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Sodium-coupled, high-affinity choline transporters (CHTs) are inhibited by 3-morpholinosydnonimine (SIN-1) [peroxynitrite(ONOO-) donor]; ONOO- can be produced from nitric oxide and reactive oxygen species during neurodegeneration. SIN-1 rapidly increases CHT internalization from the cell surface, and this correlates with decreased choline uptake. This study addresses mechanisms by which SIN-1 inhibits CHT function inhumanneuronal SH-SY5Y cells. Thus, mutant L531A-CHT, which does not constitutively internalize into cells by a clathrin-mediated process, is resistant to SIN-1 effects. This suggests that CHT inhibition is not due to oxidative-nitrosative inactivation of the protein and that decreased levels of cell surface CHT in SIN-1-treated cells is related to alterations in its trafficking and subcellular disposition. Dominant-negative proteins AP180C and dynamin-K44A, which interfere with clathrin-mediated and dynamindependent endocytosis, respectively, attenuate CHT inhibition by SIN-1. CHT in both vehicle- and SIN-1-treated cells colocalizes with Rab7, Rab9, and Lamp-1 in late endosomes and lysosomes to a similar extent. Lysosome inhibitors increase choline uptake, suggesting that CHT proteins are normally degraded by lysosomes, and this is not altered by oxidative stress. Unexpectedly, inhibitors of proteasomes, but not lysosomes, attenuate SIN-1-mediated inhibition of choline uptake, indicating that proteasomal degradation plays a role in regulating CHT disposition in SIN-1-treated cells. SIN-1 treatment also enhances CHT ubiquitination. Thus, CHT inhibition in SIN-1- treated cells is mediated by proteasomal degradation, which differs from inhibitory mechanisms for some neurotransmitter transporters under similar conditions. Increased oxidative-nitrosative stress in the microenvironment of cholinergic nerve terminals would diminish cholinergic transmission by reducing choline availability for ACh synthesis. [ABSTRACT FROM AUTHOR]

Background: Toxic amyloid-β (Aβ) peptides aggregate into higher molecular weight assemblies and accumulate not only in the extracellular space, but also in the walls of blood vessels in the brain, increasing their permeability, and promoting immune cell migration and activation. Given the prominent role of the immune system, phagocytic blood cells may contact pathological brain materials., Objective: To develop a novel method for early Alzheimer's disease (AD) detection, we used blood leukocytes, that could act as "sentinels" after trafficking through the brain microvasculature, to detect pathological amyloid by labelling with a conformationally-sensitive fluorescent amyloid probe and imaging with confocal spectral microscopy., Methods: Formalin-fixed peripheral blood mononuclear cells (PBMCs) from cognitively healthy control (HC) subjects, mild cognitive impairment (MCI) and AD patients were stained with the fluorescent amyloid probe K114, and imaged. Results were validated against cerebrospinal fluid (CSF) biomarkers and clinical diagnosis., Results: K114-labeled leukocytes exhibited distinctive fluorescent spectral signatures in MCI/AD subjects. Comparing subjects with single CSF biomarker-positive AD/MCI to negative controls, our technique yielded modest AUCs, which improved to the 0.90 range when only MCI subjects were included in order to measure performance in an early disease state. Combining CSF Aβ42 and t-Tau metrics further improved the AUC to 0.93., Conclusion: Our method holds promise for sensitive detection of AD-related protein misfolding in circulating leukocytes, particularly in the early stages of disease.

Choline uptake into cholinergic nerve terminals by the sodium-dependent high-affinity choline transporter CHT is essential for providing choline as substrate for synthesis of acetylcholine (ACh); ACh is used by cholinergic neurons to communicate information to a wide range of tissues in central and peripheral nervous systems. CHT is expressed almost exclusively in cholinergic neurons, and is subject to transcriptional and post-translational control by factors that promote or diminish cholinergic neurotransmission. The distribution of CHT proteins within cholinergic presynaptic terminals is dynamically regulated. Thus, choline uptake activity is determined largely by the plasma membrane CHT level, and this is finely controlled by a balance between internalization and recycling of CHT proteins in endosomal compartments. CHT proteins are also in synaptic vesicle membranes, thereby allowing cell surface CHT levels to increase rapidly in conjunction with exocytotic transmitter release to provide enhanced choline for ACh re-synthesis. Little is known about post-translational modification of CHT, although data is emerging that CHT activity and subcellular trafficking is modulated by kinase-mediated phosphorylation. Recent studies have also identified proteins with which CHT interacts, but this requires further investigation to reveal the role of other proteins in regulating CHT function and activity. Polymorphisms in CHT protein and modifications in its expression are linked to neurological and psychiatric disorders, and can alter function of peripheral systems that are regulated by cholinergic innervation, such as the cardiovascular system. The critical role of CHT in maintaining cholinergic transmission indicates that it could be a target for therapeutic intervention to promote ACh synthesis, but mechanisms by which this can be accomplished have not been adequately addressed.