Cell survival molecules

There is a family of proteins (the Bcl-2 family) that can regulate the potential across the inner mitochondrial membrane, and its permeability. Hence, they can influence apoptosis. Some of this family stabilise the inner membrane and maintain the potential, so that they suppress apoptosis. They are known as cell survival molecules (e.g. the proteins, Bcl-2, Bcl-X). Other members of the family destabilise the mitochondria and decrease the membrane potential which facilitates apoptosis. They are known as cell killer proteins (e.g. the proteins, Bax, Bak). The mechanisms by which they have their effects on mitochondria are not known. They are, of course, of considerable interest for the development and control of growth of tumour cells (See Chapter 21). 

Schubert, D., Kimura, H., Lacorbiere, M., Vaughan, J., Karr, D. and Fischer, W. H. (1990) Activin is a nerve cell survival molecule. Nature 344 868-870. 

OGX-011, an antisense compound that inhibits clusterin, a cancer cell survival molecule, is currently in phase II trials for metastatic breast and prostate cancers. 

Neurotrophins are peptides or protein molecules that regulate both cell survival and cell death of specific neuronal phenotypes and thus serve to influence development, maintenance, function, and plasticity of the nervous system. 

Nevertheless, SDM showed a maximum decrease in the cell survival rate of approximately 12% and 27% at the lowest and highest concentrations of microparticles, respectively (Figure 14). The massive cytotoxicity induced by CLM may be explained by the presence of remaining molecules of terephthaloyl chloride, which plays the role of cross-linking agent during the formation of CLM and is well known as a toxic substance. 

Bone metabolism has quickly become a topic of fascinating research. The bone, far from being a metabolically inactive tissue, is a tissue where different cell types and different molecules carry out numerous and varied functions. This has been due largely to the discovery of the RANKL/RANK/OPG system of cytokines. These new molecules are decisive in OCS, bone metabolism, and bone loss, but they are also important for other tissues and cells. Indeed, these proteins are critical in several systems the immune system, where they have functions that affect cell survival and the immunomodulation of T-, B-, and dendritic cells the vascular system and the endocrine system. 

Activation energies are energy barriers to chemical reactions. These barriers are crucial to life itself. The rate at which a molecule undergoes a particular reaction decreases as the activation barrier for that reaction increases. Without such energy barriers, complex macromolecules would revert spontaneously to much simpler molecular forms, and the complex and highly ordered structures and metabolic processes of cells could not exist. Over the course of evolution, enzymes have developed lower activation energies selectively for reactions that are needed for cell survival. 

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