Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The secreted protein Hedgehog (Hh) plays an important role in metazoan development and as a survival factor for many human tumors. In both cases, Hh signaling proceeds through the activation of the seven-transmembrane protein Smoothened (Smo), which is thought to convert the Gli family of transcription factors from transcriptional repressors to transcriptional activators. Here, we provide evidence that Smo signals to the Hh signaling complex, which consists of the kinesin-related protein Costal2 (Cos2), the protein kinase Fused (Fu), and the Drosophila Gli homolog cubitus interruptus (Ci), in two distinct manners. We show that many of the commonly observed molecular events following Hh signaling are not transmitted in a linear fashion but instead are activated through two signals that bifurcate at Smo to independently affect activator and repressor pools of Ci.
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PMID:Smoothened regulates activator and repressor functions of Hedgehog signaling via two distinct mechanisms. 1642 32

The Hedgehog (Hh) pathway plays important roles during embryogenesis and carcinogenesis. Here, we show that ablation of the mouse Suppressor of fused (Sufu), an intracellular pathway component, leads to embryonic lethality at approximately E9.5 with cephalic and neural tube defects. Fibroblasts derived from Sufu(-/-) embryos showed high Gli-mediated Hh pathway activity that could not be modulated at the level of Smoothened and could only partially be blocked by PKA activation. Despite the robust constitutive pathway activation in the Sufu(-/-) fibroblasts, the GLI1 steady-state localization remained largely cytoplasmic, implying the presence of an effective nuclear export mechanism. Sufu(+/-) mice develop a skin phenotype with basaloid changes and jaw keratocysts, characteristic features of Gorlin syndrome, a human genetic disease linked to enhanced Hh signaling. Our data demonstrate that, in striking contrast to Drosophila, in mammals, Sufu has a central role, and its loss of function leads to potent ligand-independent activation of the Hh pathway.
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PMID:Genetic elimination of Suppressor of fused reveals an essential repressor function in the mammalian Hedgehog signaling pathway. 1645 98

Protein kinase A (PKA) silences the Hedgehog (Hh) pathway in Drosophila in the absence of ligand by phosphorylating the pathway's transcriptional effector, Cubitus interruptus (Ci). Smoothened (Smo) is essential for Hh signal transduction but loses activity if three specific PKA sites or adjacent PKA-primed casein kinase 1 (CK1) sites are replaced by alanine residues. Conversely, Smo becomes constitutively active if acidic residues replace those phosphorylation sites. These observations suggest an essential positive role for PKA in responding to Hh. However, direct manipulation of PKA activity has not provided strong evidence for positive effects of PKA, with the notable exception of a robust induction of Hh target genes by PKA hyperactivity in embryos. Here we show that the latter response is mediated principally by regulatory elements other than Ci binding sites and not by altered Smo phosphorylation. Also, the failure of PKA hyperactivity to induce Hh target genes strongly through Smo phosphorylation cannot be attributed to the coincident phosphorylation of PKA sites on Ci. Finally, we show that Smo containing acidic residues at PKA and CK1 sites can be stimulated further by Hh and acts through Hh pathways that both stabilize Ci-155 and use Fused kinase activity to increase the specific activity of Ci-155.
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PMID:The contributions of protein kinase A and smoothened phosphorylation to hedgehog signal transduction in Drosophila melanogaster. 1678 1

The Hedgehog (HH) signaling pathway is crucial for the development of many organisms and its inappropriate activation is involved in numerous cancers. HH signal controls the traffic and activity of the seven-pass transmembrane protein Smoothened (SMO), leading to the transcriptional regulation of HH-responsive genes. In Drosophila, the intracellular transduction events following SMO activation depend on cytoplasmic multimeric complexes that include the Fused (FU) protein kinase. Here we show that the regulatory domain of FU physically interacts with the last 52 amino acids of SMO and that the two proteins colocalize in vivo to vesicles. The deletion of this region of SMO leads to a constitutive activation of SMO, promoting the ectopic transcription of HH target genes. This activation is partially dependent of FU activity. Thus, we identify a novel link between SMO and the cytoplasmic complex(es) and reveal a negative role of the SMO C-terminal region that interacts with FU. We propose that FU could act as a switch, activator in presence of HH signal or inhibitor in absence of HH.
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PMID:The last 59 amino acids of Smoothened cytoplasmic tail directly bind the protein kinase Fused and negatively regulate the Hedgehog pathway. 1718 28

