Cellular turnover and degradation of the most common missense cystathionine beta-synthase variants causing homocystinuria.
Protein Sci
; 33(8): e5123, 2024 Aug.
Article
em En
| MEDLINE
| ID: mdl-39041895
ABSTRACT
Homocystinuria (HCU) due to cystathionine beta-synthase (CBS) deficiency is the most common inborn error of sulfur amino acid metabolism. Recent work suggests that missense pathogenic mutations-regardless of their topology-cause instability of the C-terminal regulatory domain, which likely translates into CBS misfolding, impaired assembly, and loss of function. However, it is unknown how instability of the regulatory domain translates into cellular CBS turnover and which degradation pathways are involved in CBS proteostasis. Here, we developed a human HEK293-based cellular model lacking intrinsic CBS and stably overexpressing wild-type (WT) CBS or its 10 most common missense HCU mutants. We found that HCU mutants, except the I278T variant, expressed similarly or better than CBS WT, with some of them showing impaired oligomerization, activity and response to allosteric activator S-adenosylmethionine. Cellular stability of all HCU mutants, except P49L and A114V, was significantly lower than the stability of CBS WT, suggesting their increased degradation. Ubiquitination analysis of CBS WT and two representative CBS mutants (T191M and I278T) showed that proteasomal degradation is the major pathway for CBS disposal, with a minor involvement of lysosomal-autophagic and endoplasmic reticulum-associated degradation (ERAD) pathways for HCU mutants. Proteasomal inhibition significantly increased the half-life and activity of T191M and I278T CBS mutants. Lysosomal and ERAD inhibition had only a minor impact on CBS turnover, but ERAD inhibition rescued the activity of T191M and I278T CBS mutants similarly as proteasomal inhibition. In conclusion, the present study provides new insights into proteostasis of CBS in HCU.
Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Mutação de Sentido Incorreto
/
Cistationina beta-Sintase
/
Proteólise
/
Homocistinúria
Limite:
Humans
Idioma:
En
Ano de publicação:
2024
Tipo de documento:
Article