BAG-1: a multi-functional pro-survival molecule.

BAG-1 is a multi-functional protein that exists as three functionally distinct and differentially localized isoforms which originate from a single mRNA and interact with a wide range of cellular targets. These include heat shock proteins, nuclear hormone receptors, signalling molecules, the anti-apoptotic BCL-2 protein and components of the ubiquitylation/proteasome machinery. Overexpression of BAG-1 isoforms has been demonstrated to regulate apoptosis, proliferation, transcription, metastasis and cell motility in a wide variety of cell systems. Since BAG-1 has a role in many biological pathways there is increasing evidence supporting the view that BAG-1 is an important molecule in disease, for example, potentially modulating both cell survival and response to nuclear hormones in breast cancer, and BAG-1 is a potential molecular target for therapeutic intervention.