Girdin/GIV Is Upregulated By Cyclic Tension, Propagates Mechanical Signal Transduction, And Is Required For The Cellular Proliferation And Migration Of MG63 Cells

Objective:To explore how girders of actin filaments (Girdin)/Gα-interacting vesicle-associating protein (GIV) is regulated by cyclic tension and propagates downstream signals to affect cell proliferation and migration.Methods:Human osteoblast-like MG63 cells were exposed to cyclic tension force at 4000 micro-strain and 0.5 Hz for 6 h, produced by a four-point bending system. The effects of mechanical tensile force on Girdin and Akt expression and phosphorylation were detected by Western Blot. Interactions between Girdin and Akt were investigated using RNA interference and Western Blot. The effects of Girdin and Akt on MG63 proliferation and migration were tested using MTT proliferation and transwell migration assays, respectively.Results:We found that (1) the protein expression levels and phosphorylation levels of Girdin and Akt were increased under conditions of tension stimulation in human osteoblast-like MG63 cells. (2) Although the total Akt or Girdin level did not change significantly after Girdin or Akt knockdown, knockdown of Girdin attenuated the base-level and tension force-induced phosphorylation of Akt, and knockdown of Akt inhibited the base-level and tension force-induced phosphorylation of Girdin. (3) In MTT proliferation assays, Girdin-or Akt-depleted cells had significantly lower levels of proliferation compared to scrambled control siRNA-treated cells. In transwell migration assays and Wound scratch assays, Girdin- or Akt-depleted cells also migrated less than the scrambled control siRNA-treated cells.Conclusion:These findings suggest that the Girdin/Akt pathway activates in response to mechanical stimulation and may play a significant role in triggering osteoblast proliferation and migration during orthodontic treatment. This study is the first report investigation the change in and role of Girdin in MG63 cells in response to cyclic tension force. Given its role in proliferation and migration of these cells, these results indicate that Girdin upregulation and phosphorylation are important events in the movement and manipulation of teeth by orthodontic practices.