[Spatial Models of Piezo Proteins and Protein-Protein Interaction Networks in Trichoplax Animals (Placozoa)].

The marine free-living organism Trichoplax (phylum Placozoa) resembles a unicellular amoeba in shape and type of movement. Trichoplax diverged from the main evolutionary tree in the Neoproterozoic Era. Trichoplax provides one of the simplest models of multicellular animals and a strong example of how cells of an organism interact to form an ensemble during its development and movement. Two orthologs of the mouse Piezo1 protein (6B3R) were found in two Trichoplax haplotypes, H1 and H2, as a result of a search for similar sequences in the NCBI databases. Spatial models of the respective proteins XP_002112008.1 and RDD46920.1 were created via a structural alignment with 6KG7 (mouse Piezo2) template. Their domain structures were analyzed, and a limited graph of protein-protein interactions was constructed for the hypothetical mechanosensor XP_002112008.1. The possibility of signal transduction from the mechanoreceptor to membrane complexes, the cytoplasm, and the cell nucleus was shown. Trichoplax mechanoreceptors were assumed to play a role in perception of force stimuli from neighbor cells and the environment. Based on the results, the primitive Trichoplax organism was proposed as the simplest multicellular model of mechanical and morphogenetic movements.

The role of Piezo proteins and cellular mechanosensing in tuning the fate of transplanted stem cells.

Differentiation of stem cells can be modulated by a combination of internal and external signals, including mechanical cues from the surrounding microenvironment. Although numerous chemical and biological agents have been recognized in regulating stem cells' fate, little is known about their potential to directly sense the mechanical signals to choose differentiation into a specific lineage. The success of any stem cell transplantation effort, however, hinges on thorough understanding of the fate of these cells under different signals, including mechanical cues. Various proteins are involved in the mechanical sensing process. Of these, Piezo proteins, as the ion channels activated by membrane tension and mechanical signals, play an important role in translating the information of mechanical forces such as rigidity and topography of the extracellular matrix to the intracellular signaling pathways related to stem cell homing and differentiation. They also play a key role in terms of shear stresses and tensile loads in expansion systems. This review highlights key evidence for the potential of mechanically gated ion channels expressed by human stem cells, and the mechanotransduction and past mechanomemory in the fate of transplanted stem cells. With this knowledge in mind, by controlling the tissue-specific patterns of mechanical forces in the scaffolds, we may further improve the regulation of homing, the differentiation, and the fate of transplanted stem cells.