**1. General Overview**

TCTP (also referred to as: HRF, fortilin, P23; gene symbol tpt-1; in yeast: TMA19 or Mmi1) was first described almost 40 years ago as a growth factor-induced, translationally controlled protein in murine cell lines [1,2]. The elucidation of its biological importance was initially hampered by the fact that, based on its amino acid sequence, it is not related to any other known protein family. It took a considerable international research effort, spread over more than three decades, to piece together the puzzle and reveal our current picture of the biological function of TCTP and of its involvement in various diseases. Several review articles on TCTP/HRF/fortilin have been published previously, and the first 'TCTP book' appeared in 2017, a compilation of 16 individual review articles covering a wide range of topics relating to this multifunctional protein [3]. Since then, a considerable number of new papers reported various novel aspects on TCTP, and it is the aim of this review to summarise these more recent additions to the 'TCTP story'. Being part of the Special Issue 'Role of TCTP in Cell Biological and Disease Processes' in *Cells*, our review will only briefly touch on those topics that are the subject of the other review articles within this Special Issue. However, we will discuss the research papers of the Special Issue, where appropriate, to put these into context.

### **2. Importance of TCTP in Core Cell Biological and Stress Reactions**

The involvement of TCTP in a multitude of cell biological processes is reflected by the large number of interacting proteins. Compilations of the many interaction partners of TCTP have been published in the above-mentioned book [4–6]. A more recent study, using current proteomics approaches combined with in silico network and gene ontology enrichment analysis, identified 113 interacting proteins [7], which were allocated to the following gene network clusters: translation, stress response, cytoskeleton, signal transduction, proteasomes, nucleosomes and transcription, RNA binding and metabolic enzymes. These clusters can be roughly associated with the following three core biological processes. We will discuss recent advances on the participation of TCTP in these processes, as summarised in Table 1 below.
