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Phosphoinositol Pathway (phosphoinositol + pathway)
Selected AbstractsVisualization of stochastic Ca2+ signals in the formed somites during the early segmentation period in intact, normally developing zebrafish embryosDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 7 2009Christina F. Leung Localized Ca2+ signals were consistently visualized in the formed somites of intact zebrafish embryos during the early segmentation period. Unlike the regular process of somitogenesis, these signals were stochastic in nature with respect to time and location. They did, however, occur predominantly at the medial and lateral boundaries within the formed somites. Embryos were treated with modulators of [Ca2+]i to explore the signal generation mechanism and possible developmental function of the stochastic transients. Blocking elements in the phosphoinositol pathway eliminated the stochastic signals but had no obvious effect, stochastic or otherwise, on the formed somites. Such treatments did, however, result in the subsequently formed somites being longer in the mediolateral dimension. Targeted uncaging of buffer (diazo-2) or Ca2+ (NP-ethyleneglycoltetraacetic acid [EGTA]) in the presomitic mesoderm, resulted in a regular mediolateral lengthening and shortening, respectively, of subsequently formed somites. These data suggest a requirement for IP3 receptor-mediated Ca2+ release during convergence cell movements in the presomitic mesoderm, which appears to have a distinct function from that of the IP3 receptor-mediated stochastic Ca2+ signaling in the formed somites. [source] Cross-talk between olfactory second messenger pathwaysFEBS JOURNAL, Issue 14 2000Alexander Vogl 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. [source] Expression and functional characterization of the mt1 melatonin receptor from rat brain in Xenopus oocytes: evidence for coupling to the phosphoinositol pathwayJOURNAL OF PINEAL RESEARCH, Issue 3 2001Cirstin Blumenau Melatonin-sensitive receptors were expressed in Xenopus laevis oocytes following an injection of mRNA from rat brain. The administration of 0.1,100 ,mol/L melatonin to voltage-clamped oocytes activates calcium-dependent chloride currents via a pertussis toxin-sensitive G protein and the phosphoinositol pathway. To determine which melatonin receptor type (mt1, MT2, MT3) is functionally expressed in the Xenopus oocytes, we used (i) agonists and antagonists of different receptor types to characterize the pharmacological profile of the expressed receptors and (ii) a strategy of inhibiting melatonin receptor function by antisense oligonucleotides. During pharmacological screening administration of the agonists 2-iodomelatonin and 2-iodo-N-butanoyl-5-methoxytryptamine (IbMT) to the oocytes resulted in oscillatory membrane currents, whereas the administration of the MT3 agonist 5-methoxycarbonylamino-N-acetyltryptamine (GR135,531) exerted no detectable membrane currents. The melatonin response was abolished by a preceding administration of the antagonists 2-phenylmelatonin and luzindole but was unaffected by the MT3 antagonist prazosin and the MT2 antagonist 4-phenyl-2-propionamidotetralin (4-P-PDOT). In the antisense experiments, in the control group the melatonin response occurred in 45 of 54 mRNA-injected oocytes (83%). Co-injection of the antisense oligonucleotide, corresponding to the mt1 receptor mRNA, caused a marked and significant reduction in the expression level (13%; P<0.001). In conclusion, the results demonstrate that injection of mRNA from rat brain in Xenopus oocytes induced the expression of the mt1 receptor which is coupled to the phosphoinositol pathway. [source] | ||||||||||