Interaction among GSK-3, GBP, axin, and APC in Xenopus axis specification

PICK1 inhibits the malignancy of nasopharyngeal carcinoma and serves as a novel prognostic marker

Although many important advances have been made in the treatment of nasopharyngeal carcinoma (NPC) in recent years, local recurrence and distant metastasis remain the main factors affecting NPC prognosis. Biomarkers for predicting the prognosis of NPC need to be urgently identified. Here, we used whole-exon sequencing (WES) to determine whether PICK1 mutations are associated with the prognosis of NPC. Functionally, PICK1 inhibits the proliferation and metastasis of NPC cells both in vivo and in vitro. Mechanistically, PICK1 inhibited the expression of proteins related to the Wnt/β-catenin signaling pathway. PICK1 restrained the nuclear accumulation of β-catenin and accelerated the degradation of β-catenin through the ubiquitin-proteasome pathway. The reduced PICK1 levels were significantly associated with poor patient prognosis. Hence, our study findings reveal the mechanism by which PICK1 inactivates the Wnt/β-catenin signaling pathway, thereby inhibiting the progression of NPC. They support PICK1 as a potential tumor suppressor and prognostic marker for NPC.

Upregulation of long intergenic non-coding RNA LINC00326 inhibits non-small cell lung carcinoma progression by blocking Wnt/β-catenin pathway through modulating the miR-657/dickkopf WNT signaling pathway inhibitor 2 axis

BACKGROUND

Long intergenic non-coding RNA 326 (LINC00326) modulates hepatocarcinogenic lipid metabolism. However, the ability of LINC00326 to modulate the highly aggressive non-small cell lung carcinoma (NSCLC) is unknown. Here, LINC00326 in NSCLC was investigated, together with its effects on tumor malignancy and the underlying mechanisms of action.

METHODS

LINC00326 levels in tumor tissues and cell lines were measured by Real-time fluorescence quantitative polymerase chain reaction (RT-qPCR) and RNA fluorescence in situ hybridization (FISH). Proliferation and apoptosis were assessed in cell lines by Cell Counting Kit-8 (CCK-8), EdU staining assays and flow cytometry, respectively, and tumor growth was measured in mouse models. Possible microRNA targets of LINC00326 were predicted by bioinformatics and verified by RNA pull-down and immunoprecipitation and luciferase reporter assays. Western blotting was used to evaluate the expression of Wnt/β-catenin-associated proteins.

RESULTS

LINC00326 was downregulated in tumor tissues and cell lines. Knockdown of LINC00326 stimulated NSCLC cell proliferation and suppressed apoptosis in vitro, as well as enhancing xenograft tumor growth. LINC00326 sponged miR-657, and dickkopf WNT signaling pathway inhibitor 2 (DKK2) was found to be directly targeted by miR-657, with LINC00326 positively regulating its expression through sponging miR-657. The actions of LINC00326 knockdown on proliferation and apoptosis were reversed by stimulation of the miR-657/DKK2 axis. Furthermore, overexpression of miR-657 mitigated DKK2 inhibition on Wnt/β-catenin signaling.

CONCLUSIONS

LINC00326/miR-657/DKK2 axis signaling blocked tumor-associated functions in NSCLC cells through the targeting Wnt/β-catenin pathway. This suggests that this pathway could be a target for NSCLC treatment.

Lysosomes are required for early dorsal signaling in the Xenopus embryo

Lysosomes are the digestive center of the cell and play important roles in human diseases, including cancer. Previous work has suggested that late endosomes, also known as multivesicular bodies (MVBs), and lysosomes are essential for canonical Wnt pathway signaling. Sequestration of Glycogen Synthase 3 (GSK3) and of β‐catenin destruction complex components in MVBs is required for sustained canonical Wnt signaling. Little is known about the role of lysosomes during early development. In the Xenopus egg, a Wnt-like cytoplasmic determinant signal initiates formation of the body axis following a cortical rotation triggered by sperm entry. Here we report that cathepsin D was activated in lysosomes specifically on the dorsal marginal zone of the embryo at the 64-cell stage, long before zygotic transcription starts. Expansion of the MVB compartment with low-dose hydroxychloroquine (HCQ) greatly potentiated the dorsalizing effects of the Wnt agonist lithium chloride (LiCl) in embryos, and this effect required macropinocytosis. Formation of the dorsal axis required lysosomes, as indicated by brief treatments with the vacuolar ATPase (V-ATPase) inhibitors Bafilomycin A1 or Concanamycin A at the 32-cell stage. Inhibiting the MVB-forming machinery with a dominant-negative point mutation in Vacuolar Protein Sorting 4 (Vps4-EQ) interfered with the endogenous dorsal axis. The Wnt-like activity of the dorsal cytoplasmic determinant Huluwa (Hwa), and that of microinjected xWnt8 messenger RNA, also required lysosome acidification and the MVB-forming machinery. We conclude that lysosome function is required for early dorsal axis development in Xenopus. The results highlight the intertwining between membrane trafficking, lysosomes, and vertebrate axis formation.

Mechanisms and Therapeutic Implications of GSK-3 in Treating Neurodegeneration

Neurodegenerative disorders are spreading worldwide and are one of the greatest threats to public health. There is currently no adequate therapy for these disorders, and therefore there is an urgent need to accelerate the discovery and development of effective treatments. Although neurodegenerative disorders are broad ranging and highly complex, they may share overlapping mechanisms, and thus potentially manifest common targets for therapeutic interventions. Glycogen synthase kinase-3 (GSK-3) is now acknowledged to be a central player in regulating mood behavior, cognitive functions, and neuron viability. Indeed, many targets controlled by GSK-3 are critically involved in progressing neuron deterioration and disease pathogenesis. In this review, we focus on three pathways that represent prominent mechanisms linking GSK-3 with neurodegenerative disorders: cytoskeleton organization, the mammalian target of rapamycin (mTOR)/autophagy axis, and mitochondria. We also consider the challenges and opportunities in the development of GSK-3 inhibitors for treating neurodegeneration.

