Comparison of cholecystokinin metabolism by membrane preparations from the human astrocytoma clone D384 and the neuroblastoma line SH-SY5Y.
Both the sulphated and non-sulphated forms of cholecystokinin (CCK) octapeptide are susceptible to hydrolysis by the cell-surface peptidases endopeptidase-24.11 (NEP), angiotensin converting enzyme and aminopeptidase N (AP-N). Indirect studies have previously implicated an elastase-like serine endopeptidase in CCK metabolism in brain. We have therefore compared the hydrolysis of CCK, in both sulphated and non-sulphated forms by solubilized membrane preparations from the human astrocytoma clone D384 and the neuroblastoma line SH-SY5Y. Selective peptidase inhibitors were used to elucidate the principal activities involved in CCK metabolism. In the glial cell line the hydrolysis of cholecystokinin octapeptide (CCK-8), sulphated or non-sulphated, was inhibited predominantly by the NEP inhibitor, phosphoramidon (PR). In contrast, in the neuroblastoma line, angiotensin converting enzyme (ACE) was seen to play a major role in metabolism of CCK-8 with a lesser effect attributable to NEP but with some differences between sulphated and non-sulphated forms reflecting the preference of ACE for CCK-8ns. In neither cell line was a significant effect of the serine peptidase inhibitor Dip-F seen on CCK metabolism arguing against the presence of a putative CCK-degrading serine peptidase in these cell lines. Both NEP and ACE remain as candidates for inactivation of CCK at the cell surface.
Medeiros
M dos S
Mdos S
Department of Biochemistry and Molecular Biology, University of Leeds, U.K.
Turner
A J
AJ
D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000502:physiology; D001254:Astrocytoma / Q000378:metabolism; D001932:Brain Neoplasms / Q000378:metabolism; D018826:CD13 Antigens; D002462:Cell Membrane / Q000201:enzymology; D002766:Cholecystokinin / Q000378:metabolism*; D002999:Clone Cells / Q000378:metabolism; D010450:Endopeptidases / Q000502:physiology*; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D015260:Neprilysin / Q000502:physiology; D009447:Neuroblastoma / Q000378:metabolism; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D007703:Peptidyl-Dipeptidase A / Q000502:physiology; D014407:Tumor Cells, Cultured
D002766:Cholecystokinin; D010450:Endopeptidases; D000626:Aminopeptidases; D018826:CD13 Antigens; D007703:Peptidyl-Dipeptidase A; D015260:Neprilysin