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.

http://science.sciencemag.org/content/sci/282/5396/2085.full.pdf

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

Defective LPS signaling in C3 H/HeJ and C57 BL/10 ScCr mice: Mutations in Tlr4 Gene

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.

/pdf/death-receptors-signaling-and-modulation-yjd5e96rtz.pdf

Death receptors: signaling and modulation

Akt Phosphorylation of BAD Couples Survival Signals to the Cell-Intrinsic Death Machinery

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

The phosphatidylinositol 3-Kinase AKT pathway in human cancer.

Publisher Summary The mitogen-activated protein kinase (MAPK) superfamily plays an important role in transducing signals from the cell surface to the nucleus, effecting both the cell's ability to cope with outside changes as well as cellular coordination in the case of multicellular organisms. The term “MAPK” is most widely used as a general denominator of this family of protein kinases. The MAPK acronym originally described the “microtubule-associated protein-2 kinase” but evolved into mitogen-activated protein kinase when it was discovered that the enzyme was induced by a variety of hormones and mitogens. Upon the molecular cloning of these enzymes, it was realized that they existed in several classes that were structurally related but distinctly regulated. MAPK is now commonly used to denote the entire class of protein-serine kinases that share the following features: the core functional unit of a MAPK module consists of a triad of three kinases that act sequentially, where MAPKs are activated via phosphorylation on both a threonine and tyrosine residue by selective upstream regulatory kinases, MAPK kinases (MAPKKs or MAP2Ks).

Chapter 13 Mitogen-activated protein kinases and stress

GSK-3b Controls Osteogenesis through Regulating Runx2

Glycogen synthase kinase-3 (GSK-3) is a ubiquitously expressed, multifunctional serine/threonine protein kinase that plays a role in a wide variety of regulatory processes and has been implicated in diabetes, cancer, neurodegenerative diseases, and inflammation. Unlike the majority of protein kinases that require induction via an extracellular stimulus, this enzyme is highly active in resting cells and is typically regulated by signal-dependent inactivation. GSK-3 is a critical component of several signal transduction pathways including those that respond to Wnt, Notch, Hedgehog, G-protein-coupled receptors and receptor-tyrosine kinase pathways. GSK-3 modulates the function of proteins involved in metabolism, transcriptional regulation, the cytoskeleton, the cell cycle, pluripotentiality, and cell fate, and, due to its role in pathophysiological conditions, is a potential therapeutic target.

Glycogen Synthase Kinase-3

Podocytes are key cells in maintaining the integrity of the glomerular filtration barrier and preventing albuminuria. Glycogen synthase kinase 3 (GSK3) is a multi-functional serine/threonine kinase existing as two distinct but related isoforms (α and β). In the podocyte it has previously been reported that inhibition of the β isoform is beneficial in attenuating a variety of glomerular disease models but loss of both isoforms is catastrophic. However, it is not known what the role of GSK3α is in these cells. We now show that GSK3α is present and dynamically modulated in podocytes. When GSK3α is transgenically knocked down specifically in the podocytes of mice it causes mild but significant albuminuria by 6-weeks of life. Its loss also does not protect in models of diabetic or Adriamycin-induced nephropathy. In vitro deletion of podocyte GSK3α causes cell death and impaired autophagic flux suggesting it is important for this key cellular process. Collectively this work shows that GSK3α is important for podocyte health and that augmenting its function may be beneficial in treating glomerular disease.

/pdf/podocyte-gsk3a-is-important-for-autophagy-and-its-loss-4ptgwxmx2i.pdf

Podocyte GSK3α is important for autophagy and its loss detrimental for glomerular function.

The present invention relates to cell death genes, which are genes required for programmed cell death; mutant organisms, in which ectopic programmed cell death occurs in embryos to a greater than normal extent and agents which alter the ability to modulate programmed cell death of cells. A mutant form of Daktl, Daktlq in a Drosophila melanogaster has been identified. Daktl and its mammalian homolog, PKB are known to protect cells from undergoing apoptosis. A genetic screen for identifying genes related to programmed cell death by their ability to interact genetically with the mutant form of Daktl is described.

James R. Woodgett

Papers

Chapter 13 Mitogen-activated protein kinases and stress

GSK-3b Controls Osteogenesis through Regulating Runx2

Glycogen Synthase Kinase-3

Podocyte GSK3α is important for autophagy and its loss detrimental for glomerular function.

Gene screening methods and related assays