Cytoprotective functions of small stress proteins in protein conformational diseases

The mammalian small heat shock protein family comprises 10 members (HspB1-10) some of which have been implicated indirectly or directly in several neurodegenerative and neuromuscular disorders. Upregulation of some HspB members has been found in brain amyloidosis, where they are often trapped within inclusion bodies, and mutations of several HspB proteins have been associated with muscular and neurological disorders. These two findings strongly suggest an important role for the HspB proteins in the maintaining of neuronal and muscular cells viability. How these molecular chaperones can alleviate neurodegeneration and how their mutation can result in toxicity is still largely unknown. This review will summarize the current knowledge about HspB protein function and implication in neurodegenerative diseases. From this, we suggest that, besides the two most characterized biochemical properties of HspB members (chaperone activity and cytosketelal stabilization), also non-canonical pathways seem relevant to the neuroprotective actions of some HspB members.