USE OF HSP70 AS A REGULATOR OF ENZYMATIC ACTIVITY

Lysosomal membrane permeabilization is an evolutionarily conserved hallmark of stress-induced cell death. Here the inventors show that the major stress-inducible heat shock protein 70 (Hsp70) enhances cell survival by stabilizing lysosomes through a pH-dependent high affinity binding to an endo-lysosomal anionic phospholipid bis(monoacylglycero)phosphate (BMP; also referred to as lysobisphosphatidic acid). The positively charged ATPase domain of Hsp70 is responsible for the binding but the substrate-binding domain is also required for effective stabilization of lysosomes. Importantly, the cytoprotective effect can be obtained by endocytic delivery of recombinant Hsp70 and specifically reverted by extra cellular administration of BMP antibodies or Hsp70 inhibitors. Thus, this protein-lipid interaction opens exciting possibilities for the development of cytoprotective and cytotoxic lysosome-specific therapies for the treatment of degenerative diseases and cancer, respectively.