BAG5: Proteins and Enzymes

The BAG (Bcl-2-associated anthanogene) proteins are a family of chaperone regulators that modulate a number of diverse processes including proliferation, survival, stress responses, tumorigenesis, neuronal differentiation, growth arrest and apoptosis (reviewed Takayama and Reed, 2001; Doong et al, 2002, and Doukhanina et al. 2006). BAG proteins have been characterized as co-chaperones and interact with the chaperone heat shock proteins 70, both constitutive Hsc70 and inducible Hsp70. BAG proteins bind through their BAG domain to the ATPase domain of Hsc70/Hsp70, and can modulate either positively or negatively the functions of the Hsc70/Hsp70 chaperone proteins. The BAG domain has been shown to contribute to the anti-apoptotic activity of BAG-family proteins. The anti-apoptotic activities of BAG-family proteins may be dependent on their interactions with Hsc70/Asp70 and/or binding to Bcl-2. In addition to the conserved BAG domain, BAG-family proteins also contain additional domains which enable them to interact with specific target proteins or to target them to specific locations within cells. The BAG family contains at least six family members, including BAG-1 and its various isoforms [including BAG-1S , BAG-1M (RAP46/HAP46), and BAG-1L, BAG2, BAG3 (CAIR-1; Bis,), BAG4 (SODD), BAG5 and BAG6 (Scythe, BAT3). The following amino acids (aa) lengths and molecular weights (kDa) have been described for human BAG proteins (reviewed in Takayama et al, 2001 and Doong et al, 2002): BAG-1 (230 aa., 34 kDa), BAG-1S (219 aa, 29 kDa), BAG-1M (274 aa, 46 kDa), BAG-1L (345 aa, 52 kDa), BAG-2 [212 aa; 24 kDa (Arndt et al. 2005)], BAG-3 (575 aa, 74 kDa), BAG-4 (456 aa; 60 kDa), BAG-5 ([442 aa; 51 kDa (Kalia et al. 2004)], and BAG-6 (1129 aa; 150 kDa).