Characterization of a novel anti-death molecule, Aven

Programmed cell death of apoptosis is a genetically programmed and highly conserved process that plays a fundamental role during animal development, metamorphosis and tissue homeostasis in multi-cellular organisms. Aberrant regulation of apoptosis is implicated in many disease pathogenesis including autoimmune disorders, cancers and neuro-degenerative diseases. Genetic studies in the nematode Caenorhabditis elegans have revealed three phases of apoptosis (decision, execution and engulfment). In the execution phase of mammalian cells, there are three key families of proteins that form the core apoptotic machinery, caspases, Apaf-1/CED-4 and Bcl-2 families.; Bcl-2 is a prototype of a grow family of proteins. It was originally isolated as a translocation of Bcl-2 gene into the enhancer region of immunoglobulin locus in certain B&barbelow;-C&barbelow;ell L&barbelow;ymphomas. This results in up-regulation of Bcl-2 expression and confers anti-apoptotic activity to these B-lymphocytes, hence promoting tumorigenesis. One of the anti-apoptotic family members, Bcl-x_L has been shown to protect different cell types from a wide variety of apoptotic stimuli. However, the molecular mechanism of how Bcl-x_L exert its antiapoptotic function is not clearly understood.; It has been shown that Bcl-x_L is localized in the intracellular membranes including outer mitochondrial membrane, outer nuclear membrane and the endoplasmic reticulum. Bcl-x_L inhibits apoptosis at least in part due to its ability to prevent the release of cytochrome c and other apoptogenic factors from the inter-membrane space of mitochondria into the cytoplasm. In the cytosol, cytochrome c interacts with the mammalian CED-4 homologue, Apaf-1 and facilitates the activation of caspases. These activated caspases in turns proteolytically cleave cellular substrates that produce the hallmarks of apoptosis.; To further investigate anti-apoptotic mechanism of Bcl-x_L, a yeast two-hybrid screening was performed with a dimerization-defective but anti-apoptosis-competent Bcl-x_L as bait. One of the interacting factors isolated is Aven (Aventine, a Roman Empire stronghold). Aven is shown to be an anti-apoptotic molecule in several systems tested. Besides its ability to interact with Bcl-x_L and other anti-apoptotic Bcl-2 family members, Aven is also shown to be able to associate with Apaf-1 and its anti-apoptotic activity is at least in part due to interfering with Apaf-1-facilitated caspase activation.; I further showed that Aven interacted with MZF-2 (myeloid zinc finger-2) and of ATM (ataxia telangiectasia mutated). The interaction of the MZF-2 and the ability of Aven to transactivate suggest that Aven could be a transcription regulator. This transcription regulation activity seems to be important in its prosurvival function in primary neuronal cultures. The ability of Aven to interact with MZF-2 and ATM suggests that Aven may be a signal integrator and determines the outcome of the cells upon receiving these signals.