Hedgehog (HH) is a major secreted morphogen involved in development, stem cell maintenance and oncogenesis [1, 2]. In Drosophila wing imaginal discs, HH produced in the posterior compartment diffuses into the anterior compartment to control target gene transcription via the transcription factor Cubitus interruptus (CI). The first steps in the reception and transduction of the HH signal are mediated by its receptor Patched (PTC) [3] and the seven-transmembrane-domain protein Smoothened (SMO) [4, 5]. PTC and HH control SMO by regulating its stability, trafficking, and phosphorylation (for review, see [6]). SMO interacts directly with the Ser-Thr protein kinase Fused (FU) and the kinesin-related protein Costal2 (COS2), which interact with each other and with CI in an intracellular Hedgehog transducing complex [7-9]. We show here that HH induces FU targeting to the plasma membrane in a SMO-dependent fashion and that, reciprocally, FU controls SMO stability and phosphorylation. FU anchorage to the membrane is sufficient to make it a potent SMO-dependent, PTC-resistant activator of the pathway. These findings reveal a novel positive-feedback loop in HH transduction and are consistent with a model in which FU and SMO, by mutually enhancing each other's activities, sustain high levels of signaling and render the pathway robust to PTC level fluctuations.
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PMID:Evidence for a novel feedback loop in the Hedgehog pathway involving Smoothened and Fused. 1765 59

Cell signaling mediated by the Hedgehog (Hh) family of secreted proteins is essential for metazoan development and its malfunction causes congenital disorders and cancer. The seven-transmembrane protein Smoothened (Smo) transduces the Hh signal across the plasma membrane in both vertebrates and invertebrates but the underlying mechanisms remain ill defined. In Drosophila, Hh induces phosphorylation of Smo at multiple sites by PKA and CK1, leading to its cell surface accumulation and activation. Recently, we have obtained evidence that Hh-induced phosphorylation promotes Smo activity by inducing a conformational switch and dimerization of its carboxy-terminal cytoplasmic tail (C-tail). Furthermore, we provided evidence that a similar mechanism regulates mammalian Smo. We discuss how Smo conformational change regulates the intracellular signaling complex and how Smo transduces the graded Hh signaling activities through different conformational states.
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PMID:Transducing the Hedgehog signal across the plasma membrane. 1882 Apr 83

The mammalian Sonic hedgehog (Shh) signalling pathway is essential for embryonic development and the patterning of multiple organs. Disruption or activation of Shh signalling leads to multiple birth defects, including holoprosencephaly, neural tube defects and polydactyly, and in adults results in tumours of the skin or central nervous system. Genetic approaches with model organisms continue to identify novel components of the pathway, including key molecules that function as positive or negative regulators of Shh signalling. Data presented here define Tulp3 as a novel negative regulator of the Shh pathway. We have identified a new mouse mutant that is a strongly hypomorphic allele of Tulp3 and which exhibits expansion of ventral markers in the caudal spinal cord, as well as neural tube defects and preaxial polydactyly, consistent with increased Shh signalling. We demonstrate that Tulp3 acts genetically downstream of Shh and Smoothened (Smo) in neural tube patterning and exhibits a genetic interaction with Gli3 in limb development. We show that Tulp3 does not appear to alter expression or processing of Gli3, and we demonstrate that transcriptional regulation of other negative regulators (Rab23, Fkbp8, Thm1, Sufu and PKA) is not affected. We discuss the possible mechanism of action of Tulp3 in Shh-mediated signalling in light of these new data.
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PMID:Mouse hitchhiker mutants have spina bifida, dorso-ventral patterning defects and polydactyly: identification of Tulp3 as a novel negative regulator of the Sonic hedgehog pathway. 1922 90

Activation of Hedgehog (Hh) signaling requires the transmembrane protein Smoothened (Smo), a member of the G-protein coupled receptor superfamily. In mammals, Smo translocates to the primary cilium upon binding of Hh ligands to their receptor, Patched (Ptch1), but it is unclear if ciliary trafficking of Smo is sufficient for pathway activation. Here, we demonstrate that cyclopamine and jervine, two structurally related inhibitors of Smo, force ciliary translocation of Smo. Treatment with SANT-1, an unrelated Smo antagonist, abrogates cyclopamine- and jervine-mediated Smo translocation. Further, activation of protein kinase A, either directly or through activation of Galphas, causes Smo to translocate to a proximal region of the primary cilium. We propose that Smo adopts multiple inactive and active conformations, which influence its localization and trafficking on the primary cilium.
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PMID:Smoothened adopts multiple active and inactive conformations capable of trafficking to the primary cilium. 1936 51

