The cellular prion protein PrP ^c is a glycosylphosphatidylinositol-anchored cell-surface protein whose biological function is unclear. We used the murine 1C11 neuronal differentiation model to search for PrP ^c -dependent signal transduction through antibody-mediated cross-linking. A caveolin-1–dependent coupling of PrP ^c to the tyrosine kinase Fyn was observed. Clathrin might also contribute to this coupling. The ability of the 1C11 cell line to trigger PrP ^c -dependent Fyn activation was restricted to its fully differentiated serotonergic or noradrenergic progenies. Moreover, the signaling activity of PrP ^c occurred mainly at neurites. Thus, PrP ^c may be a signal transduction protein.

Direct reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) provides a unique opportunity to derive patient-specific stem cells with potential applications in tissue replacement therapies and without the ethical concerns of human embryonic stem cells (hESCs). However, cellular senescence, which contributes to aging and restricted longevity, has been described as a barrier to the derivation of iPSCs. Here we demonstrate, using an optimized protocol, that cellular senescence is not a limit to reprogramming and that age-related cellular physiology is reversible. Thus, we show that our iPSCs generated from senescent and centenarian cells have reset telomere size, gene expression profiles, oxidative stress, and mitochondrial metabolism, and are indistinguishable from hESCs. Finally, we show that senescent and centenarian-derived pluripotent stem cells are able to redifferentiate into fully rejuvenated cells. These results provide new insights into iPSC technology and pave the way for regenerative medicine for aged patients.

The cerebrospinal fluid (CSF) biochemical markers (biomarkers) Amyloidβ 42 (Aβ42), total Tau (T-tau) and Tau phosphorylated at threonine 181 (P-tau181) have proven diagnostic accuracy for mild cognitive impairment and dementia due to Alzheimer’s Disease (AD). In an effort to improve the accuracy of an AD diagnosis, it is important to be able to distinguish between AD and other types of dementia (non-AD). The concentration ratio of Aβ42 to Aβ40 (Aβ42/40 Ratio) has been suggested to be superior to the concentration of Aβ42 alone when identifying patients with AD. This article reviews the available evidence on the use of the CSF Aβ42/40 ratio in the diagnosis of AD. Based on the body of evidence presented herein, it is the conclusion of the current working group that the CSF Aβ42/40 ratio, rather than the absolute value of CSF Aβ42, should be used when analysing CSF AD biomarkers to improve the percentage of appropriately diagnosed patients.

There is currently no effective therapy for human prion diseases. However, several polyanionic glycans, including pentosan sulfate and dextran sulfate, prolong the incubation time of scrapie in rodents, and inhibit the production of the scrapie isoform of the prion protein (PrPSc), the major component of infectious prions, in cultured neuroblastoma cells. We report here that pentosan sulfate and related compounds rapidly and dramatically reduce the amount of PrPC, the non-infectious precursor of PrPSc, present on the cell surface. This effect results primarily from the ability of these agents to stimulate endocytosis of PrPC, thereby causing a redistribution of the protein from the plasma membrane to the cell interior. Pentosan sulfate also causes a change in the ultrastructural localization of PrPC, such that a portion of the protein molecules are shifted into late endosomes and/or lysosomes. In addition, we demonstrate, using PrP-containing bacterial fusion proteins, that cultured cells express saturable and specific surface binding sites for PrP, many of which are glycosaminoglycan molecules. Our results raise the possibility that sulfated glycans inhibit prion production by altering the cellular localization of PrPC precursor, and they indicate that endogenous proteoglycans are likely to play an important role in the cellular metabolism of both PrPC and PrPSc.