Reception and Transmission of Multiple Signals by Ras Protein

The path of signal transduction leads from the activated Raf kinase to the protein kinase cascade of the MAP kinase pathway (Chapter 10). 

This well characterized pathway of Ras signal transmission was the first to be discovered (see above) and involves adaptor proteins (Grb2, She) and GEFs (e.g. mSos). 

Stimulation of N-methyl-D-aspartate (NMDA) receptors (see Chapter 16) in the nervous system is linked to activation of NO synthase and creation of an intracellular NO signal (Yun et al., 1998). NO can directly activate Ras protein redox modification of Ras protein is assumed to take place in this process. 

There is evidence that signals starting from G-protein-coupled receptors run into the Ras switch station (Van Biesen et al., 1995). Pv-subunits of G-proteins are under discussion as the link between G-protein-coupled signal transduction and the Ras pathway these subunits could influence the activity of Ras protein and the subsequent MAP kinase pathway by a presently unknown mechanism. 

In addition to Raf kinase, a number of other signal proteins have been identified to which an effector function in Ras signal conduction has been attributed (review 1995 Pawson, 1995 White et al., 1995, Katz and McCormick, 1997, Vojtek and Der, 1998). These effector candidates include a very diverse collection of structmally and functionally distinct proteins, which all show preferential affinity for the active Ras form. The 

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