The role of glycogen synthase kinase 3 beta in multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) that leads to progressive neurological disability due to axonal deterioration. Although MS presents profound heterogeneity in the clinical course, its underlying central mechanism is active demyelination and neurodegeneration associated with inflammation. Multiple autoimmune and neuroinflammatory pathways are involved in the demyelination process of MS. Analysis of MS lesions has shown that inflammatory genes are upregulated. Glycogen synthase kinase-3 (GSK-3) is part of the mitogen-activated protein kinase (MAPK) family and has important roles in many signaling cascades. GSK-3 is a highly conserved serine/threonine protein kinase expressed in both the central and the peripheral nervous systems. GSK-3 modulates several biological processes through phosphorylation of protein kinases, including cell signaling, neuronal growth, apoptosis and production of pro-inflammatory cytokines and interleukins, allowing adaptive changes in events such as cellular proliferation, migration, inflammation, and immunity. GSK-3 occurs in mammals in two isoforms GSK-3α and GSK-3β, both of which are common in the brain, although GSK-3α is found particularly in the cerebral cortex, cerebellum, striated hippocampus and Purkinje cells, while GSK-3β is found in all brain regions. In patients with chronic progressive MS, expression of GSK-3β is elevated in several brain regions such as the corpus callosum and cerebral cortex. GSK-3β inhibition may play a role in glial cell activation, reducing pathological pain induced by nerve injury by formalin injection. According to the role of GSK-3β in pathological conditions, the aim of this article is review of the role of GSK-3β in multiple sclerosis and inflammation of neurons.

The F-box Protein KIB1 Mediates Brassinosteroid-Induced Inactivation and Degradation of GSK3-like Kinases in Arabidopsis

The glycogen synthase kinase-3 (GSK3) family kinases are central cellular regulators highly conserved in all eukaryotes. In Arabidopsis, the GSK3-like kinase BIN2 phosphorylates a range of proteins to control broad developmental processes, and BIN2 is degraded through unknown mechanism upon receptor kinase-mediated brassinosteroid (BR) signaling. Here we identify KIB1 as an F-box E3 ubiquitin ligase that promotes the degradation of BIN2 while blocking its substrate access. Loss-of-function mutations of KIB1 and its homologs abolished BR-induced BIN2 degradation and caused severe BR-insensitive phenotypes. KIB1 directly interacted with BIN2 in a BR-dependent manner and promoted BIN2 ubiquitination in vitro. Expression of an F-box-truncated KIB1 caused BIN2 accumulation but dephosphorylation of its substrate BZR1 and activation of BR responses because KIB1 blocked BIN2 binding to BZR1. Our study demonstrates that KIB1 plays an essential role in BR signaling by inhibiting BIN2 through dual mechanisms of blocking substrate access and promoting degradation.

Bronchial-pulmonary adenocarcinoma subtyping relates with different molecular pathways

Lung cancer is one of the most common cancers in the world with a high mortality rate. We analyzed 45 surgical samples of the adenocarcinoma, 13 with lymph node metastasis. APC, BCL2, chromogranin A, CK 5/6/18 (LP34), CK20, CK7, cyclin D1, EGFR, ERCC1, HER2, Ki67, LRP, MRP, P53, RB and TTF1 expressions were evaluated by immunohistochemistry (IHC). Higher Ki67, APC, ERCC1 expressions and lower TTF1 expression were identified in advanced stages (IIA and IIIA) of adenocarcinomas, which reflect a more aggressive, less differentiated, possibly a non-TRU adenocarcinoma. Acinar, micropapillary and BA/lepidic adenocarcinoma patterns were the most similar patterns and papillary was the most different pattern followed by solid pattern, according to expression of these markers. Different adenocarcinoma patterns are engaged with different molecular pathways for carcinogenesis, based on the differences of expression. Acinar, BA/lepidic and micropapillary showed higher TTF1 expression (type TRU), and papillary and solid patterns revealed less TTF1 expression, exhibiting a non-TRU/bronchial phenotype. Solid pattern revealed lower HER2 and higher EGFR and ERCC1 (this compared to papillary) expression; papillary higher HER2 and lower ERCC1 expressions; micropapillary higher RB expression; and acinar lower ERCC1 and higher EGFR expressions. Ciclin D1 seems to have more importance in acinar and BA/lepidic patterns than in micropapillary. ERCC1 protein expression in micropapillary, solid and BA/lepidic patterns may indicate DNA repair activation. Inhibition of apoptosis could be explained by BCL2 overexpression, present in all adenocarcinoma patterns. MRP-1 and LRP were overexpressed in all patterns, which may have implications for drug resistance. Further studies are needed to interpret these data regarding to therapy response in advanced staged bronchial-pulmonary carcinomas.

Distinct functionality of dishevelled isoforms on Ca2+/calmodulin-dependent protein kinase 2 (CamKII) in Xenopus gastrulation

CamKII is a novel binding partner of Arrb2/Dvl2 protein complexes and is required for convergent extension movements in Xenopus. CamKII physically and functionally interacts with Dvl2, whereas CamKII activity is antagonistically modulated by Dvl1 and Dvl3.

Wnt ligands trigger the activation of a variety of β-catenin–dependent and β-catenin–independent intracellular signaling cascades. Despite the variations in intracellular signaling, Wnt pathways share the effector proteins frizzled, dishevelled, and β-arrestin. It is unclear how the specific activation of individual branches and the integration of multiple signals are achieved. We hypothesized that the composition of dishevelled–β-arrestin protein complexes contributes to signal specificity and identified CamKII as an interaction partner of the dishevelled–β-arrestin protein complex by quantitative functional proteomics. Specifically, we found that CamKII isoforms interact differentially with the three vertebrate dishevelled proteins. Dvl1 is required for the activation of CamKII and PKC in the Wnt/Ca²⁺ pathway. However, CamKII interacts with Dvl2 but not with Dvl1, and Dvl2 is necessary to mediate CamKII function downstream of Dvl1 in convergent extension movements in Xenopus gastrulation. Our findings indicate that the different Dvl proteins and the composition of dishevelled–β-arrestin protein complexes contribute to the specific activation of individual branches of Wnt signaling.

Clinical significance of inactivated glycogen synthase kinase 3β in HPV-associated cervical cancer: Relationship with Wnt/β-catenin pathway activation

PROBLEM

To determine the role of inactivated GSK3β with respect to Wnt/β-catenin pathway activation in HPV-16/18-associated cervical cancer.

METHOD OF STUDY

The expression of active (pGSK3β-Try(216)), inactive (pGSK3β-Ser(9)), and c-Myc as well as HPV-16/18 infection was analyzed in cervical intra-epithelial neoplasia (CIN), squamous cell carcinoma (SCCs) and normal by immunohistochemistry and multiplex PCR. The proteins level was also compared with β-catenin and APC expression.

RESULTS

The dramatic decrease of pGSK3β-Try(216) expression but ectopic overexpression of pGSK3β-Ser(9) and c-Myc was observed both in CIN and SCCs samples compared to normal tissues. 57/67 CIN and 132/153 SCCs showed HPV-16 infection, while 3/67 CIN and 4/153 SCCs were harbored with HPV-18 infection. Both the proteins were significantly upregulated in HPV-16 infected cases (P = 0.0001; P = 0.001) and also positively correlated with nuclear β-catenin (P = 0.0001; P = 0.0001).

CONCLUSION

The process of generation of HPV-16-associated cervical tumorigenesis is synergized with GSK3β inactivation and overactivation of Wnt/β-catenin pathway.

