A two-dimensional gel electrophoretic study of proteins synthesized and released by degenerating adult mouse sciatic nerve

Previous two-dimensional (2-D) gel electrophoretic studies: of proteins sec reted by degenerating mammalian peripheral nerves (Ignatius et al., 1986, P roc. Natl; Acad. Sci; USA 83: 1125-1129; Muller et at, 1986, J. Cell Biol; 102: 393-402) detected the up-regulation of two proteins of 67-70 and 34-37 kDa, although they failed to resolve proteins smaller than about 15 kDa or with isoelectric points greater than 8. In the present study we have used 2-D gels that can resolve proteins in the molecular mass range 3.6-200 kDa and isoelectric paint range 2.4-10.6. This revealed that the incorporation of radiolabel by three diffusible proteins with apparent molecular mass/iso electric point values of 38/5-6, 27-31/4-5, and 8/>10 was increased in the distal stumps of sciatic nerves 4 days after lesion, while the radiolabel i ncorporation by a further two proteins (15/5.3 and 12.5-17.5/6.8-7.5) was i ncreased in the distal nerve stump 15 days after lesion. The possible cellu lar sources of these proteins were assessed by comparing protein secretion from unoperated nerves with nerve segments maintained in culture for 4 days (in which the contribution from recruited macrophages would be expected to be minimal) and segments of nerve that had been frozen and then replaced i n situ for 4 days (in which the contribution from nerve sheath cells would be expected to be minimal). This revealed that three of the proteins up-reg ulated in lesioned nerves (27-31/4-5, 15/5.3, and 12.5-17.5/6.8-7.5) are pr obably sheath cell-products, while the other two (38/5-6 sand 8/>10) may he secreted mainly by macrophages (sr other cells) that infiltrate the frozen nerve segments. The identity of these proteins and their possible involvem ent in axonal regeneration remain to be determined. (C) 2000 Academic Press .