Akt suppresses DLK for maintaining self-renewal of mouse embryonic stem cells

Mouse embryonic stem cells (ES cells) can proliferate indefinitely. To identify potential signals involved in suppression of self-renewal, we previously screened a kinase/phosphatase expression library in ES cells, and observed that inhibition of Dual Leucine zipper-bearing Kinase (DLK) increased relative cell numbers. DLK protein was detected in both the pluripotent and differentiated states of mouse ES cells while DLK kinase activity increased upon differentiation. Overexpression of DLK in mouse ES cells displayed reductions in relative cell/colony numbers and Nanog expression, suggesting a suppressive role of DLK in self-renewal. By examining protein sequences of DLK, we identified 2 putative Akt phosphorylation sites at S584 and T659. Blocking PI3K/Akt signaling with LY-294002 enhanced DLK kinase activity dramatically. We found that Akt interacts with and phosphorylates DLK. Mutations of DLK amino acid residues at putative Akt phosphorylation sites (S584A, T659A, or S584A and T659A) diminished the lev...