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Nuclear CaMKII inhibits neuronal differentiation of PC12 cells without affecting MAPK or CREB activation
Louis W Kutcher1, Shirelyn R Beauman, Eric I Gruenstein
1Department of Molecular Physiology, University of Cincinnati Medical School, Cincinnati, Ohio 45267, USA.
Abstract:
Ca(2+)/calmodulin-regulated protein kinase II (CaMKII) mediates many cellular events. The four CaMKII isoforms have numerous splice variants, three of which contain nuclear localization signals. Little is known about the role of nuclear localized CaMKII in neuronal development. To study this process, PC12 cells were transfected to produce CaMKII targeted to either the cytoplasm or the nucleus and then treated with nerve growth factor (NGF). NGF triggers a signaling cascade (MAPK) that results in the differentiation of PC12 cells into a neuronal phenotype, marked by neurite outgrowth. The present study found that cells expressing nuclear targeted CaMKII failed to grow neurites, whereas cells expressing cytoplasmic CaMKII readily produced neurites. Inhibition of neuronal differentiation by nuclear CaMKII was independent of MAPK signaling, as sustained Erk phosphorylation was not affected. Phosphorylation of CREB was also unaffected. Thus nuclear CaMKII modifies neuronal differentiation by a mechanism independent of MAPK and CREB activation.
Insights
Nuclear targeted Ca(2+)/calmodulin-regulated protein kinase II (CaMKII) inhibits neuronal differentiation. Cytoplasmic CaMKII promotes neurite outgrowth, independent of MAPK and CREB signaling pathways.
Area of Science:
- Neuroscience
- Cell Biology
- Molecular Biology
Background:
- Ca(2+)/calmodulin-regulated protein kinase II (CaMKII) is crucial for cellular functions.
- Multiple CaMKII isoforms and splice variants exist, some with nuclear localization signals.
- The role of nuclear CaMKII in neuronal development remains largely unexplored.
Purpose of the Study:
- To investigate the function of nuclear-localized CaMKII in neuronal differentiation.
- To determine if nuclear CaMKII affects nerve growth factor (NGF)-induced differentiation in PC12 cells.
Main Methods:
- PC12 cells were transfected to express CaMKII targeted to the cytoplasm or nucleus.
- Cells were treated with nerve growth factor (NGF) to induce differentiation.
- Neurite outgrowth and signaling pathway activation (MAPK, CREB) were assessed.
Main Results:
- Nuclear-targeted CaMKII expression prevented NGF-induced neurite outgrowth.
- Cytoplasmic-targeted CaMKII facilitated neurite outgrowth.
- Inhibition of differentiation by nuclear CaMKII was independent of MAPK and CREB signaling.
Conclusions:
- Nuclear localization of CaMKII inhibits neuronal differentiation.
- This inhibitory effect occurs through a mechanism distinct from MAPK and CREB activation.
- CaMKII's subcellular localization is critical for regulating neuronal development.