Signal transduction

About: Signal transduction is a research topic. Over the lifetime, 122628 publications have been published within this topic receiving 8209258 citations. The topic is also known as: GO:0007165.

Inhibition of the EGF-activated MAP kinase signaling pathway by adenosine 3',5'-monophosphate

Abstract: Mitogen-activated protein (MAP) kinases p42mapk and p44mapk are activated in cells stimulated with epidermal growth factor (EGF) and other agents. A principal pathway for MAP kinase (MAPK) activation by EGF consists of sequential activations of the guanine nucleotide exchange factor Sos, the guanosine triphosphate binding protein Ras, and the protein kinases Raf-1, MAPK kinase (MKK), and MAPK. Because adenosine 3',5'-monophosphate (cAMP) does not activate MAPK and has some opposing physiologic effects, the effect of increasing intracellular concentrations of cAMP with forskolin and 3-isobutyl-1-methylxanthine on the EGF-stimulated MAPK pathway was studied. Increased concentrations of cAMP blocked activation of Raf-1, MKK, and MAPK in Rat1hER fibroblasts, accompanied by a threefold increase in Raf-1 phosphorylation on serine 43 in the regulatory domain. Phosphorylation of Raf-1 in vitro and in vivo reduces the apparent affinity with which it binds to Ras and may contribute to the blockade by cAMP.

PAMPs and DAMPs: Signal 0s that Spur Autophagy and Immunity

Abstract: Pathogen-associated molecular pattern molecules (PAMPs) are derived from microorganisms and recognized by pattern recognition receptor (PRR)-bearing cells of the innate immune system as well as many epithelial cells. In contrast, damage-associated molecular pattern molecules (DAMPs) are cell-derived and initiate and perpetuate immunity in response to trauma, ischemia, and tissue damage, either in the absence or presence of pathogenic infection. Most PAMPs and DAMPs serve as so-called 'Signal 0s' that bind specific receptors [Toll-like receptors, NOD-like receptors, RIG-I-like receptors, AIM2-like receptors, and the receptor for advanced glycation end products (RAGE)] to promote autophagy. Autophagy, a conserved lysosomal degradation pathway, is a cell survival mechanism invoked in response to environmental and cellular stress. Autophagy is inferred to have been present in the last common eukaryotic ancestor and only to have been lost by some obligatory intracellular parasites. As such, autophagy represents a unifying biology, subserving survival and the earliest host defense strategies, predating apoptosis, within eukaryotes. Here, we review recent advances in our understanding of autophagic molecular mechanisms and functions in emergent immunity.

Growth factors in the extracellular matrix.

Abstract: Much recent research has focused on the study of the expression of growth factor genes and on the identification of growth factor signaling mechanisms inside cells. However, growth factor signaling can also be regulated outside of cells by extracellular matrix proteins and proteolytic enzymes. The ability of extracellular proteins to process complex information in the absence of new protein synthesis is illustrated in blood clotting and complement pathways. An increasing number of growth factors, including IGFs, FGFs, TGF-beta's, and HGF, have been found to associate with the extracellular matrix proteins or with heparan sulfate. Rapid and localized changes in the activity of these factors can be induced by release from matrix storage and/or by activation of latent forms. These growth factors, in turn, control cell proliferation, differentiation, and synthesis and remodeling of the extracellular matrix. It is therefore likely that much of the information processing necessary for construction of complex multicellular organisms occurs in the extracellular environment. This suggests that extracellular matrix plays a major role in the control of growth factor signaling.

Coactivation of Receptor Tyrosine Kinases Affects the Response of Tumor Cells to Targeted Therapies

Abstract: Targeted therapies that inhibit receptor tyrosine kinases (RTKs) and the downstream phosphatidylinositol 3-kinase (PI3K) signaling pathway have shown promising anticancer activity, but their efficacy in the brain tumor glioblastoma multiforme (GBM) and other solid tumors has been modest. We hypothesized that multiple RTKs are coactivated in these tumors and that redundant inputs drive and maintain downstream signaling, thereby limiting the efficacy of therapies targeting single RTKs. Tumor cell lines, xenotransplants, and primary tumors indeed show multiple concomitantly activated RTKs. Combinations of RTK inhibitors and/or RNA interference, but not single agents, decreased signaling, cell survival, and anchorage-independent growth even in glioma cells deficient in PTEN, a frequently inactivated inhibitor of PI3K. Thus, effective GBM therapy may require combined regimens targeting multiple RTKs.