Emerging roles of molecular chaperones and co-chaperones in selective autophagy: focus on BAG proteins

Macroautophagy is a catabolic process by which the cell degrades cytoplasmic components through the lysosomal machinery. While initially acknowledged as a rather unspecific bulk degradation process, growing lines of evidence indicate the selectivity of macroautophagy pathways in the removal of misfolded or aggregated proteins. How such substrates are recognized and specifically targeted to the macroautophagy machinery has become a hotspot of investigation, and recent evidence suggests that here molecular chaperones and co-chaperones play a central role. One emerging pathway is mediated by the co-chaperone protein Bcl-2-associated athanogene 3 (BAG 3) which seems to utilize the specificity of molecular chaperones (heat-shock proteins) towards non-native proteins as basis for targeted macroautophagic degradation. In this short review, we focus on the molecular interplay between the macroautophagy system and molecular chaperones and highlight the relevance of the pathway mediated by BAG3 to aging and age-associated protein-misfolding diseases.