James R. Woodgett

Bio: James R. Woodgett is an academic researcher from Lunenfeld-Tanenbaum Research Institute. The author has contributed to research in topics: GSK-3 & Protein kinase A. The author has an hindex of 113, co-authored 319 publications receiving 51191 citations. Previous affiliations of James R. Woodgett include Asahikawa Medical College & Texas A&M University.

The ground state of embryonic stem cell self-renewal

Abstract: In the three decades since pluripotent mouse embryonic stem (ES) cells were first described they have been derived and maintained by using various empirical combinations of feeder cells, conditioned media, cytokines, growth factors, hormones, fetal calf serum, and serum extracts. Consequently ES-cell self-renewal is generally considered to be dependent on multifactorial stimulation of dedicated transcriptional circuitries, pre-eminent among which is the activation of STAT3 by cytokines (ref. 8). Here we show, however, that extrinsic stimuli are dispensable for the derivation, propagation and pluripotency of ES cells. Self-renewal is enabled by the elimination of differentiation-inducing signalling from mitogen-activated protein kinase. Additional inhibition of glycogen synthase kinase 3 consolidates biosynthetic capacity and suppresses residual differentiation. Complete bypass of cytokine signalling is confirmed by isolating ES cells genetically devoid of STAT3. These findings reveal that ES cells have an innate programme for self-replication that does not require extrinsic instruction. This property may account for their latent tumorigenicity. The delineation of minimal requirements for self-renewal now provides a defined platform for the precise description and dissection of the pluripotent state.

The stress-activated protein kinase subfamily of c-Jun kinases.

Abstract: The mitogen-activated protein (MAP) kinases Erk-1 and Erk-2 are proline-directed kinases that are themselves activated through concomitant phosphorylation of tyrosine and threonine residues. The kinase p54 (M(r) 54,000), which was first isolated from cycloheximide-treated rats, is proline-directed like Erks-1/2, and requires both Tyr and Ser/Thr phosphorylation for activity. p54 is, however, distinct from Erks-1/2 in its substrate specificity, being unable to phosphorylate pp90rsk but more active in phosphorylating the c-Jun transactivation domain. Molecular cloning of p54 reveals a unique subfamily of extracellularly regulated kinases. Although they are 40-45% identical in sequence to Erks-1/2, unlike Erks-1/2 the p54s are only poorly activated in most cells by mitogens or phorbol esters. However, p54s are the principal c-Jun N-terminal kinases activated by cellular stress and tumour necrosis factor (TNF)-alpha, hence they are designated stress-activated protein kinases, or SAPKs. SAPKs are also activated by sphingomyelinase, which elicits a subset of cellular responses to TNF-alpha (ref. 9). SAPKs therefore define a new TNF-alpha and stress-activated signalling pathway, possibly initiated by sphingomyelin-based second messengers, which regulates the activity of c-Jun.

GSK-3: tricks of the trade for a multi-tasking kinase.

Abstract: Glycogen synthase kinase 3 (GSK-3) is a multifunctional serine/threonine kinase found in all eukaryotes. The enzyme is a key regulator of numerous signalling pathways, including cellular responses to Wnt, receptor tyrosine kinases and G-protein-coupled receptors and is involved in a wide range of cellular processes, ranging from glycogen metabolism to cell cycle regulation and proliferation. GSK-3 is unusual in that it is normally active in cells and is primarily regulated through inhibition of its activity. Another peculiarity compared with other protein kinases is its preference for primed substrates, that is, substrates previously phosphorylated by another kinase. Several recent advances have improved our understanding of GSK-3 regulation in multiple pathways. These include the solution of the crystal structure of GSK-3, which has provided insight into GSK-3's penchant for primed substrates and the regulation of GSK-3 by serine phosphorylation, and findings related to the involvement of GSK-3 in the Wnt/beta-catenin and Hedgehog pathways. Finally, since increased GSK-3 activity may be linked to pathology in diseases such as Alzheimer's disease and non-insulin-dependent diabetes mellitus, several new GSK-3 inhibitors, such as the aloisines, the paullones and the maleimides, have been developed. Although they are just starting to be characterized in cell culture experiments, these new inhibitors hold promise as therapeutic agents.

