Cholesterol‐dependent balance between evoked and spontaneous synaptic vesicle recycling

Wasser, Catherine R.; Ertunç, Mert; Liu, Xinran; Kavalali, Ege T.

doi:10.1113/jphysiol.2006.123133

Cited by 139 publications

(147 citation statements)

References 44 publications

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“…In order to avoid cholesterol depletion, the cells activate cholesterol synthesis in parallel with a down-regulation of the LXR target genes related to cholesterol efflux (ABCA1 and ApoE). Acute cholesterol depletion by cyclodextrin treatment results in altered membrane properties that can affect synaptic transmission in Purkinje cells and wildtype hippocampal neurons [57,58]. On the other hand, Sodero and coworkers have suggested that a sudden rise in excitatory neurotransmission activate CYP46A1-dependent mild cholesterol loss mechanisms to protect themselves from neuronal death [59].…”

Section: Discussionmentioning

confidence: 99%

Cholesterol 24S-Hydroxylase Overexpression Inhibits the Liver X Receptor (LXR) Pathway by Activating Small Guanosine Triphosphate-Binding Proteins (sGTPases) in Neuronal Cells

et al. 2014

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The neuronal-specific cholesterol 24S-hydroxylase (CYP46A1) is important for brain cholesterol elimination. Cyp46a1 null mice exhibit severe deficiencies in learning and hippocampal long-term potentiation, suggested to be caused by a decrease in isoprenoid intermediates of the mevalonate pathway. Conversely, transgenic mice overexpressing CYP46A1 show an improved cognitive function. These results raised the question of whether CYP46A1 expression can modulate the activity of proteins that are crucial for neuronal function, namely of isoprenylated small guanosine triphosphate-binding proteins (sGTPases). Our results show that CYP46A1 overexpression in SH-SY5Y neuroblastoma cells and in primary cultures of rat cortical neurons leads to an increase in 3-hydroxy-3-methyl-glutaryl-CoA reductase activity and to an overall increase in membrane levels of RhoA, Rac1, Cdc42 and Rab8. This increase is accompanied by a specific increase in RhoA activation. Interestingly, treatment with lovastatin or a geranylgeranyltransferase-I inhibitor abolished the CYP46A1 effect. The CYP46A1-mediated increase in sGTPases membrane abundance was confirmed in vivo, in membrane fractions obtained from transgenic mice overexpressing this enzyme. Moreover, CYP46A1 overexpression leads to a decrease in the liver X receptor (LXR) transcriptional activity and in the mRNA levels of ATPbinding cassette transporter 1, sub-family A, member 1 and apolipoprotein E. This effect was abolished by inhibition of prenylation or by co-transfection of a RhoA dominantnegative mutant. Our results suggest a novel regulatory axis in neurons; under conditions of membrane cholesterol reduction by increased CYP46A1 expression, neurons increase isoprenoid synthesis and sGTPase prenylation. This leads to a reduction in LXR activity, and consequently to a decrease in the expression of LXR target genes.

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Section: Discussionmentioning

confidence: 99%

Cholesterol 24S-Hydroxylase Overexpression Inhibits the Liver X Receptor (LXR) Pathway by Activating Small Guanosine Triphosphate-Binding Proteins (sGTPases) in Neuronal Cells

et al. 2014

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“…Many signaling pathways in the brain occur at cholesterol-rich domains known as lipid rafts. These include: signaling of GABA (40) and glutamate (41), synaptic vesicle turnover (42), BDNF protection of motor neurons (43), functioning of the calcium channel alpha2delta-2 subunit (44), and calcium-dependent neurotransmitter release (45). We speculate that in the absence of LXR␤ activation of LXR␣ by ␤-sitosterol leads to efflux of cholesterol from the brain and neuronal toxicity.…”

Section: Discussionmentioning

confidence: 99%

Liver X receptor β (LXRβ): A link between β-sitosterol and amyotrophic lateral sclerosis–Parkinson's dementia

