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Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that plays a crucial role in integrin signaling that regulates essential cellular functions including growth, motility, proliferation and survival in different types of cells. Interestingly, it has also shown to be up-regulated in various types of tumors, hence it has emerged as a significant therapeutic target for the development of selective inhibitors. In present work, with the aim of achieving further insight into the structural characteristics required for the FAK inhibitory activity, a combined approach of molecular modeling studies including molecular docking, three-dimensional quantitative structure activity relationship (3D-QSAR) and molecular dynamics (MD) simulation were carried out on a series of 7H-pyrrolo[2,3-d]pyrimidine and thieno[3,2-d]pyrimidine FAK inhibitors. The probable binding modes and interactions of inhibitors into the FAK active site were predicted by molecular docking. The 3D-QSAR models were developed using the comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods, with three ligand-based, docking-based and receptor-based alignment techniques. Both CoMFA and CoMSIA models obtained from receptor-based alignment were superior to the ones obtained by other alignment methods. However, the CoMSIA model (q2 = 0.679, r2 = 0.954 and r2pred = 0.888) depicted almost better predictive ability than the CoMFA model (q2 = 0.617, r2 = 0.932 and r2pred = 0.856). The contour map analysis revealed the relationship between the structural features and inhibitory activity. The docking results and CoMFA and CoMSIA contour maps were in good accordance. Based on the information obtained from the molecular docking and contour map analysis, a series of novel FAK inhibitors were designed that showed better predicted inhibitory activity than the most potent compound 31 in the data set. Finally, the stability of the reference molecule 31 and the designed compounds D15 and D27 were evaluated through a 30 ns of MD simulation and their binding free energies were calculated using the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) method. The result of MD simulation and binding free energy decomposition demonstrated the important role of van der Waals interactions alongside H-bond ones that were in consistent with the docking and contour maps analysis results. In sum, the results from this study may provide a significant insight for developing more effective novel FAK inhibitors. Communicated by Ramaswamy H. Sarma

Fyn is the cytoplasmic tyrosine kinase that has critical roles in many aspects of biological functions. In the central [1] and peripheral nervous systems [2] , [3] , Fyn plays the key role in initiating myelination by myelin-forming glial cells (Schwann cells and oligodendrocytes). Herein we provide the data regarding the role of Fyn in fasciculation and branching of embryonic peripheral nerves.

Janus kinase 3 (JAK3) is a cytoplasmic tyrosine kinase associated with the common gamma chain that is activated by multiple T-cell growth factors including IL-2, -4, -9, -15, and -21. From the recent reports, genetic absence or ablation of JAK3 is associated with defective T-cell immunity that results in severe combined immunodeficiency (SCID) and pharmacological inhibition has prolonged allograft survival in some models of organ transplantation. This review would provide an overview of some patents along with the role of JAK3 in the immune system and efficacy of JAK3 inhibitors in experimental allograft rejection and autoimmune disease.

Spleen tyrosine kinase (Syk) is a cytoplasmic tyrosine kinase that plays an important signaling role in several types of immune cells. To improve our understanding of the enzymology and activation mechanism of Syk, we characterized the steady state kinetics of Syk substrate phosphorylation. A new real time fluorescence kinase assay was employed that utilizes a nonnatural amino acid in the peptide substrate which undergoes an enhancement in fluorescence following phosphorylation. Characterizing the steady state kinetics using a Syk kinase domain construct [Syk(360-635)] revealed that Syk employs a ternary complex kinetic mechanism involving little cooperativity between substrate binding sites and a Km(ATP) of 36 +/- 5 microM and a Km(peptide substrate) of 4.4 +/- 0.9 microM. The order of substrate binding was determined to be either random or ordered with ATP binding first, as determined in substrate analogue inhibitor studies. Utilizing the real time capabilities of the fluorescence assay, we established that Syk demonstrates no lag phase in product formation. Furthermore, a Syk mutant lacking tyrosine in the activation loop (Syk Y525F,Y526F) exhibited activity identical to that of wild-type Syk. These two findings indicate that autophosphorylation of the activation loop of Syk does not regulate Syk(360-635) activity. We also compared the activity of Syk(360-635) to that of full-length Syk and revealed that Syk(360-635) is 10-fold more active, suggesting that residues outside the catalytic domain of Syk suppress kinase activity. The findings presented here provide the first kinetic description of the Syk enzyme mechanism.

In the past year, researchers have identified the genes responsible for X-linked severe combined immunodeficiency (encoding a cytokine receptor protein), X-linked agammaglobulinemia (encoding a cytoplasmic tyrosine kinase) and X-linked hyper IgM syndrome (encoding the ligand for CD40). Although these three genes are completely unrelated, it is of interest that all are lineage-specific genes that are involved in the control of lymphocyte proliferation or differentiation.

552 Background: Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase playing an important role as a key mediator for signal transduction. We examined the subtype specific prognostic signifi...

