McPhie et al. have done a beautiful job unraveling the signaling pathway linking FAD mutants of APP and neuronal apoptosis. Their evidence that reentry into the cell cycle is an obligatory step in this APP-induced apoptotic cascade is compelling. I'm intrigued by some similarities between the APP-driven mechanism described by McPhie and colleagues and what is seen in Niemann-Pick Type C disease:

Mutations of both the APP gene and the NPC1 gene in humans lead to activation of similar cell cycle markers, cytoskeletal pathology with neurofibrillary tangle formation, and widespread neurodegeneration.

Both proteins localize to transport vesicles and Rab-specific endosomal compartments. (Accumulation of b-amyloid in late endosomes has been described in NPC1 cells and in older NPC patients).

Therefore, I wonder if there is a critical link between the function of the endosome or transport vesicles and cell cycle regulation in postmitotic neurons; in other words, if neurons exit the cell cycle to become highly specialized communicative cells, they...  Read more

McPhie et al. have done a beautiful job unraveling the signaling pathway linking FAD mutants of APP and neuronal apoptosis. Their evidence that reentry into the cell cycle is an obligatory step in this APP-induced apoptotic cascade is compelling. I'm intrigued by some similarities between the APP-driven mechanism described by McPhie and colleagues and what is seen in Niemann-Pick Type C disease:

Mutations of both the APP gene and the NPC1 gene in humans lead to activation of similar cell cycle markers, cytoskeletal pathology with neurofibrillary tangle formation, and widespread neurodegeneration.

Both proteins localize to transport vesicles and Rab-specific endosomal compartments. (Accumulation of b-amyloid in late endosomes has been described in NPC1 cells and in older NPC patients).

Therefore, I wonder if there is a critical link between the function of the endosome or transport vesicles and cell cycle regulation in postmitotic neurons; in other words, if neurons exit the cell cycle to become highly specialized communicative cells, they might simply revert to cell cycling ("dedifferentiate") when this specialized function is compromised.

Dysregulation of the neuronal trafficking process may be a key event leading to cytoskeletal pathology and neuronal death. The latter is certainly not a new idea (Sheetz M et al., 1998; Kamal A, 2000; Morfini G et al., 2002; ARF related news story); and many more), but it may also explain a variety of disease outcomes arising from more specific or localized defects in trafficking. For instance, depending on which subset of vesicles, the type of cargo being transported, and which trafficking "arteriole" is affected, different sets of proteins/lipids may accumulate and aggregate forming different types of cytoskeletal lesions.

View all comments by Inez Vincent

We have made an antibody to an orphan GPCR that stains very strongly human neurons with NFT and human platelets. Anybody interested in collaborating? Mariano Alvira, MD marianoa@lsbio.com 206-374-1180

View all comments by Mariano Alvira