Evidence that activation of ASIC1a by acidosis increases osteoclast migration and adhesion by modulating integrin/Pyk2/Src signaling pathway
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Activated acid-sensing ion channel 1a (ASIC1a) is involved in acid-induced osteoclastogenesis by regulating activation of the transcription factor NFATc1. These results indicated that ASIC1a activation by extracellular acid may cause osteoclast migration and adhesion through Ca2+-dependent integrin/Pyk2/Src signaling pathway.
Osteoclast adhesion and migration are responsible for osteoporotic bone loss. Acidic conditions promote osteoclastogenesis. ASIC1a in osteoclasts is associated with acid-induced osteoclastogenesis through modulating transcription factor NFATc1 activation. However, the influence and the detailed mechanism of ASIC1a in regulating osteoclast adhesion and migration, in response to extracellular acid, are not well characterized.
In this study, knockdown of ASIC1a was achieved in bone marrow macrophage cells using small interfering RNA (siRNA). The adhesion and migration abilities of osteoclast precursors and osteoclasts were determined by adhesion and migration assays, in vitro. Bone resorption was performed to measure osteoclast function. Cytoskeletal changes were assessed by F-actin ring formation. αvβ3 integrin expression in osteoclasts was measured by flow cytometry. Western blotting and co-immunoprecipitation were performed to measure alterations in integrin/Pyk2/Src signaling pathway.
Our results showed that blockade of ASIC1a using ASIC1a-siRNA inhibited acid-induced osteoclast precursor migration and adhesion, as well as osteoclast adhesion and bone resorption; we also demonstrated that inhibition of ASIC1a decreased the cell surface αvβ3 integrin and β3 protein expression. Moreover, blocking of ASIC1a inhibited acidosis-induced actin ring formation and reduced Pyk2 and Src phosphorylation in osteoclasts and also inhibited the acid-induced association of the αvβ3 integrin/Src/Pyk2.
Together, these results highlight a key functional role of ASIC1a/αvβ3 integrin/Pyk2/Src signaling pathway in migration and adhesion of osteoclasts.
KeywordsAcidosis Acid-sensing ion channel 1a Adhesion Migration Osteoclast Pyk2 Src
This study was supported by the Natural Science Foundation of China (81270011; 81472125) and the Natural Science Foundation of Jiangsu Province (Grant BK20151114) and Foundation of Traditional Chinese Medicine of Jiangsu Province (YB201578).
Compliance with ethical standards
Experimental protocols of this study were approved by the Ethics Committee of Medical College of Nantong University (20141101-001).
Conflicts of interest
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