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Figure 17.3 Translocation kinetics of the PH domain, PI3K, and PTEN. (A) The wild-
type peak of translocation of the PH domain is 6 s, and the PH domain disassociates from
the membrane within 20-30 s. In pten null cells, a prolonged PH domain is observed
(>3min). (B) The translocations of PI3K and PTEN are mirror images of each other.
After global stimulation, PI3K and the PH domain translocate to the membrane. It is
notable that PI3K stays longer on the membrane than the PH domain does. For technical
reasons, it is dicult to determine which goes to membrane first. On the other hand, PTEN
delocalizes from the membrane as PI3K jumps to the membrane
amount of the PH domain remains associated with the membrane even after
3min (Figure 17.3A). These cells also exhibit a prolonged and increased level
of actin polymerization (Iijima and Devreotes, 2002) and increased
activation of Akt/PKB (Funamoto et al., 2002), as well as a chemotaxis
defect. Interestingly, pten null cells are hypersensitive to stimulation by
cAMP (10 nM cAMP compared with 1 nM cAMP for the wild-type; Iijima
and Devreotes, 2002). This finding suggests that input from receptors is
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