Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The serine/threonine protein kinase Sgk1 (serum- and glucocorticoid-inducible kinase 1) is characterized by a short half-life and has been implicated in the control of a large variety of functions in different subcellular compartments and tissues. Here, we analysed the influence of the N-terminus of Sgk1 on protein turnover and subcellular localization. Using green fluorescent protein-tagged Sgk1 deletion variants, we identified amino acids 17-32 to function as an anchor for the OMM (outer mitochondrial membrane). Subcellular fractionation of mouse tissue revealed a predominant localization of Sgk1 to the mitochondrial fraction. A cytosolic orientation of the kinase at the OMM was determined by in vitro import of Sgk1 and protease protection assays. Pulse-chase experiments showed that half-life and subcellular localization of Sgk1 are inseparable and determined by identical amino acids. Our results provide evidence that Sgk1 is primarily localized to the OMM and shed new light on the role of Sgk1 in the control of cellular function.
...
PMID:The N-terminus of the serum- and glucocorticoid-inducible kinase Sgk1 specifies mitochondrial localization and rapid turnover. 1677 52

Apoptosis is a controlled form of cell death that participates in development, elimination of damaged cells and maintenance of cell homeostasis. Also, it plays a role in neurodegenerative disorders like Alzheimer's disease. Recently, mitochondria have emerged as being pivotal in controlling apoptosis. They house a number of apoptogenic molecules, such as cytochrome c, which are released into the cytoplasm at the onset of apoptosis. When rat brain mitochondrial voltage-dependent anion channel (VDAC), an outer mitochondrial membrane protein, interacts with Bcl-2 family proteins Bax and tBid, its pore size increases, leading to the release of cytochrome c and other apoptogenic molecules into the cytosol and causing cell death. Regulation of this tBid- and Bax-induced increase in pore size of VDAC is a significant step to control cell death induced by cytochrome c. In this work, we have shown, through bilayer electrophysiological experiments, that the increase in VDAC conductance as a result of its interaction with Bax and tBid is reduced because of the action of cyclic AMP-dependent protein kinase A (PKA) in the presence of ATP. This indicates that the increase in the pore size of VDAC after its interaction with Bax and tBid is controlled via phosphorylation of this channel by PKA. This, we believe, could be a mechanism of controlling cytochrome c-mediated cell death in living cells.
...
PMID:Phosphorylation of rat brain mitochondrial voltage-dependent anion as a potential tool to control leakage of cytochrome c. 1678 24

cAMP-dependent protein kinase (PKA) mediates key cellular processes via compartmentalized activity, and the ability to track its activity in living cells should help increase our understanding of this precise regulation. Here, through systematic testing of new fluorescent proteins, we developed a new FRET-based A-kinase activity reporter (AKAR), AKAR3, with a dynamic range of 31-41%, twice that of predecessors. Visualization of PKA activity at plasma membrane, cytoplasm, nucleus, and mitochondria was achieved. Targeting AKAR3 to outer mitochondrial membrane revealed that basal PKA activity at mitochondria differs from that in the cytoplasm, indicating differential regulation of PKA activity at different subcellular locations.
...
PMID:Subcellular dynamics of protein kinase A activity visualized by FRET-based reporters. 1689 23

Transport of cholesterol into the mitochondria is the rate-determining, hormone-sensitive step in steroid biosynthesis. Here we report that the mechanism underlying mitochondrial cholesterol transport involves the formation of a macromolecular signaling complex composed of the outer mitochondrial membrane translocator protein (TSPO), previously known as peripheral-type benzodiazepine receptor; the TSPO-associated protein PAP7, which binds and brings to mitochondria the regulatory subunit RIalpha of the cAMP-dependent protein kinase (PKARIalpha); and the hormone-induced PKA substrate, steroidogenic acute regulatory protein (StAR). Hormone treatment of MA-10 Leydig cells induced the co-localization of TSPO, PAP7, PKARIalpha, and StAR in mitochondria, visualized by confocal microscopy, and the formation in living cells of a high molecular weight multimeric complex identified using photoactivable amino acids. The hormone-induced recruitment of exogenous TSPO in this complex was found to parallel the increased presence of 7-azi-5alpha-cholestan-3beta-ol in the samples. Co-expression of Tspo, Pap7, PkarIalpha, and Star genes resulted in the stimulation of steroid formation in both steroidogenic MA-10 and non-steroidogenic COS-F2-130 cells that were engineered to metabolize cholesterol. Disruption of these protein-protein interactions and specifically the PKARIalpha-PAP7 and PAP7-TSPO interactions, using PAP7 mutants where the N0 area homologous to dual A-kinase-anchoring protein-1 or the acyl-CoA signature motif were deleted or using the peptide Ht31 known to disrupt the anchoring of PKA, inhibited both basal and hormone-induced steroidogenesis. These results suggest that the initiation of cAMP-induced protein-protein interactions results in the formation of a multivalent scaffold in the outer mitochondrial membrane that mediates the effect of hormones on mitochondrial cholesterol transport and steroidogenesis.
...
PMID:Protein-protein interactions mediate mitochondrial cholesterol transport and steroid biosynthesis. 1705 May 26

