title: Activation of the PI3K/Akt signaling pathway through P2Y₂ receptors by extracellular ATP is involved in osteoblastic cell proliferation.
abstract: We studied the PI3K/Akt signaling pathway modulation and its involvement in the stimulation of ROS 17/2.8 osteoblast-like cell proliferation by extracellular ATP. A dose- and time-dependent increase in Akt-Ser 473 phosphorylation (p-Akt) was observed. p-Akt was increased by ATPγS and UTP, but not by ADPβS. Akt activation was abolished by PI3K inhibitors and reduced by inhibitors of PI-PLC, Src, calmodulin (CaM) but not of CaMK. p-Akt was diminished by cell incubation in a Ca²⁺-free medium but not by the use of L-type calcium channel blockers. The rise in intracellular Ca²⁺ induced by ATP was potentiated in the presence of Ro318220, a PKC inhibitor, and attenuated by the TPA, a known activator of PKC. ATP-dependent p-Akt was diminished by TPA and augmented by Ro318220 treatment in a Ca²⁺-containing but not in a Ca²⁺-free medium. ATP stimulated the proliferation of both ROS 17/2.8 cells and rat osteoblasts through PI3K/Akt. In the primary osteoblasts, ATP induces alkaline phosphatase activity via PI3K, suggesting that the nucleotide promotes osteoblast differentiation. These results suggest that ATP stimulates osteoblast proliferation through PI-PLC linked-P2Y₂ receptors and PI3K/Akt pathway activation involving Ca²⁺, CaM and Src. PKC seems to regulate Akt activation through Src and the Ca²⁺ influx/CaM pathway.
authors.affiliation: Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, San Juan 670, (B8000ICN) Bahía Blanca, Argentina.
authors.forename: Sebastián
authors.initials: S
authors.lastname: Katz
authors.forename: Victoria
authors.initials: V
authors.lastname: Ayala
authors.forename: Graciela
authors.initials: G
authors.lastname: Santillán
authors.forename: Ricardo
authors.initials: R
authors.lastname: Boland
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D020013:Calcium Signaling; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D020935:MAP Kinase Signaling System / Q000187:drug effects; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D058473:Receptors, Purinergic P2Y2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D002147:Calmodulin; D058473:Receptors, Purinergic P2Y2; D000255:Adenosine Triphosphate; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D002118:Calcium