Cellular ATP Synthesis Mediated by Type III Sodium-dependent Phosphate Transporter Pit-1 Is Critical to Chondrogenesis

• Published in: The Journal of biological chemistry Vol. 286; no. 4; pp. 3094 - 3103
• Main Authors: Sugita, Atsushi, Kawai, Shinji, Hayashibara, Tetsuyuki, Amano, Atsuo, Ooshima, Takashi, Michigami, Toshimi, Yoshikawa, Hideki, Yoneda, Toshiyuki
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 28.01.2011; American Society for Biochemistry and Molecular Biology
• Subjects: Adenosine Triphosphate - biosynthesis; Animals; Apoptosis; Apoptosis - drug effects; Apoptosis - genetics; ATP; ATPases; Caspase; Caspase 3 - metabolism; Caspase 9 - metabolism; Cell Biology; Chondrocyte; Chondrocytes - metabolism; Chondrogenesis - drug effects; Chondrogenesis - physiology; Differentiation; Enzyme Inhibitors - pharmacology; Familial Hypophosphatemic Rickets - genetics; Familial Hypophosphatemic Rickets - metabolism; Female; Genetic Diseases, X-Linked; Humans; Male; Mice; Mice, Mutant Strains; Osteogenesis - drug effects; Osteogenesis - physiology; Phosphates - metabolism; Pit-1; Pyruvates - pharmacology; Sodium-Phosphate Cotransporter Proteins, Type III - genetics; Sodium-Phosphate Cotransporter Proteins, Type III - metabolism; Chondrocyte; Pit-1; Caspase; ATPases; Differentiation; ATP; Apoptosis
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M110.148403

Disturbed endochondral ossification in X-linked hypophosphatemia indicates an involvement of Pi in chondrogenesis. We studied the role of the sodium-dependent Pi cotransporters (NPT), which are a widely recognized regulator of cellular Pi homeostasis, and the downstream events in chondrogenesis using Hyp mice, the murine homolog of human X-linked hypophosphatemia. Hyp mice showed reduced apoptosis and mineralization in hypertrophic cartilage. Hyp chondrocytes in culture displayed decreased apoptosis and mineralization compared with WT chondrocytes, whereas glycosaminoglycan synthesis, an early event in chondrogenesis, was not altered. Expression of the type III NPT Pit-1 and Pi uptake were diminished, and intracellular ATP levels were also reduced in parallel with decreased caspase-9 and caspase-3 activity in Hyp chondrocytes. The competitive NPT inhibitor phosphonoformic acid and ATP synthesis inhibitor 3-bromopyruvate disturbed endochondral ossification with reduced apoptosis in vivo and suppressed apoptosis and mineralization in conjunction with reduced Pi uptake and ATP synthesis in WT chondrocytes. Overexpression of Pit-1 in Hyp chondrocytes reversed Pi uptake and ATP synthesis and restored apoptosis and mineralization. Our results suggest that cellular ATP synthesis consequent to Pi uptake via Pit-1 plays an important role in chondrocyte apoptosis and mineralization, and that chondrogenesis is ATP-dependent.