P21-activated Protein Kinase γ-PAK Is Activated by Ionizing Radiation and Other DNA-damaging Agents: SIMILARITIES AND DIFFERENCES TO α-PAK

Joan Roig,Jolinda A Traugh

doi:10.1074/jbc.274.44.31119

Joan Roig, Jolinda A Traugh

Open Access

https://doi.org/10.1074/jbc.274.44.31119

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Abstract

The p21-activated protein kinase gamma-PAK is activated 2-5-fold in response to ionizing radiation (IR) in 3T3-L1 fibroblasts and U937 leukemia cells. gamma-PAK is activated in a dose- and time-dependent manner. Doses from 1 to 100 Gy result in significant stimulation of activity at 30 min, whereas maximal stimulation is observed at 120 min after irradiation. UV (80 J/m(2)) and the DNA-damaging drugs cytosine beta-D-arabinofuranoside (AraC) and cis-platinum(II)diammine dichloride (cisplatin) also induce gamma-PAK activation. The activation of gamma-PAK in response to IR or AraC is dependent on tyrosine kinase and phosphoinositide 3-kinase activity, as demonstrated by use of the inhibitors genistein and wortmannin; in contrast activation of gamma-PAK by cisplatin and UV is not affected significantly by these inhibitors, suggesting that gamma-PAK can be activated by more than one pathway in response to different types of DNA damage. In contrast to gamma-PAK, alpha-PAK and JNK are activated only by cisplatin and UV in 3T3-L1 cells, suggesting differential regulation of the protein kinases. This is the first time that members of the Ste20/PAK family of protein kinases have been shown to be involved in the cellular response to IR and other DNA-damaging agents.

Highlights

The p21-activated protein kinases (PAK)1 are activated by the small G-proteins Rac 1 and Cdc42 [1,2,3]
When 3T3-L1 cells are subjected to hyperosmotic stress, ␥-PAK is activated by a two-step mechanism involving translocation to the particulate fraction and activation of the protein kinase in a phosphoinositide 3-kinase (PI3-kinase)-dependent manner [8]. ␥-PAK involvement in cell cycle regulation is supported by data showing that the protein kinase phosphorylates and regulates Raf-1 [14]
The cells were incubated for 120 min in a CO2 incubator, and lysed in buffer containing 1% Nonidet P-40. ␥-PAK activity was determined following immunoprecipitation of the protein kinase from cell extracts with histone 4 as substrate

Summary

Introduction

The p21-activated protein kinases (PAK)1 are activated by the small G-proteins Rac 1 and Cdc42 [1,2,3]. UV and the DNA-damaging drugs cisplatin and AraC activate ␥-PAK, suggesting that different types of DNA damage trigger the activation of the protein kinase. Maximum stimulation was observed 120 min after irradiation, as longer incubation times after irradiation did not result in further increase of ␥-PAK activity (data not shown).

Results

Conclusion