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Fig. 1. The mechanisms by which PKB may regulate the cell cycle, apoptosis and
insulin signalling. Only the substrates that have been proposed to be directly
phosphorylated by PKB and discussed in the main text are shown. PKB may also
promote cell survival by phosphorylating I- B kinase- , the breast
cancer susceptibility gene 1, human telomerase reverse transcriptase, the
GTPases Rac1/CDC42 and the serine/threonine protein kinase Raf1, but the roles
that these phosphorylations play are controversial and require further
investigation. Note that, because of the limitations in the experimental
approaches that are being to dissect the PKB pathway, some of the proposed
substrates for PKB may ultimately turn out not to be phosphorylated
physiologically by PKB but by other protein kinases instead. Abreviations:
FKHR, forkhead transcription factor; 6-PF2-K, cardiac isoform of heart
6-phosphofructo-2-kinase; GSK3, glycogen synthase kinase 3; eNOS, endothelial
nitric oxide synthase; PDE-3B, phosphodiesterase 3B; Ask1, apoptosis
signal-regulating kinase 1.
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