Epidermal Growth Factor Receptor Peptide (985-996)

EGFR (epidermal growth factor receptor) exists on the cell surface and is activated by the binding of its specific ligands, including epidermal growth factor and transforming growth factor α. EGFR dimerization stimulates its intrinsic intracellular protein-tyrosine kinase activity. As a result, autophosphorylation of several tyrosine (Y) residues on the C-terminal domain of EGFR occurs. These include Y992, Y1045, Y1068, Y1148 and Y1173. This autophosphorylation elicits downstream activation and signaling by several other proteins that associate with the phosphorylated tyrosines through their own phosphotyrosine-binding SH2 domains. These downstream signaling proteins initiate several signal transduction cascades, principally the MAPK, Akt and JNK pathways, which lead to DNA synthesis and cell proliferation. Such proteins modulate phenotypes such as cell migration, adhesion, and proliferation. Activation of the receptor is important for the innate immune response in human skin.

Many therapeutic approaches are aimed at EGFR. The monoclonal antibodies block the extracellular ligand binding domain. With the binding site blocked, signal molecules can no longer attach and activate the tyrosine kinase. Another therapeutic method involves using small molecules to inhibit the EGFR tyrosine kinase on the cytoplasmic side of the receptor. Without kinase activity, EGFR is unable to activate itself, which is a prerequisite for the binding of downstream adaptor proteins. Ostensibly by halting the signaling cascade in cells that rely on this pathway for growth, tumor proliferation and migration is diminished.

Ref:

1. Yan. L, Beckman RA (October 2005). "Pharmacogenetics and pharmacogenomics in oncology therapeutic antibody development". BioTechniques 39 (4): 565–8.

2. Yosef Yarden and Joseph Schlessinger (1987). "Epidermal Growth-Factor Induces Rapid, Reversible Aggregation of the Purified Epidermal Growth-Factor Receptor". Biochemistry 26 (5): 1443–1451.

3. Downward J, Parker P, Waterfield MD (1984). "Autophosphorylation sites on the epidermal growth factor receptor". Nature 311 (5985): 483–5.

4. Oda K, Matsuoka Y, Funahashi A, Kitano H (2005). "A comprehensive pathway map of epidermal growth factor receptor signaling". Mol. Syst. Biol. 1 (1): 2005.0010.

5. David K. Moscatello2, Marina Holgado-Madruga2. "Frequent Expression of a Mutant Epidermal Growth Factor.  Receptor in Multiple Human Tumors".  Cancer Res December 1, 1995 55; 5536

The juxtamembrane, cytosolic region of the epidermal growth factor receptor is involved in association with alpha-subunit of Gs.[Pubmed:9038141]

J Biol Chem. 1997 Feb 28;272(9):5413-20.

Previously, we have demonstrated that epidermal growth factor (EGF) can stimulate adenylyl cyclase activity via activation of Gs in the heart. Moreover, we have recently shown that Gsalpha is phosphorylated by the EGF receptor protein tyrosine kinase and that the juxtamembrane region of the EGF receptor can stimulate Gs directly. Therefore, employing isolated cardiac membranes, the two-hybrid assay, and in vitro association studies with purified EGF receptor and Gsalpha we have investigated Gsalpha complex formation with the EGF receptor and elucidated the region in the receptor involved in this interaction. In isolated cardiac membranes, immunoprecipitation of EGF receptor was accompanied by co-immunoprecipitation of Gsalpha. In the yeast two-hybrid assay, the cytosolic domain of the EGF receptor and the N-terminal 64 amino acids of this region (Met644-Trp707) associated with Gsalpha. However, interactions of these regions of the EGF receptor with constitutively active Gsalpha were diminished in the two-hybrid assay. Employing purified proteins, our studies demonstrate that the EGF receptor, directly and stoichiometrically, associates with Gsalpha (1 mol of Gsalpha/mol of EGF receptor). This association was not altered in the presence or absence of ATP and therefore, was independent of tyrosine phosphorylation of either of the proteins. Peptides corresponding to the juxtamembrane region of the receptor decreased association of the EGF receptor with Gsalpha. However, neither the C-terminally truncated EGF receptor (Delta1022-1186) nor a peptide corresponding to residues 985-996 of the receptor altered association with Gsalpha, thus indicating the selectivity of the G protein interaction with the juxtamembrane region. Interestingly, peptides corresponding to N and C termini of Gsalpha did not alter the association of Gsalpha with the EGF receptor. Consistent with the findings from the two-hybrid assay where constitutively active Gsalpha poorly associated with the EGF receptor, in vitro experiments with purified proteins also demonstrated that activation of Gsalpha by guanosine 5'-3-O-(thio)triphosphate decreased the association of G protein with the EGF receptor. Thus we conclude that the juxtamembrane region of the EGF receptor, directly and stoichiometrically, associates with Gsalpha and that upon activation of Gsalpha this association is decreased.