helospectin-i and heliodermin

Exendins are secretin hormone-like peptides that are components of the toxins from two venomous lizards, Heloderma suspectum (Gila monster) and Heloderma horridium (Mexican bearded lizard). Exendins-1 and -2 are vasoactive intestinal peptide (VIP)-like, both in sequence and function, while exendins-3 and -4 are glucagon-like peptide-1 (GLP-1)-like. The evolutionary origin of these peptides, and the genes that encode them, has been unclear. Recently, genes orthologous to exendin have been identified in reptiles, birds and amphibians. Analysis of the orthologous sequences demonstrates that the Heloderma exendins diversified by gene duplication from a common exendin ancestor on the Heloderma lineage after divergence from other reptiles, including the anole lizard and Burmese python. In addition, the exendin toxin peptide sequences, but not their pro or signal peptides, have evolved very rapidly on the Heloderma lineage, likely as they adapted to their new function as toxins. Exendins-1 and -2 not only evolved rapidly but their sequences have evolved convergently upon that of VIP, resulting in a doubling of its identity with VIP, while exendins-3 and -4 have retained an ancestral property of being more GLP-1-like sequences. These results suggest that the ancestral role of exendin, which is potentially still retained in some species, had greater similarity with proglucagon-derived peptides or GIP.

Topics: Amino Acid Sequence; Animals; Evolution, Molecular; Exenatide; Intercellular Signaling Peptides and Proteins; Lizards; Molecular Sequence Data; Peptides; Phylogeny; Venoms; Vertebrates

Vasoactive intestinal polypeptide (VIP) is known as an important regulator of airway function. It has been suggested that VIP is involved in the pathogenesis of asthma due to its relaxant effects on smooth muscles. The present study was designed to characterize the effects of the peptides of the VIP family on airway mucus secretion. The peptides VIP, PHI, PACAP-27, PACAP-38, GLP-I, exendin-4, helodermin, helospectin I and helospectin II were investigated using isolated rat trachea. Data show that PACAP-27 is the most potent stimulator of airway mucus secretion (225% stimulation). The rank order of potency was PACAP-27 > VIP > helospectin II > PHI > exendin-4 = helodermin = helospectin I = PACAP-38. The addition of the protease inhibitor thiorphan enhanced the effects of PHI and helodermin, but not of the other peptides. These data show that the peptides of the VIP family stimulate airway mucus secretion differently.

Topics: Animals; Exenatide; Glucagon; Glucagon-Like Peptide 1; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Male; Mucus; Neuropeptides; Peptide Fragments; Peptide PHI; Peptides; Pituitary Adenylate Cyclase-Activating Polypeptide; Protease Inhibitors; Protein Precursors; Rats; Rats, Sprague-Dawley; Thiorphan; Trachea; Vasoactive Intestinal Peptide; Venoms

The present study was designed to study the localization and effects of some VIP-related peptides on the cerebral circulation in cats. A rich supply of nerve fibres containing vasoactive intestinal peptide- (VIP) was seen. Nerve fibres containing pituitary adenylate cyclase activating peptide and helospectin-like immunoreactivity (-IR) were moderate in numbers whereas only a sparse supply of fibres containing helodermin-IR was seen. Double immunostaining revealed that the majority of PACAP- and helospectin-IR nerve fibres contained VIP. Using a sensitive in vitro system prostaglandin F2 alpha-precontracted circular segments of the cat middle cerebral artery relaxed upon administration of VIP, PACAP, helospectin I, helospectin II and helodermin. These effects were non-endothelium dependent with pD2-values varying between 7.6 and 8.1. The maximum relaxation varied between 47% and 79% of precontraction. Local cerebral blood flow was studied in anaesthetised cats. Cortical injection of PACAP-38, helospectin or helodermin, 5 micrograms in a volume of 1 microliter, revealed moderate and consistent increases in flow. The increase in cerebral blood flow was rapid and concentration-dependent with maximum increases of 18 +/- 6% for PACAP, 21 +/- 5% for helodermin, 16 +/- 7% for helospectin I and 19 +/- 5% for helospectin II. The vehicle caused no significant response (2 +/- 4%).

