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

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

We studied the signaling pathways coupling gonadotropin-releasing hormone (GnRH) secretion to elevations in cAMP levels in the GT1 GnRH-secreting neuronal cell line. We hypothesized that increased cAMP could be acting directly by means of cyclic nucleotide-gated (CNG) cation channels or indirectly by means of activation of cAMP-dependent protein kinase (PKA). We showed that GT1 cells express the three CNG subunits present in olfactory neurons (CNG2, -4.3, and -5) and exhibit functional cAMP-gated cation channels. Activation of PKA does not appear to be necessary for the stimulation of GnRH release by increased levels of cAMP. In fact, pharmacological inhibition of PKA activity caused an increase in the basal secretion of GnRH. Consistent with this observation activation PKA inhibited adenylyl cyclase activity, presumably by inhibiting adenylyl cyclase V expressed in the cells. Therefore, the stimulation of GnRH release by elevations in cAMP appears to be the result of depolarization of the neurons initiated by increased cation conductance by cAMP-gated cation channels. Activation of PKA may constitute a negative-feedback mechanisms for lowering cAMP levels. We hypothesize that these mechanisms could result in oscillations in cAMP levels, providing a biochemical basis for timing the pulsatile release of GnRH.
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PMID:Role of the cAMP signaling pathway in the regulation of gonadotropin-releasing hormone secretion in GT1 cells. 1067 47

The molecular mechanisms underlying cell cycle control in neuronal progenitors have been investigated with adult mouse olfactory epithelium as a model system. Odor receptive neurons of mammalian olfactory epithelium are short-lived and renewed in the adult by mitotic division of intrinsic neuronal progenitors. Ablation of the synaptic target, olfactory bulb, induces sequentially extensive apoptosis of sensory neurons and then stimulation of progenitor proliferation, peaking at 36 h and 4 days, respectively, postlesion. Known molecular effectors of G1 phase entry have been assessed on protein extracts of olfactory organs sampled at various postbulbectomy times in adult mice. The decay of betaIII-tubulin and olfactory marker protein levels and the rise of proliferating cell nuclear antigen (PCNA) levels, starting 1 and 3 days, respectively, postlesion, provided the kinetic frame of neuronal dynamics. Cyclin D1, cyclin E, and cyclin-dependent kinase cdk2 levels, low in olfactory organ of intact mice, increased 3 days after bulbectomy in parallel with PCNA levels; cdk4 content was initially high and unaffected by lesioning. Western blots of the known cdk inhibitors revealed proliferation-related decreases of p18, p21, and p27 from high expression in intact organs. Immunoprecipitation of cdk2 and cdk4 fractions of protein extracts at 4 days postlesion (mitotic reaction peak) versus control, followed by cyclin D1 immunoblotting, and vice versa, revealed that levels of both cyclin D1/cdk2 and cyclin D1/cdk4 complexes, as well as their kinase activities, were dramatically increased after lesion. In vivo proliferation of olfactory neuronal lineage cells thus involves functional binding of cyclin D1 with cdk2 and cdk4, with differential activation mechanisms for cdk2 and cdk4. In addition, the RT-PCR-detected cyclin D1 mRNA level remained unaffected after bulbectomy, which indicated that the cyclin D1 rise should involve posttranscriptional mechanisms in this in vivo neuronal system. These observations are discussed, along with their relevance to cell cycle control and to olfactory neuron dynamics.
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PMID:Unusual regulation of cyclin D1 and cyclin-dependent kinases cdk2 and cdk4 during in vivo mitotic stimulation of olfactory neuron progenitors in adult mouse. 1082 Jan 94

