ENDOGENOUS RELATIVES OF ADP-RIBOSYLATING BACTERIAL TOXINS IN MICE ANDMEN - POTENTIAL REGULATORS OF IMMUNE CELL-FUNCTION

ADP-ribosylation of proteins, like phosphorylation, is a post-translat ional modification that can modulate protein function. Bacterial mono( ADP-ribosyl)transferases have been well studied, since potent and clin ically important pathogenic exoenzymes such as diphtheria, cholera and pertussis toxins belong to this group. Some of these enzymes interfer e with signal transduction mechanims of host cells, and have become wi dely used as research tools in cell biology because of their high pote ncy and selectivity. Recently relatives of these toxins have been clon ed from vertebrates. Seven members of a novel multigene family have be en identified to date. Surprisingly all are predicted to be extracellu lar proteins. Prefer-red tissues of expression are skeletal and cardia c muscle, testis and hematopoietic cells. ADP-ribosylation of target p roteins on the cell surface of T cells and leukocytes have been found to modulate the transmission of extracellular signals to the cell inte rior.