Scratching the surface: Actin' and other roles for the C-terminal Eps15 homology domain protein, EHD2

The C-terminal Eps15 homology domaincontaining (EHD) proteins participate in multiple aspects of endocytic membrane trafficking. Of the four mammalian EHD proteins, EHD2 appears to be the most disparate, both in terms of sequence homology, and in subcellular localization/function. Since its initial description as a plasma membrane-associated protein, the precise function of EHD2 has remained enigmatic. Various reports have suggested roles for EHD2 at the plasma membrane, within the endocytic transport system, and even in the nucleus. For example, EHD2 facilitates membrane fusion/repair in muscle cells. Recently the focus has shifted to the role of EHD2 in regulating caveolae. Indeed, EHD2 is highly expressed in tissues rich in caveolae, including fat, muscle and blood vessels. This review highlights cumulative evidence linking EHD2 to actin-rich structures at the plasma membrane, where the plasma membraneassociated phospholipid phosphatidylinositol 4,5- bisphosphate controls EHD2 recruitment. Herein we examine the key pathways where EHD2 might function, and address its potential involvement in these processes.