Function Of Atp6v1c1 In Osteoclast, Tumor Cell Growth And Migration

V-ATPase exsits in all eukaryotic cells and palys a role by regulating pHcyt and pHex.The extracellular acidification function of vacuolar ATPase(V-ATPase) proton pump(s) present in the activated osteoclasts plasma membrane is necessary to osteoclast bone resorption.The exact configuration of osteoclast-specific ruffled border V-ATPase remains largely unknown.In this study,we found that V-ATPase subunit Atp6v1cl(C1) is highly expressed in osteoclasts but not subunits Atp6v1c2a (C2a) or Atp6v1c2b(C2b);the expression level of C1 is highly induced by RANKL during osteoclast differentiation;C1 interacts with Atp6v0a3(a3) and is mainly localized on the ruffled border of activated osteoclasts.In vitro,C1 co-localized with tublin just in cytoplasma in mature osteoclast.Our data showed for the first time that C1 silencing by lentivirus-mediated RNA interference severely impaired osteoclast acidification activity and bone resorption while cell differentiation did not appear to be affected,which is similar to a3 silencing;F-actin ring formation was severely defected in C1-depleted osteoclasts but not in a3-depleted and a3^-/- osteoclasts;and that C1 is co-localized with F-actin in cytoplasm,however,the co-localization is largely moved to plasma membranes of mature osteoclasts.Our study demonstrated that Atp6v1c1 is an essential component of the proton pump at the osteoclast ruffled border,and may regulate F-actin ring formation in osteoclast activation.In this study, we used retrovirus-mediated C1 overexpression in osteoclast,and found that C1 overexpression didn't inhibit the distruction of F-actin ring due to PP2(Src inhibitor), our study demonstrated that C1 needs other factors together to regulate the F-actin formation during osteoclast activation.In tumor cells,plasma memebrane V-ATPase(pmV-ATPase) are critical to cell growth,cell migration,apoptosis and drug resistance in cancer cells.Though subunit C1 was found sample wide over-expression in OSCC tumor cells compared to normal cells,the role of C1 higher expression in tumor cells growth and migration is not yet clear.In this study,we found that Atp6v1c1 ubiquitously expressed in tumor cells and the cell growth was retarded in C1-depleted mouse breast cancer cell line 4T1 and C1-depleted rat osteosarcoma cell line UMR-106,furthermore,the cell migration ability obviously decreased in the two C1-depleted cell lines.Our results suggested that Atp6v1c1 was involved in the regulation of tumor cells growth and migration.