GASTROINTESTINAL PEPTIDES R. P. KOROLKIEWICZ, M.D., Ph.D. Z. KONSTANSKI, M.D. Department of Pharmacology Medical University of Gdańsk, Poland

Motilin kStructure: 22 aa peptide isolated from upper small intestine entire molecule required for full biological activity kSynthesis: small intestine endocrine cells, pituitary and pineal glands kCirculating levels: variable, depend on duodenal motility, meals inhibit release of motilin

GASTROINTESTINAL PEPTIDES R. P. KOROLKIEWICZ, M.D., Ph.D. Z. KONSTANSKI, M.D. Department of Pharmacology Medical University of Gdańsk, Poland

Motilin k t 1/2 = 5 min k Elimination: kidneys k Action in fasted animals: muscle contraction of LES, stomach, duodenum k Receptor agonists: erythromycin

Motilin k Human motilin precursor: 115 aa 25 aa signal peptide 66 aa MAP k Motilin mRNA: duodenum k Function: regulates interdigestive migration complexes

Amino acid sequences of galanin GlyTrpThrLeuAsnSerAlaGlyTyrLeuLeuGlyProHisAlavalglyasnHisArgSerPheserAspLysasnGlyLeuthrser GlyTrpThrLeuAsnSerAlaGly TyrLeuLeuGlyProHisAlaileaspasnHisArgSerPhehisAspLystyrGlyLeuAlaNH 2 GlyTrpThrLeuAsnSerAlaGlyTyrLeuLeuGlyProHisAlaileaspasnHisArgSerPheserAspLyshisGlyLeuThrNH 2 Human Pig Rat

k Biological actions: contraction of colon, defecation inhibition of pentagastrin-stimulated acid secretion stimulation of exocrine pancreatic secretion increased blood flow, capillary permeability k Dumping syndrome:  neurotensin release Neurotensin

k NT: 13 aa from bovine hypothalamus k NmN: 6 aa from porcine spinal cord k Xenin: 25 aa from human gastric mucosa k NT: widely spread in the body k Release stimulant: meal (fat) k t 1/2 = min. k Receptors: 3 types capable of  increasing cGMP, cAMP and inositol levels Neurotensin (NT), neurmodulin (NmN), xenin

k GRP : heptacosapeptide, porcine stomach k Neuromedin B, C: porcine intestines, spinal cord k Gene location: chromosome 18 k Structure: 23-aa signal peptide, 27-aa GRP 95-aa extension peptide k Distribution: GI tract, CNS, peripheral nervous system Gastrin-releasing polypeptide (GRP), bombesin-like peptides neuromedin B, C

GRP-bombesin: bombesin=neuromedin C=GRP>neuromedin B Neuromedin B: neuromedin B>GRP, bombesin BRS-3: GRP, bombesin > neuromedin B Biological actions:  gastrin, PP, CCK, PYY, insulin release mitogens for cell proliferation, tumor growth factor, inhibition of food intake, satiety GRP; bombesin-like peptides; neuromedin receptors

Galanin (Gal) k Gal: 29 or 30 aa peptide kIsolation: pig upper intestinal extracts kStructure of human Gal G W T L N S A G Y L L G P H A V G N H R S F S D K N G L T S - - C - N - H - C - N - -- OH - C - O - H - O - H - O --

Galanin  t 1/2 in nervous tissue: min k Reasons for stability: specific horse-shoe aligment of the N-and C-terminal portions k Important pharmacophores: Gly, Trp, Asn, Tyr, Leu

Galanin antagonists k Where does the idea come from  k Structure k Drawbacks: peptide nature lack of blood-brain barrier penetration peptidase sensitivity agonist-like effects

Galanin k PreproGal: chromosome 11 (11q ) k PreproGal: Galanin + GMAP k Regulation of Gal gene expression: steroids (oestrogens) thyroid hormones NGF peripheral nerve injuryprotein kinase C

Galanin actions k Stimulation of food intake (esp. pure fat) k Alzheimer’s and Parkonson’s disease: impairment of memory role of Gal antagonists k Role in neuronal damage: periphery  trophic activity CNS  inhibition of EAA release

Galanin effects k The influence of Gal on the adrenergic noradrenergic systems serotonergic k Nociception k Neoplasmatic trophic factor k Hyperglicaemic agent k Cardiovascular action k Smooth muscle

