Is PDK1 regulated by dimerization?

SCHULZE, JÖRG; HERBRAND, AMANDA; SACERDOTI, MARIANA; POTTER, BARRY; PASTOR-FLORES, DANIEL; LEROUX, ALEJANDRO E.; RILEY, ANDREW; SUESS, EVELYN; BIONDI, RICARDO M.; FROESE, KARIN; BAUER, ANGELIKA; CZIER, GYLES; GROSS, LISSY

Bariloche

Congreso; South American Spring Symposium in Signal Transduction and Molecular Medicine 2018; 2018

Along with the increase in life expectancy, there isan inevitable rise of the risk to develop cancer. Overactivation of the phosphoinositide3-kinase (PI3K) pathway is one of the most frequent events in cancer. A keyPI3K downstream event is the phosphorylation of PKB/Akt, S6K, SGK and RSK bythe master kinase phosphoinositide-dependent protein kinase-1 (PDK1) which alsophosphorylates other protein kinases constitutively. Throughout the years wehave investigated different mechanisms used by PDK1 to specifically and timelyphosphorylate its substrates. Phosphorylation of substrates from differentfamilies like S6K, SGK, PKC, PRK/PKN rely on a docking interaction, where aC-terminal hydrophobic motif interacts with a regulatory site, PIF-pocket,located on the small lobe of the kinase domain. Since some substrates interactbetter with PDK1 when the HM is phosphorylated, this acts as a regulateddocking interaction. In addition, the interaction with the PIF-pocketallosterically ?activates? the kinase, stabilizing a closed-active structure ofthe catalytic domain.We provide exhaustive evidence that the binding of theHM or small compounds to the PIF-pocket allostericallyaffects the ATP-binding site. Allostery implies that the reverse modulation,i.e. from the ATP-binding site to the regulatory PIF-pocket, should also bepossible. Indeed, we show that small molecules binding at the ATP-binding sitecan inhibit or enhance the docking interaction at the PIF-pocket. This isimportant for the action of drugs.Interestingly, the interaction with thePIF-pocket of PDK1 is not a requirement for the phosphorylation of PKB/Aktafter PI3K activation. Although the HM of PKB/Akt does interact with thePIF-pocket of PDK1, we believe that other mechanisms must regulate thatinteraction. PDK1 has been described to dimerize. We will here providepreliminary data and discuss if dimerization could also be part of themechanism by which PDK1 phosphorylates its substrates.