Fer is a nuclear and cytoplasmic tyrosine kinase that is ubiquitously expressed in mammalian cells. Herein we show that Fer sustains a key signaling step in hypoxic cells. Knock-down of the Fer protein using a specific siRNA decreased the production of VEGF by the hypoxic cells. Conversely, ectopic expression of this kinase led to an elevated production of VEGF under hypoxia. At the molecular level, Fer was found to associate with ERK1/2 and this interaction was intensified under hypoxia. Moreover, Fer increased the activation levels of ERK1/2, and reducing the level of Fer, impaired the activation of ERK1/2 in hypoxic cells. Blocking the MEK-ERK1/2 signaling pathway with the MEK inhibitors U0126, or PD98059 led to the abrogation of ERK1/2 activity in hypoxic cells, an effect that was counteracted by Fer. Hence, Fer sustains the activation of ERK1/2 and increases the production of VEGF in hypoxic cells, without affecting the MEK-ERK signaling pathway.

8580 Background: Spleen Tyrosine Kinase (SYK) is a non-receptor cytoplasmic tyrosine kinase that is a common member of various signal transduction cascades in cells of the hematopoietic lineage inc...

Worby and Margolis highlight advances in our understanding of signaling from growth factor receptors using the worm Caenorhabditis elegans as a model organism. ARK-1, a cytoplasmic tyrosine kinase, appears to be a negative regulator of multiple pathways in C. elegans . The authors discuss several models for how this negative regulation may occur. The adaptor protein (Grb2 in mammals or SEM-5 in C. elegans ) may serve as a regulated scaffold for the binding of other signaling proteins that include both positive (Ras) and negative (ACK) regulators. Thus, Grb2 may function in a cellular decision point for transducing the incoming signals.

The pleckstrin homology (PH) domain is extended in the Btk kinase family by a region designated the TH (Tec homology) domain, which consists of about 80 residues preceding the SH3 domain. The TH domain contains a conserved 27 amino acid stretch designated the Btk motif and a proline-rich region. Sequence similarity was found to a putative Ras GTPase activating protein and a human interferon-γ binding protein both in the PH domain and the Btk motif region. SLK1/SSP31 protein kinase and a non-catalytic p85 subunit of PI-3 kinase had similarity only with the proline rich region. The identification of a PH domain extension in some signal transduction proteins in different species suggests that this region is involved in protein—protein interactions.

e13635 Background: Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase that is overexpressed of a variety of human malignancies including colon cancer. As such, FAK represents a potential ...

13162 Background: Focal adhesion kinase (FAK) is a non-receptor cytoplasmic tyrosine kinase that regulates multiple cell functions. Elevated expression levels of FAK have been detected in various tumor samples and are closely correlated with invasive potential. Activation of integrins and the growth factor receptors result in FAK autophosphorylation at Y397 and the presentation of suitable binding sites for proteins containing either SH2 or phosphotyrosine binding domains. Recent evidences suggest that FAK plays important roles in cancer cell proliferation and survival. IGF-IR function is required for tumor cell survival, but dispensable for survival of normal cells. Therefore, a dual inhibitor of both kinases may selectively block the growth, migration, and survival of FAK- and IGF-IR- expressing tumor cells compared to proliferating and migrating normal cells. Methods: In this study, anti-cancer activity of NVP-TAE226 that is identified as a potent and selective FAK inhibitor was evaluated in cancer cell lines panel and MIA PaCa-2 pancreatic carcinoma in vivo model. Results: Mean GI50 value of NVP-TAE226 against 37 cancer cell lines was 0.76 μmole/L. Inhibition of cancer cell proliferation was not affected by expression of P-glycoprotein, suggesting that NVP-TAE226 is not served as a substrate of P-glycoprotein. Oral administration of NVP-TAE226 efficiently inhibited MIA PaCa-2 human pancreatic tumor growth at all doses tested. Tumor stasis was observed at a dose of 30 mg/kg, qd for 7×/week and tumor regression was observed at a dose of 100 mg/kg, qd for 5×/week. All animals tolerated NVP-TAE226 treatment up to 100 mg/kg, 5×/wk, qd, po for 2 weeks with no body weight loss. Inhibition of downstream signaling such as phosphorylation of Akt at Serine473 was accompanied by inhibition of FAK phosphorylation in human pancreatic carcinoma cell lines. Conclusions: NVP-TAE226 is a novel class of selective and small molecule kinase inhibitors with a potent in vivo activity and potential therapeutic application. No significant financial relationships to disclose.

Tec family protein tyrosine kinases have in their N-terminus two domains. The PH domain is followed by Tec homology (TH) domain, which consists of two motifs. The first pattern, Btk motif, is also present in some Ras GAP molecules. C-terminal half of the TH domain, a proline-rich region, has been shown to bind to SH3 domains. Mutations in Bruton's tyrosine kinase (Btk) belonging to the Tec family cause X-linked agammaglobulinemia (XLA) due to developmental arrest of B cells. Here we present the first missense mutations in the TH domain. The substitutions affect a conserved pair of cysteines, residues 154 and 155, involved in Zn2+ binding and thereby the mutations alter protein folding and stability.