Endoglin Regulates Cytoskeletal Organization through Binding to ZRP-1, a Member of the Lim Family of Proteins

Abstract

Endoglin is a component of the transforming growth factor-␤ receptor complex abundantly expressed at the surface of endothelial cells and plays an important role in cardiovascular development and vascular remodeling. By using the cytoplasmic domain of endoglin as a bait for screening protein interactors, we have identified ZRP-1 (zyxin-related protein 1), a 476-amino acid member that belongs to a family of LIM containing proteins that includes zyxin and lipoma-preferred partner. The endoglin interacting region was mapped within the three double zinc finger LIM domains of the ZRP-1 C terminus. Analysis of the subcellular distribution of ZRP-1 demonstrated that in the absence of endoglin, ZRP-1 mainly localizes to focal adhesion sites, whereas in the presence of endoglin ZRP-1 is found along actin stress fibers. Because the LIM family of proteins has been shown to associate with the actin cytoskeleton, we investigated the possibility of a regulatory role for endoglin with regard to this structure. Expression of endoglin resulted in a dramatic reorganization of the actin cytoskeleton. In the absence of endoglin, F-actin was localized to dense aggregates of bundles, whereas in the presence of endoglin, expressed in endothelial cells, F-actin was in stress fibers and colocalized with ZRP-1. Furthermore, small interfering RNA-mediated suppression of endoglin or ZRP-1, or clustering of endoglin in endothelial cells, led to mislocalization of Factin fibers. These results suggest a regulatory role for endoglin, via its interaction with ZRP-1, in the actin cytoskeletal organization.

Endoglin expression in breast tumor cells suppresses invasion and metastasis and correlates with improved clinical outcome

“…This is consistent with the previous data in endothelial cells where endoglin has been shown to bind directly to zyxin and to sequester zyxin and its binding partners p130cas and CrkII away from focal adhesion complexes (Conley et al, 2004). In addition, endoglin has been shown to interact with zyxin-related protein 1 resulting in a dramatic change in the structure of the actin cytoskeleton and the localization of zyxinrelated protein 1 (Sanz-Rodriguez et al, 2004). Second, in addition to TGF-b1, endoglin can bind, in association with different TGF-b superfamily receptors, to BMP2, BMP7, BMP9, activin A and TGF-b3 (Cheifetz et al, 1992;Barbara et al, 1999;Scharpfenecker et al, 2007), and has been reported to have a functional role in modulating responses to BMP2 (Ishibashi et al, 2010) and BMP7 (Scherner et al, 2007) in periodontal ligament cells and myoblasts, respectively.…”

Activin receptor‐like kinase 1 inhibits human microvascular endothelial cell migration: Potential roles for JNK and ERK

“…Taken together, these data led us to postulate that ALK1 could play an important role in the transition of endothelial cells to the maturation phase of angiogenesis through inhibition of proliferation and migration of endothelial cells. It is interesting to remark that similarly to our observations, recent investigations have revealed a novel function for endoglin, the non-signaling member of the TGFb1 receptor family, in which mutations are responsible of HHT1, in modulating actin cytoskeleton organization and cell migration (Conley et al, 2004;Sanz-Rodriguez et al, 2004;Muenzner et al, 2005).…”

Characterization of murine S-endoglin isoform and its effects on tumor development

“…Therefore, in cells in which both isoforms are cosynthesized, the presence of L-S heterodimers, in addition to L-L and S-S homodimers, would add a new level of functional complexity to the endoglin molecule. In this respect, it is tempting to speculate that the ability to modulate TGF-b responses, as a result of the interaction of the L and S cytoplasmic domains with TGF-b receptors (Guerrero-Esteo et al, 2002), or the association with cytoskeletal components (Conley et al, 2004;Sanz-Rodriguez et al, 2004) would be different for the distinct endoglin dimers. Endoglin is upregulated in angiogenic endothelial cells, and several studies suggest that it is required for angiogenesis (reviewed in Li et al, 2001;Duff et al, 2003).…”