Bez tytułu slajdu - British Pharmacological Society
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Transcript Bez tytułu slajdu - British Pharmacological Society
GASTROINTESTINAL PEPTIDES
R. P. KOROLKIEWICZ, M.D., Ph.D.
Z. KONSTANSKI, M.D.
Department of Pharmacology
Medical University of Gdańsk, Poland
Motilin
Structure: 22 aa peptide isolated from upper small intestine
entire molecule required for full biological
activity
Synthesis: small intestine endocrine cells, pituitary and
pineal glands
Circulating 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
t1/2=
5 min
Elimination:
kidneys
Action in fasted animals: muscle contraction of
LES,
Receptor agonists:
stomach, duodenum
erythromycin
Motilin
Human motilin precursor: 115 aa
25 aa signal peptide
66 aa MAP
Motilin mRNA: duodenum
Function: regulates interdigestive migration complexes
Amino acid sequences of galanin
1
5
10
15
20
25
29
GlyTrpThrLeuAsnSerAlaGlyTyrLeuLeuGlyProHisAlavalglyasnHisArgSerPheserAspLysasnGlyLeuthrser
Human
GlyTrpThrLeuAsnSerAlaGly TyrLeuLeuGlyProHisAlaileaspasnHisArgSerPhehisAspLystyrGlyLeuAlaNH2
Pig
GlyTrpThrLeuAsnSerAlaGlyTyrLeuLeuGlyProHisAlaileaspasnHisArgSerPheserAspLyshisGlyLeuThrNH2
Rat
Neurotensin
Biological actions: contraction of colon, defecation
inhibition of pentagastrin-stimulated
acid secretion
stimulation of exocrine pancreatic secretion
increased blood flow, capillary permeability
Dumping syndrome: neurotensin release
Neurotensin (NT), neurmodulin (NmN), xenin
NT:
13 aa from bovine hypothalamus
NmN:
6 aa from porcine spinal cord
Xenin:
25 aa from human gastric mucosa
NT:
widely spread in the body
Release stimulant: meal (fat)
t 1/2 =
Receptors:
1.2-6 min.
3 types capable of increasing cGMP,
cAMP and inositol levels
Gastrin-releasing polypeptide (GRP), bombesin-like peptides
neuromedin B, C
GRP :
heptacosapeptide, porcine stomach
Neuromedin B, C: porcine intestines, spinal cord
Gene location:
Structure:
Distribution:
system
chromosome 18
23-aa signal peptide, 27-aa GRP
95-aa extension peptide
GI tract, CNS, peripheral nervous
GRP; bombesin-like peptides; neuromedin receptors
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
Galanin (Gal)
Gal: 29 or 30 aa peptide
Isolation: pig upper intestinal extracts
Structure of human Gal
1
5
10
15 16
20
25
GWTLNSAGYLLGPHA VGNHRSFSDK NGLTS
-
O
O H
-
-C-O-H
-
O H
-C-N-H
- C-N-
Galanin
t1/2 in nervous tissue: 100 - 120 min
Reasons for stability: specific horse-shoe aligment
of the N-and C-terminal portions
Important pharmacophores: Gly, Trp, Asn, Tyr, Leu
Galanin antagonists
Where does the idea come from
Structure
Drawbacks: peptide nature
lack of blood-brain barrier penetration
peptidase sensitivity
agonist-like effects
Galanin
PreproGal: chromosome 11 (11q 13.3-13.5)
PreproGal: Galanin + GMAP
Regulation of Gal gene expression:
steroids
(oestrogens)
thyroid
hormones
NGF
peripheral
nerve injury
protein kinase
C
Galanin actions
Stimulation of food intake (esp. pure fat)
Alzheimer’s and Parkonson’s disease: impairment of
memory
role of Gal
antagonists
Role in neuronal damage: periphery trophic activity
CNS inhibition of EAA release
Galanin effects
The influence of Gal on the adrenergic
noradrenergic systems
serotonergic
Nociception
Neoplasmatic trophic factor
Hyperglicaemic agent
Cardiovascular action
Smooth muscle
Guanylin, uroguanylin, lymphoguanylin
Guanylin: isolated from rat jejunum
Uroguanylin: isolated from opposum urine
Rceptor(s): guanylyl cyclase
Function: regulation of intestinal, renal fluid & electrolyte
transportation
Location: guanylin-intestine (distal colon)
uroguanylin-stomach, kidney, lung, pancreas,
intestine
lympohguanylin-kidney, myocardium, immune
system
Sorbin
Isolation: porcine intestinal extracts
Function:
increases water & sodium absorption
in the intestine and in the gallbladder
Monitor peptide, luminal CCK-releasing factor
Isolation: rat pancreatic juice & small intestine
Function:
pancreatic
CCK release in response to food
growth stimulation of fibroblasts,
tumor cells
Cleavage: lumenal trypsin
Peptide families
Gastrin-CCK
Secretin-glucagon-VIP
secretin
glucagon
PHI, GIP, VIP,
PACAP, GLP17-
CCK
gastri
n
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)
Peptide YY (PYY)
Urogastrone/
epidermal growth factor
Motilin
Peptide YY
Somatostatin (SST)
Preprohormone: 119 aa
Stimulation of expression: cAMP
Bioactive peptide: tissue specific different length-gastric
antrum, pancreatic islets (14 aa), small
intestine (28 aa)
Receptors: SST1-5, some coupled to G proteins
Somatostatin (SST)
Function: negative feedback on acid secretion
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
Binding profiles: different affinities in various tissues
Interactions with multiple signal transduction pathways
M40, M15, M35 or C7 can act as agonists, partial agonists
or antagonist in different systems
hGAL1 receptor
Isolated: human Bowes melanoma cells
Structure: 349 aa coupled to Gi/o proteins
Mapping: 18q23
Location:
foetal brain, GI tract, Bowes melanoma
Plasticity : hypothalamic GAL1 mRNA elevated more in
females than males, varies across oestrous
cycle
Function: cAMP concentration, opens inwardly rectifying
K+ channels, stimulates MAPK
Pathology: children with growth insufficiency
gal2
Isolation: rat
Structure: cloned hgal2 387 aa, 15 aa more than rat in C terminal
85% similarity between rat and human
Distribution: widely spread in central and peripheral tissues
hypothalamus
hippocampus
pituitary
amygdala
cerebral cortex
heart
lung
GI tract
gal2
Pharmacological profile: high affinity for full-length & N-terminal
Gal
fragments
Coupling: Gq/11 positive effects on Ca2+ influx and exocytosis
Gi/Go inhibition of exocytosis
The effect depends on the host cell or G-protein repertoire
Intracellular signalling: stimulation of phospholipase C
intracellular Ca2+ mobilization
Ca2+-dependent Cl- channel activation
can inhibit cAMP accumulation
Pathology:
hereditary neurologic amyotrophy
Russell-Silver syndrome
protection in Alzheimer’s disease ()
gal3
Isolation:
rat
hgal3 was cloned from a genetic
library
based on structural similarity to
hGAL1, gal2
Location:
22q 12.2-13.1
Structure:
hgal3 368 aa
90% similarity of human to rat
Tissues:
heart, spleen, testes
gal3
Coupling:
Gi/Go
Pharmacology: combination of GAL1 and gal2
Actions: activation of inward K+ current, hiperpolarization
consistent with inhibition of exocytosis, control
of emotions, feeding, pituitary hormones
release,
nociception, metabolism, insulin, glucose
homeostasis