HSP47, a molecular chaperone which interacts with procollagens in the endoplasmic reticulum

HSP47 is an endoplasmic reticulum(ER)-resident glycoprotein with an ER- retention signal, Arg-Asp-Glu-Leu, at its C-terminus. This protein belongs to serine protease inhibitor (serpin) family, although the protease-inhibitory activity has not yet been detected. The expression of HSP47 under stress conditions is regulated by the heat shock transcription factor (HSF) system, and that under non-stress condition is well correlated with collagen expression in various cell lines and tissues. In the collagen producing cells, HSP47 tentatively interacts with procollagen during its translation, folding and/or modification steps, and releases procollagen at cis-Golgi. HSP47 shows the affinity to all types of collagen tested as well as simple collagen model peptides (Pro-Pro-Gly)n (n≥7) in vitro. Recent studies have suggested that chaperone proteins including HSP47 would facilitate or control the collagen biosynthesis in the ER.