Figure 7.

Schematic diagram of Sec61-dependent trafficking of EGF receptor from the cell surface to the nucleus. Steps 1–4 represent the well described binding of EGF to its receptor, dimerization activation, translocation to cell surface coated pits, and internalization. Endosomal sorting directly to the ER or indirectly via the Golgi is presented in steps 5–7. ER association of the receptor with Sec61 (step 8) leads to retrotranslocation to the cytosol (step 9) and association with HSP70 (step 10). Interaction with importin β (Lo et al., 2006) precedes nuclear localization (step 11) and interaction with target promoters, such as cyclin D (step 12). Because Lin et al. (2001) have reported the presence of EGF in the nucleus, the intact ligand receptor:complex is depicted.