Pig splenic nerve: peptides derived from chromogranins by proteolytic processing during axonal transport

We have investigated the proteolytic processing of chromogranin A, chromogranin B and NESP55 (a novel chromogranin-like protein) during axonal transport using pig splenic nerve as a model. We have also studied the presence of chromogranin-derived peptides in the perfusate during electrical stimulation of this nerve. High-performance gel filtration chromatography followed by radioimmunoassay (RLA) revealed that chromogranins are proteolytically processed to varying degrees during axonal transport. For chromogranin A and NESP55, the precursor is still present in the proximal part of the nerve, whereas in the distal part and nerve terminals, intermediate-sized peptides and the free peptides GE-25 and GAIPLRRH dominate, respectively. For chromogranin B, the precursor has already been processed to an intermediate-sized peptide in the proximal part of the nerve, which is also present in the distal parts together with the free peptide PE-11. For chromogranin B and NESP55, only the free peptides PE-11 and GAIPIRRH, or in the case of chromogranin A, the free peptide GE-25 plus an intermediate-sized one, are released from the terminals into the splenic perfusate. These results demonstrate that chromogranins are processed to smaller peptides during axonal transport. (C) 1999 Elsevier Science B.V. All rights reserved.