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Science 1 December 2006:
Vol. 314. no. 5804, p. 1349
DOI: 10.1126/science.314.5804.1349n
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This Week in Science
Many cellular proteins are inhibited when phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] is hydrolyzed by phospholipase C, and reactivated when a kinase restores the PtdIns(4,5)P2 (see the Perspective by McLaughlin, published online 9 November). Whether depletion of PtdIns(4,5)P2 is the direct signal closing KCNQ potassium channels, an important ion channel in the nervous system, upon receptor activation is still controversial. Suh et al. (p. 1454, published online 21 September) now show that a loss of PtdIns(4,5)P2 indeed suffices to close the channel. Furthermore, KCNQ channel opening was stimulated by synthesis of extra PtdIns(4,5)P2 but only minimally affected by production of extra phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)P3]. Small GTPases (guanosine triphosphatases) have many roles in cellular regulation and often transiently associate with the plasma membrane. Heo et al. (p. 1458, published online 9 November) monitored the cellular localization of fluorescently tagged small GTPases and found that the majority of the enzymes that associated with the membrane contained a cluster of positively charged amino acids. Suspecting that these regions might bind negatively charged lipids, the authors showed that PtdIns(4,5)P2 and PtdIns(3,4,5)P3 were required for targeting the GTPases to the plasma membrane. The lipids may act as signaling hubs that control multiple aspects of cellular control systems.
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