IBMS BoneKEy | Perspective

EPHs and ephrins: Many pathways to regulate osteoblasts and osteoclasts

Natalie A Sims



The EPH/Ephrin family of receptor tyrosine kinases has been shown recently to play important roles in communication between osteoblasts and osteoclasts, and within the osteoblast lineage that regulates the differentiation of these cells. This Perspective provides a brief overview of EPH/Ephrin signaling from work carried out in other cell and organ systems, and reviews the current literature on the actions of these kinases in bone. The EPH/Ephrin family provides multiple signaling pathways that themselves may be important within bone cells. They also interact with other pathways known to regulate osteoblast and osteoclast activity (e.g., FGFs, metalloproteinases, integrins and connexins). EPH/Ephrin signaling pathways demonstrate a high level of promiscuity within the family, and are particularly interesting by virtue of the ability of the EPH/Ephrin interaction to simultaneously induce signal transduction within two cells. At this stage, there are few studies of the actions of EPH/Ephrin signaling within bone cells. Although we now know a few members of the EPH/Ephrin family that modify both osteoblast and osteoclast differentiation, we do not know how they elicit their effects in bone, which pathways are most important, and which other regulatory pathways are influenced by the EPH/Ephrin family within the skeleton.

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