Signal transduction cross talk

Two tyrosine kinase-based mechanisms have been described the IR and the JAK/ STAT cascades. It should not be assumed that these are either/or mechanisms as there may be parallel transduction (cross-talk) between the two pathways. For example, leptin, an appetite suppressor described more fully in Chapter 9 is a cytokine-like peptide produced by adipose tissue, which signals in the hypothalamus of the brain via JAK2/STAT3, but also influences the IRS/PI3K pathway. 

This linear scheme of signal transduction (Fig. 12) from hypothetical membrane receptors to [Ca " ] and IP3 increases, calcium-calmodulin interaction, kinases activation and gene transcription is clearly an oversimplification of the reality several receptors must exist that are connected to different transduction cascades that activate a series of defense genes. Cross-talking between the pathways further complicates the picture. However, this represents a starting model on which to elaborate more refined hypotheses. 

A significant contribution was made to the science of plant cell culture production of paditaxel. Methyl jasmonate solutions that had been pipetted into cell suspension cultures caused transient increases in paditaxel production [27]. This was the first report of modeling that indicated ethylene and methyl jasmonate may participate in cross-talk signal transduction in plants. Other papers have subsequently appeared which demonstrate enhancement of paditaxel productivity by the application of methyl jasmonate to several Taxus species [87,88]. 

On the other hand, the impact of ethylene in the composition of headspace gases fed to Taxus sp. cultures was very evident. The positive involvement of ethylene was also noted when cultures were elicited with both dissolved and volatilized methyl jasmonate and with chitin- and chitosan-derived oligosaccharides. The effect of the latter compounds on biosynthesis of ethylene by the plant cell cultures brings us to a better understanding of the interdependence of elicitor and hormone concentrations and of cross-talk signal transduction in plants. 

Fig. 2 Outline of signal transduction pathways for stress kinases, JNKs, and for Map kinases, p38 and ERKl/2. Shown is the cross-talk between the various pathways. Map kinases MEKKl/2/3 activate the MAP kinases MKK4 (JNKKl) and MKK7 (JNKK2). MKK4/7 can also be activated by the Map kinases TAKl and Askl, which can also activate MKK3/6 of the p38 s pathway. Activation of Rap-GTP is capable of activating the p38 and ERKl/2 pathways. As indicated, ceramide can activate the p38 pathway, and, also, has been suggested to play a role in activation of the ERKl/2 pathway...

The stimulus-response mechanisms in platelets are complex and involve foe variety of substances that stimulate different effector-systems in foe platelets, foe autocrine stimulation in response to platelet activation by a primary agonist as well as by cross-tall between signal transduction pathways. Cross-talk can happen at several stages of foe signal transduction pathway. The most studied are foe competition between stimulatory and inhibitory pathways, and examples are foe action of thrombin via G and PGIj via G,... 

In summary, the participation of the GPI/IPG system in cell activation by insulin is supported by the following evidences First, insulin induces tlie hydrolysis of GPI and the release of IPG second, impaired GPI metabolism or treatment with anti-IPG antibodies neutralize insulin actions and, third, natural and synthetic IPG have insulin-like activity. Several other diffusible factors activate GPI hydrolysis with the concomitant release of IPG. The next question is at which points IPG second messengers cross talk with the established signal transduction pathways. 

Adhesion molecules. Molecules, belonging mainly to the immunoglobulin or integrin superfamily of molecules (e.g. LFA-1, ICAM-1), expressed on the membrane of various cells of the immune system. Interactions with each other as receptors and corresponding ligands facilitate cooperation (cross-talk) of cells, signal transduction, and information transfer between cells. 

Evidence for Cross-Talk Between CXCR4 and IGF-1 R Signal Transduction in Breast Cancer Metastasis... 

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