The role of the cyclin-dependent kinase (CDK) inhibitor p21 as a mediator of p53-induced growth arrest is well established. In addition, recent data provide strong evidence for new emerging functions of p21, including a role as a modulator of apoptosis. The mechanisms, however, by which p21 interferes with the death machinery, especially following ionizing radiation (IR), are largely unknown. Here, we report that IR induced caspase-9 and caspase-3 activation and subsequent apoptosis only in p21-deficient colon carcinoma cells, whereas similar treated wild-type cells were permanently arrested in the G(2)-M phase, correlating with the induction of cellular senescence. Interestingly, activation of the mitochondrial pathway, including caspase-2 processing, depolarization of the outer mitochondrial membrane, and cytochrome c release, was achieved by IR in both cell lines, indicating that p21 inhibits an event downstream of mitochondria but preceding caspase-9 activation. IR-induced p21 protein expression was restricted to the nucleus, and no evidence for a mitochondrial or cytoplasmic association was found. In addition, p21 did neither interact with caspase-3 or caspase-9, suggesting that these events are not required for the observed protection. Consistent with this assumption, we found that CDK inhibitors potently abrogated IR-induced caspase processing and activation without affecting mitochondrial events. In addition, in vitro caspase activation assays yielded higher caspase-3 activities in extracts of irradiated p21-deficient cells compared with extracts of similar treated wild-type cells. Thus, our results strongly indicate that p21 protects cells from IR-induced apoptosis by suppression of CDK activity that seems to be required for activation of the caspase cascade downstream of the mitochondria.
...
PMID:p21 blocks irradiation-induced apoptosis downstream of mitochondria by inhibition of cyclin-dependent kinase-mediated caspase-9 activation. 1714 70

This study examines the role of c-jun N-terminal kinase (JNK) in mitochondrial signaling and bioenergetics in primary cortical neurons and isolated rat brain mitochondria. Exposure of neurons to either anisomycin (an activator of JNK/p38 mitogen-activated protein kinases) or H2O2 resulted in activation (phosphorylation) of JNK (mostly p46(JNK1)) and its translocation to mitochondria. Experiments with mitochondria isolated from either rat brain or primary cortical neurons and incubated with proteinase K revealed that phosphorylated JNK was associated with the outer mitochondrial membrane; this association resulted in the phosphorylation of the E(1alpha) subunit of pyruvate dehydrogenase, a key enzyme that catalyzes the oxidative decarboxylation of pyruvate and that links two major metabolic pathways: glycolysis and the tricarboxylic acid cycle. JNK-mediated phosphorylation of pyruvate dehydrogenase was not observed in experiments carried out with mitoplasts, thus suggesting the requirement of intact, functional mitochondria for this effect. JNK-mediated phosphorylation of pyruvate dehydrogenase was associated with a decline in its activity and, consequently, a shift to anaerobic pyruvate metabolism: the latter was confirmed by increased accumulation of lactic acid and decreased overall energy production (ATP levels). Pyruvate dehydrogenase appears to be a specific phosphorylation target for JNK, for other kinases, such as protein kinase A and protein kinase C did not elicit pyruvate dehydrogenase phosphorylation and did not decrease the activity of the complex. These results suggest that JNK mediates a signaling pathway that regulates metabolic functions in mitochondria as part of a network that coordinates cytosolic and mitochondrial processes relevant for cell function.
...
PMID:c-Jun N-terminal kinase regulates mitochondrial bioenergetics by modulating pyruvate dehydrogenase activity in primary cortical neurons. 1794 12

The steroidogenic acute regulatory protein (StAR) is required for adrenal and gonadal steroidogenesis and for male sexual differentiation. StAR acts on the outer mitochondrial membrane (OMM) to facilitate movement of cholesterol from the OMM to the inner mitochondrial membrane to be converted to pregnenolone, the precursor of all steroid hormones. The mechanisms of the action of StAR remain unclear; the peripheral benzodiazepine receptor, an OMM protein, appears to be involved, but the identity of OMM proteins that interact with StAR remain unknown. Here we demonstrate that phosphorylated StAR interacts with voltage-dependent anion channel 1 (VDAC1) on the OMM, which then facilitates processing of the 37-kDa phospho-StAR to the 32-kDa intermediate. In the absence of VDAC1, phospho-StAR is degraded by cysteine proteases prior to mitochondrial import. Phosphorylation of StAR by protein kinase A requires phosphate carrier protein on the OMM, which appears to interact with StAR before it interacts with VDAC1. VDAC1 and phosphate carrier protein are the first OMM proteins shown to contact StAR.
...
PMID:Steroidogenic activity of StAR requires contact with mitochondrial VDAC1 and phosphate carrier protein. 1825 Jan 66

