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La N-glicosilación cotranslacional y posttranslacional de polipéptidos por distintas isoformas de OST de mamíferos

Catalina Ruiz-Canada¹, Daniel J Kelleher, Reid Gilmore

¹Department of Biochemistry and Molecular Pharmacology University of Massachusetts Medical School, Worcester, MA 01605, USA.

|January 27, 2009

Resumen

Las células de los mamíferos utilizan dos isoformas de oligosacáriltransferasa (OST), STT3A y STT3B, que trabajan juntas secuencialmente. STT3A maneja la glicosilación cotranslacional inicial, mientras que STT3B media tanto en la N-glicosilación cotranslacional como en la posttranslacional.

Área de la Ciencia:

Biología Molecular Biología Molecular
Biología celular Biología celular.
La bioquímica es la bioquímica.

Sus antecedentes:

La proteína N-glicosilación es una modificación post-traducional crítica que ocurre en el retículo endoplasmático.
El complejo oligosacáriltransferasa (OST) cataliza la N-glucosilación, con distintas isoformas (STT3A y STT3B) que coexisten en las células de los mamíferos.

Objetivo del estudio:

Aclarar las funciones distintas y cooperativas de las isoformas OST (STT3A y STT3B) en la N-glicosilación de proteínas.
Comprender la acción secuencial de las isoformas OST en la mediación de la glicosilación cotranslacional y posttranslacional.

Principales métodos:

Se utilizó ARN pequeño interferente (siRNA) para la eliminación específica de las isoformas STT3A y STT3B.
Se evaluó el impacto del agotamiento de la isoforma en la N-glucosilación de polipéptidos nacientes y desplegados.

Principales resultados:

Se demostró que STT3A media principalmente la glicosilación cotranslacional de los polipéptidos nacientes que entran en el ER.
Se muestra que STT3B es crucial para la glicosilación cotranslacional eficiente cerca de las secuencias de señales y para la glicosilación posttranslacional de proteínas desplegadas.
Se reveló un mecanismo secuencial y cooperativo entre STT3A y STT3B para una eficiente N-glucosilación.

Conclusiones:

Las isoformas OST STT3A y STT3B poseen distintas propiedades enzimáticas y roles complementarios.
Su acción secuencial asegura la máxima eficiencia y fidelidad de la N-glucosilación mediante el escaneo de polipéptidos en busca de sitios aceptores.

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