Cholinergic involvement in Alzheimer's disease. A link with NGF maturation and degradation.
Basal forebrain cholinergic neurons are highly dependent on nerve growth factor (NGF) supply for the maintenance of their cholinergic phenotype as well as their cholinergic synaptic integrity. The precursor form of NGF, proNGF, abounds in the CNS and is highly elevated in Alzheimer's disease. In order to obtain a deeper understanding of the NGF biology in the CNS, we have performed a series of ex vivo and in vivo investigations to elucidate the mechanisms of release, maturation and degradation of this neurotrophin. In this short review, we describe this NGF metabolic pathway, its significance for the maintenance of basal cholinergic neurons, and its dysregulation in Alzheimer's disease. We are proposing that the conversion of proNGF to mature NGF occurs in the extracellular space by the coordinated action of zymogens, convertases, and endogenous regulators, which are released in the extracellular space in an activity-dependent fashion. We further discuss our findings of a diminished conversion of the NGF precursor molecule to its mature form in Alzheimer's disease as well as an augmented degradation of mature NGF. These combined effects on NGF metabolism would explain the well-known cholinergic atrophy found in Alzheimer's disease and would offer new therapeutic opportunities aimed at correcting the NGF dysmetabolism along with Abeta-induced inflammatory responses.
Cuello
A Claudio
AC
Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, H3G 1Y6, Canada. claudio.cuello@mcgill.ca
Bruno
Martin A
MA
Allard
Simon
S
Leon
Wanda
W
Iulita
M Florencia
MF
D000109:Acetylcholine / Q000378:metabolism*; D000544:Alzheimer Disease / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D000818:Animals; D020532:Basal Nucleus of Meynert / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D002470:Cell Survival / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D006801:Humans; D009410:Nerve Degeneration / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D020932:Nerve Growth Factor / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism
D016326:Extracellular Matrix Proteins; D011498:Protein Precursors; C061397:pro-nerve growth factor, human; D020932:Nerve Growth Factor; D000109:Acetylcholine
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