Realization of phosphorylation hypothesis of sleep by mammalian CaMKIIβ

ABSTRACTThe reduced sleep duration observed in Camk2a and Camk2b knockout mice revealed the role of Ca2+/calmodulin-dependent protein kinase II (CaMKII)α/CAMKIIβ as sleep-promoting kinases and lead to the phosphorylation hypothesis of sleep. However, the underlying mechanism of sleep regulation by kinases and protein phosphorylation is largely unknown. Here, we demonstrate that the phosphorylation states of CaMKIIβ regulates sleep duration and sleep needs. Importantly, the activation or inhibition of CaMKIIβ can increase or decrease sleep duration by almost two-fold, supporting the role of CaMKIIβ as a core sleep regulator in mammals. This sleep regulation depends on the kinase activity of CaMKIIβ in excitatory neurons. Furthermore, CaMKIIβ mutants mimicking different phosphorylation states can regulate various sleep steps including sleep induction, sleep maintenance, and sleep cancelation. Key CaMKIIβ residues responsible for the mode switch undergo ordered (auto-)phosphorylation. We thus propose that ordered multi-site phosphorylation of CaMKIIβ underlies multi-step sleep regulation in mammals.

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The role of calcium/calmodulin-dependent protein kinase II on the inactivation of MAP kinase and p34cdc2 kinase during fertilization and activation in pig oocytes

Reproduction ◽

10.1530/rep.1.00230 ◽

2004 ◽

Vol 128 (4) ◽

pp. 409-415 ◽

Cited By ~ 16

Author(s):

Junya Ito ◽

Natsuko Kawano ◽

Masumi Hirabayashi ◽

Masayuki Shimada

Keyword(s):

Protein Kinase ◽

Map Kinase ◽

Kinase Activity ◽

Cyclin B1 ◽

Dependent Protein Kinase ◽

Protein Kinase Ii ◽

Sperm Penetration ◽

Dependent Protein ◽

Pronuclear Formation

The objective of this study was to investigate the role of calmodulin-dependent protein kinase II (CaMKII) during fertilization in the pig. Since it has been reported that CaMKII is involved in the capacitation and acrosome reaction of spermatozoa, we tested whether supplementation with the CaMKII inhibitor, KN-93, in the fertilization medium affected sperm penetration. The results showed that the addition of KN-93 in the fertilization medium significantly reduced the rate of sperm penetration into oocytes. However, pre-treatment with KN-93 beforein vitrofertilization (IVF) did not significantly affect sperm penetration, but it did affect pronuclear formation in a dose-dependent manner. In the oocytes pre-treated with KN-93 before IVF and then co-cultured with spermatozoa without the drug, the decrease in p34cdc2kinase and the cyclin B1 level were significantly suppressed as compared with those in penetrated oocytes without treatment with KN-93. However, the decrease in MAP kinase activity was not affected by KN-93. Additional treatment with KN-93 after Ca2+ionophore treatment also inhibited the reduction in p34cdc2kinase activity and the cyclin B1 level, but not MAP kinase activity. Treatment with KN-92, an inactive KN-93 analogue, did not significantly affect sperm penetration and pronuclear formation. In conclusion, the activation of CaMKII by artificial stimuli or sperm stimulated the disruption of cyclin B1 and the inactivation of p34cdc2kinase, but did not affect MAP kinase inactivation during oocyte activation in pigs.

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