Kim¹,

Fan²,

Gabbi³

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

122

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Administration of ␤-sitosterol (42 mg/kg per day) for 3 weeks to 8-month-old male LXR␤ ؊/؊ mice resulted in the death of motor neurons in the lumbar region of the spinal cord and loss of tyrosine hydroxylase-positive dopaminergic neurons in the substantia nigra. In mice at 5 months of age, ␤-sitosterol had no observed toxicity but at 16 months of age, it caused severe paralysis and symptoms typical of dopaminergic dysfunction in LXR␤ ؊/؊ mice. WT mice were not affected by these doses of ␤-sitosterol. In 5-month-old mice, levels of the intestinal transporters, ABCG5/8 and Niemann-Pick C1 Like 1, were not affected by loss of liver X receptor (LXR) ␤ and/or treatment with ␤-sitosterol nor were there changes in plasma levels of cholesterol or ␤-sitosterol. In 8-monthold LXR␤ ؊/؊ mice there was activation of microglia in the substantia nigra pars reticulata and aggregates of ubiquitin and TDP-43 in the cytoplasm of large motor neurons in the lumbar spinal cord. Brain cholesterol concentrations were higher in LXR␤ ؊/؊ than in their WT counterparts, and treatment with ␤-sitosterol reduced brain cholesterol in both WT and LXR␤ ؊/؊ mice. In LXR␤ ؊/؊ mice but not in WT mice levels of 24-hydrocholesterol were increased upon ␤-sitosterol treatment. These data indicate that multiple mechanisms are involved in the sensitivity of LXR␤ ؊/؊ mice to ␤-sitosterol. These include activation of microglia, accumulation of protein aggregates in the cytoplasm of large motor neurons, and depletion of brain cholesterol.central nervous system ͉ cholesterol ͉ microglia ͉ neurodegenerative disease ͉ nuclear receptor

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“…Thus, synaptophysin may function with cholesterol in renewing synaptic-vesicle membranes [46], suggesting that cholesterol availability is critical for synaptic vesicle docking and fusion [45]. Although there is regional variation in the glial influence on synapse development and neurite outgrowth [47], data from brain slice and primary neuron cultures also suggest a critical role for astrocyte-derived signals, including astrocyte-secreted cholesterol, as endogenous modulators of neurotransmission in both cortex and hippocampus [47,48]. The local interaction between the perisynaptic astroglial processes and the synapses are critical for synaptogenesis and fine manipulation of synaptic plasticity in mature brain [49].…”

Section: Reduced Cholesterolssecretionmentioning

confidence: 99%

Apolipoprotein E4 domain interaction: Synaptic and cognitive deficits in mice

Zhong

Scearce‐Levie

Ramaswamy

et al. 2008

Alzheimer's & Dementia

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BackgroundApolipoprotein E4 (apoE4), the major genetic risk factor for Alzheimer's disease (AD) and other neurodegenerative diseases, has three structural and biophysical properties that distinguish it from the other isoforms—domain interaction, reduced stability, and lack of cysteine. Assessing their relative contributions to effects of apoE4‐associated pathogenesis in AD is important from a mechanistic and therapeutic perspective, that is not possible using human apoE transgene or knock‐in models.MethodsWe analyzed Arg‐61 apoE mice, a gene‐targeted model that selectively displays domain interaction.ResultsThe mice displayed age‐dependent loss of the synaptic protein synaptophysin in neocortex and hippocampus and had lower levels of the postsynaptic neuroligin‐1. Activation of dentate gyrus granule neurons increased Arc expression 3.5‐fold in wildtype mice but only 2.3‐fold in Arg‐61 mice. The losses of synaptic proteins caused a mild memory deficit in Arg‐61 mice in the water‐maze test. Since synaptic integrity requires efficient glutamate uptake, we measured astrocyte glutamate transporter 1 in the hippocampus. The level was reduced in Arg‐61 mice, suggesting that inefficient glutamate uptake by astrocytes causes chronic excitotoxicity. Consistent with the reduced secretion of Arg‐61 apoE by astrocytes in this model, cholesterol secretion was also reduced 34%. This reduction could also contribute to the synaptic deficits by limiting the availability of cholesterol for neuronal repair.ConclusionsDomain interaction in the absence of other structural characteristics of apoE4 is sufficient to cause synaptic pathology and functional synaptic deficits, potentially associated with astrocyte dysfunction and impaired maintenance of neurons. Therapeutic targeting of domain interaction might blunt effects of apoE4 in neurodegenerative disease.

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Cholesterol‐dependent balance between evoked and spontaneous synaptic vesicle recycling

Cited by 139 publications

References 44 publications

Cholesterol 24S-Hydroxylase Overexpression Inhibits the Liver X Receptor (LXR) Pathway by Activating Small Guanosine Triphosphate-Binding Proteins (sGTPases) in Neuronal Cells

Cholesterol 24S-Hydroxylase Overexpression Inhibits the Liver X Receptor (LXR) Pathway by Activating Small Guanosine Triphosphate-Binding Proteins (sGTPases) in Neuronal Cells

Liver X receptor β (LXRβ): A link between β-sitosterol and amyotrophic lateral sclerosis–Parkinson's dementia

Apolipoprotein E4 domain interaction: Synaptic and cognitive deficits in mice

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