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Cytostatic p21 G protein-activated protein kinase gamma-PAK
1Department of Biochemistry, University of California, Riverside, Riverside, California 92504, USA.
Abstract:
The p21-activated protein kinase gamma-PAK, also known as PAK2, has very different properties from the other two highly conserved isoforms of the PAK family, alpha-PAK (PAK1) and beta-PAK (PAK3). gamma-PAK has cytostatic activity, as shown by inhibition of cleavage of early frog embryos following microinjection of gamma-PAK and by inhibition of growth when expressed in mammalian cells. gamma-PAK is activated in response to a variety of stresses including radiation- and chemically-induced DNA damage, hyperosmolarity, addition of sphingosine, serum starvation, and contact inhibition. Activation occurs through at least two signaling pathways, depending on the type of stress, one of which requires phosphoinositide 3-kinase and/or tyrosine kinase activity. During apoptosis gamma-PAK is cleaved by caspase 3 and activated and appears to have a role in the apoptotic response. gamma-PAK is present in the cytosol, associated with the membrane and in secretory granules. A wide variety of substrates have been identified for gamma-PAK. We propose gamma-PAK may be involved in coordinating the stress response, possibly in conjunction with other stress response proteins.
Insights
The p21-activated protein kinase gamma-PAK (PAK2) exhibits cytostatic activity and is activated by various cellular stresses. It plays a role in apoptosis and may coordinate stress responses.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- The p21-activated protein kinase (PAK) family comprises conserved isoforms: alpha-PAK (PAK1), beta-PAK (PAK3), and gamma-PAK (PAK2).
- gamma-PAK (PAK2) possesses distinct properties compared to PAK1 and PAK3.
Purpose of the Study:
- To investigate the cytostatic activity of gamma-PAK (PAK2).
- To identify the stress conditions that activate gamma-PAK (PAK2).
- To elucidate the role of gamma-PAK (PAK2) in cellular stress responses and apoptosis.
Main Methods:
- Microinjection of gamma-PAK (PAK2) into frog embryos.
- Expression of gamma-PAK (PAK2) in mammalian cells.
- Analysis of gamma-PAK (PAK2) activation pathways under various stress conditions.
- Investigation of gamma-PAK (PAK2) cleavage by caspase 3 during apoptosis.
Main Results:
- gamma-PAK (PAK2) demonstrated cytostatic activity, inhibiting embryonic development and cell growth.
- gamma-PAK (PAK2) activation was observed in response to DNA damage, hyperosmolarity, sphingosine, serum starvation, and contact inhibition.
- Activation involves phosphoinositide 3-kinase and/or tyrosine kinase pathways.
- gamma-PAK (PAK2) is cleaved and activated by caspase 3 during apoptosis, suggesting a role in this process.
- gamma-PAK (PAK2) localizes to the cytosol, membrane, and secretory granules.
- Numerous substrates for gamma-PAK (PAK2) have been identified.
Conclusions:
- gamma-PAK (PAK2) exhibits significant cytostatic effects and is a key mediator of cellular stress responses.
- Its activation pathways and role in apoptosis highlight its importance in cellular homeostasis.
- gamma-PAK (PAK2) may function in coordinating cellular reactions to diverse stresses.