P2Y receptors activated by diadenosine polyphosphates reestablish Ca2+ transients in achondroplasic chondrocytes

Achondroplasia is the most common type of dwarfism, characterised by a mutation in the gene that encodes the fibroblast growth factor receptor 3 (FGFR3). Achondroplasia mainly affects the chondrocytes and therefore bones do not grow properly since intracellular pathways are altered. In this sense, defective calcium signaling by mutant FGFR3 has been previously described. The purpose of this study was to investigate the presence of purinergic P2Y receptors and how the activation of these receptors can have influence on defective calcium signaling observed in achondroplasic chondrocytes. The presence of P2Y receptors was determined by immunocytochemical and western blot techniques. Calcium mobilization after stimulation with nucleotides, dinucleotides, or, FGF9 application, was measured using the ratiometric dye fura-2/AM and fluorescence imaging. Our results demonstrate the expression of P2Y1, P2Y2, P2Y6 and P2Y11 receptors in achondroplasic chondrocytes, as well as the activation of these receptors after nucleotides and dinucleotides exposure. The altered calcium signaling of achondroplasic chondrocytes was confirmed, since FGF9 treatment fails to induce calcium mobilization. However, achondroplasic chondrocytes pre-treated with Ap4A are able to respond with increases in intracellular calcium after FGF9 stimulation. These findings show the rescue effect of diadenosine tetraphosphate (Ap4A), acting by means of P2Y receptors, on defective calcium response triggered by achondroplasic FGFR3.