| 摘要 |
The present invention provides methods and compositions for enhancing an effect or effects of a neurotrophin, preferably, but not limited to, enhancing the growth and survival promoting properties of neurotrophins. The cytoplasmic region of the common neurotrophin receptor (p75NTR) (rat, human, chick) contains a putative membrane-associating domain implicated in intracellular signalling. A peptide (R3) identical to this domain (p75NTR367-379) and various analogues of this peptide displayed circular dichroism spectra in aqueous and non-polar environments identical to the amphiphilic tetradecapeptide mastoparan (MP), and were internalized by PC12 rat pheochromocytoma cells. The R3 peptide enhanced neurite growth in PC12 cells, chick embryo primary sensory neurons, and fetal rat primary sensory neurons in vitro in the presence of sub-saturating concentrations of NGF. Peptide analogues of R3 not faithful to the distance and angular relationships of ionic groups, and the putative amphiphilic structure of p75NTR367-379, while still providing some enhancement, nevertheless displayed reduced potency to enhance NGF-mediated neurite growth. The common neurotrophin receptor p75NTR activates and translocates the nuclear transcription factor NFkB and displays pro-apoptotic effects similar to other members of the TNF receptor superfamily. A peptide mimic of the amphiphilic domain 367-379 of p75NTR that enhances TrkA mediated neurite growth by NGF, was used to affinity purify cytoplasmic proteins from PC12 cells. Isolated proteins contained a predominant species with an apparent molecular weight of 65 kDa. The affinity purified 65 kDa protein, as well as a protein of similar molecular mass from crude cell extracts, were identified by immunoblotting with antibody to NFkB. The 65 kDa species was chemically cross-linked to the radiolabeled analogue of the peptide mimic of p75NTR and immunoprecipitated by antibody to NFkB. These observations, taken together with the finding that a p75NTR-selective NGF antagonist blocked mediated neurite growth in limiting NGF conditions, support the view that p75NTR participates in neurite growth via a signaling pathway involving the translocation of NFkB.
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