Synthesis and secretion of beta-nerve growth factor by mouse teratocarcinoma cell lines

Peptides other than the neurotrophins that can be cleaved from proneurotrophins: a neglected story

The members of the family of neurotrophic factors known as neurotrophins, NGF, BDNF, NT-3 and NT4/5 are known to be cleaved intracellularly from immature precursors, the proneurotrophins. NGF and the other neurotrophins regulate neurite outgrowth and neuronal survival during development via binding to Trk receptor tyrosine kinases and the p75 neurotrophin receptor. Surprisingly, the proneurotrophins were shown to be also biologically active ligands. ProNGF and proBDNF induce neuronal apoptosis via binding to a complex of p75 and sortilin. Therefore, life and death seems to be a delicate interplay between 'cleavage' or 'not cleavage' of the proneurotrophins. However, there is a third aspect to this story. In general, peptide-hormone precursors are known to give rise to several biologically active peptides from one precursor molecule. The paradox with the proneurotrophins is that although they have several additional potential cleavage sites that would necessarily give rise to other peptides besides the neurotrophins and thus new members in the neurotrophin family, this aspect has been largely neglected. This article aims to review evidence for biologically active peptides other than the NGF and NT-3 that can be generated from the proNGF and proNT-3.

Glial implants in gliomatosis peritonei arise from normal tissue, not from the associated teratoma

Metaplasia of subcoelomic mesenchyme has been implicated, but not proven, in the pathogenesis of common gynecological diseases such as endometriosis and rarer entities such as leiomyomatosis peritonealis disseminata and gliomatosis peritonei (GP). GP is associated with ovarian teratomas and is characterized by numerous peritoneal and omental implants composed of glial tissue. Two theories to explain the origin of GP have been proposed. In one, glial implants arise from the teratoma, whereas in the other, pluripotent Müllerian stem cells in the peritoneum or subjacent mesenchyme undergo glial metaplasia. To address the origin of GP, we exploited a unique characteristic of many ovarian teratomas: they often contain a duplicated set of maternal chromosomes and are thus homozygous at polymorphic microsatellite (MS) loci. In contrast, DNA from matched normal or metaplastic tissue (containing genetic material of both maternal and paternal origin) is expected to show heterozygosity at many of these same MS loci. DNA samples extracted from paraffin-embedded normal tissue, ovarian teratoma and three individual laser-dissected glial implants were studied in two cases of GP. In one case, all three implants and normal tissue showed heterozygosity at each of three MS loci on different chromosomes, whereas the teratoma showed homozygosity at the same MS loci. Similar results were observed in the second case. Our findings indicate that glial implants in GP often arise from cells within the peritoneum, presumably pluripotent Müllerian stem cells, and not from the associated ovarian teratoma. This finding has important implications for more common gynecological entities with debatable pathogenesis, such as endometriosis, by definitively demonstrating the metaplastic potential of stem cells within the peritoneal cavity.

A teratocarcinoma-derived neurotrophic activity

In a search for nerve growth factor (NGF) in tissue extracts of a murine transplantable teratocarcinoma that harbours immature neural tissue in abundance, a trypsin-sensitive and heat labile neurotrophic activity was identified. The final protein fraction obtained by cation exchange chromatography contained five proteins with mol. wts ranging from 52 to 72 kD. It supported the growth and differentiation of immature neurones in neonatal rat cerebellar cultures but had no effect on embryonic chick dorsal root ganglia which are the classical targets for NGF.

Serum contains a macromolecular effector promoting the synthesis of nerve growth factor (NGF) in L cells

Addition of serum to the culture medium of murine L cells increased both the cellular level of NGF mRNA and the secretion of mature factor. Stimulation of NGF production by the serum was dose-dependent and appeared mediated by some specific factor(s). After gel filtration chromatography of serum, most of the biological activity formed a major peak with an apparent MW of about 160 kDa. This promoting factor was sensitive to heat at neutral pH, but resisted after heating at pH4. An activity inducing NGF synthesis, and displaying a comparable thermal sensitivity was also detected in Cohn fraction IV of human or bovine plasma.