PDKl kinases

The most potent PDKl kinase inhibitor reported to date is UCN-01 (compound 16 Fig. 4 IC50 = 6 to 33 nM) [101], a staurosporine analogue isolated from the culture broth of Streptomyces sp. Originally developed as an inhibitor of calcium-dependent PKC, UCN-01 has the capacity to inhibit a broad spectrum of kinases [102], including other members of the AGC subfamily of kinases (e.g., IC5o = 491nM for PKB) [103]. UCN-Ol-induced PDKl inhibition has also been observed in in vivo murine and human tumor xenografts [101]. 

In addition to UCN-01 and other staurosporine or maleimide derivatives (e.g., compounds 17 and 18 Fig. 4) [102,103,105-107], PDKl kinase activity is inhibited by aminopyrimidines. A representative example of this compound class is BX-320 (compound 19, Fig. 4), a PDKl inhibitor (IC50 = 30 nM) that displays good selectivity over protein kinase A (PKA, 35-fold) [108]. BX-320 blocks the growth in soft agar of a wide range of tumor cell lines (IC50 = 0.093 to 1.32 xM), and shows efficacy in a metastasis mouse model (200 mg/kg bid). 

Tyrosine phosphorylated IRS interacts with and activates PI 3-kinase [3]. Binding takes place via the SRC homology 2 (SH2) domain of the PI 3-kinase regulatory subunit. The resulting complex consisting of INSR, IRS, and PI 3-kinase facilitates interaction of the activated PI 3-kinase catalytic subunit with the phospholipid substrates in the plasma membrane. Generation of PI 3-phosphates in the plasma membrane reemits phospholipid dependent kinases (PDKl and PDK2) which subsequently phosphorylate and activate the serine/threonine kinase Akt (synonym protein... 

Kuhiak We found in mouse oocytes undergoing GVBD that Rsk is phosphorylated by two successive steps, one of which is dependent on Cdc2 and the following one on MAP kinase. There is also evidence of phosphorylation of Rsk by another kinase, which is Pdkl. 

Anderson, K.E., CoadweU, J., Stephens, L.R., and Hawkins, P.T., 1998, Translocation of PDKl to the plasma membrane is important in allowing PDK-1 to activate protein kinase B. Curr. Biol, 8 684-691. 

The 3-phosphoinositide-dependent protein kinase-1 (PDKl) is a 556-amino acid enzyme composed of three well-differentiated motifs an N-terminal domain, a constitutively activated serine/threonine kinase domain, and a Pleck-strin homology (PH) domain at its C-terminus [87-91]. The attractiveness of PDKl as a potential anticancer target is hnked to its ability to control the activity of a diverse set of AGC kinase members, in particular the three PKB isoforms [92], Full activation of PKB requires phosphorylation at two sites. 

The membrane-associated Akt kinase is now a substrate for protein kinase PDKl that phosphorylates a specific Thr and Ser residue of Akt kinase. The double phosphorylation converts Akt kinase to the active form. It is assumed that the Akt kinase now dissociates from the membrane and phosphorylates cytosolic substrates such as glycogen synthase kinase, 6-phosphofructo-2-kinase and ribosomal protein S6 kinase, p70 . According to this mechanism, Akt kinase regulates central metabolic pathways of the cell. Furthermore, it has a promoting influence on cell division and an inhibitory influence on programmed cell death, apoptosis. A role in apoptosis is suggested by the observation that a component of the apoptotic program. Bad protein (see Chapter 15) has been identified as a substrate of Akt kinase. 

Wu, S. and Kaufman, R.J., fran,y-autophosphorylation by the isolated kinase domain is not sufficient for dimerization of activation of the dsRNA-activated protein kinase PKR, Biochemistry 43, 11027-11034, 2004 Shi, G.W., Chen, J., Concepcion, F. et ah. Light causes phosphorylation of nonactivated visual pigments in intact mouse rod photoreceptor cells, J. Biol. Chem. 280, 41184-41191, 2005 Gao, X. and Harris, T.K., Steady-state kinetic mechanism of PDKl, J. Biol. Chem., 281, 21670-21681, 2006. 

