p75NTR undergoes a process of regulated intramembrane proteolysis (RIP) similar to other transmembrane proteins such as NOTCH, beta-amyloid precursor protein (APP), and ERBB4. Each of these proteins is subjected to two sequential cleavages. The first one occurs in the extracellular part of the protein and is mediated by the metalloproteinase alpha-secretase which causes shedding of the extracellular domain. The second cleavage occurs in the intramembrane region and is mediated by gamma-secretase and causes release of the intracellular domain, ICD, and of a small peptide. The ICD often traffics to the nucleus and, in some instances (e.g. NOTCH), was found to act as transcriptional regulator. Whether the p75NTR ICD does translocate to the nucleus to regulate gene expression in a way similar to the NOTCH receptor remains to be seen. The alpha- and gamma-secretase mediated cleavage of p75 appears to be regulated by neurotrophin (NGF, BDNF) binding to TRKA or TRKB. p75NTR processing also occurs in response to MAG in cerebellar granule neurons.
Bronfman, FC
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