WITHDRAWN: Bronchial-pulmonary adenocarcinoma subtyping relates with different molecular pathways

This article has been withdrawn for editorial reasons because the journal will be published only in English. In order to avoid duplicated records, this article can be found at http://dx.doi.org/10.1016/j.rppnen.2014.05.006. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Glycogen synthase kinase-3β (GSK-3β) and its dysregulation in glioblastoma multiforme

Glioblastoma multiforme (GBM) is the most frequently occurring and devastating human brain malignancy, retaining almost universal mortality and a median survival of only 14 months, even with recent advances in multimodal treatments. Gliomas are characterised as being both highly resistant to chemo- and radiotherapy and highly invasive, rendering conventional interventions palliative. The continual dismal prognosis for GBM patients identifies an urgent need for the evolutionary development of new treatment modalities. This includes molecular targeted therapies as many signaling molecules and associated pathways have been implicated in the development and survival of malignant gliomas including the protein kinase, glycogen synthase kinase 3 beta (GSK-3β). Here we review the activity and function of GSK-3β in a number of signaling pathways and its role in gliomagenesis.

Knockdown of FRAT1 expression by RNA interference inhibits human glioblastoma cell growth, migration and invasion

BACKGROUND

FRAT1 positively regulates the Wnt/β-catenin signaling pathway by inhibiting GSK-3-mediated phosphorylation of β-catenin. It was originally characterized as a protein frequently rearranged in advanced T cell lymphoma, but has recently also been identified as a proto-oncogene involved in tumorigenesis. Our previous studies showed that FRAT1 was dramatically overexpressed in gliomas and its expression level was significantly increased along with clinicopathological grades.

METHODS

In the current study, we used RT-PCR and Western blotting to assess the mRNA and protein levels of FRAT1 in three glioma cell lines. In addition, to evaluate its functional role in gliomas, we examined the effects of FRAT1 knockdown on proliferation, migration and invasion in vitro and tumor growth in vivo using glioblastoma U251 cells and RNAi.

RESULTS

FRAT1 was highly expressed in all three glioma cell lines. RNAi-mediated down-regulation of endogenous FRAT1 in human glioblastoma U251 cells resulted in suppression of cell proliferation, arrest of cell cycle, inhibition of cell migration and invasion in vitro. Moreover, FRAT1 depletion significantly impaired tumor xenograft growth in nude mice.

CONCLUSIONS

Our results highlight the potential role of FRAT1 in tumorigenesis and progression of glioblastoma. These findings provide a biological basis for FRAT1 as a potential molecular marker for improved pathological grading and as a novel candidate therapeutic target for glioblastoma management.

MicroRNA-222 promotes tumorigenesis via targeting DKK2 and activating the Wnt/β-catenin signaling pathway

MiR-222 in glioma can regulate cell cycle progression and apoptosis. However, the relationship between miR-222 and Wnt/β-catenin signaling pathway in glioma remains unknown. Here, we found that the Dickkopf-2 gene (DKK2) was a direct target of miR-222 by target prediction analysis and dual luciferase reporter assay. RNA interference silencing of DKK2 proved that miR-222 overexpression led to constitutive activation of β-catenin through inhibition of DKK2 expression in glioma cells. Furthermore, miR-222 siRNA significantly inhibited tumorigenesis in vivo. Finally, Western blot analysis showed that miR-222 could regulate the expression of β-catenin and the downstream genes of Wnt/β-catenin signaling pathway. Taken together, our findings reveal a new regulatory mechanism of miR-222 and suggest that miR-222 might be a potential target in glioma therapy.

The way Wnt works: components and mechanism

The canonical Wnt/β-catenin pathway is an ancient and evolutionarily conserved signaling pathway that is required for the proper development of all metazoans, from the basal demosponge Amphimedon queenslandica to humans. Misregulation of Wnt signaling is implicated in many human diseases, making this pathway an intense area of research in industry as well as academia. In this review, we explore our current understanding of the molecular steps involved in the transduction of a Wnt signal. We will focus on how the critical Wnt pathway component, β-catenin, is in a "futile cycle" of constant synthesis and degradation and how this cycle is disrupted upon pathway activation. We describe the role of the Wnt pathway in major human cancers and in the control of stem cell self-renewal in the developing organism and in adults. Finally, we describe well-accepted criteria that have been proposed as evidence for the involvement of a molecule in regulating the canonical Wnt pathway.

Beyond cell adhesion: the role of armadillo proteins in the heart

Plakoglobin (PG, γ-Catenin, JUP), a member of the armadillo protein family and close homolog of β-catenin, functions to link cell surface cadherin molecules with the cytoskeleton. PG is the only junctional component found in both desmosomes and adherens junctions and thus plays a critical role in the regulation of cell-cell adhesion. Similar to β-catenin, PG is able to interact with components of the Wnt signaling pathway and directly affect gene expression by binding with LEF/TCF transcription factors. In addition, it has been proposed that PG functions primarily as a competitive inhibitor of β-catenin transcriptional activity by sequestering LEF/TCF. Compared to β-catenin, the contribution of PG as a transcriptional regulator in either physiological or pathological conditions is poorly understood. There is increasing clinical interest in PG as both a structural protein as well as a signaling molecule as mutations have been identified in the human PG gene that cause Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) and cutaneous syndromes. This review will discuss the connection between altered cell adhesion and gene expression and its contribution to disease pathogenesis.

Lithium regulates keratinocyte proliferation via glycogen synthase kinase 3 and NFAT2 (nuclear factor of activated T cells 2)

Certain environmental factors including drugs exacerbate or precipitate psoriasis. Lithium is the commonest cause of drug-induced psoriasis but underlying mechanisms are currently unknown. Lithium inhibits glycogen synthase kinase 3 (GSK-3). As lithium does not exacerbate other T-cell-mediated chronic inflammatory diseases, we investigated whether lithium may be acting directly on epidermal keratinocytes by inhibiting GSK-3. We report that lithium-induced keratinocyte proliferation at therapeutically relevant doses (1-2 mM) and increased the proportion of cells in S phase of the cell cycle. Inhibition of GSK-3 in keratinocytes by retroviral transduction of GSK-binding protein (an endogenous inhibitory protein) or through a highly selective pharmacological inhibitor also resulted in increased keratinocyte proliferation. Nuclear factor of activated T cells (NFAT) is an important substrate for GSK-3 and for cyclosporin, an effective treatment for psoriasis that inhibits NFAT activation in keratinocytes as well as in lymphocytes. Both lithium and genetic/pharmacological inhibition of GSK-3 resulted in increased nuclear localization of NFAT2 (NFATc1) and increased NFAT transcriptional activation. Finally, retroviral transduction of NFAT2 increased keratinocyte proliferation whereas siRNA-mediated knockdown of NFAT2 reduced keratinocyte proliferation and decreased epidermal thickness in an organotypic skin equivalent model. Taken together, these data identify GSK-3 and NFAT2 as key regulators of keratinocyte proliferation and as potential molecular targets relevant to lithium-provoked psoriasis.

