More than scratching the surface: Mitogen receptors as transcription factors?

Receptor tyrosine kinases (RTK) are a large family of transmembrane receptors that stimulate several responses including differentiation, proliferation and generation of extracellular matrix. To initiate these responses, RTK activate a variety of signaling pathways at the intracellular cell surface upon binding of ligand. Recent studies demonstrate that, in addition to stimulating effectors at the plasma membrane, the C-terminal domain of the epidermal growth factor receptor and ErbB-4 receptor translocate into the nucleus. Interestingly, localization to the nucleus might be crucial to the growth response of these receptors.