Topics: Animals; Cats; Cerebral Arteries; Cerebrovascular Circulation; Dinoprost; Endothelium, Vascular; Immunohistochemistry; Intercellular Signaling Peptides and Proteins; Laser-Doppler Flowmetry; Neuropeptides; Peptides; Pituitary Adenylate Cyclase-Activating Polypeptide; Vasoactive Intestinal Peptide

Helodermin and helospectin are peptides structurally similar to vasoactive intestinal polypeptide (VIP) which were recently isolated from the salivary gland venom of the lizard Heloderma suspectum. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been isolated from ovine hypothalamus and also shows sequence homology to VIP. A helodermin-like peptide has been detected by combined immunohistochemical and immunochemical techniques in the thyroid C-cells. In the present study, lizard helodermin was found to cause a time- and dose-dependent stimulation of cyclic AMP (cAMP) formation in neonatal mouse calvarial bones. Also, helospectin I, PACAP 27, and the C-terminally extended PACAP 38 stimulated cAMP accumulation in the mouse calvariae. The cAMP rise in response to helodermin was comparable to that induced by VIP, both in terms of potency and magnitude of the response. Helodermin, helospectin I, PACAP 27, and PACAP 38, at concentrations of 1 mumol/liter, stimulated cAMP accumulation in enzymatically isolated mouse calvarial bone cells. A significant response to all peptides was observed in both early and late released bone cells isolated from the calvariae, with low and high alkaline phosphatase activity, respectively. Helodermin and VIP stimulated cAMP accumulation in the cloned mouse calvarial osteoblastic cell line MC3T3-E1, in rat (UMR 106-01), and human (Saos-2) osteoblastic osteosarcoma cell lines, but not in the rat osteosarcoma cell line ROS 17/2.8. The effect of helodermin was synergistically and dose-dependently enhanced by forskolin (0.1 and 1 mumol/liter). These data show that bone cells, including osteoblasts, respond to several peptides of the VIP family, including helodermin, helospectin I, PACAP 27, and PACAP 38.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: 3T3 Cells; Analysis of Variance; Animals; Cell Line; Cyclic AMP; Intercellular Signaling Peptides and Proteins; Lizards; Mice; Neuropeptides; Neurotransmitter Agents; Osteoblasts; Osteosarcoma; Peptides; Phospholipases A; Pituitary Adenylate Cyclase-Activating Polypeptide; Rats; Tumor Cells, Cultured

The lower airways of guinea pigs were analysed for helospectin and helodermin using immunocytochemistry. A moderate supply of helospectin/helodermin-like immunoreactive nerve fibers and few nerve fibers displaying helodermin immunoreactivity was seen in the smooth muscle, around seromucous glands and small blood vessels in the trachea and around bronchi and pulmonary blood vessels. Helospectin I-, helospectin II- and helodermin-induced suppression of smooth muscle responses were analysed using isolated circular segments of trachea and pulmonary arteries of guinea pigs. In both airways and arteries the peptides caused a concentration-dependent relaxation of precontracted segments. The maximal relaxant activity observed was more pronounced in the airways than in the arteries. The effects of the helospectins and helodermin were compared to those of vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), pituitary adenylate cyclase activating peptide (PACAP) and acetylcholine (ACh). All peptides, with the exception of PACAP, caused a total or nearly total relaxation of the precontracted tracheal segments. In the trachea PACAP was significantly more potent than the other five peptides whereas only small potency differences were seen in the pulmonary artery. The relaxant responses to helospectin I, helospectin II and helodermin in the trachea and the intrapulmonary arteries were unaffected by pretreatment with atropine, prazosin, yohimbine, propranolol, mepyramine and cimetidine. Conceivably, nerve fibers containing helospectin and helodermin may play a role in the regulation of airway resistance and in the regulation of local pulmonary blood flow.

Topics: Acetylcholine; Animals; Guinea Pigs; Immunohistochemistry; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Lung; Male; Neuropeptides; Peptide PHI; Peptides; Pituitary Adenylate Cyclase-Activating Polypeptide; Pulmonary Artery; Tissue Distribution; Trachea; Vasoactive Intestinal Peptide; Vasodilation

We have compared the effects of vasoactive intestinal peptide (VIP) and of the VIP-related peptides pituitary adenylate cyclase activating peptide (PACAP) 1-27 and 1-38, helodermin, helospectin I and helospectin II, on the electrically evoked twitches in the isolated vas deferens of the rat. While VIP was virtually without effect, PACAP 1-38 suppressed the electrically evoked twitches effectively and in a concentration-dependent manner (pIC50 value 7.5). The naturally occurring N-terminal fragment PACAP 1-27 was less effective than PACAP 1-38 (Imax values 37.2% suppression compared to 76.5%) and less potent. The C-terminal fragment PACAP 16-38 was virtually inactive. Also helodermin and helospectin I+II suppressed the electrically evoked twitches effectively and in a concentration-dependent manner (pIC50 values 6.9; 7.2; 6.8, respectively). The three peptides produced similar maximum reduction of the twitches (74-80%). The findings suggest that PACAP, helodermin and helospectin suppress the electrically evoked contractions in the rat vas deferens via receptors distinct from VIP receptors.