Guanylin, uroguanylin, lymphoguanylin k Guanylin: isolated from rat jejunum k Uroguanylin: isolated from opposum urine k Rceptor(s): guanylyl cyclase k Function: regulation of intestinal, renal fluid & electrolyte transportation k Location:guanylin-intestine (distal colon) uroguanylin-stomach, kidney, lung, pancreas, intestine lympohguanylin-kidney, myocardium, immune system

Sorbin k Isolation: porcine intestinal extracts k Function: increases water & sodium absorption in the intestine and in the gallbladder Monitor peptide, luminal CCK-releasing factor k Isolation: rat pancreatic juice & small intestine k Function: CCK release in response to food growth stimulation of fibroblasts, pancreatic tumor cells k Cleavage: lumenal trypsin

Peptide families Gastrin-CCK CCK gastri n Secretin-glucagon-VIP secretin glucagon PHI, GIP, VIP, PACAP, GLP Pancreatic polypeptide pancreatic polypeptide neuropeptide Y peptide YY Other GRP motilin galanin neurotensin somatostatin

Peptides as endocrine, neurocrine or paracrine substances ENDOCRINE NEUROCRINE PARACRINE Somatostatin Somatostatin Somatostatin Cholecystokinin CCK Peptide YY Gastrin GRP Secretin Opioids Insulin Substance P Glucagon VIP Enteroglucagon Neuropetide Y (NPY) Pancreatic polypeptide Neurotensin

Peptides as endocrine and neurocrine substances ENDOCRINE PEPTIDES NEUROCRINE PEPTIDES Neurotensin Motilin Pancreastatin Glucose-dependent insulinotropic Galanin peptide (GIP) Motilin Peptide YY (PYY) Peptide YY Urogastrone/ epidermal growth factor

Somatostatin (SST) k Preprohormone: 119 aa k Stimulation of expression: cAMP k Bioactive peptide: tissue specific different length-gastric antrum, pancreatic islets (14 aa), small intestine (28 aa) k Receptors: SST 1-5, some coupled to G proteins

Somatostatin (SST) k Function: negative feedback on acid secretion k Use: gastrointestinal bleeding from esophageal varices diarrhoea (Crohn’s diseases, HIV, short bowel syndrome) endocrine tumors (e.g. VIP secreting)

Arguments in favour of multiple Gal receptors in native systems kBinding profiles: different affinities in various tissues kInteractions with multiple signal transduction pathways kM40, M15, M35 or C7 can act as agonists, partial agonists or antagonist in different systems

hGAL1 receptor k Isolated: human Bowes melanoma cells k Structure: 349 aa coupled to G i/o proteins k Mapping: 18q23 k Location: foetal brain, GI tract, Bowes melanoma k Plasticity : hypothalamic GAL1 mRNA elevated more in females than males, varies across oestrous cycle k Function:  cAMP concentration, opens inwardly rectifying K + channels, stimulates MAPK k Pathology: children with growth insufficiency

gal2 k Isolation: rat k Structure: cloned hgal2 387 aa, 15 aa more than rat in C terminal 85% similarity between rat and human k Distribution: widely spread in central and peripheral tissues hypothalamus  pituitary  cerebral cortex  lung  hippocampus amygdala heart GI tract

k Pharmacological profile: high affinity for full-length & N-terminal Gal fragments k Coupling: G q/11  positive effects on Ca 2+ influx and exocytosis G i /G o  inhibition of exocytosis The effect depends on the host cell or G-protein repertoire gal2 k Intracellular signalling: stimulation of phospholipase C intracellular Ca 2+ mobilization Ca 2+ -dependent Cl - channel activation can inhibit cAMP accumulation k Pathology: hereditary neurologic amyotrophy Russell-Silver syndrome protection in Alzheimer’s disease (  )

gal3 k Isolation: rat hgal3 was cloned from a genetic library based on structural similarity to hGAL1, gal2 k Location: 22q k Structure: hgal3 368 aa 90% similarity of human to rat k Tissues: heart, spleen, testes

k Coupling: G i /G o k Pharmacology: combination of GAL1 and gal2 k Actions:activation of inward K + current, hiperpolarization consistent with inhibition of exocytosis, control of emotions, feeding, pituitary hormones release, nociception, metabolism, insulin, glucose homeostasis gal3