Related Experiment Videos
Proapoptotic stimuli induce nuclear accumulation of glycogen synthase kinase-3 beta
1Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, Alabama 35294, USA.
Abstract:
The goal of this study was to determine whether the intracellular distribution of the proapoptotic enzyme glycogen synthase kinase-3 beta (GSK-3 beta) is dynamically regulated by conditions that activate apoptotic signaling cascades. In untreated human neuroblastoma SH-SY5Y cells, GSK-3 beta was predominantly cytosolic, although a low level was also detected in the nucleus. The nuclear level of GSK-3 beta was rapidly increased after exposure of cells to serum-free media, heat shock, or staurosporine. Although each of these conditions caused changes in the serine 9 and/or tyrosine phosphorylation of GSK-3 beta, neither of these modifications was correlated with nuclear accumulation of GSK-3 beta. Heat shock and staurosporine treatments increased nuclear GSK-3 beta prior to activation of caspase-9 and caspase-3, and this nuclear accumulation of GSK-3 beta was unaltered by pretreatment with a general caspase inhibitor. The GSK-3 beta inhibitor lithium did not alter heat shock-induced nuclear accumulation of GSK-3 beta but increased the nuclear level of cyclin D1, indicating that cyclin D1 is a substrate of nuclear GSK-3 beta. Thus, the intracellular distribution of GSK-3 beta is dynamically regulated by signaling cascades, and apoptotic stimuli cause increased nuclear levels of GSK-3 beta, which facilitates interactions with nuclear substrates.
Insights
Apoptotic stimuli dynamically alter the location of glycogen synthase kinase-3 beta (GSK-3 beta) within cells. This enzyme moves to the nucleus before apoptosis activation, interacting with nuclear substrates like cyclin D1.
Area of Science:
- Cell Biology
- Molecular Biology
- Neuroscience
Background:
- Glycogen synthase kinase-3 beta (GSK-3 beta) is a key enzyme involved in various cellular processes.
- Its intracellular distribution may play a crucial role in regulating apoptosis.
- Understanding GSK-3 beta's localization is vital for comprehending cell death signaling.
Purpose of the Study:
- To investigate if apoptotic signaling cascades dynamically regulate the intracellular distribution of GSK-3 beta.
- To determine the relationship between GSK-3 beta phosphorylation and its nuclear accumulation.
- To explore the functional consequences of nuclear GSK-3 beta accumulation during apoptosis.
Main Methods:
- Human neuroblastoma SH-SY5Y cells were used as a model system.
- Cells were exposed to apoptotic stimuli including serum-free media, heat shock, and staurosporine.
- Intracellular GSK-3 beta levels and localization were assessed, along with phosphorylation status and caspase activation.
- The effect of a GSK-3 beta inhibitor (lithium) on nuclear GSK-3 beta and cyclin D1 was examined.
Main Results:
- In untreated cells, GSK-3 beta was primarily cytosolic with some nuclear presence.
- Apoptotic stimuli (serum-free media, heat shock, staurosporine) rapidly increased nuclear GSK-3 beta levels.
- Neither serine 9 nor tyrosine phosphorylation changes correlated with nuclear GSK-3 beta accumulation.
- Nuclear GSK-3 beta increased before caspase-9 and caspase-3 activation and was unaffected by caspase inhibitors.
- Lithium treatment did not affect heat shock-induced nuclear GSK-3 beta but increased nuclear cyclin D1, suggesting cyclin D1 is a nuclear GSK-3 beta substrate.
Conclusions:
- The intracellular distribution of GSK-3 beta is dynamically regulated by signaling cascades.
- Apoptotic stimuli induce increased nuclear levels of GSK-3 beta.
- Nuclear GSK-3 beta accumulation facilitates its interaction with nuclear substrates, potentially influencing apoptotic pathways.