The integration of multiple transmembrane signals is especially important during
development and maintenance of the nervous system, communication between cells of the
immune system, evolution of transformed cells, and metabolic control (H unter 1997).
Tyrosine phosphorylation plays a key role in many of these processes by directly controlling
the activity of receptors or enzymes at early steps in signaling cascades, or by the assembly
of multicomponent signaling complexes around activated receptors or their cellular …

New molecules discovered during the past ten years have created a rational framework to
understand signalling transduction by a broad range of growth factors and cytokines,
including insulin. Insulin action is initiated through the insulin receptor, a transmembrane
glycoprotein with intrinsic protein tyrosine kinase activity. The tyrosine kinase mediates the
insulin response through tyrosine phosphorylation of various cellular substrates, in particular
the IRS-proteins. During insulin-stimulated tyrosine phosphorylation, the IRS-proteins …