Epidermal Growth Factor, latrophilin and seven transmembrane domain-containing protein 1; member of the class B2 family of seven-transmembrane G protein-coupled receptors
ETL (EGF-TM7-latrophilin-related protein) belongs to Group I adhesion GPCRs, which also include latrophilins (also called lectomedins or latrotoxin receptors). All adhesion GPCRs possess large N-terminal extracellular domains containing multiple structural motifs, which play critical roles in cell-cell adhesion and cell-matrix interactions, coupled to a seven-transmembrane domain. ETL, for instance, contains EGF-like repeats, which also present in other EGF-TM7 adhesion GPCRs, such as Cadherin EGF LAG seven-pass G-type receptors (CELSR1-3), EGF-like module receptors (EMR1-3), CD97, and Flamingo. ETL is highly expressed in heart, where developmentally regulated, as well as in normal smooth cells. Furthermore, almost all adhesion receptors, except GPR123, contain an evolutionarily conserved GPCR-autoproteolysis inducing (GAIN) domain that undergoes autoproteolytic processing at the GPCR proteolysis site (GPS) motif located immediately N-terminal to the first transmembrane region, to generate N- and C-terminal fragments (NTF and CTF), which may serve important biological functions.