The multifunctional roles of the four-and-a-half-LIM only protein FHL2

Numerous cellular processes require the concerted action of multiple proteins that assemble in functional complexes. Protein-protein interaction domains allow specific proteins to combine with certain partners. Specificity of protein-protein association can be obtained by an interaction code predicted by conserved amino acid sequences. One of the protein-protein interaction motifs is the LIM domain, a conserved cysteine-rich module present in more than 100 different human proteins. The human four-and-a-half-LIM-only protein family consists of the members FHL1, FHL2, FHL3, FHL4 and ACT. They are expressed in a cell- and tissue-specific manner and participate in various cellular processes, including regulation of cell survival, transcription and signal transduction. Here, we review the current knowledge of the best-studied member of this family, FHL2. We describe the transcription regulation, the expression profile, the interaction partners, the subcellular localization, the biological functions and discuss the possible involvement of FHL2 in human diseases.