Protein kinase B (PKB) becomes partially activated by binding to PI 3-phosphates. Its full activation requires phosphorylation by another kinase (PDKl), which also is recruited to the membrane by binding to PI 3-phosphates (see Figure 14-27). 

Mora, A., Komander, D., van Aalten, D. M., and Alessi, D. R. PDKl, the master regulator of AGC kinase signal transduction. Semin Cell Dev Biol 15 (2004) 161-170. 

Fig. 12. Some signaling targets and pathways affected by sphingolipid backbones that are metabolically interrelated. PKA, protein kinase A PDKl, 3-phosphoinositide-dependent kinase 1 SDKl, sphingosine-dependent kinase 1 PKC, protein kinase C PPl, protein phosphatase 1 PP2A, protein phosphatase 2A aSMase, acid sphingomyelinase PLA, phospholipase Aj SIP, sphingosine-l-phosphase MATIA, methionine adenosyl-transferase (liver specific) SFl, steroidogenic factor 1. The biophysical properties of ceramides and ceramide 1-phosphates may play important roles in membrane structure, including tendencies to form rafts, membrane curvature, and leakiness.

F. 11.14. The insulin receptor-protein kinase B signaling pathway. Abbreviations Ins, insulin IRS, insulin receptor substrate PH domains, pleckstrin homology domains PDKl, phosphoinositide-dependent protein kinase 1 PKB, protein kinase B. The final phosphorylation step that activates PKB is shown in blue. 

B and PDKl (phosphoinositide-dependent kinase-1) are recruited to the membrane by their PH domains, where PDKl phosphorylates and activates protein kinase B. Many other signal transducer proteins have PH domains and are docked at the membrane, where they can find and bind each other. Thus, the insulin signal diverges again and again. Insulin is covered in more detail in Chapters 26, 36 and 43. 

This is still poorly understood. Proteins that bind to PI(3,4)P2 or Pl(3,4,5)Pj have PH domains (pleckstrin homology domains). One example of such a protein is protein kinase B PKB) this is activated by phosphorylation that is catalyzed by another PH domain kinase, PDKl (phosphatidylinositol-dependent kinase). Activated PKB phosphorylates a ribosomal protein, protein S6, which leads to increased rates of translation of selected mRNA molecules. 

The next example illustrates how two-photon time domain FLIM can be used for detecting the interaction of two protein kinases PDKl (3,4,5-phosphoinositide protein kinase) and PKB (protein kinase B) at the plasma membrane of NIH3T3 cells. Both PDKl and PKB associate with PtdIns(3,4,5)P3 and PtdIns(3,4)P2 via their plecktrin homology (PH) domains. It seems that this mutual interaction with such lipids leads these enzymes to co-localize at the plasma membrane and in turn to activate PKB. However, until recently it had not been shown that these molecules actually associate at the plasma membrane. 

Figure 50. PTEN. The tumor suppressor gene and gene product protein PTEN (phosphatase tensin homolog deleted on chromosome ten, human 10q23.3) (Table VIII), is the natural inhibitor of oncogenes PI3K/Akt (phosphatidyl inositol kinase 3 protein kinase 3 phosphatidylinositol 3 phosphate Jacob Furth s AK mouse strain thymic lymphoma retroviral oncogene phosphoinosite-dependent kinase). The PTEN protein inactivates PIP3 by dephosphorylation PDKl (phosphoinositol-dependent kinase) is not recruited to the plasma membrane to activate Akt by phosphorylation. Sarah M. Planchon et al. The nuclear affairs of PTEN. J Cell Sci 2008 121 249-253. doi 10.1242/jcs.022459...

Selective 3-phosphoinositide-dependent kinase 1 (PDKl) inhibitors Dissecting the function and pharmacology of PDKl 13JMC2726. Staurosporine analogues from microbial and synthetic sources and their biological activities 13CMD3872. 

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