Topics: Amino Acid Sequence; Animals; Electric Stimulation; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Male; Molecular Sequence Data; Muscle Contraction; Muscle, Smooth; Neuropeptides; Peptides; Pituitary Adenylate Cyclase-Activating Polypeptide; Rats; Rats, Sprague-Dawley; Vas Deferens; Vasoactive Intestinal Peptide

Helodermin is an amidated peptide of 35 amino acid residues isolated from the lizard Heloderma suspectum. Homologous peptides, helospectins I and II, peptides of 38 and 37 amino acid residues, respectively, have been isolated from the lizard Heloderma horridum. This group of peptides stimulates the adenylate cyclase activity. Helodermin- and helospectin-like immunoreactivities were studied in the rat brain by using immunohistochemistry and radioimmunoassay in combination with high-performance liquid chromatography. The highest concentrations of helodermin-like immunoreactivity were found in the cerebellum and hypothalamus. The chromatographic analysis of rat brain extract revealed one main immunoreactive peak with elution properties similar to those of authentic lizard helodermin. Helodermin-immunoreactive neurons were located in the supraoptic nucleus, suprachiasmatic nucleus, periventricular nucleus, arcuate nucleus and central gray. Fibers and terminals of varying densities were observed in the bed nucleus of the stria terminalis, medial part of the central nucleus of amygdala, external layer of the median eminence, thalamus and central gray. The highest concentrations of helospectin-like immunoreactivity were found in the cerebral cortex, hypothalamus and medulla. The chromatographic analysis of brain extract revealed one major peak with elution properties similar to those of authentic helospectin I. Helospectin-immunoreactive neurons were located in the suprachiasmatic nucleus, central gray, cerebral cortex, dorsomedial hypothalamic nucleus and supramammillary nucleus. Helospectin-immunoreactive fibers and terminals were found in the bed nucleus of the stria terminalis, medial part of the central nucleus of amygdala, median eminence, lateral parabrachial nucleus, central gray, cerebral cortex, thalamus and nucleus of the solitary tract. The present study has revealed novel neuronal systems in the rat brain by using antisera against the lizard peptides helodermin and helospectin. The patterns of immunostaining suggest a role for the helodermin- and helospectin-like peptides in the hypothalamo-hypophyseal control of endocrine functions.

Topics: Animals; Antibody Specificity; Brain; Chromatography, High Pressure Liquid; Cross Reactions; Immunochemistry; Immunohistochemistry; Intercellular Signaling Peptides and Proteins; Lizards; Peptides; Radioimmunoassay; Rats; Rats, Inbred Strains; Vasoactive Intestinal Peptide

1. Helodermin, helospectin I and helospectin II, peptides recently isolated from the salivary gland venom of Heloderma suspectum, were compared to vasoactive intestinal peptide (VIP) with respect to effects on systemic blood pressure and on isolated femoral arteries in the rat. 2. They all reduced blood pressure in a dose-dependent manner; helodermin was less effective than VIP. However, at doses higher than 1 nmol kg-1 all four peptides reduced blood pressure to about the same extent. 3. The half-life of the hypotensive effect of VIP was longer than that of helodermin and the helospectins. 4. VIP and helodermin were equally potent in relaxing femoral arteries precontracted with phenylephrine or prostaglandin F2 alpha. 5. Helospectin I and II relaxed phenylephrine-contracted vessels to the same extent as VIP but with a lower potency. 6. Addition of VIP 1 microM to preparations exposed to helodermin 1 microM or to either of the helospectins did not produce a further relaxation. 7. The findings indicate that VIP, helodermin and helospectin I and II have a similar profile of action and therefore may act on a common receptor.

Topics: Amino Acid Sequence; Animals; Blood Pressure; Dinoprost; Female; Half-Life; Hemodynamics; In Vitro Techniques; Intercellular Signaling Peptides and Proteins; Male; Molecular Sequence Data; Peptides; Phenylephrine; Rats; Rats, Inbred Strains; 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