METABOLISM OF NEUROPEPTIDE-Y AND CALCITONIN-GENE-RELATED PEPTIDE BY CULTIVATED NEURONS AND GLIAL-CELLS

Neuropeptide Y and calcitonin gene-related peptide are abundant neurop eptides in the mammalian central and peripheral nervous systems. Their enzymatic degradation by cultivated neurons, astrocytes, and microgli a, as well as by purified urokinase-type plasminogen activator, plasmi n, thrombin, and trypsin, was investigated in an in vitro approach to elucidate the role of matrix-degrading serine proteinases for inactiva tion of neuropeptides, especially those of higher amino acid chain len gth, in the brain. Astrocytes were almost unable to catabolize the pep tides. Cultivated neurons and microglia digested neuropeptide Y throug h cleavage after Arg(19), Arg(25), Arg(33), and Arg(35), calcitonin ge ne-related peptide was cleaved after Arg(11) and Arg(18). The same cle avage pattern was observed, when neuropeptide Y and calcitonin gene-re lated peptide were degraded by purified urokinase-type plasminogen act ivator, plasmin, thrombin, and trypsin. For further characterization o f the neuropeptide-degrading serine proteinase activities from cell cu ltures, urokinase-type plasminogen activator was identified on microgl ia by immunostaining, whereas tissue-type plasminogen activator mRNA o ccurred in neurons and astrocytes, but not in microglia. The data are consistent with the possibility that the neuropeptide-degrading serine proteinase activity on neurons and microglia is due to a mixture of p lasmin and plasminogen activator activities.