Regulation of epidermal growth factor receptor kinase activity by polyions.
We investigated polyionic agents with regard to their effects as modulators of epidermal growth factor receptor (EGF-R) kinase activity. Many synthetic polypeptides containing glutamine as well as casein were phosphorylated, while polycationic compounds with tyrosine residues were not phosphorylatable and thus inhibited the EGF-R activity. Polyarginine, protamine sulfate, spermidine, heparin, and poly-L-lysine with a chain length of < 20.5 kDa triggered the phosphorylation of poly(Tyr1, Glu4). On the other hand, dextran sulfate and poly-L-lysine with chain lengths of > 20.5 kDa inhibited the EGF-R kinase activity. Alteration of the state of autophosphorylation of EGF-R is not in agreement with the activity of EGF-R kinase towards poly(Tyr1, Glu4). Casein and histone H1 both increased the autophosphorylation of EGF-R in a concentration-dependent manner, but only casein increased the activity of the enzyme towards an exogenous substrate. The compounds enhancing the EGF-R activity, such as poly-L-lysine, protamine, and poly-L-arginine, down-modulated the autophosphorylation reaction. We discuss the consequences of these effects as to in vivo conditions.
Institut für Medizinische Mikrobiologie und Immunologie, Universitaetsklinik Eppendorf, Federal Republic of Germany.
P
P
Borowski
S
S
Medem
R
R
Laufs
W
W
Weber
D000595:Amino Acid Sequence; D066246:ErbB Receptors / Q000378:metabolism*; D007477:Ions; D007700:Kinetics; D008969:Molecular Sequence Data; D010766:Phosphorylation; D013379:Substrate Specificity
D007477:Ions; D066246:ErbB Receptors