Receptor Specific Pathways

Signalling specificity can occur at the level of the receptor. In this model, the outcome of receptor activation is modulated by different intracellular components. For example, two types of cell may express the same receptor, but have distinct signalling

Fig. 3 MAPK specificity. Diverse extracellular inputs stimulate the Ras/Raf/MEK/ERK cascade, and each can elicit a distinct cellular outcome. Although models have been proposed to explain how a specific signalling cue produces a specific response, this aspect of MAPK function is poorly understood. GPCR, G-protein coupled receptor

Fig. 3 MAPK specificity. Diverse extracellular inputs stimulate the Ras/Raf/MEK/ERK cascade, and each can elicit a distinct cellular outcome. Although models have been proposed to explain how a specific signalling cue produces a specific response, this aspect of MAPK function is poorly understood. GPCR, G-protein coupled receptor molecules. Therefore, a single kind of receptor would activate distinct signalling cascades in separate tissues. Consequently, the physiological outcome of receptor stimulation will be different. While conceptually appealing, there is limited evidence to support this theory. Some adaptor proteins, such as the Rac1 GEF, VAV (Adams et al. 1992) that are associated with receptors, are tissue-specific. In addition, the receptor tyrosine kinase LET-23 controls development of five different tissues in C. elegans, but the MAPK pathway participates in only four of these. Therefore, although LET-23 activates MAPK in some tissues, it also activates alternative signalling cascades in others (Tan and Kim 1999). Consequently, a degree of specificity for MAPK signalling can occur at the level of the receptor. How important receptor specificity is for other activators of MAPKs is unknown.

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