Role of sulfhydryl groups in the binding of vasoactive intestinal peptide to its receptor on murine lymphocytes.
The effect of sulfhydryl-containing compounds on the specific binding of the neuropeptide vasoactive intestinal peptide (VIP) to murine lymphocytes was studied. Both 2-mercaptoethanol (2ME) and dithiothreitol (DTT) inhibited VIP-binding to lymphocytes at millimolar concentrations. A sulfhydryl-containing analogue of VIP, [Cys2]VIP, was synthesized. This compound competed for the binding of [125I]VIP about 150,000 x more effectively than 2ME, but was approximately 100 x less effective than VIP itself. Both VIP and [Cys2]VIP increased intracellular cyclic AMP and inhibited the proliferative response of lymphocyte cultures to concanavalin A (ConA), but the molar potency of [Cys2]VIP on these lymphocyte activities was approximately 100 x less than that of VIP. The effects of VIP and [Cys2]VIP on intracellular cyclic AMP and ConA-stimulated proliferation were competed for by the VIP receptor antagonist [4Cl-D-Phe6,Leu17]VIP. Replacement of serine2 with L-cysteine disrupts the ability of VIP to occupy and activate lymphocyte VIP receptors. This may reflect a role of serine2 in hydrogen-bond formation during ligand-receptor interactions, or a functional role of sulfhydryl-containing residues of the VIP receptor in maintaining the integrity of the binding site of the VIP receptor on lymphocytes.
Ottaway
C A
CA
Department of Medicine, University of Toronto, Canada.
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D003208:Concanavalin A / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism*; D051379:Mice; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism*; D018005:Receptors, Vasoactive Intestinal Peptide; D013438:Sulfhydryl Compounds / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000037:antagonists & inhibitors / Q000378:metabolism*
D011964:Receptors, Gastrointestinal Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D013438:Sulfhydryl Compounds; D003208:Concanavalin A; D014660:Vasoactive Intestinal Peptide; D000242:Cyclic AMP