Protein kinases A and C have been postulated to exert multiple effects on different elements of signal transduction pathways in olfactory receptor neurons. However, little is known about the modulation of olfactory responses by protein kinases in intact olfactory receptor neurons. To further elucidate the details of the modulation of odorant responsiveness by these protein kinases, we investigated the action of two protein kinase inhibitors: H89, an inhibitor of protein kinase A, and N-myristoylated EGF receptor, an inhibitor of protein kinase C, on odorant responsiveness in intact olfactory neurons. We isolated individual olfactory neurons from the adult human and rat olfactory epithelium and measured responses of the isolated cells to odorants or biochemical activators that have been shown to initiate cyclic AMP or inositol 1,4,5-trisphospate production in biochemical preparations. We employed calcium imaging techniques to measure odor-elicited changes in intracellular calcium that occur over several seconds. In human olfactory receptor neurons, the protein kinase A and C inhibitors affected the responses to different sets of odorants. In rats, however, the protein kinase C inhibitor affected responses to all odorants, while the protein kinase A inhibitor had no effect. In both species, the effect of inhibition of protein kinases was to enhance the elevation and block termination of intracellular calcium levels elicited by odorants. Our results show that protein kinases A and C may modulate odorant responses of olfactory neurons by regulating calcium fluxes that occur several seconds after odorant stimulation. The effects of protein kinase C inhibition are different in rat and human olfactory neurons, indicating that species differences are an important consideration when applying data from animal studies to apply to humans.
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PMID:Modulation of odor-induced increases in [Ca(2+)](i) by inhibitors of protein kinases A and C in rat and human olfactory receptor neurons. 1085 24

The previously described site-selected P-element mutagenesis of a Drosophila gene encoding the regulatory subunit of cAMP-dependent protein kinase generates mutants that have defective behavior in the olfactory learning test. Here we describe the effect of the same mutations in a courtship conditioning assay. Wild-type males can distinguish between virgin females (which they court vigorously), and fertilized females (which they court less vigorously). After exposure to fertilized females, wild-type males modify their behavior by decreasing courtship to subsequent target virgins, an effect that may last for many hours. Like wild-type males, PKA-RI mutant males are also able to distinguish between virgin and fertilized females. PKA-RI males also modify their behavior towards virgin females after prior exposure to a fertilized female, but such an effect is short-lived, suggesting a defect in memory rather than learning. We also show that under these conditions the behavior of PKA-RI males is similar to that of amnesiac, dunce and rutabaga males.
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PMID:Abnormal courtship conditioning in males mutant for the RI regulatory subunit of Drosophila protein kinase A. 1085 19

The second messengers 3'-5'-cyclic-monophosphate (cAMP) and inositol 1,4,5-trisphosphate (InsP3) have been implicated in olfactory signal transduction in various species. The results of the present study provide evidence that the two olfactory second messenger pathways in rat olfactory neurons do not work independently but rather show a functional antagonism: whereas inhibition of phospholipase C (PLC) in isolated olfactory cilia by U-73122 led to an augmentation of odor-induced cAMP signaling, activation of the phosphoinositol pathway resulted in attenuation of odor-induced cAMP formation. Furthermore, this study indicates that elevated cAMP levels cause suppression of odor-induced InsP3 signaling, whereas inhibition of adenylate cyclase (AC) by cisN-(2-phenylcyclopentyl)azacylotridec-1-en-2-amine (MDL-12,330 A) results in potentiation of odor-induced InsP3 formation. Concerning the molecular mechanism involved in cross-interaction, the experimental data indicate that the observed antagonism of elevated cAMP is based on inhibition of PLC activation rather than on stimulation of InsP3 degradation. As blockage of the endogenous protein kinase A (PKA) prevented the inhibitory effect of cAMP, the suppression of odor-induced InsP3 signaling by cAMP may be mediated by a PKA-controlled reaction.
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PMID:Cross-talk between olfactory second messenger pathways. 1088 Sep 77

