Human Latrophilin-2 is Expressed in the Cytotrophoblast and Syncytiotrophoblast of Placenta and in Endothelial Cells

Latrophilin-2 is a member of the family of adhesion-GPCRs that is characterised by a long N-terminus which contains motifs identified in proteins involved in cell adhesion. We were interested in determining the expression pattern of human latrophilin-2 and to perform a biochemical characterisation of this protein. The expression pattern of latrophilin-2 was analysed in human organs, tissues and cell lines. RT-PCR analyses detect a very strong signal for latrophilin-2 in human placenta and in situ hybridisation further showed that latrophilin-2 is predominantly expressed in the cytotrophoblast and syncytiotrophoblast. Moreover, latrophilin-2 expression is visible in adherent cells with a remarkably strong signal in microvascular endothelial cells (MVEC) and in human umbilical vein endothelial cells (HUVEC). Deglycosylation experiments using glycosidase F demonstrated that the N-terminal fragment of human latrophilin-2 is highly glycosylated. Using specific antibodies and latrophilin-2 stable cell lines we could show that human latrophilin-2 is cleaved into a 135 kDa N-terminal and a 70 kDa C-terminal fragment. It was also possible to detect the N-terminal fragment of latrophilin-2 in cell culture supernatant of HUVEC indicating that endogenous latrophilin-2 is expressed on the protein level in human vascular endothelial cells and that post-translational modification and generation of a 135 kDa N-terminal fragment takes place. The role of this fragment in the activation of the transmembrane domain of latrophilin-2 or in other cellular processes remains to be elucidated.