RESUMEN
Human cystatin C (CysC) is a cysteine proteinase inhibitor with many potential applications. To facilitate further studies of the functions and applications of CysC, we improved the heterologous expression of CysC using a basic codon optimization method. In this study, we cloned the high-GC content wild-type sequence of the CysC gene and also designed a slightly AT-biased sequence, with codons optimized for expression in the Pichia pastoris GS115 strain. Our results showed that the optimized coding sequence of human CysC increased the expression and secretion of the CysC protein by approximately 3- to 5-fold (90-96 mg CysC/L) in yeast, compared with the expression levels of the native CysC gene (17.9-18.4 mg CysC/L). We designed, constructed, and applied an optimized version of the CysC gene for the Pichia expression system. Our results demonstrate that the optimized coding sequence provides a higher yield of secreted CysC than that produced using the wild-type gene. Our data also serve as a practical example demonstrating a rational design strategy for the heterologous expression of secreted proteins.
Asunto(s)
Clonación Molecular/métodos , Codón , Cistatina C/genética , Pichia/genética , Secuencia de Aminoácidos , Composición de Base , Secuencia de Bases , Cistatina C/biosíntesis , Cistatina C/química , Expresión Génica , Humanos , Datos de Secuencia Molecular , Pichia/metabolismo , Ingeniería de Proteínas , Proteínas Recombinantes/biosíntesis , Proteínas Recombinantes/química , Proteínas Recombinantes/genéticaRESUMEN
Cathepsin B is one of the major lysosomal cysteine proteases involved in neuronal protein catabolism. This cathepsin is released after traumatic injury and increases neuronal death; however, release of cystatin C, a cathepsin inhibitor, appears to be a self-protective brain response. Here we describe the effect of cystatin C intracerebroventricular administration in rats prior to inducing a traumatic brain injury. We observed that cystatin C injection caused a dual response in post-traumatic brain injury recovery: higher doses (350 fmoles) increased bleeding and mortality, whereas lower doses (3.5 to 35 fmoles) decreased bleeding, neuronal damage and mortality. We also analyzed the expression of cathepsin B and cystatin C in the brains of control rats and of rats after a traumatic brain injury. Cathepsin B was detected in the brain stem, cerebellum, hippocampus and cerebral cortex of control rats. Cystatin C was localized to the choroid plexus, brain stem and cerebellum of control rats. Twenty-four hours after traumatic brain injury, we observed changes in both the expression and localization of both proteins in the cerebral cortex, hippocampus and brain stem. An early increase and intralysosomal expression of cystatin C after brain injury was associated with reduced neuronal damage.