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cAMP Signaling Pathway (camp + signaling_pathway)
Selected AbstractsPML/RAR, fusion protein mediates the unique sensitivity to arsenic cytotoxicity in acute promyelocytic leukemia cells: Mechanisms involve the impairment of cAMP signaling and the aberrant regulation of NADPH oxidase,JOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2008Lingna Li Acute promyelocytic leukemia (APL) cells are characterized by PML/RAR, fusion protein, high responsiveness to arsenic trioxide (ATO)-induced cytotoxicity and an abundant generation of reactive oxygen species (ROS). In this study we investigated the association among these three features in APL-derived NB4 cells. We found that NADPH oxidase-derived ROS generation was more abundant in NB4 cells compared with monocytic leukemia U937 cells. By using PR9, a sub-line of U937 stably transduced with the inducible PML/RAR, expression vectors, we attributed disparities on ROS generation and ATO sensitivity to the occurrence of PML/RAR, fusion protein, since PML/RAR,-expressing cells appeared higher NADPH oxidase activity, higher ROS level and higher sensitivity to ATO. On the other hand, the basal intensity of cAMP signaling pathway was compared between NB4 and U937 as well as between PR9 cells with or without PML/RAR,, demonstrating that PML/RAR,-expressing cells had an impaired cAMP signaling pathway which relieved its inhibitory effect on NADPH oxidase derived ROS generation. In summary, the present study demonstrated the correlation of PML/RAR, with cAMP signaling pathway, NADPH oxidase and ROS generation in APL cells. PML/RAR, that bestows NB4 cells various pathological features, paradoxically also endows these cells with the basis for susceptibility to ATO-induced cytotoxcity. J. Cell. Physiol. 217: 486,493, 2008. © 2008 Wiley-Liss, Inc. [source] cAMP-induced differentiation of human neuronal progenitor cells is mediated by nuclear fibroblast growth factor receptor-1 (FGFR1)JOURNAL OF NEUROCHEMISTRY, Issue 6 2003E. K. Stachowiak Abstract Activation of cAMP signaling pathway and its transcriptional factor cyclic AMP response element binding protein (CREB) and coactivator are key determinants of neuronal differentiation and plasticity. We show that nuclear fibroblast growth factor receptor-1 (FGFR1) mediates cAMP-induced neuronal differentiation and regulates CREB and CREB binding protein (CBP) function in ,-internexin-expressing human neuronal progenitor cells (HNPC). In proliferating HNPC, FGFR1 was associated with the cytoplasm and plasma membrane. Treatment with dB-cAMP induced nuclear accumulation of FGFR1 and caused neuronal differentiation, accompanied by outgrowth of neurites expressing MAP2 and neuron-specific neurofilament-L protein and enolase. HNPC transfected with nuclear/cytoplasmic FGFR1 or non-membrane FGFR1(SP-/NLS), engineered to accumulate exclusively in the cell nucleus, underwent neuronal differentiation in the absence of cAMP stimulation. In contrast, FGFR1/R4, with highly hydrophobic transmembrane domain of FGFR4, was membrane associated, did not enter the nucleus and failed to induce neuronal differentiation. Transfection of tyrosine kinase-deleted dominant negative receptor mutants, cytoplasmic/nuclear FGFR1(TK-) or nuclear FGFR1(SP-/NLS)(TK-), prevented cAMP-induced neurite outgrowth. Nuclear FGFR1 localized in speckle-like domains rich in phosphorylated histone 3 and splicing factors, regions known for active RNA transcription and processing, and activated the neurofilament-L gene promoter. FGFR1(SP-/NLS) transactivated CRE, up-regulated phosphorylation and transcriptional activity of CREB and stimulated the activity of CBP several-fold. Thus, cAMP-induced nuclear accumulation of FGFR1 provides a signal that triggers molecular events leading to neuronal differentiation. [source] Temporal coupling of cyclic AMP and Ca2+/calmodulin-stimulated adenylyl cyclase to the circadian clock in chick retinal photoreceptor cellsJOURNAL OF NEUROCHEMISTRY, Issue 4 2006Shyam S. Chaurasia Abstract cAMP signaling pathways play crucial roles in photoreceptor cells and other retinal cell types. Previous studies demonstrated a circadian rhythm of cAMP level in chick photoreceptor cell cultures that drives the rhythm of activity of the melatonin synthesizing enzyme arylalkylamine N -acetyltransferase and the rhythm of affinity of the cyclic nucleotide-gated channel for cGMP. Here, we report that the photoreceptor circadian clock generates a rhythm in Ca2+/calmodulin-stimulated adenylyl cyclase activity, which accounts for the temporal changes in the cAMP levels in the photoreceptors. The circadian rhythm of cAMP in photoreceptor cell cultures is abolished by treatment with the l -type Ca2+ channel antagonist nitrendipine, while the Ca2+ channel agonist, Bay K 8644, increased cAMP levels with continued circadian rhythmicity in constant darkness. These results