Signal cascades hormones

Growth factor and hormone signalling cascades link mTORCl dysregulation to cancer and Hamartoma syndromes. 

The transcription factors AP-1 and NFkB are at the end of a signal cascade activated by growth factors (see chapters 9,10,11), The ability of steroid hormone receptors in certain situations to nullify the effect other transcription factors demonstrates that two different signaling pathways can converge at the level of transcription. 

Figure 11-13 (A) A simplified version of the mitogen-activated kinase (MAPK) signaling cascade. At left is shown a hormone receptor, e.g., that for the epidermal growth factor (EGF). The receptor tyrosine kinase undergoes autophosphorylation on numerous tyrosines. The resulting phosphotyrosyl (Y-P) groups bind to SH2 domains of adapters such as Grb2 and She.

Isoprenoids are one of the largest classes of natural products that comprise at least 35,000 reported members (48). Many of these compounds play crucial roles in human metabolism as hormones, vitamins (vitamins A, D, E and K), quinine-type cofactors of respiratory chain enzymes (ubiquinone), membrane constituents, and functionally important side chains of signal cascade proteins (Fig. 11). Chlorophyll (17, Fig. 2) and heme a (18) have isoprenoid side chains. 

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