The innate immune system in drosophila and mammals senses the invasion of microorganisms using the family of Toll receptors, stimulation of which initiates a range of host defense mechanisms. In drosophila antimicrobial responses rely on two signaling pathways: the Toll pathway and the IMD pathway. In mammals there are at least 10 members of the Toll-like receptor (TLR) family that recognize specific components conserved among microorganisms. Activation of the TLRs leads not only to the induction of inflammatory responses but also to the development of antigen-specific adaptive immunity. The TLR-induced inflammatory response is dependent on a common signaling pathway that is mediated by the adaptor molecule MyD88. However, there is evidence for additional pathways that mediate TLR ligand-specific biological responses.

Toll-like receptors.

https://archive-ouverte.unige.ch/unige:18229/ATTACHMENT01

TOR signaling in growth and metabolism.

The specificities of 28 commercially available compounds reported to be relatively selective inhibitors of particular serine/threonine-specific protein kinases have been examined against a large panel of protein kinases. The compounds KT 5720, Rottlerin and quercetin were found to inhibit many protein kinases, sometimes much more potently than their presumed targets, and conclusions drawn from their use in cell-based experiments are likely to be erroneous. Ro 318220 and related bisindoylmaleimides, as well as H89, HA1077 and Y 27632, were more selective inhibitors, but still inhibited two or more protein kinases with similar potency. LY 294002 was found to inhibit casein kinase-2 with similar potency to phosphoinositide (phosphatidylinositol) 3-kinase. The compounds with the most impressive selectivity profiles were KN62, PD 98059, U0126, PD 184352, rapamycin, wortmannin, SB 203580 and SB 202190. U0126 and PD 184352, like PD 98059, were found to block the mitogen-activated protein kinase (MAPK) cascade in cell-based assays by preventing the activation of MAPK kinase (MKK1), and not by inhibiting MKK1 activity directly. Apart from rapamycin and PD 184352, even the most selective inhibitors affected at least one additional protein kinase. Our results demonstrate that the specificities of protein kinase inhibitors cannot be assessed simply by studying their effect on kinases that are closely related in primary structure. We propose guidelines for the use of protein kinase inhibitors in cell-based assays.

/pdf/specificity-and-mechanism-of-action-of-some-commonly-used-2r15uc4rwj.pdf

Specificity and mechanism of action of some commonly used protein kinase inhibitors

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.

/pdf/the-ground-state-of-embryonic-stem-cell-self-renewal-41xqrmi7s8.pdf

The ground state of embryonic stem cell self-renewal

Mitogen-activated protein kinase (MAPK) cascades are key signaling pathways involved in the regulation of normal cell proliferation, survival and differentiation. Aberrant regulation of MAPK cascades contribute to cancer and other human diseases. In particular, the extracellular signal-regulated kinase (ERK) MAPK pathway has been the subject of intense research scrutiny leading to the development of pharmacologic inhibitors for the treatment of cancer. ERK is a downstream component of an evolutionarily conserved signaling module that is activated by the Raf serine/threonine kinases. Raf activates the MAPK/ERK kinase (MEK)1/2 dual-specificity protein kinases, which then activate ERK1/2. The mutational activation of Raf in human cancers supports the important role of this pathway in human oncogenesis. Additionally, the Raf-MEK-ERK pathway is a key downstream effector of the Ras small GTPase, the most frequently mutated oncogene in human cancers. Finally, Ras is a key downstream effector of the epidermal growth factor receptor (EGFR), which is mutationally activated and/or overexpressed in a wide variety of human cancers. ERK activation also promotes upregulated expression of EGFR ligands, promoting an autocrine growth loop critical for tumor growth. Thus, the EGFR-Ras-Raf-MEK-ERK signaling network has been the subject of intense research and pharmaceutical scrutiny to identify novel target-based approaches for cancer treatment. In this review, we summarize the current status of the different approaches and targets that are under evaluation and development for the therapeutic intervention of this key signaling pathway in human disease.

Targeting the Raf-MEK-ERK mitogen-activated protein kinase cascade for the treatment of cancer.

LPS stimulation of RAW264 macrophages triggered the activation of mitogen- and stress-activated protein kinases-1 and -2 (MSK1, MSK2) and their putative substrates, the transcription factors cyclic AMP response element-binding protein (CREB) and activating transcription factor-1 (ATF1). The activation of MSK1/MSK2 was prevented by preincubating the cells with a combination of two drugs that suppress activation of the classical mitogen-activated protein kinase cascade and stress-activated protein kinase/p38, respectively, but inhibition was only partial in the presence of either inhibitor. The LPS-stimulated activation of CREB and ATF1, the transcription of the cyclooxygenase-2 (COX-2) and IL-1 beta genes (the promoters of which contain a cyclic AMP response element), and the induction of the COX-2 protein were prevented by the same drug combination, as well as by Ro 318220 or H89, potent inhibitors of MSK1/MSK2. Two other transcription factors, C/EBP beta and NF-kappa B, have been implicated in the transcription of the COX-2 gene. However, PD 98059 and/or SB 203580 did not prevent the LPS-induced increase in the level of the transcription factor C/EBP beta, and none of the four inhibitors used in this study prevented the activation of NF-kappa B. Our results demonstrate that two different mitogen-activated protein kinase cascades are rate limiting for the LPS-induced activation of CREB/ATF1 and the transcription of the COX-2 and IL-1 beta genes. They also suggest that MSK1 and MSK2 may play a role in these processes and hence are potential targets for the development of novel antiinflammatory drugs.

Role of Mitogen-Activated Protein Kinase Cascades in Mediating Lipopolysaccharide-Stimulated Induction of Cyclooxygenase-2 and IL-1β in RAW264 Macrophages

The Induction of Cyclooxygenase-2 mRNA in Macrophages Is Biphasic and Requires both CCAAT Enhancer-binding protein β (C/EBPβ) and C/EBPδ Transcription Factors

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/S0014-5793%2898%2900578-X

Matilde Caivano

Papers

Specificity and mechanism of action of some commonly used protein kinase inhibitors

Role of Mitogen-Activated Protein Kinase Cascades in Mediating Lipopolysaccharide-Stimulated Induction of Cyclooxygenase-2 and IL-1β in RAW264 Macrophages

The Induction of Cyclooxygenase-2 mRNA in Macrophages Is Biphasic and Requires both CCAAT Enhancer-binding protein β (C/EBPβ) and C/EBPδ Transcription Factors

Role of MAP kinase cascades in inducing arginine transporters and nitric oxide synthetase in RAW264 macrophages

The Transcription Factor C/EBPβ Is Essential for Inducible Expression of the cox-2 Gene in Macrophages but Not in Fibroblasts