Age-related attenuation of HSP47 heat response in fibroblasts

The collagen-binding heat shock protein of molecular weight 47,000 (HSP47), resident in the endoplasmic reticulum (ER), is assumed to play a specific role as a molecular chaperon in the processing of procollagen molecules. The present investigation of age-related alteration in the HSP47 heat response in cultured murine and human fibroblasts revealed expression in cells with a low population doubling level (PDL) derived from young mice and people more inducible by heat treatment than those from older mice and people. On the other hand, cells with a high PDL showed a very low heat response in terms of HSP47 expression regardless of the donor age. Northern blot analysis of HSP47 m-RNA indicated that the age related attenuation of HSP47 expression was regulated by transcriptional mechanisms. Furthermore, immunofluorescent analysis using a monoclonal antibody against the carboxylterminal propeptide of type I procollagen revealed far greater retention of procollagen molecules in the ER lumen of cells from old persons than in those from young persons. This was particularly prominent in heat-treated cells from old persons, indicating the possibility that the observed decrease in HSP47 heat response might cause blockage of procollagen transport to the Golgi and therefore secretion.