title: The F309S mutation increases factor VIII secretion in human cell line.
abstract: OBJECTIVE
  The capacity of a human cell line to secrete recombinant factor VIII with a F309S point mutation was investigated, as was the effect of the addition of chemical chaperones (betaine and sodium-4-phenylbutyrate) on the secretion of factor VIII.
  
  
  METHODS
  This work used a vector with a F309S mutation in the A1 domain to investigate FVIII production in the HEK 293 human cell line. Factor VIII activity was measured by chromogenic assay. Furthermore, the effects of chemical drugs on the culture were evaluated.
  
  
  RESULTS
  The addition of the F309S mutation to a previously described FVIII variant increased FVIII secretion by 4.5 fold. Moreover, the addition of betaine or sodium-4-phenylbutyrate increased the secretion rate of FVIIIΔB proteins in HEK 293 cells, but the same effect was not seen for FVIIIΔB-F309S indicating that all the recombinant protein produced had been efficiently secreted.
  
  
  CONCLUSIONS
  Bioengineering factor VIII expressed in human cells may lead to an efficient production of recombinant factor VIII and contribute toward low-cost coagulation factor replacement therapy for hemophilia A. FVIII-F309S produced in human cells can be effective in vivo.
authors.affiliation: Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil; Hemocentro de Ribeirão Preto, Ribeirão Preto, SP, Brazil. Electronic address: anny_damac@yahoo.com.br.
authors.forename: Daianne Maciely Carvalho
authors.initials: DM
authors.lastname: Fantacini
authors.affiliation: Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil.
authors.forename: Aparecida Maria
authors.initials: AM
authors.lastname: Fontes
authors.affiliation: Hemocentro de Ribeirão Preto, Ribeirão Preto, SP, Brazil.
authors.forename: Mário Soares
authors.initials: MS
authors.lastname: de Abreu Neto
authors.affiliation: Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil; Hemocentro de Ribeirão Preto, Ribeirão Preto, SP, Brazil.
authors.forename: Dimas Tadeu
authors.initials: DT
authors.lastname: Covas
authors.affiliation: Universidade de São Paulo (USP), Ribeirão Preto, SP, Brazil; Hemocentro de Ribeirão Preto, Ribeirão Preto, SP, Brazil.
authors.forename: Virgínia
authors.initials: V
authors.lastname: Picanço-Castro
keywords: Betaine; F309S mutation; HEK 293 cells; Recombinant factor VIII; Sodium-4-phenylbutyrate