Cortical rotation and messenger RNA localization in Xenopus axis formation

In Xenopus eggs, fertilization initiates a rotational movement of the cortex relative to the cytoplasm, resulting in the transport of critical determinants to the future dorsal side of the embryo. Cortical rotation is mediated by microtubules, resulting in activation of the Wnt/β-catenin signaling pathway and expression of organizer genes on the dorsal side of the blastula. Similar cytoplasmic localizations resulting in β-catenin activation occur in many chordate embryos, suggesting a deeply conserved mechanism for patterning early embryos. This review summarizes the experimental evidence for the molecular basis of this model, focusing on recent maternal loss-of-function studies that shed light on two main unanswered questions: (1) what regulates microtubule assembly during cortical rotation and (2) how is Wnt/β-catenin signaling activated dorsally? In addition, as these processes depend on vegetally localized molecules in the oocyte, the mechanisms of RNA localization and novel roles for localized RNAs in axis formation are discussed. The work reviewed here provides a beginning framework for understanding the coupling of asymmetry in oogenesis with the establishment of asymmetry in the embryo.

Lithium suppresses astrogliogenesis by neural stem and progenitor cells by inhibiting STAT3 pathway independently of glycogen synthase kinase 3 beta

Transplanted neural stem and progenitor cells (NSCs) produce mostly astrocytes in injured spinal cords. Lithium stimulates neurogenesis by inhibiting GSK3b (glycogen synthetase kinase 3-beta) and increasing WNT/beta catenin. Lithium suppresses astrogliogenesis but the mechanisms were unclear. We cultured NSCs from subventricular zone of neonatal rats and showed that lithium reduced NSC production of astrocytes as well as proliferation of glia restricted progenitor (GRP) cells. Lithium strongly inhibited STAT3 (signal transducer and activator of transcription 3) activation, a messenger system known to promote astrogliogenesis and cancer. Lithium abolished STAT3 activation and astrogliogenesis induced by a STAT3 agonist AICAR (5-aminoimidazole-4-carboxamide 1-beta-D-ribofuranoside), suggesting that lithium suppresses astrogliogenesis by inhibiting STAT3. GSK3β inhibition either by a specific GSK3β inhibitor SB216763 or overexpression of GID5-6 (GSK3β Interaction Domain aa380 to 404) did not suppress astrogliogenesis and GRP proliferation. GSK3β inhibition also did not suppress STAT3 activation. Together, these results indicate that lithium inhibits astrogliogenesis through non-GSK3β-mediated inhibition of STAT. Lithium may increase efficacy of NSC transplants by increasing neurogenesis and reducing astrogliogenesis. Our results also may explain the strong safety record of lithium treatment of manic depression. Millions of people take high-dose (>1 gram/day) lithium carbonate for a lifetime. GSK3b inhibition increases WNT/beta catenin, associated with colon and other cancers. STAT3 inhibition may reduce risk for cancer.

Neural cell adhesion molecule potentiates the growth of murine melanoma via β-catenin signaling by association with fibroblast growth factor receptor and glycogen synthase kinase-3β

The neural cell adhesion molecule (NCAM) was recently shown to be involved in the progression of various tumors with diverse effects. We previously demonstrated that NCAM potentiates the cellular invasion and metastasis of melanoma. Here we further report that the growth of melanoma is obviously retarded when the expression of NCAM is silenced. We found that the proliferation of murine B16F0 melanoma cells, their colony formation on soft agar, and growth of transplanted melanoma in vivo are clearly inhibited by the introduction of NCAM siRNA. Interestingly, change of NCAM expression level is shown to regulate the activity of Wnt signaling molecule, β-catenin, markedly. This novel machinery requires the function of FGF receptor and glycogen synthase kinase-3β but is independent of the Wnt receptors, MAPK-Erk and PI3K/Akt pathways. In addition, NCAM is found to form a functional complex with β-catenin, FGF receptor, and glycogen synthase kinase-3β. Moreover, up-regulation of NCAM140 and NCAM180 appears more potent than NCAM120 in activation of β-catenin, suggesting that the intracellular domain of NCAM is required for facilitating the β-catenin signaling. Furthermore, the melanoma cells also exhibit distinct differentiation phenotypes with the NCAM silencing. Our findings reveal a novel regulatory role of NCAM in the progression of melanoma that might serve as a new therapeutic target for the treatment of melanoma.

Mechanism of kinase inactivation and nonbinding of FRATide to GSK3β due to K85M mutation: molecular dynamics simulation and normal mode analysis

As a serine/threonine protein kinase, glycogen synthase kinase 3β (GSK3β) is an essential component of several cellular processes, including insulin, growth factor, and Wnt signaling. The conserved K85 is important to GSK3β activity and FRATide binding. To elucidate the mechanisms concerning kinase inactivation and nonbinding of FRATide to GSK3β, molecular dynamics (MD) simulation, molecular mechanics generalized Born/surface area (MM_GBSA) calculation, and normal mode analysis (NMA) were performed on both the wild-type (WT) and the K85M mutation of the GSK3β-FRATide complex. The results revealed that the periodic open-closed conformational change of the G loop, together with the compact conformation of the RD pocket, was disturbed in the K85M mutant, in contrast to those in the WT. This in turn caused inhibition of GSK3β. Specifically, the correct folding pattern of GSK3β was disrupted in the K85M mutant, resulting in the loss of two key hydrogen bonds between K214 of FRATide and E290 and K292 of GSK3β, respectively. Furthermore, MM_GBSA calculations indicated that the K85M mutation could lead to a less energy-favorable GSK3β-FRATide complex. In addition, NMA demonstrated that the "rocking" of the N- and C-terminal domains of GSK3β, which coordinates the mutual movement of both lobes, inducing the opening and closing of the active site of GSK3β, which may assist the entry of ATP into the ATP binding site and the release of the ADP product. Strikingly, this phenomenon was not clearly observed in the K85M mutation. This study provides a structural basis for the effect of the K85M mutation on the GSK3β-FRATide complex.

