Geneeskundige Stichting Koningin Elisabeth ... - GSKE - FMRE

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including NPY. After DPP IV/CD26 activity, NPY becomes an angiogenic factor (Zukowska-
Goric et al., 1998). Likewise it is hypothetised that the DPP IV processing of the peptides MK-
27 and SR-17 may be part of a physiological mechanism that modulates their biological activity
as potential immunomodulators (Depreitere et al., in preparation a+b).
Immunohistochemical analysis of porcine spleen sections revealed the presence of both the
MK-27 and SR-17 sequence / peptide exclusively in nerve terminals localised in the reticuloendothelial
compartment lining the Billroth cords, in the trabeculae, and in the vessel wall of central
arteries. Immunoreactivity was also seen in the larger branches of the splenic nerve. In
contrast, pancreastatin (a chromogranin A fragment) imunostaining could not be detected in
nerves or nerve endings but was localised in specific subsets of leukocytes in the white pulp and
red pulp. This interesting observation was confirmed by in-situ hybridisation (in collaboration
with Dr. L. Arckens & Prof. Dr. F. Vandesande, K.U.L.), implying that the observed pancreastatin
immunoreactivity in these bleukocytes was indeed produced by these cells and was not the
result of an uptake process of chromogranin originating from other sources.
GN-17 (pCgA 292-308) is a new peptide derived from CgA, located in the middle part of the
molecule. It shares a similar concensus motif with many substrates of protein kinase II.
Preliminary results confirm that this peptide inhibits in a dose-dependently way the casein kinase
II (CKII) activity, whereas peptide WE-14, used as a negative control, has no effect. The
mechanism of inhibition remains to be further investigated. The interesting part is that this CKIIlike
activity has been found on the cell surface of both T-lymphocytes and mast cells and that
phosphorylation sites of CKII are present on the T-cell receptor. This may be suggestive for a
modulating action of GN-17 on T-lymphocyte function.
We also compared the antibacterial activity against Micrococcus luteus of the lysate of porcine
and bovine chromaffin granules. In the bovine adrenal medulla, antibacterial activity was
found; this is in accordance with the known antibacterial activity of bovine secretolytin. No activity
against Micrococcus luteus was found in porcine chromaffin granule extracts, nor in preparations
of the pure synthetic porcine secretolytin-like peptide KR-11. We therefore conclude
that the secretolytin-like peptide KR-11 does not possess antibacterial activity. This activity is
probably situated in the C-terminal part of secretolytin, where KR-11 differs in one amino acid
from the real (=bovine) secretolytin.
In conclusion : Several new peptides derived from CgB and one from CgA have been identified
in porcine chromaffin granules and some functional properties could be establised. Two
of them are good substrates for DPP IV/CD26 and another one is an inhibitor of the CKII activity.
Three of them are released from the splenic nerve after electrical stimulation.