indicate that the circadian rhythm of cAMP is dependent, in part, on Ca2+ influx. Photoreceptor cell cultures exhibit a circadian rhythm in Ca2+/calmodulin-stimulated adenylyl cyclase enzyme activity with high levels at night and low levels during the day, correlating with the temporal changes of cAMP in these cells. Transcripts encoding two of the Ca2+/calmodulin-stimulated adenylyl cyclases, type 1 and type 8 (Adcy1 and Adcy8), displayed significant daily rhythms of mRNA expression under a light,dark cycle, but only the Adcy1 transcript rhythm persisted in constant darkness. Similar rhythms of Adcy1 mRNA level and Ca2+/calmodulin-stimulated adenylyl cyclase activity were observed in retinas of 2-week-old chickens. These results indicate that a circadian clock controls the expression of Adcy1 mRNA and Ca2+/calmodulin-stimulated adenylyl cyclase activity; and calcium influx into these cells gates the circadian rhythm of cAMP, a key component in the regulation of photoreceptor function. [source] Development of functional LH Receptors on pig cumulus,oocyte complexes cultured in vitro by a novel two-step culture systemMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 8 2009Radek Procházka We show in the present study that freshly isolated pig cumulus,oocyte complexes (COCs) display a limited response to LH, as assessed by the expression of hyaluronan synthase 2 (Has2) mRNA, activation of protein kinase A (PKA), production of hyaluronic acid (HA) and progesterone, cumulus cell expansion and resumption of meiosis. These data indicate that freshly isolated COCs do not possess a sufficient number of functional LH receptors (LHR). However, the expression of Lhr significantly increased during the culture of COCs in vitro in a medium supplemented with FSH. Assuming that the effect of FSH on LHR induction is mediated via cAMP signaling pathways, we developed a new culture system, in which the COCs were pre-cultured for 72 hr in a medium supplemented with dbcAMP. The pre-cultured COCs remained in the germinal vesicle stage, their cumulus investment underwent a dramatic increase in size and gap junctions between the cumulus cells were preserved. The stimulation of such COCs with either FSH or LH led to the resumption and completion of meiosis, activation of PKA, expression of Has2, synthesis of large amounts of HA and progesterone, and extensive expansion of cumulus cells. We conclude that the formation of functional LHR is stimulated in cumulus cells during the culture in vitro in a cAMP-dependent pathway. The dbcAMP-treated COCs thus represent a new model in which the resumption of meiosis and cumulus expansion can be induced exclusively by the action of recombinant LH. Mol. Reprod. Dev. 76: 751,761, 2009. © 2009 Wiley-Liss, Inc. [source] Modulation of perch connexin35 hemi-channels by cyclic AMP requires a protein kinase A phosphorylation siteJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2003Georgia Mitropoulou Abstract Retinal neurons are coupled via gap junctions, which function as electrical synapses that are gated by ambient light conditions. Gap junctions connecting either horizontal cells or AII amacrine cells are inhibited by the neurotransmitter dopamine, via the activation of the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway. Fish connexin35 (Cx35) and its mouse ortholog, Cx36, are good candidates to undergo dopaminergic modulation, because they have been detected in the inner plexiform layer of the retina, where Type II amacrine cells establish synaptic contacts. We have taken advantage of the ability of certain connexins to form functional connexons (hemi-channels), when expressed in Xenopus oocytes, to investigate whether pharmacological elevation of cAMP modulates voltage-activated hemi-channel currents in single oocytes. Injection of perch Cx35 RNA into Xenopus oocytes induced outward voltage-dependent currents that were recorded at positive membrane potentials. Incubation of oocytes with 8-bromoadenosine 3,,5,-cyclic monophosphate (8-Br-cAMP), a membrane permeable cAMP analog, resulted in a dose-dependent and reversible inhibition of hemi-channel currents at the more positive voltage steps. In contrast, treatment with 8-Br-cAMP did not have any effect on hemi-channel currents induced by skate Cx35. Amino acid sequence comparison of the two fish connexins revealed, in the middle cytoplasmic loop of perch Cx35, the presence of a PKA consensus sequence that was absent in the skate connexin. The results obtained with two constructs in which the putative PKA phosphorylation site was either suppressed (perch Cx35R108Q) or introduced (skate Cx35Q108R) indicate that it is responsible for the inhibition of hemi-channel currents. These studies demonstrate that perch Cx35 is a target of the cAMP/PKA signaling pathway and identify a consensus PKA phosphorylation site that is required for channel gating. © 2003 Wiley-Liss, Inc. [source] | ||||||||||