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Bases estructurales de la regulación suavizada por sus dominios extracelulares

Eamon F X Byrne¹, Ria Sircar², Paul S Miller¹

¹Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK.

|July 21, 2016

Resumen

El camino del erizo (Hh)

Área de la Ciencia:

La bioquímica
Biología molecular
Biología estructural

Sus antecedentes:

Las señales de desarrollo se transducen por receptores acoplados a proteínas G de clase Frizzled (GPCR).
La regulación de la señalización GPCR por grandes dominios extracelulares aún no está clara.
Smoothened (SMO) es un transductor de la vía Hh y una oncoproteína GPCR.

Objetivo del estudio:

Aclarar el mecanismo estructural de la activación y regulación de la SMO.
Comprender cómo los dominios extracelulares influyen en la señalización transmembrana en los GPCR.

Principales métodos:

Cristalografía de rayos X para determinar la estructura del SMO.
Mutagénesis guiada por la estructura para sondear las interfaces funcionales.
Ensayos bioquímicos para evaluar la señalización de Hh y la unión al colesterol.

Principales resultados:

Las estructuras cristalinas revelaron SMO con sitios de unión de ligandos distintos en el dominio transmembrana (TMD) y el dominio rico en cisteína (CRD).
Se encontró una molécula de colesterol unida en el sitio del CRD, esencial para la transducción de la señal Hh.
La unión del antagonista a la TMD indujo cambios conformacionales que afectaron la interfaz CRD-linker-TMD y la unión del colesterol.

Conclusiones:

La actividad de la GPCR está regulada por interacciones inducidas por ligandos entre los dominios extracelulares y transmembrana.
La unión del colesterol al CRD es crítica para la señalización de la vía Hh a través de SMO.
El CRD, el enlazador y la interfaz TMD estabilizan el estado inactivo de SMO.

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