T-cadherin, also known as cadherin 13, H-cadherin (heart), and CDH13, is a unique member of the cadherin superfamily of proteins because it lacks the transmembrane and cytoplasmic domains common to all other cadherins and is instead anchored to the cell's plasma membrane by the GPI anchor. Unlike classical cadherins, which are necessary for cell–cell adhesion, dynamic regulation of morphogenetic processes in embryos, and tissue integrity in adult organisms, and function as membrane receptors mediating signals received from the extracellular space, activate small GTPases and the beta-catenin/Wnt pathway, and play important roles in dynamic cytoskeleton reorganization, the GPI-anchored T-cadherin lacks direct contact with the cytoskeleton and therefore is not involved in cell–cell adhesion. It is instead involved in low-density lipoprotein (LDL) hormone-like effects on Ca2+ mobilization and increased cell migration as well as phenotypic changes. The exact signaling partners and adaptor proteins recognized by T-cadherin remain to be elucidated. Mediation of intracellular signaling in vascular cells Though T-cadherin can mediate weak adhesion in aggregation assays in vitro, the lack of intracellular domain suggests that T-cadherin is not involved in stable cell-cell adhesion. In vivo T-cadherin was detected on the apical cell surface of the chick intestinal epithelium. In cultures of transfected MDCS cells, T-cadherin was also expressed apically, whereas N-cadherin located basolaterally corresponded to the zone of cell contacts. The apical cell surface distribution of T-cadherin was proposed to possibly endow T-cadherin with recognition functions. In confluent cultures of vascular cells, T-cadherin was distributed equally over the entire cell surface, in contrast to VE-cadherin, which was restricted to the cell junctions. In migrating vascular cells, T-cadherin was located at the leading edge as revealed by confocal microscopy. The distribution of T-cadherin on the cell membrane is restricted to lipid rafts where it co-localizes with signal-transducing molecules. These data strongly implicates T-cadherin in intracellular signaling rather than adhesion. Studying signaling effects of low density lipoproteins (LDL) in vascular smooth muscles (VSMCs), T-cadherin was isolated and identified as new LDL receptor using human aortic media and the ligand-blotting method. The properties of T-cadherin as an LDL receptor were markedly different from the presently known types of LDL receptors. LDL binding to T-cadherin leads to the activation of Erk 1/2 tyrosine kinase and the nuclear translocation of NF-kappaB. T-cadherin overexpression in ECs facilitates spontaneous cell migration, formation of stress fibers and change of the phenotype from quiescent to promigratory. T-cadherin expression results in LDL-induced