Minisymposium 2: Signaling

Abs # 12002: Phosphatidic Acid as a Pivotal Lipid Messenger in Cell Signaling in Plants

Presenter:	Xuemin, Wang , wangs@ksu.edu
Authors	Xuemin, Wang  (A)   Wenhua, Zhang  (A)   Jian, Zhao  (A)   Shivakumar, Devaiah  (A)   Weiqi, Li  (A)   Maoyin, Li  (A)   Yueyun, Hong  (A)   Ruth, Welti  (B)
Affiliations:	(A): Dept. of Biochemistry, Kansas State University (B): Division of Biology, Kansas State University
Web Site:	http://www.ksu.edu/lipid/lipidomics

Signal transduction and many other critical cellular functions are initiated by the assembly of protein complexes to defined sites of cellular membranes. Binding to lipid ligands are required for the recruitment and/or regulation of these proteins. Lipid mediators, such as phosphoinositides, are produced in response to given stimuli and bind to effector proteins at specific structural folds, such as pleckstrin homology (PH), Phox homology (PX), and FYVE domains. These specific lipid-protein interactions are critical for cellular activities of many proteins. Phosphatidic acid (PA) has recently emerged as an important lipid mediator in many cellular processes, including cell proliferation and survival, cell patterning and growth, and stress responses. However, the mechanism by which PA regulates cellular processes is not well understood. We have obtained evidence that PA interacts directly with protein kinases and phosphatases. Our results also indicate that PA regulates the activity and intracellular distribution of its effector proteins. In addition, we have identified the protein motifs required for the PA-effector interaction and have observed that the PA binding induces changes in protein conformation. We are currently testing the hypotheses that PA interacts with effector proteins through a specific structural fold and that the PA-induced structural changes promote the protein interaction with membranes and/or other proteins in the signaling complexes. Furthermore, we have demonstrated the regulatory functions of PA through manipulating the PA-producing enzymes, phospholipase Ds (PLD), and through lipid profiling and cellular/physiological analyses. These results unveil a complex signaling network in which PA and PLD interact with G protein, protein kinase, and protein phosphatase to mediate plant responses to hormones, reactive oxygen species, biotic and abiotic stresses. Li et al., (2004) Nature Biotechnology (in press); Zhao and Wang (2004) J. Biol. Chem. 279, 1794-1800; Wang (2004) Curr. Opin. Plant Biol. (in press); Zhang et al., (2003) Plant Cell 15, 2285-2295; Wang (2002) Curr. Opin. Plant Biol. 5, 408-414; Welti et al., (2002) J. Biol. Chem. 277, 31994-32002. Supported by grants from NSF and USDA