A-kinase anchor protein 121 (AKAP121) assembles a multivalent signalling complex on the outer mitochondrial membrane that controls persistence and amplitude of cAMP and src signalling to mitochondria, and plays an essential role in oxidative metabolism and cell survival. Here, we show that AKAP121 levels are regulated post-translationally by the ubiquitin/proteasome pathway. Seven In-Absentia Homolog 2 (Siah2), an E3-ubiquitin ligase whose expression is induced in hypoxic conditions, formed a complex and degraded AKAP121. In addition, we show that overexpression of Siah2 or oxygen and glucose deprivation (OGD) promotes Siah2-mediated ubiquitination and proteolysis of AKAP121. Upregulation of Siah2, by modulation of the cellular levels of AKAP121, significantly affects mitochondrial activity assessed as mitochondrial membrane potential and oxidative capacity. Also during cerebral ischaemia, AKAP121 is degraded in a Siah2-dependent manner. These findings reveal a novel mechanism of attenuation of cAMP/PKA signaling, which occurs at the distal sites of signal generation mediated by proteolysis of an AKAP scaffold protein. By regulating the stability of AKAP121-signalling complex at mitochondria, cells efficiently and rapidly adapt oxidative metabolism to fluctuations in oxygen availability.
...
PMID:Proteolysis of AKAP121 regulates mitochondrial activity during cellular hypoxia and brain ischaemia. 1832 79

Inhibition of glycogen synthase kinase (GSK)-3 reduces ischemia/reperfusion injury by mechanisms that involve the mitochondria. The goal of this study was to explore possible molecular targets and mechanistic basis of this cardioprotective effect. In perfused rat hearts, treatment with GSK inhibitors before ischemia significantly improved recovery of function. To assess the effect of GSK inhibitors on mitochondrial function under ischemic conditions, mitochondria were isolated from rat hearts perfused with GSK inhibitors and were treated with uncoupler or cyanide or were made anoxic. GSK inhibition slowed ATP consumption under these conditions, which could be attributable to inhibition of ATP entry into the mitochondria through the voltage-dependent anion channel (VDAC) and/or adenine nucleotide transporter (ANT) or to inhibition of the F(1)F(0)-ATPase. To determine the site of the inhibitory effect on ATP consumption, we measured the conversion of ADP to AMP by adenylate kinase located in the intermembrane space. This assay requires adenine nucleotide transport across the outer but not the inner mitochondrial membrane, and we found that GSK inhibitors slow AMP production similar to their effect on ATP consumption. This suggests that GSK inhibitors are acting on outer mitochondrial membrane transport. In sonicated mitochondria, GSK inhibition had no effect on ATP consumption or AMP production. In intact mitochondria, cyclosporin A had no effect, indicating that ATP consumption is not caused by opening of the mitochondrial permeability transition pore. Because GSK is a kinase, we assessed whether protein phosphorylation might be involved. Therefore, we performed Western blot and 1D/2D gel phosphorylation site analysis using phos-tag staining to indicate proteins that had decreased phosphorylation in hearts treated with GSK inhibitors. Liquid chromatographic-mass spectrometric analysis revealed 1 of these proteins to be VDAC2. Taken together, we found that GSK-mediated signaling modulates transport through the outer membrane of the mitochondria. Both proteomics and adenine nucleotide transport data suggest that GSK regulates VDAC and that VDAC may be an important regulatory site in ischemia/reperfusion injury.
...
PMID:Glycogen synthase kinase 3 inhibition slows mitochondrial adenine nucleotide transport and regulates voltage-dependent anion channel phosphorylation. 1894 28

Individual cells within a population undergo apoptosis at distinct, apparently random time points. By analyzing cellular mitotic history, we identified that sibling HeLa cell pairs, in contrast to random cell pairs, underwent apoptosis synchronously. This allowed us to use high-speed cellular imaging to investigate mitochondrial outer membrane permeabilization (MOMP), a highly coordinated, rapid process during apoptosis, at a temporal resolution approximately 100 times higher than possible previously. We obtained new functional and mechanistic insight into the process of MOMP: We were able to determine the kinetics of pore formation in the outer mitochondrial membrane from the initiation phase of cytochrome-c-GFP redistribution, and showed differential pore formation kinetics in response to intrinsic or extrinsic apoptotic stimuli (staurosporine, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)). We also detected that the onset of mitochondrial permeabilization frequently proceeded as a wave through the cytosol, and that the frequency of wave occurrence in response to TRAIL was reduced by inhibition of protein kinase CK2. Computational analysis by a partial differential equation model suggested that the spread of permeabilization signals could sufficiently be explained by diffusion-adsorption velocities of locally generated permeabilization inducers. Taken together, our study yielded the first comprehensive analysis of clonal cell-to-cell variability in apoptosis execution and allowed to visualize and explain the dynamics of MOMP in cells undergoing apoptosis.
...
PMID:Dynamics of outer mitochondrial membrane permeabilization during apoptosis. 1913 37


<< Previous 1 2 3 4 5 6 7 8 Next >>

---