Expression of the complement alternative pathway by human myoblastsin vitro: Biosynthesis of C3, factor B, factor H and factor I

摘要

AbstractIn this study, we demonstrate expressionin vitroof complement alternative pathway components C3, factor B, factor H and factor I by normal human myoblasts and human rhabdomyosarcoma cell lines CRL1558 and HTB153. Proteins in culture supernatants were detected by Western (protein) blot analysis and biosynthetic labeling followed by immunoprecipitation experiments, and quantified by ELISA. Newly secreted proteins were structurally and functionally similar to their serum counterparts. An additional polypeptide of 43 kDa with factor H immunoreactivity was detected, which could correspond to the N‐terminal truncated form found in plasma. Protein expression was correlated with mRNA expression by reverse transcriptase‐polymerase chain reaction analysis. The major proteins of complement alternative pathway C3, factor B and factor H were produced constitutively by skeletal muscle cells at a rate of 50 to 150 ng/106cells/ml and factor I was expressed 20 ng/106cells/ml. These synthesesin vitrowere regulated by inflammatory cytokines. Interferon‐γ significantly upregulated C3, factor B and factor H expression, but had no effect on factor I production. Interleukin‐1β strongly enhanced C3 and factor B production and had a weak enhancing or no effect on factor I and factor H secretion. Human myoblast cell lines constitute an interesting model to analyze complement biosynthesis by human skeletal muscle cells. Local complement expression by skeletal musclein vivomay be implicated in some muscular inflammatory or pathological