Expression by endothelial precursors of a new family of receptors sharing similarities with CXC chemokine receptors.

Characterization of a new family of G protein-coupled receptors is reported . Expression of these receptors is associated with endothelial lineage. Clo ning of the Xenope X-msr receptor allowed to show that embryonic expression of this receptor occurred in the heart and developing primary blood vessel s. Furthermore, within these cardiovascular structures, expression was rest ricted to the endothelial layer. Because structural similarities with the h uman orphan receptor h-APJ were found the msr/apj receptor was cloned in mi ce. This showed that embryonic expression of this receptor was also confine d to endothelial precursors. Thus, this receptor is the orthological equiva lent in mice to the amphibian receptor X-msr. Molecular phylogenesis studie s showed that the X-msr, msr/apj, and h-APJ receptors shared considerable h omology with two CXC chemokine receptors, namely LCR1, whose name was recen tly changed to CXCR4, and RDC1, which is structurally similar to the CXCR2 receptor. The human h-APJ receptor is a co-receptor for entry of the HIV in to T cells, a property associated only with CXC chemokine receptors in the lymphocyte population. These data suggest that this new signaling system ma y participate in endothelial precursor migration during developmental angio genesis and in endothelial cell migration and proliferation during neoangio genesis in adults.