Heterodimerization of the epidermal-growth-factor (EGF) receptor and ErbB2 and the affinity of EGF binding are regulated by different mechanisms.
Biochem J
; 356(Pt 1): 87-96, 2001 May 15.
Article
in En
| MEDLINE
| ID: mdl-11336639
ABSTRACT
When clathrin-dependent endocytosis is inhibited in HeLa cells by overexpression of a K44A (Lys(44)-->Ala) mutant of the GTPase dynamin, high-affinity binding of epidermal growth factor (EGF) to the EGF receptor (EGFR) is disrupted [Ringerike, Stang, Johannessen, Sandnes, Levy and Madshus (1998) J. Biol. Chem. 273, 16639-16642]. We now report that the effect of [K44A]dynamin on EGF binding was counteracted by incubation with the non-specific kinase inhibitor staurosporine (SSP), implying that a protein kinase is responsible for disrupted high-affinity binding of EGF upon overexpression of [K44A]dynamin. The effect of [K44A]dynamin on EGF binding was not due to altered phosphorylation of the EGFR, suggesting that the activated kinase is responsible for phosphorylation of a substrate other than EGFR. The number of EGFR molecules was increased in cells overexpressing [K44A]dynamin, while the number of proto-oncoprotein ErbB2 molecules was unaltered. EGF-induced receptor dimerization was not influenced by overexpression of [K44A]dynamin. ErbB2-EGFR heterodimer formation was found to be ligand-independent, and the number of heterodimers was not altered by overexpression of [K44A]dynamin. Neither SSP nor the phorbol ester PMA, which disrupts high-affinity EGF-EGFR interaction, had any effect on the EGFR homo- or hetero-dimerization. Furthermore, the EGF-induced tyrosine phosphorylation of ErbB2 was not affected by overexpression of [K44A]dynamin, implying that EGFR-ErbB2 dimers were fully functional. Our results strongly suggest that high-affinity binding of EGF and EGFR-ErbB2 heterodimerization are regulated by different mechanisms.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Receptor, ErbB-2
/
Epidermal Growth Factor
/
ErbB Receptors
Limits:
Humans
Language:
En
Journal:
Biochem J
Year:
2001
Document type:
Article
Affiliation country:
Norway