1. VNUT/SLC17A9, a vesicular nucleotide transporter, regulates osteoblast differentiation
- Author
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Kazumasa Morikawa, Tatsuo Kawamoto, Shoichiro Kokabu, Tomohiko Shirakawa, Asako Inoue, Mitsushiro Nakatomi, Kaori Kometani-Gunjigake, Kazuma Yasuda, Masahiro Mizuhara, Takuma Matsubara, Misa Ito-Sago, Kayoko Nakao-Kuroishi, and Yukiyo Tada-Shigeyama
- Subjects
0301 basic medicine ,musculoskeletal diseases ,compressive force ,General Biochemistry, Genetics and Molecular Biology ,03 medical and health sciences ,chemistry.chemical_compound ,Mice ,0302 clinical medicine ,Downregulation and upregulation ,Extracellular ,medicine ,Animals ,VNUT ,lcsh:QH301-705.5 ,Research Articles ,Cells, Cultured ,Gene knockdown ,Osteoblasts ,Chemistry ,Purinergic receptor ,Osteoblast ,Cell Differentiation ,3T3 Cells ,Cell biology ,RUNX2 ,ATP ,030104 developmental biology ,medicine.anatomical_structure ,P2 receptor ,lcsh:Biology (General) ,030220 oncology & carcinogenesis ,osteoblast differentiation ,Nucleotide Transport Proteins ,osteoblast ,Alkaline phosphatase ,Adenosine triphosphate ,Research Article - Abstract
Osteoblasts release adenosine triphosphate (ATP) out of the cell following mechanical stress. Although it is well established that extracellular ATP affects bone metabolism via P2 receptors [such as purinergic receptor P2X7 (P2X7R) and purinergic receptor P2Y2 (P2Y2R)], the mechanism of ATP release from osteoblasts remains unknown. Recently, a vesicular nucleotide transporter [VNUT, solute carrier family 17 member 9 (SLC17A9)] that preserves ATP in vesicles has been identified. The purpose of this study was to elucidate the role of VNUT in osteoblast bone metabolism. mRNA and protein expression of VNUT were confirmed in mouse bone and in osteoblasts by quantitative real‐time PCR (qPCR) and immunohistochemistry. Next, when compressive force was applied to MC3T3‐E1 cells by centrifugation, the expression of Slc17a9, P2x7r, and P2y2r was increased concomitant with an increase in extracellular ATP levels. Furthermore, compressive force decreased the osteoblast differentiation capacity of MC3T3‐E1 cells. shRNA knockdown of Slc17a9 in MC3T3‐E1 cells reduced levels of extracellular ATP and also led to increased osteoblast differentiation after the application of compressive force as assessed by qPCR analysis of osteoblast markers such as Runx2, Osterix, and alkaline phosphatase (ALP) as well as ALP activity. Consistent with these observations, knockdown of P2x7r or P2y2r by siRNA partially rescued the downregulation of osteoblast differentiation markers, caused by mechanical loading. In conclusion, our results demonstrate that VNUT is expressed in osteoblasts and that VNUT inhibits osteoblast differentiation in response to compressive force by mechanisms related to ATP release and P2X7R and/or P2Y2R activity., In this study, we show that VNUT (SLC17A9), a vesicular nucleotide transporter, regulates osteoblast differentiation in response to mechanical loading. Mechanical loading promotes adenosine triphosphate (ATP) exocytosis via VNUT. Extracellular ATP subsequently inhibits osteoblast differentiation via activation of P2X7 and/or P2Y2 receptors. Thus, VNUT modulation of purinergic signaling contributes to the regulation of bone metabolism by mechanical loading.
- Published
- 2020