Dissection of the difference between the group I metal ions in inhibiting GSK3β: a computational study

Glycogen synthase kinase 3β (GSK3β) is a serine/threonine kinase that requires two cofactor Mg(2+) ions for catalysis in regulating many important cellular signals. Experimentally, Li(+) is a competitive inhibitor of GSK3β relative to Mg(2+), while this mechanism is not experienced with other group I metal ions. Herein, we use native Mg(2)(2+)-Mg(1)(2+) GSK3β and its Mg(2)(2+)-M(1)(+) (M = Li, Na, K, and Rb) derivatives to investigate the effect of metal ion substitution on the mechanism of inhibition through two-layer ONIOM-based quantum mechanics/molecular mechanics (QM/MM) calculations and molecular dynamics (MD) simulations. The results of ONIOM calculations elucidate that the interaction of Na(+), K(+), and Rb(+) with ATP is weaker compared to that of Mg(2+) and Li(+) with ATP, and the critical triphosphate moiety of ATP undergoes a large conformational change in the Na(+), K(+), and Rb(+) substituted systems. As a result, the three metal ions (Na(+), K(+), and Rb(+)) are not stable and depart from the active site, while Mg(2+) and Li(+) can stabilize in the active site, evident in MD simulations. Comparisons of Mg(2)(2+)-Mg(1)(2+) and Mg(2)(2+)-Li(1)(+) systems reveal that the inline phosphor-transfer of ATP and the two conserved hydrogen bonds between Lys85 and ATP, together with the electrostatic potential at the Li(1)(+) site, are disrupted in the Mg(2)(2+)-Li(1)(+) system. These computational results highlight the possible mechanism why Li(+) inhibits GSK3β.

Postgenomic technologies targeting the Wnt signaling network

The recent development of high-throughput sequencing technologies and the availability of whole genome sequences of a variety of living organisms, including that of humans, have led to an enormous push in the quest for a comprehensive inquiry for the function of each and every gene discovered in different model organisms. A major conclusion from the sequencing projects was that while forward genetics had been extremely successful in identifying key genes/components of many biological processes, such as signal transduction cascades, the function(s) of the majority of genes in the genome remains a mystery. In this article, we discuss the use of a variety of high-throughput postgenomic tools, including functional genomics, proteomics, and chemical genetics that are being implemented in an exhaustive molecular dissection of a key evolutionarily conserved signal transduction pathway, namely the Wnt/wingless (wg) pathway and its associated signaling network.

Inhibition of proprotein convertase SKI-1 blocks transcription of key extracellular matrix genes regulating osteoblastic mineralization

Mineralization, a characteristic phenotypic property of osteoblastic lineage cells, was blocked by 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride (AEBSF) and decanoyl-Arg-Arg-Leu-Leu-chloromethyl ketone (dec-RRLL-cmk), inhibitors of SKI-1 (site 1; subtilisin kexin like-1) protease. Because SKI-1 is required for activation of SREBP and CREB (cAMP-response element-binding protein)/ATF family transcription factors, we tested the effect of these inhibitors on gene expression. AEBSF decreased expression of 140 genes by 1.5-3.0-fold including Phex, Dmp1, COL1A1, COL11A1, and fibronectin. Direct comparison of AEBSF and dec-RRLL-cmk, a more specific SKI-1 inhibitor, demonstrated that expression of Phex, Dmp1, COL11A1, and fibronectin was reduced by both, whereas COL1A2 and HMGCS1 were reduced only by AEBSF. AEBSF and dec-RRLL-cmk decreased the nuclear content of SKI-1-activated forms of transcription factors SREBP-1, SREBP-2, and OASIS. In contrast to AEBSF, the actions of dec-RRLL-cmk represent the sum of its direct actions on SKI-1 and indirect actions on caspase-3. Specifically, dec-RRLL-cmk reduced intracellular caspase-3 activity by blocking the formation of activated 19-kDa caspase-3. Conversely, overexpression of SKI-1-activated SREBP-1a and CREB-H in UMR106-01 osteoblastic cells increased the number of mineralized foci and altered their morphology to yield mineralization nodules, respectively. In summary, SKI-1 regulates the activation of transmembrane transcription factor precursors required for expression of key genes required for mineralization of osteoblastic cultures in vitro and bone formation in vivo. Our results indicate that the differentiated phenotype of osteoblastic cells and possibly osteocytes depends upon the non-apoptotic actions of SKI-1.

Segregation of myoblast fusion and muscle-specific gene expression by distinct ligand-dependent inactivation of GSK-3β

Myogenic differentiation involves myoblast fusion and induction of muscle-specific gene expression, which are both stimulated by pharmacological (LiCl), genetic, or IGF-I-mediated GSK-3β inactivation. To assess whether stimulation of myogenic differentiation is common to ligand-mediated GSK-3β inactivation, myoblast fusion and muscle-specific gene expression were investigated in response to Wnt-3a. Moreover, crosstalk between IGF-I/GSK-3β/NFATc3 and Wnt/GSK-3β/β-catenin signaling was assessed. While both Wnt-3a and LiCl promoted myoblast fusion, muscle-specific gene expression was increased by LiCl, but not by Wnt-3a or β-catenin over-expression. Furthermore, LiCl and IGF-I, but not Wnt-3a, increased NFATc3 transcriptional activity. In contrast, β-catenin-dependent transcriptional activity was increased by Wnt-3a and LiCl, but not IGF-I. These results for the first time reveal a segregated regulation of myoblast fusion and muscle-specific gene expression following stimulation of myogenic differentiation in response to distinct ligand-specific signaling routes of GSK-3β inactivation.

Striking the target in Wnt-y conditions: intervening in Wnt signaling during cancer progression

Wnt signaling can be divided into three pathways, namely the canonical Wnt/beta-catenin pathway, and the non-canonical (or heretical) Wnt/Ca(2+) and planar cell polarity (PCP) pathways. Although the canonical Wnt/beta-catenin pathway is the best described in cancer, increasing data points to the importance of the heretical Wnt pathways in several aspects of tumor progression. The recent advances in understanding the players and mechanisms by which these Wnt pathways contribute to cancer progression have led to the identification of numerous molecules that are already, or could be considered, targets for cancer therapy.

The expression profile of FRAT1 in human gliomas

FRAT1 was originally characterized as a protein frequently rearranged in advanced T cell lymphoma, which inhibits GSK-3-mediated phosphorylation of beta-catenin and positively regulates the Wnt signaling pathway. FRAT1 has been identified as a proto-oncogene involved in tumorigenesis. Previous studies have shown that FRAT1 is strikingly overexpressed in some human cancers. However, the relationship between FRAT1 and human gliomas is unclear. In this study, we detected the expression of FRAT1 in human gliomas by immunohistochemistry, Western blot and RT-PCR. FRAT1 was found to be specifically expressed in the majority of glioma samples, and their expression levels increased markedly with the increase of WHO grades. In addition, there was a positive correlation between FRAT1 immunoreactivity score (IRS) and beta-catenin IRS. Our results suggest that FRAT1 may be an important factor in the tumorigenesis and progression of gliomas, and could be used as a potential molecular marker for pathological diagnosis and a target for biological therapy.

