Biology of Extracellular HSP60

The exposure of cells or organisms to high temperature leads to the release of alert molecules such as Heat Shock Protein: the HSP. This protein family has been initially described in Drosophila. The cellular response to a heat shock involving HSP is conserved across species, from bacteria to humans and including plants. Other stresses, such as ischemia, heavy metal poisoning, nutrient deprivation, irradiations, infections, oxidative stress and inflammation, can also induce the HSP expression. HSP form a large family of proteins which are classified according to their molecular weight: HSP100, HSP90, HSP70, HSP60, HSP40, HSP from 20 to 30 kDa and HSP10. HSP60 has different functions depending on its localization. Intracellular HSP60 can be found in the cytosol, mitochondria and the chloroplast. Therein, it has a chaperone activity by assisting the proteins folding. On the cell surface or in the extracellular medium, HSP60 acts as a danger signaling molecule. Thus, stressed or damaged cells can stimulate the immune system. Indeed, this extracellular HSP60 are involved in several inflammatory pathologies.