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Ca2+/calmodulin-dependent protein kinase IV stimulates nuclear factor-kappa B transactivation via phosphorylation of
1Center for Ligand and Transcription, Chonnam National University, Kwangju 500-757, Seoul 151-742, Korea.
Abstract:
Calmodulin-dependent protein kinase IV (CaMKIV) is a key mediator of Ca(2+)-induced gene expression. In this study, CaMKIV was found to directly associate with and phosphorylate the nuclear factor-kappaB (NFkappaB) component p65 both in vitro and in vivo. The phosphorylation of p65 by CaMKIV resulted in recruitment of transcription coactivator cAMP-response element-binding protein-binding protein and concomitant release of corepressor silencing mediator for retinoid and thyroid hormone receptors, as demonstrated by the glutathione S-transferase pull down and mammalian two hybrid assays. In addition, cotransfection of CaMKIV resulted in cytosolic translocation of the silencing mediator for retinoid and thyroid hormone receptors. Consistent with these results, cotransfected CaMKIV dramatically stimulated the NFkappaB transactivation in mammalian cells. From these results, NFkappaB is suggested to be a novel downstream effector molecule of CaMKIV.
Insights
Calmodulin-dependent protein kinase IV (CaMKIV) directly phosphorylates the NF-kappaB component p65. This interaction enhances gene expression by altering transcription coactivator and corepressor binding, revealing NF-kappaB as a novel CaMKIV effector.
Area of Science:
- Molecular Biology
- Cellular Signaling
- Gene Regulation
Background:
- Calmodulin-dependent protein kinase IV (CaMKIV) is a crucial regulator of calcium-induced gene expression.
- Understanding CaMKIV's downstream targets is essential for elucidating cellular signaling pathways.
Purpose of the Study:
- To investigate the direct interaction between CaMKIV and nuclear factor-kappaB (NF-kappaB) component p65.
- To determine the functional consequences of CaMKIV-mediated p65 phosphorylation on gene transcription.
Main Methods:
- In vitro and in vivo association and phosphorylation assays.
- Glutathione S-transferase pull-down and mammalian two-hybrid assays to study protein interactions.
- Cotransfection experiments to assess CaMKIV's effect on NF-kappaB activity and protein localization.
Main Results:
- CaMKIV directly binds and phosphorylates NF-kappaB p65.
- CaMKIV-induced p65 phosphorylation promotes the recruitment of cAMP-response element-binding protein-binding protein and the release of silencing mediator for retinoid and thyroid hormone receptors.
- CaMKIV cotransfection leads to cytosolic translocation of silencing mediator and significantly enhances NF-kappaB transactivation.
Conclusions:
- NF-kappaB is identified as a novel downstream effector of CaMKIV.
- CaMKIV modulates NF-kappaB activity through direct phosphorylation and subsequent alterations in transcriptional co-regulator complex assembly.
- These findings provide new insights into the molecular mechanisms linking calcium signaling to gene expression via the CaMKIV-NF-kappaB pathway.