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Eludir la actividad de una quinasa con un fármaco competitivo con el ATP
Feroz R Papa1, Chao Zhang, Kevan Shokat
1Department of Medicine, University of California, San Francisco, CA 94143-2200, USA. frpapa@medicine.ucsf.edu
Science (New York, N.Y.)
|October 18, 2003
Resumen
La respuesta de proteína desplegada (UPR) es desencadenada por el estrés en el retículo endoplasmático. La activación del dominio de la Ire1 quinasa, sorprendentemente, requiere un cofactor ligando, no una fosforilación, para inducir la UPR.
Área de la Ciencia:
- Biología Molecular Biología Molecular
- Biología celular Biología celular.
- La bioquímica es la bioquímica.
Sus antecedentes:
- Las proteínas desplegadas en el retículo endoplasmático (ER) activan la quinasa transmembrana Ire1.1.
- La activación de Ire1 conduce a la actividad de la endoribonucleasa y el empalme no convencional del ARNm HAC1.
- Este proceso inicia la respuesta de proteína desplegada (UPR).
Objetivo del estudio:
- Para investigar el papel del dominio de la quinasa de Ire1 en la activación de la UPR.
- Para explorar el mecanismo de activación de Ire1 utilizando un inhibidor químico.
Principales métodos:
- Mutagénesis dirigida al sitio para sensibilizar el dominio de Ire1 quinasa a 1NM-PP1.1.
- Utilizando el inhibidor competitivo de ATP 1NM-PP1 como un cofactor para la activación de Ire1.
- Evaluación de la inducción de la UPR en mutantes Ire1 sensibilizados a fármacos.
Principales resultados:
- El mutante Ire1, sensibilizado a 1NM-PP1, paradójicamente requirió el fármaco para la activación, no la inhibición.
- 1NM-PP1 actuó como un cofactor, permitiendo la activación de Ire1 incluso con mutaciones inactivadoras de la quinasa.
- El Ire1 activado indujo una UPR completa, evitando la necesidad de actividad de la quinasa.
Conclusiones:
- La activación de Ire1 se desencadena por un cambio de conformación en el dominio de la quinasa tras la unión del ligando.
- La ocupación de ligandos del sitio activo, en lugar de la fosforilación, es la clave para activar las funciones aguas abajo de Ire1.
- Este hallazgo redefine el mecanismo de iniciación de la UPR a través de la señalización Ire1.
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