peptide-phi and Lymphoma

The proliferation of human lymphoblastoma cell line (H9) was differently stimulated by Peptide Histidine Methionine (PHM) and Vasoactive Intestinal Peptide (VIP). PHM induced a cyclic AMP (cAMP) accumulation, abolished by Adenylate Cyclase (AC) inhibitors leading to a loss of proliferative effect. VIP mitogenic activity was Pertussis toxin (PTX) sensitive and AC inhibitors insensitive. Pharmacological experiments performed on H9 membranes with or without a GTP analogue indicated expression of both GTP-insensitive and -sensitive PHM/VIP high-affinity binding sites (HA). H9 cells expressed only the VPAC1 receptor. VIP(10-28), known as a VPAC1 antagonist, bond to all GTP-insensitive PHM sites and inhibited evenly the PHM and VIP mitogenic actions. These data strongly suggested different mechanisms initiated by VIP and PHM and highlighted the key role of GTP-insensitive binding sites in the control of cell proliferation.

Topics: Adenine; Adenylyl Cyclase Inhibitors; Analysis of Variance; Blotting, Southern; Bromodeoxyuridine; Cell Line, Tumor; Cell Proliferation; Cyclic AMP; Dose-Response Relationship, Drug; Drug Interactions; Gene Expression; Guanosine Triphosphate; Guanylyl Imidodiphosphate; Humans; Imines; Iodine Isotopes; Lymphoma; Peptide Fragments; Peptide PHI; Pertussis Toxin; Protein Binding; Radioligand Assay; Receptors, Cell Surface; Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; Receptors, Vasoactive Intestinal Peptide; Receptors, Vasoactive Intestinal Peptide, Type II; Receptors, Vasoactive Intestinal Polypeptide, Type I; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Time Factors; Vasoactive Intestinal Peptide

1. Based on radioligand binding and adenylate cyclase activation, functional receptors to vasoactive intestinal peptide(VIP)/helodermin, were shown to coexist with beta 2-adrenoceptors and prostaglandin receptors in membranes from a cultured cloned BL/VL3 cell line of murine T-cell lymphoma induced by a radiation leukemia virus. 2. The relative potency of VIP-related peptides to stimulate adenylate cyclase activity was: helodermin greater than VIP greater than peptide histidine isoleucinamide. Five VIP analogs inhibited 125I-iodo-VIP binding and stimulated adenylate cyclase activity, their decreasing order of potency being: VIP greater than [D-Asp3]VIP greater than [D-Ser2]VIP greater than [D-Ala4]VIP = [D-His1]VIP = [D-Phe2]VIP. [D-Phe2]VIP acted as a partial agonist (with an intrinsic activity of 0.1 as compared to that of VIP = 1.0) and competitively inhibited helodermin- and VIP-stimulated adenylate cyclase activity with a similar Ki (0.07-0.10 microM). These data suggest the existence, in this murine T-cell lymphoma, of VIP receptors of the 'helodermin-preferring' subtype that are coupled to adenylate cyclase.

Topics: Adenylyl Cyclases; Alprostadil; Animals; Catecholamines; Cell Membrane; Enzyme Activation; Intercellular Signaling Peptides and Proteins; Leukemia, Radiation-Induced; Lymphoma; Mice; Peptide PHI; Peptides; Receptors, Adrenergic, beta; Receptors, Gastrointestinal Hormone; Receptors, Prostaglandin; Receptors, Vasoactive Intestinal Peptide; Retroviridae; T-Lymphocytes; Tumor Cells, Cultured; Vasoactive Intestinal Peptide

1. Functional vasoactive intestinal peptide (VIP)/helodermin receptors and beta 2-adrenoceptors coexist in membranes from a cultured cloned BL/VL3 cell line of murine T-cell lymphoma induced by a radiation leukemia virus (see preceding paper in this journal). 2. Short-term (5-30 min) exposures of BL/VL3 cells to VIP or isoproterenol induced both homologous and heterologous desensitization. The potency of VIP and isoproterenol to desensitize was similar to their potency to occupy receptors and activate adenylate cyclase. 3. Long-term (16-h) exposure of BL/VL3 cells to VIP induced homologous down regulation only, whereas isoproterenol induced both homologous and heterologous down regulation. The potency of VIP, peptide histidine isoleucinamide, helodermin, helospectin, and [D-Phe2]VIP on the one hand, and of isoproterenol on the other hand, to decrease homologous responses was comparable to their potency for receptor occupancy and adenylate cyclase activation.

Topics: Adenylyl Cyclases; Animals; Cell Membrane; Drug Tolerance; Enzyme Activation; Guanylyl Imidodiphosphate; Intercellular Signaling Peptides and Proteins; Isoproterenol; Leukemia, Radiation-Induced; Lymphoma; Mice; Peptide PHI; Peptides; Receptors, Adrenergic, beta; Retroviridae; Sodium Fluoride; T-Lymphocytes; Tumor Cells, Cultured; Vasoactive Intestinal Peptide

A new type of VIP receptor was characterized in human SUP-T1 lymphoblasts. The order of potency of unlabeled peptides, in the presence of [125I]helodermin, was: helodermin(1-35)-NH2 = helodermin(1-27)-NH2 greater than helospectin greater than VIP = PHI greater than [D-Ser2]VIP greater than [D-Asp3]VIP greater than [D-His1]VIP greater than or equal to [D-Ala4]VIP greater than or equal to secretin = GRF. This specificity was distinct from that of all VIP receptors described so far in that: (i) the affinity for helodermin (Kd = 3 nM) was higher than that of VIP (Kd = 15 nM) and PHI (Kd = 20 nM); and (ii) position 4 played an important role in ligand binding. The labeled sites were likely to be functional receptors as adenylate cyclase in crude lymphoblastic membranes (200-10,000 x g pellets) was stimulated by peptides, in the presence of GTP, with the following order of potency: helodermin(1-35)-NH2 greater than helodermin(1-27)-NH2 greater than helospectin = VIP = PHI.

Topics: Adenylyl Cyclases; Cell Membrane; Guanosine Triphosphate; Humans; Intercellular Signaling Peptides and Proteins; Kinetics; Lymphoma; Peptide Fragments; Peptide PHI; Peptides; Receptors, Gastrointestinal Hormone; Receptors, Vasoactive Intestinal Peptide; T-Lymphocytes; Tumor Cells, Cultured; Vasoactive Intestinal Peptide