Regulatory interaction of the Gα protein with phospholipase A 2 in the plasma membrane of Eschscholzia californica

• Published in: The Plant journal : for cell and molecular biology Vol. 52; no. 6; pp. 1041 - 1051
• Main Authors: Heinze, Michael, Steighardt, Jörg, Gesell, Andreas, Schwartze, Wieland, Roos, Werner
• Format: Journal Article
• Language: English
• Published: 01.12.2007
• DOI: 10.1111/j.1365-313X.2007.03300.x
• ISSN: 0960-7412

Summary Plant heterotrimeric G‐proteins are involved in a variety of signaling pathways, though only one α and a few βγ isoforms of their subunits exist. In isolated plasma membranes of California poppy ( Eschscholzia californica ), the plant‐specific Gα subunit was isolated and identified immunologically and by homology of the cloned gene with that of several plants. In the same membrane, phospholipase A 2 (PLA 2 ) was activated by yeast elicitor only if GTPγS (an activator of Gα) was present. From the cholate‐solubilized membrane proteins, PLA 2 was co‐precipitated together with Gα by a polyclonal antiserum raised against the recombinant Gα. In this immunoprecipitate and in the plasma membrane (but not in the Gα‐free supernatant) PLA 2 was stimulated by GTPγS. Plasma membranes and immunoprecipitates obtained from antisense transformants with a low Gα content allowed no such stimulation. An antiserum raised against the C‐terminus (which in animal Gαs is located near the target coupling site) precipitated Gα without any PLA 2 activity. Using non‐denaturing PAGE, complexes of solubilized plasma membrane proteins were visualized that contained Gα plus PLA 2 activity and dissociated at pH 9.5. At this pH, PLA 2 was no longer stimulated by GTPγS. It is concluded that a distinct fraction of the plasma membrane‐bound PLA 2 exists in a detergent‐resistant complex with Gα that can be dissociated at pH 9.5. This complex allows the Gα‐mediated activation of PLA 2 .