The Bag family of proteins are characterized by the presence of a 45 amino acid Bag domain through which they bind with high affinity to the ATPase domain of HSP 70, thereby negatively regulating HSP 70 chaperone activity. Bag-3 (Bcl-2-associated athanogene 3), also known as BIS or CAIR-1, is a 575 amino acid protein that contains one C-terminal Bag domain and two N-terminal WW domains. Like other members of the Bag family, Bag-3 functions to inhibit the chaperone activity of HSP 70, specifically by promoting the release of HSP 70-bound substrates. Additionally, Bag-3 exhibits anti-apoptotic activity via cell cycle control, suggesting a possible role for Bag-3 in tumor progression. The gene encoding Bag-3 maps to human chromosome 10, which houses over 1,200 genes and comprises nearly 4.5% of the human genome.
Background References
1. Pasillas MP et al. Proteomic analysis reveals a role for Bcl2-associated athanogene 3 and major vault protein in resistance to apoptosis in senescent cells by regulating ERK1/2 activation. Mol Cell Proteomics 14:1-14 (2015).
2. Boiani M et al. The stress protein BAG3 stabilizes Mcl-1 protein and promotes survival of cancer cells and resistance to antagonist ABT-737. J Biol Chem 288:6980-90 (2013).
Western blot analysis of Bag3 on different lysates with Rabbit anti-Bag3 antibody (ET1704-73) at 1/1,000 dilution.
Lane 1: Neuro-2a cell lysate (20 µg/Lane) Lane 2: Mouse heart tissue lysate (40 µg/Lane)
Predicted band size: 62 kDa Observed band size: 75 kDa
Exposure time: Lane 1: 3 minutes; Lane 2: 18 seconds; ECL: K1801;
4-20% SDS-PAGE gel.
Proteins were transferred to a PVDF membrane and blocked with 5% NFDM/TBST for 1 hour at room temperature. The primary antibody (ET1704-73) at 1/1,000 dilution was used in 5% NFDM/TBST at 4℃ overnight. Goat Anti-Rabbit IgG - HRP Secondary Antibody (HA1001) at 1/50,000 dilution was used for 1 hour at room temperature.
Immunohistochemical analysis of paraffin-embedded human fetal skeletal muscle tissue using anti-Bag3 antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 8.0-8.4) for 20 minutes.The tissues were blocked in 5% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (ET1704-73, 1/50) for 30 minutes at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.