A G-PROTEIN-COUPLED RECEPTOR WITH LOW-DENSITY LIPOPROTEIN-BINDING MOTIFS SUGGESTS A ROLE FOR LIPOPROTEINS IN G-LINKED SIGNAL-TRANSDUCTION

We have isolated and analyzed a cDNA from the central nervous system o f the mollusc Lymnaea stagnalis encoding a putative receptor, which mi ght be a natural hybrid between two different classes of receptor prot eins. Preceded by a signal peptide, two types of repeated sequences ar e present in the N-terminal part of the protein. The first repeat disp lays a high sequence similarity to the extracellular binding domains o f the low density lipoprotein receptor, which binds and internalizes c holesterol-containing apolipoproteins. The second repeat and the C-ter minal part of the Lymnaea receptor are very similar to regions of a sp ecific class of guanine nucleotide-binding protein-coupled receptors, the mammalian glycoprotein hormone receptors. The mRNA encoding the re ceptor is predominantly expressed in a small number of neurons within The central nervous system and to a lesser extent in the heart.