Characterization of two forms of cocaine- and amphetamine-regulated transcript (CART) peptide precursors in goldfish: molecular cloning and distribution, modulation of expression by nutritional status, and interactions with leptin.
Complementary DNAs encoding two forms of cocaine- and amphetamine-regulated transcript (CART) peptide precursors were identified from goldfish brain and named CART I and CART II. Each cDNA contains a signal peptide sequence, the putative CART-like peptide, and a carboxy-terminal extension peptide. Form I encodes a 117-amino acid pro-CART, whereas form II encodes a 120-amino acid pro-CART. Both forms resemble mammalian CART peptides. Each goldfish CART precursor is encoded by three exons interrupted by two introns within genomic DNA. RT-PCR, slot blot, and Northern blot analysis showed that the mRNAs for form I and II precursors have a widespread distribution. Form I and II are present in the brain, pituitary, eye, gonads, and kidney. Form I is also present in the gill. In the brain, form I is predominant in the olfactory bulb and hypothalamus, and form II is predominant in the optic tectum. Food deprivation for 96 h induced a decrease in form I mRNA levels in the telencephalon-preoptic region, hypothalamus, and olfactory bulb and in form II mRNA expression in the olfactory bulb. An increase in mRNA levels was observed 2 h following a meal in the olfactory bulbs and hypothalamus for form I whereas no postprandial changes in form II mRNA levels were observed. Intracerebroventricular injections of human CART alone induced a significant decrease in food intake. Injections of leptin reinforced the inhibition of feeding behavior and food intake seen in CART-treated fish. Central injection of leptin induced an increase in CART I mRNA in the optic tectum, hypothalamus, and olfactory bulbs but had no effect on CART II mRNA expression in the brain. These results suggest that CART peptides act as leptin-regulated satiety factors in goldfish and that they might have other physiological roles besides feeding, possibly in sensory information processing.
Volkoff
H
H
Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada.
Peter
R E
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D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D004435:Eating / Q000187:drug effects; D005260:Female; D005508:Food Deprivation / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects; D016678:Genome; D006054:Goldfish / Q000378:metabolism*; D006801:Humans; D007276:Injections, Intraventricular; D020738:Leptin / Q000494:pharmacology / Q000502:physiology; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D009752:Nutritional Status; D019518:Postprandial Period; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D014018:Tissue Distribution; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein
D018076:DNA, Complementary; D020738:Leptin; D009419:Nerve Tissue Proteins; D020033:Protein Isoforms; D011498:Protein Precursors; D012333:RNA, Messenger; D000098882:Cocaine- and Amphetamine-Regulated Transcript Protein; D004247:DNA