title: Nonsulfated cholecystokinins in cerebral neurons.
abstract: Cholecystokinin (CCK) is a widely expressed neuropeptide system originally discovered in the gut. Both cerebral and peripheral neurons as well as endocrine I-cells in the small intestine process proCCK to tyrosyl-O-sulfated and α-carboxyamidated peptides. Recently, we reported that gut endocrine I-cells also synthetize nonsulfated CCK in significant amounts. Accordingly, we have now examined whether porcine and rat cerebral tissues (four cortical regions, hypothalamus and cerebellum) also synthesize nonsulfated CCK. A new, specific radioimmunoassay showed that all brain samples from pigs (n=15) and rats (n=6) contained nonsulfated CCK. The highest concentrations were measured in the neocortex; 4.7±0.25pmol/g (7.4%) in the rat and 4.3±1.88pmol/g (2.3%) in the pig. Chromatography of porcine cortical extracts revealed that 96.4% of the CCK was O-sulfated CCK-8. A higher fraction of the larger peptides (CCK-58 and CCK-33) was nonsulfated in comparison with the shorter forms (CCK-22 and CCK-8), i.e., 8.1% and 4.3% versus 0.9% and 1.5%. Immunohistochemical analysis of the rat brain showed an overall similar distribution pattern in selected regions when comparing the antibody specific for nonsulfated CCK-8 with an antibody recognizing both sulfated and nonsulfated CCK. However, nonsulfated CCK immunoreactivity was stronger than that of sulfated CCK in cell bodies and weaker in nerve terminals. We conclude that only a small fraction of neuronal CCK is nonsulfated. The intracellular distribution of nonsulfated CCK in neurons suggests that they contribute only modestly to the CCK transmitter activity.
authors.affiliation: Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Mikkel
authors.initials: M
authors.lastname: Agersnap
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Ming-Dong
authors.initials: MD
authors.lastname: Zhang
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden; Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, Vienna, Austria.
authors.forename: Tibor
authors.initials: T
authors.lastname: Harkany
authors.affiliation: Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Tomas
authors.initials: T
authors.lastname: Hökfelt
authors.affiliation: Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark. Electronic address: jens.f.rehfeld@regionh.dk.
authors.forename: Jens F
authors.initials: JF
authors.lastname: Rehfeld
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002766:Cholecystokinin / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D013552:Swine
chemical_list: D002766:Cholecystokinin
keywords: Cholecystokinin (CCK); Neuropeptides; O-sulfation; Peptidergic neurotransmission; Posttranslational processing; proCCK