Stimulation of calcium sequestration by mezerein, a protein kinase C activator, in saponized rabbit platelets

Nishio, Hiroaki; Ikegami, Yuri; Segawa, Tomio; Nakata, Yoshihiro

doi:10.1016/0306-3623(94)90189-9

Cited by 4 publications

(1 citation statement)

References 13 publications

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“…Because the modulatory domain of the IP 3 receptor is a substrate for several protein kinases (Supattapone et al 1988), including PKC (Ferris et al 1991), PKC may attenuate Ca 2ϩ efflux via receptor phosphorylation. PKC also may act farther down stream in the cascade by promoting Ca 2ϩ sequestration (Nishi et al 1994;Shivan and Alexander 1995;Werth et al 1996). PKC also acts up stream, preventing PIP 2 hydrolysis (Luo et al 1995;Shimizu et al 1993).…”

Section: Protein Kinase C Inhibits Ip 3 Responses In Nmmentioning

confidence: 99%

Glutamate Regulates IP₃-Type and CICR Stores in the Avian Cochlear Nucleus

Kato

Rubel

1999

Journal of Neurophysiology

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Neurons of the avian cochlear nucleus, nucleus magnocellularis (NM), are activated by glutamate released from auditory nerve terminals. If this stimulation is removed, the intracellular calcium ion concentration ([Ca2+]i) of NM neurons rises and rapid atrophic changes ensue. We have been investigating mechanisms that regulate [Ca2+]i in these neurons based on the hypothesis that loss of Ca2+ homeostasis causes the cascade of cellular changes that results in neuronal atrophy and death. In the present study, video-enhanced fluorometry was used to monitor changes in [Ca2+]i stimulated by agents that mobilize Ca2+ from intracellular stores and to study the modulation of these responses by glutamate. Homobromoibotenic acid (HBI) was used to stimulate inositol trisphosphate (IP3)-sensitive stores, and caffeine was used to mobilize Ca2+ from Ca2+-induced Ca2+ release (CICR) stores. We provide data indicating that Ca2+ responses attributable to IP3- and CICR-sensitive stores are inhibited by glutamate, acting via a metabotropic glutamate receptor (mGluR). We also show that activation of C-kinase by a phorbol ester will reduce HBI-stimulated calcium responses. Although the protein kinase A accumulator, Sp-cAMPs, did not have an effect on HBI-induced responses. CICR-stimulated responses were not consistently attenuated by either the phorbol ester or the Sp-cAMPs. We have previously shown that glutamate attenuates voltage-dependent changes in [Ca2+]i. Coupled with the present findings, this suggests that in these neurons mGluRs serve to limit fluctuations in intracellular Ca2+ rather than increase [Ca2+]i. This system may play a role in protecting highly active neurons from calcium toxicity resulting in apoptosis.

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Section: Protein Kinase C Inhibits Ip 3 Responses In Nmmentioning

confidence: 99%

Glutamate Regulates IP₃-Type and CICR Stores in the Avian Cochlear Nucleus

Kato

Rubel

1999

Journal of Neurophysiology

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Approaches to Study Posttranslational Regulation of Intermediate Filament Proteins

Kochin

Pallari

Pant

et al. 2004

Intermediate Filament Cytoskeleton

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Various Phosphorylation Pathways, Depending on Agonist and Antagonist Binding to Endogenous Estrogen Receptor α (ERα), Differentially Affect ERα Extractability, Proteasome-Mediated Stability, and Transcriptional Activity in Human Breast Cancer Cells

Marsaud

Gougelet

Maillard

et al. 2003

Molecular Endocrinology

138

115

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Estrogen receptor-alpha (ER) is down-regulated in the presence of its cognate ligand, estradiol (E2), as well as in the presence of antiestrogens, through the ubiquitin proteasome pathway. Here, we show that, at pharmacological concentrations, the degradation rate of pure antagonist/endogenous ER complexes from human breast cancer MCF-7 cells is 10 times faster than that of ER-E2 complexes, while 4-hydroxy-tamoxifen (4-OH-T)-ER complexes are stable. Whereas pure antagonist-ER complexes are firmly bound to a nuclear compartment from which they are not extractable, the 4-OH-T-ER accumulates in a soluble cell compartment. No difference was observed in the fate of ER whether bound to pure antiestrogens ICI 182,780 or RU 58668. Cycloheximide experiments showed that, while the proteasome-mediated destruction of E2-ER (unlike that of RU 58668- and ICI 182,780-ER) complexes could implicate (or not) a protein synthesis-dependent process, both MAPKs (p38 and ERKs p44 and p42) are activated. By using a panel of kinase inhibitors/activators to study the impact of phosphorylation pathways on ER degradation, we found that protein kinase C is an enhancer of proteasome-mediated degradation of both ligand-free and ER bound to either E2, 4-OH-T, and pure antagonists. On the contrary, protein kinase A, MAPKs, and phosphatidyl-inositol-3 kinase all impede proteasome-mediated destruction of ligand free and E2-bound ER while only MAPKs inhibit the degradation of pure antiestrogens/ER species. In addition, no correlation was found between the capacity of kinase inhibitors to affect ER stability and the basal or E2-induced transcription. These results suggest that, in MCF-7 breast cancer cells, ER turnover, localization, and activity are maintained by an equilibrium between various phosphorylation pathways, which are differently modulated by ER ligands and protein kinases.

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Stimulation of calcium sequestration by mezerein, a protein kinase C activator, in saponized rabbit platelets

Cited by 4 publications

References 13 publications

Glutamate Regulates IP₃-Type and CICR Stores in the Avian Cochlear Nucleus

Glutamate Regulates IP₃-Type and CICR Stores in the Avian Cochlear Nucleus

Approaches to Study Posttranslational Regulation of Intermediate Filament Proteins

Various Phosphorylation Pathways, Depending on Agonist and Antagonist Binding to Endogenous Estrogen Receptor α (ERα), Differentially Affect ERα Extractability, Proteasome-Mediated Stability, and Transcriptional Activity in Human Breast Cancer Cells

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Stimulation of calcium sequestration by mezerein, a protein kinase C activator, in saponized rabbit platelets

Cited by 4 publications

References 13 publications

Glutamate Regulates IP3-Type and CICR Stores in the Avian Cochlear Nucleus

Glutamate Regulates IP3-Type and CICR Stores in the Avian Cochlear Nucleus

Approaches to Study Posttranslational Regulation of Intermediate Filament Proteins

Various Phosphorylation Pathways, Depending on Agonist and Antagonist Binding to Endogenous Estrogen Receptor α (ERα), Differentially Affect ERα Extractability, Proteasome-Mediated Stability, and Transcriptional Activity in Human Breast Cancer Cells

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Glutamate Regulates IP₃-Type and CICR Stores in the Avian Cochlear Nucleus

Glutamate Regulates IP₃-Type and CICR Stores in the Avian Cochlear Nucleus