Mechanosensor polycystin-1 potentiates differentiation of human osteoblastic cells by upregulating Runx2 expression via induction of JAK2/STAT3 signaling axis
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Polycystin-1 (PC1) has been proposed as a chief mechanosensing molecule implicated in skeletogenesis and bone remodeling. Mechanotransduction via PC1 involves proteolytic cleavage of its cytoplasmic tail (CT) and interaction with intracellular pathways and transcription factors to regulate cell function. Here we demonstrate the interaction of PC1-CT with JAK2/STAT3 signaling axis in mechanically stimulated human osteoblastic cells, leading to transcriptional induction of Runx2 gene, a master regulator of osteoblastic differentiation. Primary osteoblast-like PC1-expressing cells subjected to mechanical-stretching exhibited a PC1-dependent increase of the phosphorylated(p)/active form of JAK2. Specific interaction of PC1-CT with pJAK2 was observed after stretching while pre-treatment of cells with PC1 (anti-IgPKD1) and JAK2 inhibitors abolished JAK2 activation. Consistently, mechanostimulation triggered PC1-mediated phosphorylation and nuclear translocation of STAT3. The nuclear phosphorylated(p)/DNA-binding competent pSTAT3 levels were augmented after stretching followed by elevated DNA-binding activity. Pre-treatment with a STAT3 inhibitor either alone or in combination with anti-IgPKD1 abrogated this effect. Moreover, PC1-mediated mechanostimulation induced elevation of Runx2 mRNA levels. ChIP assays revealed direct regulation of Runx2 promoter activity by STAT3/Runx2 after mechanical-stretching that was PC1-dependent. Our findings show that mechanical load upregulates expression of Runx2 gene via potentiation of PC1–JAK2/STAT3 signaling axis, culminating to possibly control osteoblastic differentiation and ultimately bone formation.
KeywordsPolycystin-1 Mechanosensor JAK/STAT pathway Mechanotransduction Runx2 Gene regulation Osteoblastic differentiation
We thank Dr. O. Ibraghimov-Beskrovnaya and H. Husson (Genzyme Co., MA, USA) for their generous gift of the anti-IgPKD1 inhibitory antibody. “Studies utilized resources provided by the NIDDK sponsored Baltimore Polycystic Kidney Disease Research and Clinical Core Center, P30 DK090868”.
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Conflict of interest
The authors declare that there are no conflicts of interest with any financial organization regarding the material discussed in the manuscript.
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