Latrophilin fragments behave as independent proteins that associate and signal on binding of LTX(N4C).
Heptahelical, or G-protein-coupled, receptors control many cellular functions and normally consist of one polypeptide chain. In contrast, heptahelical receptors that belong to the long N-terminus, group B (LNB) family are cleaved constitutively into two fragments. The N-terminal fragments (NTFs) resemble cell-adhesion proteins and the C-terminal fragments (CTFs) are typical G-protein-coupled receptors (GPCRs) with seven transmembrane regions. However, the functional roles of this cleavage and of any subsequent NTF-CTF interactions remain to be identified. Using latrophilin, a well-studied member of the LNB family, we now demonstrate that cleavage is critical for delivery of this receptor to the cell surface. On the plasma membrane, NTF and CTF behave as separate membrane proteins involved, respectively, in cell-surface reception and signalling. The two fragments can also internalise independently. However, separated NTF and CTF can re-associate on solubilisation. Agonist binding to NTF on the cell surface also induces re-association of fragments and provokes signal transduction via CTF. These findings define a novel principle of structural and functional organisation of the cleaved, two-subunit GPCRs.
Department of Biological Sciences, Imperial College, London, UK.
Kirill E
KE
Volynski
John-Paul
JP
Silva
Vera G
VG
Lelianova
M
M
Atiqur Rahman
Colin
C
Hopkins
Yuri A
YA
Ushkaryov
D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002522:Chlorocebus aethiops; D036681:Fluorescence Recovery After Photobleaching; D019084:Fluorescent Antibody Technique, Indirect; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D018613:Microscopy, Confocal; D008954:Models, Biological; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism*; D018000:Receptors, Peptide / Q000737:chemistry / Q000378:metabolism*; D015398:Signal Transduction
D008565:Membrane Proteins; D010446:Peptide Fragments; D011506:Proteins; D018000:Receptors, Peptide; C034800:alpha-latrotoxin receptor