Cellular Function and Regulation of the Translationally Controlled Tumour Protein TCTP

The 'translationally controlled tumour protein' TCTP was originally discovered 30 years ago by researchers in- terested in proteins regulated at the translational level. Cloning and sequencing confirmed the conservation of this protein among all eukaryotic kingdoms, but did not reveal any functional clue, and TCTP was listed in the databases as a 'family' of its own. The functional characterisation of this protein extended over more than a decade, leading to a plethora of indi- vidual functions and interactions that have been ascribed to this protein. A major addition to the functional characterisa- tion of TCTP was the identification in 1995 of its histamine releasing factor (HRF) activity in allergic conditions, which for the first time described an extracellular activity for TCTP in human disease. This triggered a host of additional publi- cations aimed at characterising this HRF activity, which are discussed in other articles of this issue. Another milestone in the elucidation of TCTP's function was the demonstration of its anti-apoptotic activity in 2001. Evidence is also accumu- lating for a role of TCTP in the cell cycle and in early development. This article provides an overview of the main cellular activities of TCTP. The second part will summarise our current knowledge on the mechanisms involved in regulating in- tracellular TCTP levels.