Brain and gastrointestinal cholecystokinin receptor family: structure and functional expression.

Abstract

Cholecystokinin was one of the first gastrointestinal peptides discovered in the mammalian brain. In the central nervous system there is evidence for CCKA and CCKB receptor subtypes. The CCKA receptors occur in a few localized areas of the central and peripheral nervous systems where they modulate feeding and dopamine-induced behavior. CCKB receptors occur throughout the central nervous system where they modulate anxiety, analgesia, arousal, and neuroleptic activity. We have recently purified and cloned a CCKA receptor cDNA from rat pancreas that allowed isolation of an identical cDNA from rat brain by using the polymerase chain reaction. Using low-stringency hybridization screening of cDNA libraries from rat brain and AR42-J cells, which possess large numbers of CCKB receptors, we identified previously unreported cDNAs, the sequence of which were identical in both tissues. The cDNA sequence encodes a 452-amino acid protein that is 48% identical to the CCKA receptor and contains seven transmembrane domains characteristic of guanine nucleotide-binding regulatory protein-coupled receptors. COS-7 cells transfected with this cDNA expressed binding sites for agonists and antagonists characteristic of a CCKB receptor subtype. We conclude that this cDNA isolated from rat brain and AR42-J cells is a receptor of the CCKB subtype and that the respective cDNAs for both CCKA and CCKB are identical in the brain and gastrointestinal system. The cholecystokinin (CCK) family of peptides was originally isolated from the mammalian gastrointestinal tract (1) and was one of the first gastrointestinal peptides to be discovered in the brain (2, 3), where the predominant molecular form, cholecystokinin octapeptide (CCK-8), exists in sulfated and desulfated forms (2, 4).The receptors for CCK in both the central nervous system (CNS) and peripheral tissues can be classified into two subtypes, CCKA and CCKB, on the basis of their affinity (i) for a structurally and functionally related family of peptides with identical COOH-terminal pentapeptide sequences and differing sulfation at the sixth (gastrin) and seventh (CCK) tyrosyl residues and (ii) for specific antagonists. CCKA receptors are highly selective (500-to 1000-fold higher affinity) for sulfated analogues and the antagonist L-364,718, whereas CCKB receptors have similarly high affinity for both sulfated and nonsulfated peptide analogues (only a 3-to 10-fold higher affinity for sulfated peptide analogues) and the antagonist L-365,260 (5-8).A CCKA receptor subtype predominates in the gastrointestinal system but occurs also in highly localized areas of the rat CNS, where it modulates feeding and dopamine-induced behavior (9-11). We recently purified the CCKA receptor and cloned its cDNA from rat pancreas (12). This cDNA did not hybridize to poly(A)+ RNA from rat brain on Northern blot analysis, which raised the possibility that the rat brain CCK receptor with a CCKA receptor-subtype pharmacology was different from the rat pancreatic CCKA receptor (12).The CCKB receptor subtype...

Annexin II binds progastrin and gastrin-like peptides, and mediates growth factor effects of autocrine and exogenous gastrins on colon cancer and intestinal epithelial cells

“…Several receptor (R)-subtypes bind gastrin and choecystokinin octapeptide (CCK)-like peptides. Cholecystokinin type 1 receptor (CCK 1 R) mainly bind CCK-like peptides and have negligible affinity for gastrins (Kopin et al, 1992;Wank et al, 1992). Cholecystokinin type 2 receptor (CCK 2 R) bind amidated gastrins and CCK with almost equal affinity, but demonstrate negligible affinity for non-amidated gastrins (Kopin et al, 1992).…”

Gastrin stimulates the growth of gastric pit cell precursors by inducing its own receptors

“…Expression of mouse CCKB-R mRNA was assessed by RT-PCR (Super Script Preamplification System, GIBCO) using 5Ј-CTTTGATGGTGATAATGACAGCGA-3Ј and 5Ј-GCACGTAGCAGCCATCACTGT-3Ј by amplifying the 155-bp DNA for the mRNA encoding a part of the third loop of CCKB-R (12,46,47). These primers also amplify the 349-bp genomic DNA for the same region including the 194-bp intron, which was used as a control.…”

“…CCKA-Rs exhibit a 500-to 1,000-fold higher affinity for sulfated analogs of CCK than for gastrin, whereas CCKB-Rs have approximately equal affinity for both sulfated and non-sulfated peptide analogs of CCK and gastrin (32,34,46,47). CCKB-Rs are present in parietal, ECL, and probably somatostatin cells (2,4,23,27,28,41 (2,28).…”

Effect of CCK receptor antagonists on the antinociceptive, reinforcing and gut motility properties of morphine

“…CCK interacts with at least two distinct types of receptor (Innis & Snyder, 1980;Moran et al, 1986;Wank et al, 1992): CCKB receptors, which represent the predominant form in the rodent CNS (Pelaprat et al, 1987;Hill & Woodruff, 1990) and CCKA receptors, the abundant form in peripheral tissues (Zetler, 1984;Van Dijk et al, 1984;Chang & Lotti, 1986) but are also found in discrete nuclei of the CNS (Hill et al, 1987a;. Molecular cloning and pharmacological studies have demonstrated a close relationship between CCKB and gastrin receptors found mainly in the parietal cells of the gastric mucosa (Chang et al, 1989;Pisegna et al, 1992;Hunter et al, 1993).…”