Fig. 1
From: The mechanosensor of mesenchymal stem cells: mechanosensitive channel or cytoskeleton?
Two different models of the transient receptor potential melastatin 7 (TRPM7) mediation of mechanical stimulation in MSCs. Left: The bilayer lipid model. When mechanical stimulus is applied to the plasma membrane, TRPM7 is activated by membrane tension conducting Ca2+ influx. At the same time, cytophospholipase C (PLC) is activated and may hydrolyze phosphatidylinositol 4,5-bisphosphate (PIP2) to produce inositol trisphosphate (IP3) which subsequently activates inositol trisphosphate receptor type 2 (IP 3 R2) on the endoplasmic reticulum (ER) conducting Ca2+ release. Right: The cytoskeleton tether model. When mechanical stimulus is applied to the cytoskeleton, it transmits stress that activates TRPM7-conducting Ca2+ influx, followed by activation of ER-conducting Ca2+ release. The exact linkage mechanism between TRPM7 and ER IP3Rs is still unknown. With mechanical stimulation, transcription factors like NFATc1 translocate to the nucleus and promote the osteogenic gene expression. Alkaline phosphatase (ALP), Bone Morphogenetic Proteins (BMP), Diacylglycerols (DAG), Fibronectin (Fn)