Phosphorylation of c- jun mediated by MAP kinases

Abstract: THE proto-oncogene c-jun is a component of the AP-1 transcription factor family involved in the mediation of nuclear events elicited by extracellular stimuli1–3. The c-jun protein is negatively regulated by phosphorylation of residues near the carboxy terminus which are dephosphorylated in response to phorbol esters4. Here we identify two serine residues in the amino terminal Al transactivation domain which are phosphorylated in response to a variety of mitogens, phorbol esters and activated ras (ref. 5). We present evidence that mitogen-activated protein-serine (MAP) kinases (pp54 and pp42/44) specifically phosphorylate these sites and that their phosphorylation positively regulates the transacting activity of c-jun. The MAP kinase enzymes pp54 and pp42/44 are regulated by tyrosine as well as serine/threonine phosphorylation6,7. MAP kinase activation of c-jun may underlie the common stimulation of this transcription factor by mitogens, growth factors and oncogenes.

Requirement for glycogen synthase kinase-3β in cell survival and NF-κB activation

Abstract: Glycogen synthase kinase-3 (GSK-3)-α and -β are closely related protein-serine kinases, which act as inhibitory components of Wnt signalling during embryonic development and cell proliferation in adult tissues1,2. Insight into the physiological function of GSK-3 has emerged from genetic analysis in Drosophila3,4, Dictyostelium 5 and yeast6,7. Here we show that disruption of the murine GSK-3β gene results in embryonic lethality caused by severe liver degeneration during mid-gestation, a phenotype consistent with excessive tumour necrosis factor (TNF) toxicity, as observed in mice lacking genes involved in the activation of the transcription factor activation NF-κB. GSK-3β-deficient embryos were rescued by inhibition of TNF using an anti-TNF-α antibody. Fibroblasts from GSK-3β-deficient embryos were hypersensitive to TNF-α and showed reduced NF-κB function. Lithium treatment (which inhibits GSK-3; refs 8, 9) sensitized wild-type fibroblasts to TNF and inhibited transactivation of NF-κB. The early steps leading to NF-κB activation (degradation of I-κB and translocation of NF-κB to the nucleus) were unaffected by the loss of GSK-3β, indicating that NF-κB is regulated by GSK-3β at the level of the transcriptional complex. Thus, GSK-3β facilitates NF-κB function.

Defective LPS Signaling in C3H/HeJ and C57BL/10ScCr Mice: Mutations in Tlr4 Gene

Abstract: Mutations of the gene Lps selectively impede lipopolysaccharide (LPS) signal transduction in C3H/HeJ and C57BL/10ScCr mice, rendering them resistant to endotoxin yet highly susceptible to Gram-negative infection. The codominant Lpsd allele of C3H/HeJ mice was shown to correspond to a missense mutation in the third exon of the Toll-like receptor-4 gene (Tlr4), predicted to replace proline with histidine at position 712 of the polypeptide chain. C57BL/10ScCr mice are homozygous for a null mutation of Tlr4. Thus, the mammalian Tlr4 protein has been adapted primarily to subserve the recognition of LPS and presumably transduces the LPS signal across the plasma membrane. Destructive mutations of Tlr4 predispose to the development of Gram-negative sepsis, leaving most aspects of immune function intact.

Death receptors: signaling and modulation

Abstract: Apoptosis is a cell suicide mechanism that enables metazoans to control cell number in tissues and to eliminate individual cells that threaten the animal's survival. Certain cells have unique sensors, termed death receptors, on their surface. Death receptors detect the presence of extracellular death signals and, in response, they rapidly ignite the cell's intrinsic apoptosis machinery.

The phosphatidylinositol 3-Kinase AKT pathway in human cancer.

Abstract: One signal that is overactivated in a wide range of tumour types is the production of a phospholipid, phosphatidylinositol (3,4,5) trisphosphate, by phosphatidylinositol 3-kinase (PI3K) This lipid and the protein kinase that is activated by it — AKT — trigger a cascade of responses, from cell growth and proliferation to survival and motility, that drive tumour progression Small-molecule therapeutics that block PI3K signalling might deal a severe blow to cancer cells by blocking many aspects of the tumour-cell phenotype