Second messenger system

Summary

Second messengers are intracellular signaling molecules released by the cell in response to exposure to extracellular signaling molecules—the first messengers. (Intercellular signals, a non-local form of cell signaling, encompassing both first messengers and second messengers, are classified as autocrine, juxtacrine, paracrine, and endocrine depending on the range of the signal.) Second messengers trigger physiological changes at cellular level such as proliferation, differentiation, migration, survival, apoptosis and depolarization. They are one of the triggers of intracellular signal transduction cascades. Examples of second messenger molecules include cyclic AMP, cyclic GMP, inositol triphosphate, diacylglycerol, and calcium. First messengers are extracellular factors, often hormones or neurotransmitters, such as epinephrine, growth hormone, and serotonin. Because peptide hormones and neurotransmitters typically are biochemically hydrophilic molecules, these first messengers may n

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Molecular Hydrogen Messengers Can Lead to Structural Infidelity: A Cautionary Tale of Protonated Glycine

Antoine Louis Claude Masson, Thomas Rizzo, Evan Rowland Williams

The effects of tagging protonated glycine with either He or with between 1 and 14 H2 molecules on the infrared photodissociation (IRPD) spectra and the ion structure was investigated. Differences in the IR spectra with either a single He atom or H2 molecule attached indicate that even a single H2 molecule can affect the frequencies of some vibrational bands of this simple ion. The protonation site is the preferred location of the tag with He and with up to two H2 molecules, but evidence for H2 attachment to the hydrogen atom of the uncharged carboxylic acid is observed for ions tagged with three or more H2 molecules. This results in a 55 cm-1 red shift in the carboxylic acid OH stretch, and evidence for some structural isomers where the hydrogen bond between the protonated nitrogen and the carbonyl oxygen is partially broken as a result H2 molecules attached to this site is observed. These results are supported by theory, which indicates that H2 molecules can effectively break this weak hydrogen bond with three or more H2 molecules. These results indicate that large spectral shifts as a result of H2 molecules attaching to sites remote from the charge can occur and affect stretching frequencies as a result of charge transfer, and that tagging with multiple H2 molecules can change the structure of the ion itself.

American Institute of Physics2015

Diacylglycerol (DAG) and phorbol esters strongly potentiate transmitter release at synapses by activating protein kinase C (PKC) and members of the Munc13 family of presynaptic vesicle priming proteins. This PKC/Munc13 pathway has emerged as a crucial regulator of release probability during various forms of activity-dependent enhancement of release. Here, we investigated the relative roles of PKC and Munc13-1 in the phorbol ester potentiation of evoked and spontaneous transmitter release at the calyx of Held synapse. The phorbol ester phorbol 12,13-dibutyrate (1 mu M) potentiated the frequency of miniature EPSCs, and the amplitudes of evoked EPSCs with a similar time course. Preincubating slices with the PKC blocker Ro31-82200 reduced the potentiation, mainly by affecting a late phase of the phorbol ester potentiation. The Ro31-8220-insensitive potentiation was most likely mediated by Munc13-1, because in organotypic slices of Munc13-1H567K knock-in mice, in which DAG binding to Munc13-1 is abolished, the potentiation of spontaneous release by phorbol ester was strongly suppressed. Using direct presynaptic depolarizations in paired recordings, we show that the phorbol ester potentiation does not go along with an increase in the number of readily releasable vesicles, despite an increase in the cumulative EPSC amplitude during 100 Hz stimulation trains. Our data indicate that activation of Munc13 and PKC both contribute to an enhancement of the fusion probability of readily releasable vesicles. Thus, docked and readily releasable vesicles are a substrate for modulation via intracellular second-messenger pathways that act via Munc13 and PKC.

Society for Neuroscience2008

We have described previously a transcription-dependent induction of glycogen resynthesis by the vasoactive intestinal peptide (VIP) or noradrenaline (NA) in astrocytes, which is mediated by cAMP. Because it has been postulated that the cAMP-mediated regulation of energy balance in hepatocytes and adipocytes is channeled at least in part through the CCAAT/enhancer binding protein (C/EBP) family of transcription factors, we tested the hypothesis that C/EBP isoforms could be expressed in mouse cortical astrocytes and that their level of expression could be regulated by VIP, by the VIP-related neuropeptide pituitary adenylate cyclase-activating peptide (PACAP), or by NA. We report in this study that in these cells, C/EBP beta and C/EBP delta are induced by VIP, PACAP, or NA via the cAMP second-messenger pathway. Induction of C/EBP beta and -delta mRNA by VIP occurs in the presence of a protein synthesis inhibitor. Thus, c/ebp beta and c/ebp delta behave as cAMP-inducible immediate-early genes in astrocytes. Moreover, transfection of astrocytes with expression vectors selectively producing the transcriptionally active form of C/EBP beta, termed liver-enriched transcriptional activator protein, or C/EBP delta enhance the glycogen resynthesis elicited by NA, whereas an expression vector producing the transcriptionally inactive form of C/EBP beta, termed liver-enriched transcriptional inhibitory protein, reduces this resynthesis. These results support the idea that C/EBP beta and -delta regulate gene expression of energy metabolism-related enzymes in astrocytes.

1996