Wnt modulators in the biotech pipeline

The purpose of this review is to provide a better understanding for the LRP co-receptor-mediated Wnt pathway signaling. Using proteomics, we have also subdivided the LRP receptor family into six sub-families, encompassing the twelve family members. This review includes a discussion of proteins containing a cystine-knot protein motif (i.e., Sclerostin, Dan, Sostdc1, Vwf, Norrin, Pdgf, Mucin) and discusses how this motif plays a role in mediating Wnt signaling through interactions with LRP.

Znrg, a novel gene expressed mainly in the developing notochord of zebrafish

The notochord, a defining characteristic of the chordate embryo is a critical midline structure required for axial skeletal formation in vertebrates, and acts as a signaling center throughout embryonic development. We utilized the digital differential display program of the National Center for Biotechnology Information, and identified a contig of expressed sequence tags (no. Dr. 83747) from the zebrafish ovary library in Genbank. Full-length cDNA of the identified gene was cloned by 5'- and 3'- RACE, and the resulting sequence was confirmed by polymerase chain reaction and sequencing. The cDNA clone contains 2,505 base pairs and encodes a novel protein of 707 amino acids that shares no significant homology with any known proteins. This gene was expressed in mature oocytes and at the one-cell stage, and persisted until the 5th day of development, as determined by RT-PCR. Transcripts were detected by whole-mount RNA in situ hybridization from the two-cell stage to 72 h of embryonic development. This gene was uniformly distributed from the cleavage stage up to the blastula stage. During early gastrulation, it was present in the dorsal region, and became restricted to the notochord and pectoral fin at 48 and 72 h of embryonic development. Based on its abundance in the notochord, we hypothesized that the novel gene may play an important role in notochord development in zebrafish; we named this gene, zebrafish notochord-related gene, or znrg.

Characterization of the interaction between latency-associated nuclear antigen and glycogen synthase kinase 3beta

The latency-associated nuclear antigen (LANA) of Karposi's sarcoma-associated herpesvirus has been reported to interact with glycogen synthase kinase 3beta (GSK-3beta) and regulate its activity, leading to inhibition of GSK-3-dependent beta-catenin degradation. In this study, the interaction between LANA and GSK-3beta was characterized further. LANA was found to interact with GSK-3beta in vitro as well as in intact cells. However, LANA did not regulate GSK-3beta kinase activity and LANA-induced upregulation of beta-catenin was GSK-3beta independent. LANA did not regulate the stability of beta-catenin or of its reported interaction partners p53 and von Hippel-Lindau protein. Additional targets of LANA are likely to mediate its malignancy-promoting function.

GSK3 beta N-terminus binding to p53 promotes its acetylation

The prevalence in human cancers of mutations in p53 exemplifies its crucial role as a tumor suppressor transcription factor. Previous studies have shown that the constitutively active serine/threonine kinase glycogen synthase kinase-3β (GSK3β) associates with the C-terminal basic domain of p53 and regulates its actions. In this study we identified the GSK3β N-terminal amino acids 78–92 as necessary for its association with p53. Inhibitors of GSK3 impaired the acetylation of p53 at Lys373 and Lys382 near the GSK3β binding region in p53, indicating that GSK3β facilitates p53 acetylation. We also found that acetylation of p53 reduced its association with GSK3β, as well as with GSK3α. These results indicate that the N-terminal region of GSK3β binds p53, this association promotes the acetylation of p53, and subsequently acetylated p53 dissociates from GSK3.

p38 mitogen-activated protein kinase regulates canonical Wnt–β-catenin signaling by inactivation of GSK3β

The Wnt–β-catenin canonical signaling pathway is crucial for normal embryonic development, and aberrant expression of components of this pathway results in oncogenesis. Upon scanning for the mitogen-activated protein kinase (MAPK) pathways that might intersect with the canonical Wnt–β-catenin signaling pathway in response to Wnt3a, we observed a strong activation of p38 MAPK in mouse F9 teratocarcinoma cells. Wnt3a-induced p38 MAPK activation was sensitive to siRNAs against Gαq or Gαs, but not against either Gαo or Gα11. Activation of p38 MAPK is critical for canonical Wnt–β-catenin signaling. Chemical inhibitors of p38 MAPK (SB203580 or SB239063) and expression of a dominant negative-version of p38 MAPK attenuate Wnt3a-induced accumulation of β-catenin, Lef/Tcf-sensitive gene activation, and primitive endoderm formation. Furthermore, epistasis experiments pinpoint p38 MAPK as operating downstream of Dishevelleds. We also demonstrate that chemical inhibition of p38 MAPK restores Wnt3a-attenuated GSK3β kinase activity. We demonstrate the involvement of G-proteins and Dishevelleds in Wnt3a-induced p38 MAPK activation, highlighting a critical role for p38 MAPK in canonical Wnt–β-catenin signaling.

The pseudoreceptor BMP and activin membrane-bound inhibitor positively modulates Wnt/beta-catenin signaling

The canonical Wnt/beta-catenin pathway plays a pivotal role in regulating embryogenesis and tumorigenesis by promoting cell proliferation. BAMBI (BMP and activin membrane-bound inhibitor) has previously been shown to negatively regulate the signaling activity of transforming growth factor-beta, activin, and BMP and was identified as a target of beta-catenin in colorectal and hepatocellular tumor cells. In this study, we provide evidence that BAMBI can promote the transcriptional activity of Wnt/beta-catenin signaling. Overexpression of BAMBI enhances the expression of Wnt-responsive reporters, whereas knockdown of endogenous BAMBI attenuates them. Accordingly, BAMBI also promotes the nuclear translocation of beta-catenin. BAMBI interacts with Wnt receptor Frizzled5, coreceptor LRP6, and Dishevelled2 and increases the interaction between Frizzled5 and Dishevelled2. Finally we show that BAMBI promotes the expression of c-myc and cyclin D1 and increases Wnt-promoted cell cycle progression. Altogether, our data indicate that BAMBI can function as a positive regulator of the Wnt/beta-catenin pathway to promote cell proliferation.

Unexpectedly robust assembly of the Axin destruction complex regulates Wnt/Wg signaling in Drosophila as revealed by analysis in vivo

Secreted proteins in the Wnt family regulate gene expression in target cells by causing the accumulation of the transcriptional activator beta-catenin. In the absence of Wnt, a protein complex assembled around the scaffold protein Axin targets beta-catenin for destruction, thereby preventing it from transducing inappropriate signals. Loss of Axin or its binding partners APC and GSK3 results in aberrant activation of the Wnt signaling response. We have analyzed the effects of mutant forms of Drosophila Axin with large internal deletions when expressed at physiological levels in vivo, either in the presence or absence of wild type Axin. Surprisingly, even deletions that completely remove the binding sites for fly APC, GSK3 or beta-catenin, though they fail to rescue to viability, these mutant forms of Axin cause only mild developmental defects, indicating largely retained Axin function. Furthermore, two lethal Axin deletion constructs, AxinDeltaRGS and AxinDeltabeta cat(DeltaArm), can complement each other and restore viability. Our findings support a model in which the Axin complex is assembled through cooperative tripartite interactions among the binding partners, making the assembly of functional complexes surprisingly robust.

