Proteasomal-Mediated Degradation of AKAP150 Accompanies AMPAR Endocytosis during cLTD.

The number and function of synaptic AMPA receptors (AMPARs) tightly regulates excitatory synaptic transmission. Current evidence suggests that AMPARs are inserted into the postsynaptic membrane during long-term potentiation (LTP) and are removed from the membrane during long-term depression (LTD). Dephosphorylation of GluA1 at Ser-845 and enhanced endocytosis are critical events in the modulation of LTD. Moreover, changes in scaffold proteins from the postsynaptic density (PSD) could be also related to AMPAR regulation in LTD. In the present study we analyzed the effect of chemical LTD (cLTD) on A-kinase anchoring protein (AKAP)150 and AMPARs levels in mouse-cultured neurons. We show that cLTD induces AKAP150 protein degradation via proteasome, coinciding with GluA1 dephosphorylation at Ser-845 and endocytosis of GluA1-containing AMPARs. Pharmacological inhibition of proteasome activity, but not phosphatase calcineurin (CaN), reverted cLTD-induced AKAP150 protein degradation. Importantly, AKAP150 silencing induced dephosphorylation of GluA1 Ser-845 and GluA1-AMPARs endocytosis while AKAP150 overexpression blocked cLTD-mediated GluA1-AMPARs endocytosis. Our results provide direct evidence that cLTD-induced AKAP150 degradation by the proteasome contributes to synaptic AMPARs endocytosis.

Altered microRNAs related to synaptic function as potential plasma biomarkers for Alzheimer's disease.

BACKGROUND: Several evidences suggest that failure of synaptic function occurs at preclinical stages of Alzheimer's disease (AD) preceding neuronal loss and the classical AD pathological hallmarks. Nowadays, there is an urgent need to identify reliable biomarkers that could be obtained with non-invasive methods to improve AD diagnosis at early stages. Here, we have examined plasma levels of a group of miRNAs related to synaptic proteins in a cohort composed of cognitive healthy controls (HC), mild cognitive impairment (MCI) and AD subjects. METHODS: Plasma and brain levels of miRNAs were analysed in two different cohorts including 38 HC, 26 MCI, 56 AD dementia patients and 27 frontotemporal dementia (FTD) patients. D'Agostino and Pearson and Shapiro-Wilk tests were used to evaluate data normality. miRNA levels between groups were compared using a two-sided nonparametric Mann-Whitney test and sensitivity and specificity was determined by receiver operating characteristic curve analysis. RESULTS: Significant upregulation of miR-92a-3p, miR-181c-5p and miR-210-3p was found in the plasma of both MCI and AD subjects. MCI patients that progress to AD showed higher plasma levels of these miRNAs. By contrast, no changes in miR-92a-3p, miR-181c-5p or miR-210-3p levels were observed in plasma obtained from a cohort of FTD. CONCLUSION: Our study shows that plasma miR-92a-3p, miR-181c-5p and miR-210-3p constitute a specific molecular signature potentially useful as a potential biomarker for AD.

Blood-brain barrier dysfunction underlying Alzheimer's disease is induced by an SSAO/VAP-1-dependent cerebrovascular activation with enhanced Aß deposition.

Dysfunctions of the vascular system directly contribute to the onset and progression of Alzheimer's disease (AD). The blood-brain barrier (BBB) shows signs of malfunction at early stages of the disease. When Abeta peptide (Aß) is deposited on brain vessels, it induces vascular degeneration by producing reactive oxygen species and promoting inflammation. These molecular processes are also related to an excessive SSAO/VAP-1 (semicarbazide-sensitive amine oxidase) enzymatic activity, observed in plasma and in cerebrovascular tissue of AD patients. We studied the contribution of vascular SSAO/VAP-1 to the BBB dysfunction in AD using in vitro BBB models. Our results show that SSAO/VAP-1 expression is associated to endothelial activation by altering the release of pro-inflammatory and pro-angiogenic angioneurins, most highly IL-6, IL-8 and VEGF. It is also related to a BBB structure alteration, with a decrease in tight-junction proteins such as zona occludens or claudin-5. Moreover, the BBB function reveals increased permeability and leukocyte adhesion in cells expressing SSAO/VAP-1, as well as an enhancement of the vascular Aß deposition induced by mechanisms both dependent and independent of the enzymatic activity of SSAO/VAP-1. These results reveal an interesting role of vascular SSAO/VAP-1 in BBB dysfunction related to AD progression, opening a new window in the search of alternative therapeutic targets for fighting AD.