKC epsilon knockout hearts. Importantly, GM-1 but not S1P, increased the proportion of PKC epsilon localized to particulate fractions. Our results suggest that GM-1, which enhances endogenous S1P production, reduces cardiac injury through PKC epsilon-dependent intracellular pathways. In contrast, extracellular S1P induces equivalent cardioprotection through PKC epsilon-independent signaling pathways.

Protein kinase C epsilon signaling complexes include metabolism- and transcription/translation-related proteins: complimentary separation techniques with LC/MS/MS

The serine/threonine kinase protein kinase C epsilon (PKC epsilon) has been shown to be a critical component in the heart's resistance to cell death following ischemic insult. Recent studies have indicated that PKC epsilon forms multi-protein signaling complexes to accomplish signal transduction in cardiac protection. Using two-dimensional electrophoresis (2DE), combined with matrix-assisted laser desorption ionization mass spectrometry (MS), the initial analysis of these complexes identified signaling molecules, structural proteins, and stress-activated proteins. The initial analysis, although fruitful, was limited by the number of proteins revealed on the 2D gels. It was also apparent that many known cardiac protective functions of PKC epsilon could not be fully accounted for by the proteins identified in the initial analysis. Here we reported the identification of an additional 57 proteins in PKC epsilon complexes using complimentary separation techniques, combined with high sensitivity MS. These techniques include 2DE or large format 1D SDS-PAGE followed by LC/MS/MS and solution trypsin digestion followed by LC/MS/MS, all of which yielded novel data regarding PKC epsilon protein complexes. Nanoscale LC/MS/MS for the analysis of gel-isolated proteins was performed with sub-femtomole sensitivity. In contrast to 2DE analyses, the identification of proteins from 1D gels was independent of their visualization via staining and allowed for the identification of proteins with high isoelectric points. We found that PKC epsilon complexes contain numerous structural and signaling molecules that had escaped detection by our previous analyses. Most importantly, we identified two new groups of proteins that were previously unrecognized as components of the PKC epsilon complex: metabolism-related proteins and transcription/translation-related proteins.