Nmp4/CIZ inhibits mechanically induced β-catenin signaling activity in osteoblasts

✍ Scribed by Zhouqi Yang; Joseph P. Bidwell; Suzanne R. Young; Rita Gerard-O'Riley; Haifang Wang; Fredrick M. Pavalko

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 291 KB
• Volume: 223
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.22057

✦ Synopsis

Abstract

Cellular mechanotransduction, the process of converting mechanical signals into biochemical responses within cells, is a critical aspect of bone health. While the effects of mechanical loading on bone are well recognized, elucidating the specific molecular pathways involved in the processing of mechanical signals by bone cells represents a challenge and an opportunity to identify therapeutic strategies to combat bone loss. In this study we have for the first time examined the relationship between the nucleocytoplasmic shuttling transcription factor __n__uclear __m__atrix __p__rotein‐4/cas interacting zinc finger protein (Nmp4/CIZ) and β‐catenin signaling in response to a physiologic mechanical stimulation (oscillatory fluid shear stress, OFSS) in osteoblasts. Using calvaria‐derived osteoblasts from Nmp4‐deficient and wild‐type mice, we found that the normal translocation of β‐catenin to the nucleus in osteoblasts that is induced by OFSS is enhanced when Nmp4/CIZ is absent. Furthermore, we found that other aspects of OFSS‐induced mechanotransduction generally associated with the β‐catenin signaling pathway, including ERK, Akt, and GSK3β activity, as well as expression of the β‐catenin‐responsive protein cyclin D1 are also enhanced in cells lacking Nmp4/CIZ. Finally, we found that in the absence of Nmp4/CIZ, OFSS‐induced cytoskeletal reorganization and the formation of focal adhesions between osteoblasts and the extracellular substrate is qualitatively enhanced, suggesting that Nmp4/CIZ may reduce the sensitivity of bone cells to mechanical stimuli. Together these results provide experimental support for the concept that Nmp4/CIZ plays an inhibitory role in the response of bone cells to mechanical stimulation induced by OFSS. J. Cell. Physiol. 223: 435–441, 2010. © 2010 Wiley‐Liss, Inc.