Cyclic AMP is a ubiquitous second messenger that coordinates diverse cellular functions. Current methods for measuring cAMP lack both temporal and spatial resolution, leading to the pervasive notion that, unlike Ca(2+), cAMP signals are simple and contain little information. Here we show the development of adenovirus-expressed cyclic nucleotide-gated channels as sensors for cAMP. Homomultimeric channels composed of the olfactory alpha subunit responded rapidly to jumps in cAMP concentration, and their cAMP sensitivity was measured to calibrate the sensor for intracellular measurements. We used these channels to detect cAMP, produced by either heterologously expressed or endogenous adenylyl cyclase, in both single cells and cell populations. After forskolin stimulation, the endogenous adenylyl cyclase in C6-2B glioma cells produced high concentrations of cAMP near the channels, yet the global cAMP concentration remained low. We found that rapid exchange of the bulk cytoplasm in whole-cell patch clamp experiments did not prevent the buildup of significant levels of cAMP near the channels in human embryonic kidney 293 (HEK-293) cells expressing an exogenous adenylyl cyclase. These results can be explained quantitatively by a cell compartment model in which cyclic nucleotide-gated channels colocalize with adenylyl cyclase in microdomains, and diffusion of cAMP between these domains and the bulk cytosol is significantly hindered. In agreement with the model, we measured a slow rate of cAMP diffusion from the whole-cell patch pipette to the channels (90% exchange in 194 s, compared with 22-56 s for substances that monitor exchange with the cytosol). Without a microdomain and restricted diffusional access to the cytosol, we are unable to account for all of the results. It is worth noting that in models of unrestricted diffusion, even in extreme proximity to adenylyl cyclase, cAMP does not reach high enough concentrations to substantially activate PKA or cyclic nucleotide-gated channels, unless the entire cell fills with cAMP. Thus, the microdomains should facilitate rapid and efficient activation of both PKA and cyclic nucleotide-gated channels, and allow for local feedback control of adenylyl cyclase. Localized cAMP signals should also facilitate the differential regulation of cellular targets.
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PMID:Cyclic nucleotide-gated channels colocalize with adenylyl cyclase in regions of restricted cAMP diffusion. 1091 62

Unilateral naris closure produced dramatic down-regulation of tyrosine hydroxylase (TH) gene expression in periglomerular dopaminergic neurons in the olfactory bulb. To explore molecular mechanisms of TH gene regulation, the present study investigated the regional distribution of protein kinase A (PKAalpha), protein kinase C (PKCalpha), and CaM kinases II (CaMKIIalpha, beta) and IV (CaMKIV) in the normal olfactory bulb and in response to odor deprivation. Strong PKAalpha immunostaining was found in the glomerular, granule cell, external plexiform and olfactory nerve layers. PKCalpha staining was strong in granule cell and external plexiform layers but weak in the glomerular layer. Whereas CaMKIV was primarily found in granule cells, CaMKII was present in the glomerular, external plexiform, mitral cell and granule cell layers. No change in immunoreactivities of these kinases occurred in the olfactory bulb ipsilateral to naris closure. The expression of PKAalpha, PKCalpha and CaMKII, but not CaMKIV, in periglomerular cells suggests that these three kinases may play a role in TH gene regulation in the olfactory bulb. The lack of change in kinase protein levels after naris closure also suggests that any involvement of these kinases in TH gene expression in the olfactory bulb must be through altered kinase activity and not protein levels.
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PMID:Regional distribution of protein kinases in normal and odor-deprived mouse olfactory bulbs. 1094 3

