RESUMEN

It is well known that S5a and hRpn13 are two major ubiquitin (Ub) receptors in the proteasome but little is known about their functional difference in recruiting ubiquitinated substrates. In this study using siRNA-mediated knockdown of S5a or hRpn13, we found that two Ub receptors had different substrate specificity although similar level of accumulation of high molecular weight Ub-conjugates was observed. Interesting enough, depletion of S5a, but not hRpn13, resulted in the Ub-containing aggregates and induced ER chaperones such as Grp78 and Grp94. ERAD substrates such as alpha-TCR and alpha1-antitrypsin were also stabilized by the depletion of S5a but not hRpn13. Our results suggest that there is different substrate specificity between S5a and hRpn13 at the level of delivery and S5a may be the major docking site for ERAD substrates.

Asunto(s)

Glicoproteínas de Membrana/metabolismo , Complejo de la Endopetidasa Proteasomal/metabolismo , Ubiquitina/metabolismo , Retículo Endoplásmico/metabolismo , Chaperón BiP del Retículo Endoplásmico , Técnicas de Silenciamiento del Gen , Proteínas HSP70 de Choque Térmico/metabolismo , Células HeLa , Proteínas de Choque Térmico/metabolismo , Humanos , Péptidos y Proteínas de Señalización Intracelular , Glicoproteínas de Membrana/genética , Proteínas de la Membrana/metabolismo , Chaperonas Moleculares/metabolismo , Complejo de la Endopetidasa Proteasomal/genética , Estabilidad Proteica , ARN Interferente Pequeño/genética , Proteínas de Unión al ARN , Especificidad por Sustrato