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Molecular and Cellular Biology, April 2005, p. 3194-3208, Vol. 25, No. 8
0270-7306/05/$08.00+0 doi:10.1128/MCB.25.8.3194-3208.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Activation
Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Republic of Korea,1 Institute of Molecular Oncology, Showa University, Shinagawa-ku, Tokyo, Japan2
Received 1 June 2004/ Returned for modification 2 August 2004/ Accepted 7 January 2005
It has been established that protein kinase C
(PKC
) participates in diverse signaling pathways and cellular functions in a wide variety of cells, exhibiting properties relevant to cellular survival and proliferation. Currently, however, the regulation mechanism of PKC
remains elusive. Here, for the first time, we determine that phospholipase D2 (PLD2) enhances PKC
activity through direct interaction in a lipase activity-independent manner. This interaction of the PLD2-Phox homology (PX) domain with the PKC
-kinase domain also induces the activation loop phosphorylation of PKC
and downstream signal stimulation, as measured by p70 S6 kinase phosphorylation. Furthermore, only the PLD2-PX domain directly stimulates PKC
activity in vitro, and it is necessary for the formation of the ternary complex with phosphoinositide-dependent kinase 1 and PKC
. The mutant that substitutes the triple lysine residues (Lys101, Lys102, and Lys103) within the PLD2-PX domain with alanine abolishes interaction with the PKC
-kinase domain and activation of PKC
. Moreover, breast cancer cell viability is significantly affected by PLD2 silencing. Taken together, these results suggest that the PLD2-mediated PKC
activation is induced by its PX domain performing both direct activation of PKC
and assistance of activation loop phosphorylation. Furthermore, we find it is an important factor in the survival of breast cancer cells.
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