Regulation of glycogen synthase kinase 3beta functions by modification of the small ubiquitin-like modifier

Modification of the Small Ubiquitin-like Modifier (SUMO) (SUMOylation) appears to regulate diverse cellular processes, including nuclear transport, signal transduction, apoptosis, autophagy, cell cycle control, ubiquitin-dependent degradation and gene transcription. Glycogen synthase kinase 3beta (GSK 3beta) is a serine/threonine kinase that is thought to contribute to a variety of biological events, including embryonic development, metabolism, tumorigenesis, and cell death. GSK 3beta is a constitutively active kinase that regulates many intracellular signaling pathways by phosphorylating substrates such as beta-catenin. We noticed that the putative SUMOylation sites are localized on K(292 )residueof (291)FKFPQ(295) in GSK 3beta based on analysis of the SUMOylation consensus sequence. In this report, we showed that the SUMOylation of GSK 3beta occurs on its K(292) residue, and this modification promotes its nuclear localization in COS-1. Additionally, our data showed that the GSK 3beta SUMO mutant (K292R) decreased its kinase activity and protein stability, affecting cell death. Therefore, our observations at first time suggested that SUMOylation on the K(292) residue of GSK 3beta might be a GSK 3beta regulation mechanism for its kinase activation, subcellular localization, protein stability, and cell apoptosis.

Osteocytes, mechanosensing and Wnt signaling

The majority of bone cell biology focuses on activity on the surface of the bone with little attention paid to the activity that occurs below the surface. However, with recent new discoveries, osteocytes, cells embedded within the mineralized matrix of bone, are becoming the target of intensive investigation. In this article, the distinctions between osteoblasts and their descendants, osteocytes, are reviewed. Osteoblasts are defined as cells that make bone matrix and osteocytes are thought to translate mechanical loading into biochemical signals that affect bone (re)modeling. Osteoblasts and osteocytes should have similarities as would be expected of cells of the same lineage, yet these cells also have distinct differences, particularly in their responses to mechanical loading and utilization of the various biochemical pathways to accomplish their respective functions. For example, the Wnt/beta-catenin signaling pathway is now recognized as an important regulator of bone mass and bone cell functions. This pathway is important in osteoblasts for differentiation, proliferation and the synthesis bone matrix, whereas osteocytes appear to use the Wnt/beta-catenin pathway to transmit signals of mechanical loading to cells on the bone surface. New emerging evidence suggests that the Wnt/beta-catenin pathway in osteocytes may be triggered by crosstalk with the prostaglandin pathway in response to loading which then leads to a decrease in expression of negative regulators of the pathway such as Sost and Dkk1. The study of osteocyte biology is becoming an intense area of research interest and this review will examine some of the recent findings that are reshaping our understanding of bone/bone cell biology.

Wnt signaling pathway in invasive ductal carcinoma of the breast: relationship between beta-catenin, dishevelled and cyclin D1 expression

OBJECTIVE

The Wnt/beta-catenin signaling cascade is an important signal transduction pathway in human cancers. Overexpression of beta-catenin and its downstream effector, cyclin D1, is implicated in malignant transformation and acquisition of an invasive tumor phenotype. This study aimed to determine the clinical significance of Wnt/beta-catenin canonical pathway components in breast cancer.

METHODS

Expression of beta-catenin, dishevelled (Dvl) and cyclin D1 was examined in invasive ductal carcinomas (IDCs) of the breast by immunohistochemical analysis.

RESULTS

Of the 98 IDCs analyzed, 30% of tumors displayed both nuclear and cytoplasmic staining of Dvl protein, while 52% showed nuclear localization. Loss of cell surface beta-catenin was observed in 66% of breast carcinomas, whereas nuclear expression was observed in 48% IDCs. Cyclin D1 overexpression was observed in 60% IDCs; 31/59 (53%) of these tumors showed nuclear expression of beta-catenin, suggesting upregulation of the canonical Wnt/beta-catenin pathway. Our study demonstrates a significant association between nuclear localization of Dvl and beta-catenin (p < 0.01, OR = 15.8).

CONCLUSION

To our knowledge, this is the first study showing an association between nuclear localization of Dvl and beta-catenin in IDCs and suggests the upregulation of Wnt/beta-catenin pathway components, beta-catenin, Dvl and cyclin D1 in IDCs of the breast.

Wnt/beta-catenin signaling: new (and old) players and new insights

Wnt/beta-catenin signaling has central roles in embryogenesis and human diseases including cancer. A central scheme of the Wnt pathway is to stabilize the transcription coactivator beta-catenin by preventing its phosphorylation-dependent degradation. Significant progress has been made toward the understanding of this crucial regulatory pathway, including the protein complex that promotes beta-catenin phosphorylation-degradation, and the mechanism by which the extracellular Wnt ligand engages cell surface receptors to inhibit beta-catenin phosphorylation-degradation. Here we review some recent discoveries in these two areas, and highlight some crucial questions that remain to be resolved.

Dual positive and negative regulation of wingless signaling by adenomatous polyposis coli

The evolutionarily conserved Wnt/Wingless signal transduction pathway directs cell proliferation, cell fate, and cell death during development in metazoans and is inappropriately activated in several types of cancer. The majority of colorectal carcinomas contain truncating mutations in the adenomatous polyposis coli (APC) tumor suppressor, a negative regulator of Wnt/Wingless signaling. Here, we demonstrate that Drosophila Apc homologs also have an activating role in both physiological and ectopic Wingless signaling. The Apc amino terminus is important for its activating function, whereas the beta-catenin binding sites are dispensable. Apc likely promotes Wingless transduction through down-regulation of Axin, a negative regulator of Wingless signaling. Given the evolutionary conservation of APC in Wnt signal transduction, an activating role may also be present in vertebrates with relevance to development and cancer.

Increased nuclear beta-catenin in suprabasal involved psoriatic epidermis

BACKGROUND

Psoriasis is a common inflammatory skin disease characterized by abnormal keratinocyte proliferation and differentiation, increased angiogenesis and inflammation. There is evidence that some keratinocyte differentiation events are controlled by changes in cell-cell adhesion. beta-catenin is a 94-kDa protein which has a dual function as a component of intercellular adherens junctions and also as a transcription factor as part of the Wnt signalling pathway. beta-catenin is not required for keratinocyte proliferation but has been shown to regulate keratinocyte stem cells and hair follicle morphogenesis.

