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Of ghrelin, cone cultivation, dinoflagellate eyes, and the cyanobacterial circadian clock.

Adler EM - J. Gen. Physiol. (2015)

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This month’s installment of Generally Physiological considers inhibition of calcium channels through distinct agonist-dependent and -independent GHSR1a pathways, how rods support cone survival, the complex origins of a chimeric “eye” in a unicellular eukaryote, and the role of a metamorphic protein in the cyanobacterial circadian clock... Ghrelin, the only known orexigenic peptide, signals through GHSR1a (growth hormone secretagogue receptor type 1a), a GPCR with high constitutive activity, to modulate neurotransmitter release from presynaptic nerve terminals... In this issue, noting that activation of various GPCRs leads to the inhibition of presynaptic voltage-gated calcium channels (see Weiss and Zamponi), López Soto et al. explored the effects of constitutive and ghrelin-dependent GHSR1a signaling on Cav2.1 and Cav2.2 function in primary cultures of hypothalamic neurons and when heterologously expressed in HEK 293 cells... Intriguingly, they found that, although both constitutive and agonist-dependent GHSR1a signaling inhibited Cav2.1 and Cav2.2 activity, they did so through distinct mechanisms involving different signaling pathways... Both constitutive and agonist-dependent GHSR1a signaling decreased GABA release from hypothalamic neurons, suggesting that GHSR1a signaling could promote the disinhibition (and thereby the activation) of postsynaptic neurons... Thus, loss of rods in the genetic disorder retinitis pigmentosa leads to the subsequent degeneration of cones and thereby to blindness... Lack of rod-derived cone viability factor (RdCVF) contributes to cone degeneration; however, the mechanism whereby RdCVF promotes cone viability has been unknown (see ). used far-Western analysis of cone-enriched cultures from chicken embryos to identify the transmembrane protein basigin-1 as binding to RdCVF, and then determined that silencing basigin-1 decreased RdCVF-mediated cone survival... In addition to its role in determining KaiC phosphorylation status, KaiB also regulates the antagonistic clock output enzymes SasA and CikA, competing with SasA for binding to KaiC... SasA is stimulated by binding to KaiC, and KaiB variants that favored the fsKaiB conformation decreased SasA signaling and increased CikA signaling... The authors thus propose that the rare transition to fsKaiB enables its binding to KaiC, enabling the inhibition of KaiA to initiate KaiC dephosphorylation, and outcompeting SasA to link timekeeping with output in the cyanobacterial circadian clock... In a separate study by a different group, explored the role of the slow ATPase activity of KaiC in determining the frequency of the cyanobacterial circadian clock.

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The warnowiid dinoflagellate ocelloid is a complex structure, made up of components with endogenous and distinct endosymbiotic origins. (Reprinted by permission from Macmillan Publishers, Ltd. T.A. Richards and S.L. Gomes. Nature. http://dx.doi.org/10.1038/nature14630, copyright 2015.)
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fig2: The warnowiid dinoflagellate ocelloid is a complex structure, made up of components with endogenous and distinct endosymbiotic origins. (Reprinted by permission from Macmillan Publishers, Ltd. T.A. Richards and S.L. Gomes. Nature. http://dx.doi.org/10.1038/nature14630, copyright 2015.)


Of ghrelin, cone cultivation, dinoflagellate eyes, and the cyanobacterial circadian clock.

Adler EM - J. Gen. Physiol. (2015)

The warnowiid dinoflagellate ocelloid is a complex structure, made up of components with endogenous and distinct endosymbiotic origins. (Reprinted by permission from Macmillan Publishers, Ltd. T.A. Richards and S.L. Gomes. Nature. http://dx.doi.org/10.1038/nature14630, copyright 2015.)
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4555473&req=5

fig2: The warnowiid dinoflagellate ocelloid is a complex structure, made up of components with endogenous and distinct endosymbiotic origins. (Reprinted by permission from Macmillan Publishers, Ltd. T.A. Richards and S.L. Gomes. Nature. http://dx.doi.org/10.1038/nature14630, copyright 2015.)

View Article: PubMed Central - HTML - PubMed

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

This month’s installment of Generally Physiological considers inhibition of calcium channels through distinct agonist-dependent and -independent GHSR1a pathways, how rods support cone survival, the complex origins of a chimeric “eye” in a unicellular eukaryote, and the role of a metamorphic protein in the cyanobacterial circadian clock... Ghrelin, the only known orexigenic peptide, signals through GHSR1a (growth hormone secretagogue receptor type 1a), a GPCR with high constitutive activity, to modulate neurotransmitter release from presynaptic nerve terminals... In this issue, noting that activation of various GPCRs leads to the inhibition of presynaptic voltage-gated calcium channels (see Weiss and Zamponi), López Soto et al. explored the effects of constitutive and ghrelin-dependent GHSR1a signaling on Cav2.1 and Cav2.2 function in primary cultures of hypothalamic neurons and when heterologously expressed in HEK 293 cells... Intriguingly, they found that, although both constitutive and agonist-dependent GHSR1a signaling inhibited Cav2.1 and Cav2.2 activity, they did so through distinct mechanisms involving different signaling pathways... Both constitutive and agonist-dependent GHSR1a signaling decreased GABA release from hypothalamic neurons, suggesting that GHSR1a signaling could promote the disinhibition (and thereby the activation) of postsynaptic neurons... Thus, loss of rods in the genetic disorder retinitis pigmentosa leads to the subsequent degeneration of cones and thereby to blindness... Lack of rod-derived cone viability factor (RdCVF) contributes to cone degeneration; however, the mechanism whereby RdCVF promotes cone viability has been unknown (see ). used far-Western analysis of cone-enriched cultures from chicken embryos to identify the transmembrane protein basigin-1 as binding to RdCVF, and then determined that silencing basigin-1 decreased RdCVF-mediated cone survival... In addition to its role in determining KaiC phosphorylation status, KaiB also regulates the antagonistic clock output enzymes SasA and CikA, competing with SasA for binding to KaiC... SasA is stimulated by binding to KaiC, and KaiB variants that favored the fsKaiB conformation decreased SasA signaling and increased CikA signaling... The authors thus propose that the rare transition to fsKaiB enables its binding to KaiC, enabling the inhibition of KaiA to initiate KaiC dephosphorylation, and outcompeting SasA to link timekeeping with output in the cyanobacterial circadian clock... In a separate study by a different group, explored the role of the slow ATPase activity of KaiC in determining the frequency of the cyanobacterial circadian clock.

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