Adult carboxypeptidase E-deficient fat/fat mice have a near-total depletion of brain CCK 8 accompanied by a massive accumulation of glycine and arginine extended CCK: identification of CCK 8 Gly as the immediate precursor of CCK 8 in rodent brain.
Cholecystokinin (CCK) amide concentrations were reduced over 85% in all the major brain regions of carboxypeptidase E (Cpe)(fat)/Cpe(fat) mice in comparison to control mice. Using an radioimmunoassay (RIA) specific for glycine-extended CCK (CCK Gly), low levels of CCK Gly were detected in control (0.65 ng/g tissue) and were even lower in Cpe(fat)/Cpe(fat) (0.246 ng/g) mice brain extracts. After treatment with carboxypeptidase B, the level of CCK Gly in Cpe(fat)/Cpe(fat) in these brain extracts was elevated to 33.5 ng/g, about 51-fold higher than in control. On gel-filtration chromatography and high-performance liquid chromatography (HPLC), this material coeluted with CCK 8 Gly. These results demonstrate that CPE is required for the correct processing of arginine- and glycine-extended CCK in all major regions of the mouse brain. These results support the hypothesis that CCK 8 Gly is the immediate precursor of CCK 8 amide in mouse brain, not larger amidated forms like CCK 22 or CCK 33.
Wang
W
W
Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, MA 02111, USA.
Cain
B M
BM
Beinfeld
M C
MC
D000818:Animals; D001921:Brain / Q000378:metabolism*; D043423:Carboxypeptidase H; D002268:Carboxypeptidases / Q000172:deficiency*; D002766:Cholecystokinin / Q000378:metabolism*; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D051379:Mice; D008820:Mice, Obese; D011498:Protein Precursors / Q000378:metabolism*; D021382:Protein Sorting Signals / Q000378:metabolism*; D011863:Radioimmunoassay / Q000379:methods; D012844:Sincalide / Q000378:metabolism*
D011498:Protein Precursors; D021382:Protein Sorting Signals; C061391:cholecystokinin, Gly-; D002766:Cholecystokinin; D002268:Carboxypeptidases; D043423:Carboxypeptidase H; D012844:Sincalide