CYP2A5 is induced by a large number of chemicals including some cAMP modifiers. In a primary hepatocyte model, stimulation of the cAMP signal transduction pathway by glucagon and isoproterenol, acting via specific G-protein coupled plasma membrane receptors, produced up to 17-fold increases in the marker activity of CYP2A5, coumarin 7-hydroxylase. In contrast, glucagon and isoproterenol caused no significant effects on two other major CYP forms, CYP2B10 and CYP1A1/2. Phenobarbital (PB) elicited a 3-fold increase in CYP2A5 expression (catalytic activity and mRNA), while the cAMP and protein kinase A (PKA) stimulators dibutyryl-cAMP, forskolin and Sp-cAMPs caused up to 18-fold increases in the amount of CYP2A5 mRNA. Coadministration of PB and cAMP/PKA stimulating agents produced an additive inducing effect. The expression of CYP2A5, but not CYP2B10 or CYP1A1/2, in DBA/2 mice displayed a marked circadian rhythm, the level of expression being highest in the evening. These results suggest that among xenobiotic metabolizing CYP enzymes, CYP2A5 is uniquely upregulated by cAMP, possibly having the physiological function of priming the olfactory and digestive systems for nocturnal feeding.
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PMID:cAMP mediated upregulation of CYP2A5 in mouse hepatocytes. 1116 86

The avoidance response to repellent odorants in Drosophila melanogaster, a response essential for survival, provides an advantageous model for studies on the genetic architecture of olfactory behavior. Transposon tagging in a highly inbred strain of flies in combination with a rapid and simple statistical behavioral assay enables the identification of not only large phenotypic effects, but also small aberrations from wild-type avoidance behavior. The recent completion of the sequence of the Drosophila genome facilitates the molecular characterization of transposon-tagged genes and correlation between gene expression and behavior in smell-impaired (smi) mutant lines. Quantitative genetic analyses of a collection of smi lines in a co-isogenic background revealed an extensive network of epistatic interactions among genes that shape the olfactory avoidance response. Candidate genes for several of these transposon-tagged smi loci implicate genes that mediate odorant recognition, including a novel odorant binding protein; signal propagation, including a voltage-gated sodium channel; and a protein containing multiple leucine rich repeats and PDZ domains likely to be involved in postsynaptic organization in the olfactory pathway. Several novel genes of unknown function have also been implicated, including a novel tyrosine-regulated protein kinase. The discovery and characterization of novel gene products that have major, hitherto unappreciated effects on olfactory behavior will provide new insights in the generation and regulation of odor-guided behavior. The identification and functional characterization of proteins encoded by smi genes that form part of the olfactory subgenome and correlation of polymorphisms in these genes with variation in odor-guided behavior in natural populations will advance our understanding of the genetic architecture of chemosensory behavior.
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PMID:Functional genomics of odor-guided behavior in Drosophila melanogaster. 1123 54

Effects of cGMP on voltage-gated currents in the somatic membrane of isolated newt olfactory receptor cells were investigated using the whole-cell mode of the patch-clamp technique. Under voltage clamp, membrane depolarization generated time- and voltage-dependent current responses, a transient inward current and a sustained outward current. When cGMP or a membrane permeant analog of cGMP, 8-p-chlorophenylthio-cGMP (CPT-cGMP), was applied to the recorded cell, the amplitude of the transient inward current increased markedly, but that of the sustained outward current did not change significantly. When each current was isolated by pharmacological agents, 0.1 mM CPT-cGMP increased the peak amplitude of a Na(+) current (I(Na)) by approximately 40%, a T-type Ca(2+) current (I(Ca,T)) by approximately 40%, and an L-type Ca(2+)current (I(Ca,L)) by approximately 10%; however it did not change significantly the amplitude of a delayed rectifier K(+) current (I(K)). A selective cGMP-dependent protein kinase inhibitor, KT5823, blocked the enhancement by cGMP of I(Na) and I(Ca,T), suggesting that cGMP increases these currents via cGMP-dependent phosphorylation. Under current-clamp conditions, application of CPT-cGMP lowered the current threshold of action potentials induced by current injection, and increased the maximum spike frequency in response to strong stimuli. We suggest that cGMP may lower the threshold in olfactory perception by decreasing the current threshold to generate spikes, and also prevent the saturation of odor signals by increasing the maximum spike frequency.
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PMID:Modulation by cGMP of the voltage-gated currents in newt olfactory receptor cells. 1124 73


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