Cellular responses to the expression of unstable secretory proteins in the filamentous fungus Aspergillus oryzae.
Appl Microbiol Biotechnol
; 101(6): 2437-2446, 2017 Mar.
Article
en En
| MEDLINE
| ID: mdl-28064367
Filamentous fungi are often used as cell factories for recombinant protein production because of their ability to secrete large quantities of hydrolytic enzymes. However, even using strong transcriptional promoters, yields of nonfungal proteins are generally much lower than those of fungal proteins. Recent analyses revealed that expression of certain nonfungal secretory proteins induced the unfolded protein response (UPR), suggesting that they are recognized as proteins with folding defects in filamentous fungi. More recently, however, even highly expressed endogenous secretory proteins were found to evoke the UPR. These findings raise the question of whether the unfolded or misfolded state of proteins is selectively recognized by quality control mechanisms in filamentous fungi. In this study, a fungal secretory protein (1,2-α-D-mannosidase; MsdS) with a mutation that decreases its thermostability was expressed at different levels in Aspergillus oryzae. We found that, at moderate expression levels, wild-type MsdS was secreted to the medium, while the mutant was not. In the strain with a deletion for the hrdA gene, which is involved in the endoplasmic reticulum-associated degradation pathway, mutant MsdS had specifically increased levels in the intracellular fraction but was not secreted. When overexpressed, the mutant protein was secreted to the medium to a similar extent as the wild-type protein; however, the mutant underwent hyperglycosylation and induced the UPR. Deletion of α-amylase (the most abundant secretory protein in A. oryzae) alleviated the UPR induction by mutant MsdS overexpression. These findings suggest that misfolded MsdS and unfolded species of α-amylase might act synergistically for UPR induction.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Aspergillus oryzae
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Proteínas Fúngicas
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Regulación Fúngica de la Expresión Génica
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Alfa-Amilasas
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Respuesta de Proteína Desplegada
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Manosidasas
Idioma:
En
Revista:
Appl Microbiol Biotechnol
Año:
2017
Tipo del documento:
Article
País de afiliación:
Japón
Pais de publicación:
Alemania