Mouse and rat cystatin C: Escherichia coli production, characterization and tissue distribution

Abstract

Recombinant mouse ( Mus musculus) and rat ( Rattus norvegicus) cystatin C were produced by expression in Escherichia coli, isolated and functionally characterized. The mouse and rat inhibitors were both fully active in titrations of papain. Determination of equilibrium constants for dissociation ( K i ) for their complexes with the target proteinase, cathepsin B, produced values not largely different from that for human cystatin C ( K i 0.07−0.13 nM). Rabbit antisera against mouse and rat cystatin C were produced and used for improved affinity purification of the recombinant inhibitors. Affinity purified immunoglobulins isolated from the antiserum against mouse cystatin C were used for construction of a sensitive enzyme-linked immunosorbent assay. The assay was used to demonstrate a high degree of immunological cross-reactivity between mouse and rat cystatin C and could be used for cystatin C quantification in mouse and rat tissue homogenates. All tissues analyzed contained cystatin C, with a relative content very similar to that of human tissues. For all species, brain tissue contained the highest cystatin C amounts and liver the lowest, whereas kidney, spleen and muscle tissues were intermediate in content. In the mouse, a notable high cystatin C content in parotid gland tissue was observed. The high degree of similarity in distribution pattern and functional properties for mouse, rat and human cystatin C indicates that: a murine model should be relevant for studies of the human disease, hereditary cystatin C amyloid angiopathy.