Another protein of interest uncovered in this study is BCL2associated athanogene 3 (BAG3). In the current study, BAG3 was found to have increased phosphorylation at Ser377 upon bortezomib treatment. BAG3 belongs to the evolutionarily conserved BAG family of proteins that were originally isolated based on their ability to interact with the anti-apoptotic protein Bcl-2 [35, 36] . It is involved in a wide variety of cellular processes, including cell survival, cellular stress response, apoptosis and virus replication [16, 37, 38] . Recent evidence implicates an additional function of BAG3 in the regulation of the autophagy pathway. These findings indicate that autophagosome formation and turnover may depend on BAG3 and that BAG3 can stimulate autophagy processes [39, 40] . Autophagy is a major intracellular degradation system. Unlike the ubiquitin-proteasome system (UPS), autophagy is mainly responsible for the degradation of long-lived proteins and subcellular organelles [41, 42] . Autophagy plays important roles in development, cellular homeostasis and cell survival and is frequently activated in tumor cells exposed to chemotherapy or radiation and confers therapeutic resistance [43, 44] . The UPS and autophagy have been viewed as distinct degradation systems, but recent studies suggested that they are functionally coupled and that suppression of the proteasome promotes autophagy [45, 46] . However, the functional connection and the inter-regulation between the two systems are not well understood.