OBJECTIVES

To investigate the distribution and function of beta-catenin in involved psoriatic epidermis and in epidermal keratinocytes.

METHODS

Biopsies were obtained from patients with psoriasis and from normal controls. The distribution of beta-catenin was investigated using antibodies to both total and unphosphorylated active beta-catenin. Luciferase assays were used to measure transcriptional activation of transglutaminase 1 (TGase 1) and involucrin and to investigate the functional role of beta-catenin in interfollicular keratinocytes.

RESULTS

Increased nuclear beta-catenin was seen in lesional suprabasal psoriatic epidermis compared with uninvolved or normal skin. Increased active unphosphorylated beta-catenin was also detected within the differentiating compartment of involved psoriatic epidermis. Expression of TGase 1 overlapped with beta-catenin in suprabasal lesional psoriasis. The TGase 1 promoter was positively regulated by activated beta-catenin and by the glycogen synthase kinase binding protein, suggesting that beta-catenin and glycogen synthase kinase 3beta may regulate TGase 1 expression.

CONCLUSIONS

This is the first report to convincingly demonstrate increased beta-catenin in involved psoriasis and to implicate beta-catenin in the regulation of TGase 1. This evidence suggests a role for beta-catenin signalling in regulating keratinocyte differentiation in interfollicular skin in addition to previously reported functions in stem cell fate determination, hair follicle regulation and skin tumorigenesis.

The role of GSK3 in glucose homeostasis and the development of insulin resistance

GSK3 has been implicated in the development of insulin resistance, primarily based on its role in regulation of glycogen synthesis. However, GSK3 is involved in many other important signaling cascades which may regulate glucose homeostasis and the development of insulin resistance. In addition, GSK3 is composed of two isoforms, GSK3alpha and beta, which do not completely share their physiological roles, and this raises a possibility that GSK3alpha and beta may function differently in glucose homeostasis. In this review, we will give an overview to examine potential mechanisms for the roles of GSK3 in the development of insulin resistance.

The Arabidopsis thaliana GSK3/Shaggy like kinase AtSK3-2 modulates floral cell expansion

The GSK3/Shaggy family of serine/threonine protein kinases is involved in a series of biological processes in animals, plants and yeast [Charrier et al. (2002) Plant Physiol 130:577-590; Jope and Johnson (2004) Trends Biochem Sci 29:95-102; Li and Nam (2002) Science 295:1299-1301; Piao et al. (2001) Plant J 27:305-314]. In Arabidopsis thaliana, out of the 10 members of the GSK3/Shaggy-like gene family (AtSKs), a biological function has been assigned to only 1 member (AtSK2-1) by mutation. In the present work, a study was undertaken to elucidate the function of AtSK3-2. We have generated mutated versions of the A. thaliana Shaggy-like kinase 3-2 (AtSK3-2), in which Lys(167) and Arg(178), respectively homologues to Lys(85) and Arg(96) of the mammal GSK3beta, were modified into Ala by site-directed mutagenesis. In vitro kinase activity assays of the mutated recombinant protein AtSK3-2-R178A showed that the "primed activity" of the mutated kinase was reduced by 90% while the "non-primed" activity was only 20% reduced compared to the wild-type protein kinase. However, the mutant protein AtSK3-2-K167A showed no activity. Arabidopsis transgenic lines over-expressing AtSK3-2-R178A displayed smaller floral organs, namely pedicels, sepals and petals. Conversely, over-expression of both the wild-type AtSK3-2 protein and the AtSK3-2-K167A mutated version, displayed no altered morphogenesis. Scanning electron microscopic analyses of the AtSK3-2-R178A transgenic plants clearly showed a reduced cell size in flower organs, in which quantitative RT-PCR expression analyses of cell wall expansion enzymes showed reduced transcript levels of three xyloglucan endotransglycosylases (XET), namely XTH22 (TCH4), XTH23 (XTR6) and XTH30 (XTR4). Our data show that AtSK3-2 plays an important role in the control of cell elongation in flower development.

Glycogen synthase kinase 3beta as a target for the therapy of shock and inflammation

After the discovery that glycogen synthase kinase (GSK) 3beta plays a fundamental role in the regulation of the activity of nuclear factor kappaB, a number of studies have investigated the effects of this protein kinase in the regulation of the inflammatory process. The GSK-3beta inhibition, using genetically modified cells and chemically different pharmacological inhibitors, affects the regulation of various inflammatory mediators in vitro and in vivo. Insulin, an endogenous inhibitor of GSK-3 in the pathway leading to the regulation of glycogen synthase activity, has recently been clinically used in the therapy for septic shock. The beneficial anti-inflammatory effects of insulin in preclinical and clinical studies could possibly be due, at least in part, to the inhibition of GSK-3 and not directly correlated to the regulation of blood glucose. We describe the latest studies describing the effects of GSK-3 inhibition as potential target of the therapy for diseases associated with inflammation, ischemia/reperfusion, and shock.

The maternally localized RNA fatvg is required for cortical rotation and germ cell formation

Fatvg is a localized maternal transcript that translocates to the vegetal cortex of Xenopus laevis oocytes through both the METRO and Late RNA localization pathways. It is a member of a gene family that functions in vesicular trafficking. Depletion of the maternal store of fatvg mRNA results in a dual phenotype in which embryos are ventralized and also lack primordial germ cells. This complex fatvg loss of function phenotype is the result of stabilization of the dorsalizing factor beta-catenin at the vegetal pole and the inability of the germ cell determinants to move to their proper locations. This is coincident with the inhibition of cortical rotation and the abnormal aggregation of the germ plasm. Fatvg protein is located at the periphery of vesicles in the oocyte and embryo, supporting its proposed role in vesicular trafficking in the embryo. These results point to a common fundamental mechanism that is regulated by fatvg through which germ cell determinants and dorsalizing factors segregate during early development.

Peptides targeting protein kinases: strategies and implications

Protein kinases are important key regulators in most, if not all, biological processes and are linked with many human diseases. Protein kinases thus became attractive targets for drug design. Intracellularly active peptides that selectively interfere with kinase function and or kinase-mediated signaling pathways are potential drug compounds with therapeutic implications.

beta-catenin destruction complex: insights and questions from a structural perspective

At the heart of the canonical Wnt signaling pathway is the beta-catenin destruction complex, which functions in the absence of Wnt signaling to keep the cytosolic and nuclear levels of beta-catenin very low by promoting the phosphorylation and ubiquitination of beta-catenin. Structural studies, combined with other experimental approaches, have begun to provide important insights into the mechanism of the destruction complex. We suggest a working model for the destruction complex based on the existing structural and experimental data, and focus on the questions that this model and other studies have raised about the function of the complex in both the normal and Wnt-inhibited states.