Identification of Proteins Associating with Glycosylphosphatidylinositol- Anchored T-Cadherin on the Surface of Vascular Endothelial Cells: Role for Grp78/BiP in T-Cadherin-Dependent Cell Survival

Abstract

There is scant knowledge regarding how cell surface lipid-anchored T-cadherin (T-cad) transmits signals through the plasma membrane to its intracellular targets. This study aimed to identify membrane proteins colocalizing with atypical glycosylphosphatidylinositol (GPI)-anchored T-cad on the surface of endothelial cells and to evaluate their role as signaling adaptors for T-cad. Application of coimmunoprecipitation from endothelial cells expressing c-myc-tagged T-cad and high-performance liquid chromatography revealed putative association of T-cad with the following proteins: glucose-related protein GRP78, GABA-A receptor ␣1 subunit, integrin ␤ 3 , and two hypothetical proteins, LOC124245 and FLJ32070. Association of Grp78 and integrin ␤ 3 with T-cad on the cell surface was confirmed by surface biotinylation and reciprocal immunoprecipitation and by confocal microscopy. Use of anti-Grp78 blocking antibodies, Grp78 small interfering RNA, and coexpression of constitutively active Akt demonstrated an essential role for surface Grp78 in T-cad-dependent survival signal transduction via Akt in endothelial cells. The findings herein are relevant in the context of both the identification of transmembrane signaling partners for GPI-anchored T-cad as well as the demonstration of a novel mechanism whereby Grp78 can influence endothelial cell survival as a cell surface signaling receptor rather than an intracellular chaperone.

Malignant Transformation in Skin is Associated with the Loss of T-Cadherin Expression in Human Keratinocytes and Heterogeneity in T-Cadherin Expression in Tumor Vasculature

“…In line with that, it was shown that T-cadherin mediated activation of PI3K/Akt/GSK3β signaling which protects endothelial cells from oxidative stressinduced apoptosis (Joshi et al, 2005). The effects of T-cadherin on Akt activation and survival require T-cadherin interacting partner Grp78, which is also known to be upregulated in cancers Philippova et al, 2008). High molecular weight adiponectin activates NF-kB and inhibits endothelial cell apoptosis suggesting that T-cadherin binding to adiponectin could prevent apoptosis of endothelial cells in tumor vessels (Adachi et al, 2006).…”

A novel pathogenic role of the ER chaperone GRP78/BiP in rheumatoid arthritis

“…For example, binding of activated 2-macroglobulin to GRP78 induces the UPR and cancer cell proliferation (Misra et al, 2006). Interaction of GRP78 with cell surface T-cadherin promotes endothelial cell survival (Philippova et al, 2008). In a recent study, surface-expressed citrullinated GRP78 on monocytes/macrophages was found to bind anti-CCP antibodies and stimulate TNF production (Lu et al, 2010).…”

C-ERC/mesothelin provokes lymphatic invasion of colorectal adenocarcinoma

“…This result might be explained by the possible positive feedback mechanism in which the over-expressed C-ERC could enhance the endogenous gene expression, and could be another aspect for biological malignancy of mesothelin. GPI-anchored proteins such as T-cadherin can transduce molecular signals that modulate cell migration and invasion with integrin-linked kinase [34] and integrin β3 [35]; in addition, an association between the expression of integrin and mesothelin in malignant pleural mesothelioma was reported using gene array [21].…”