RESUMEN
BiP is a major endoplasmic reticulum (ER) chaperone and is suggested to act as primary sensor in the activation of the unfolded protein response (UPR). How BiP operates as a molecular chaperone and as an ER stress sensor is unknown. Here, by reconstituting components of human UPR, ER stress and BiP chaperone systems, we discover that the interaction of BiP with the luminal domains of UPR proteins IRE1 and PERK switch BiP from its chaperone cycle into an ER stress sensor cycle by preventing the binding of its co-chaperones, with loss of ATPase stimulation. Furthermore, misfolded protein-dependent dissociation of BiP from IRE1 is primed by ATP but not ADP. Our data elucidate a previously unidentified mechanistic cycle of BiP function that explains its ability to act as an Hsp70 chaperone and ER stress sensor.
Asunto(s)
Estrés del Retículo Endoplásmico , Endorribonucleasas/metabolismo , Proteínas de Choque Térmico/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , eIF-2 Quinasa/metabolismo , Adenosina Trifosfato/metabolismo , Chaperón BiP del Retículo Endoplásmico , Endorribonucleasas/química , Proteínas HSP70 de Choque Térmico/química , Proteínas HSP70 de Choque Térmico/metabolismo , Proteínas de Choque Térmico/química , Humanos , Modelos Moleculares , Pliegue de Proteína , Dominios y Motivos de Interacción de Proteínas , Mapas de Interacción de Proteínas , Proteínas Serina-Treonina Quinasas/química , Respuesta de Proteína Desplegada , eIF-2 Quinasa/químicaRESUMEN
Inhibiting tumor angiogenesis is a well-established approach for anticancer therapeutic development. A Disintegrin-like and Metalloproteinase with ThromboSpondin Motifs 5 (ADAMTS5) is a secreted matrix metalloproteinase in the ADAMTS family that also functions as an anti-angiogenic/anti-tumorigenic molecule. Its anti-angiogenic/anti-tumorigenic function is independent from its proteinase activity, but requires its first thrombospondin type 1 repeat (TSR1). However, it is not known if recombinant TSR1 (rTSR1) can function as an anticancer therapeutic. In this report, we expressed and purified a 75-residue recombinant TSR1 polypeptide from E. coli and investigated its ability to function as an anticancer therapeutic in mice. We demonstrate that rTSR1 is present in the blood circulation as well as in the tumor tissue at 15 min post intraperitoneal injection. Intraperitoneal delivery of rTSR1 potently suppressed subcutaneous B16F10 melanoma growth as a single agent, accompanied by diminished tumor angiogenesis, increased apoptosis, and reduced cell proliferation in the tumor tissue. Consistently, rTSR1 dose-dependently induced the apoptosis of cultured human umbilical vein endothelial cells (HUVECs) in a caspase-dependent manner. This work indicates that rTSR1 of ADAMTS5 can function as a potent anticancer therapy in mice. It thus has the potential to be further developed into an anticancer drug.