Combined targeting of distinct cellular signaling mechanisms may improve the efficacy and reduce the toxicity of therapy in pancreatic cancer. Histone deacetylases (HDACs) control cellular functions through epigenetic modulation, and HDACs inhibitors suppress cell growth in pancreatic adenocarcinoma. The Hedgehog (Hh) pathway regulates the development of the pancreas, and aberrant Hh signaling promotes the initiation and progression of pancreatic neoplasia. We hypothesize that HDACs and the Hh pathway cooperatively interact to regulate cellular proliferation of the exocrine pancreas. A combination of the HDAC inhibitor SAHA and the Smoothened antagonist SANT-1 was evaluated for their ability to suppress growth of the Gemcitabine-resistant pancreatic adenocarcinoma cell lines Panc-1 and BxPC-3. The combination of SAHA and SANT-1 supra-additively suppressed cellular proliferation and colony formation. Flow cytometric and immunohistochemical analyses indicated that enhanced induction of apoptotic cell death, cell cycle arrest in G(0)/G(1) phase, and ductal epithelial differentiation are involved. Cell death was associated with nuclear localization of survivin, increased bax expression, and activation of caspases 3 and 7. Consistent with the cell cycle arrest and cytodifferentiation, the cyclin-dependent kinase inhibitors p21(waf) and p27(kip1) were upregulated, and cyclin D1 downregulated. The potentiated anti-proliferative effect by the combination of SAHA and SANT-1 may involve cooperative suppression of the Hh pathway activity, as shown by the upregulation of HHIP by SAHA, and enhanced repression of of Ptc-1 mRNA expression. In summary, we have developed a molecular target-based therapeutic approach that overcomes chemoresistance in pancreatic cancer cells by chemically inhibiting HDACs and Hh signaling in combination.
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PMID:Combined targeting of histone deacetylases and hedgehog signaling enhances cytoxicity in pancreatic cancer. 1944 37

GLI family members are zinc-finger transcription factors, which are involved in embryogenesis and carcinogenesis through transcription regulation of GLI1, CCND1, CCND2, FOXA2, FOXC2, RUNX2, SFRP1, and JAG2. GLI1 transcription is upregulated in a variety of human tumors, such as basal cell carcinoma, lung cancer, breast cancer, gastric cancer, pancreatic cancer, and esophageal cancer. Hedgehog signaling via Smoothened cascade and receptor tyrosine kinase (RTK) signaling via PI3K-AKT cascade induce stabilization of GLI1 protein, whereas G-protein coupled receptor (GPCR) signaling via Gs-PKA cascade induces degradation of GLI1 protein. Here we report integrative genomic analyses of the GLI1 gene. The GLI1 and ARHGAP9 genes are located in a tail-to-tail manner with overlapping 3'-ends. ARHGAP9 was expressed in bone marrow, spleen, thymus, monocytes, and macrophages, whereas GLI1 was almost undetectable in normal tissues or cells with predominant ARHGAP9 expression. Because overlapping sense and anti-sense transcripts are annealed to each other to give rise to double-stranded RNAs functioning as endogenous RNAi, GLI1 expression might be negatively regulated by ARHGAP9 transcripts. GLI-binding element with one base substitution at the +1589-bp position from the transcriptional start site (TSS) of the human GLI1 gene was completely conserved in chimpanzee GLI1, mouse Gli1, and rat Gli1 genes. Ten Smad-binding elements, double E-boxes for EMT regulators, and double N-boxes for HES/HEY family members within intron 1 of the human GLI1 gene were also conserved in mammalian GLI1 orthologs. GLI1 transcription is upregulated due to Hedgehog, and TGFbeta signaling activation, whereas GLI1 transcription is downregulated due to Snail/Slug, and Notch signaling activation. Together these facts indicate that Hedgehog, TGFbeta, and RTK signals positively regulate GLI1, and that Notch, and GsPCR signals negatively regulate the GLI1.
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PMID:Integrative genomic analyses on GLI1: positive regulation of GLI1 by Hedgehog-GLI, TGFbeta-Smads, and RTK-PI3K-AKT signals, and negative regulation of GLI1 by Notch-CSL-HES/HEY, and GPCR-Gs-PKA signals. 1951 67


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