The activating role of phospho-(Tyr)-calmodulin on the epidermal growth factor receptor.
Biochem J
; 472(2): 195-204, 2015 Dec 01.
Article
en En
| MEDLINE
| ID: mdl-26399481
ABSTRACT
The activity of calmodulin (CaM) is modulated not only by oscillations in the cytosolic concentration of free Ca(2+), but also by its phosphorylation status. In the present study, the role of tyrosine-phosphorylated CaM [P-(Tyr)-CaM] on the regulation of the epidermal growth factor receptor (EGFR) has been examined using in vitro assay systems. We show that phosphorylation of CaM by rat liver solubilized EGFR leads to a dramatic increase in the subsequent phosphorylation of poly-L-(GluTyr) (PGT) by the receptor in the presence of ligand, both in the absence and in the presence of Ca(2+). This occurred in contrast with assays where P-(Tyr)-CaM accumulation was prevented by the presence of Ca(2+), absence of a basic cofactor required for CaM phosphorylation and/or absence of CaM itself. Moreover, an antibody against CaM, which inhibits its phosphorylation, prevented the extra ligand-dependent EGFR activation. Addition of purified P-(Tyr)-CaM, phosphorylated by recombinant c-Src (cellular sarcoma kinase) and free of non-phosphorylated CaM, obtained by affinity-chromatography using an immobilized anti-phospho-(Tyr)-antibody, also increased the ligand-dependent tyrosine kinase activity of the isolated EGFR toward PGT. Also a CaM(Y99D/Y138D) mutant mimicked the effect of P-(Tyr)-CaM on ligand-dependent EGFR activation. Finally, we demonstrate that P-(Tyr)-CaM binds to the same site ((645)R-R-R-H-I-V-R-K-R-T-L-R-R-L-L-Q(660)) as non-phosphorylated CaM, located at the cytosolic juxtamembrane region of the EGFR. These results show that P-(Tyr)-CaM is an activator of the EGFR and suggest that it could contribute to the CaM-mediated ligand-dependent activation of the receptor that we previously reported in living cells.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Tirosina
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Calmodulina
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Membrana Celular
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Procesamiento Proteico-Postraduccional
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Proteínas Proto-Oncogénicas pp60(c-src)
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Receptores ErbB
Límite:
Animals
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Humans
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Male
Idioma:
En
Revista:
Biochem J
Año:
2015
Tipo del documento:
Article
País de afiliación:
España