Conserved reduction of m6A marks during aging and neurodegeneration is linked to altered translation of synaptic transcripts
Ontology highlight
ABSTRACT: N6-methyladenosine (m6A) plays diverse roles in the regulation of mRNA metabolism. In the mammalian brain it has been linked to developmental processes, memory function and plasticity. However, the precise role of m6A in the context synaptic plasticity and especially during impaired cognition are not fully understood. Here, we describe the mouse and human brain m6A epi-transcriptome in a tissue-specific manner. We furthermore show that m6A levels undergo massive decreases across mouse brain regions as a consequence of aging. Equally, Alzheimer’s disease in humans correlates with decreased N6-methylation in a similar population of transcripts that are linked to synaptic function and localized to synapses, such as the calcium/calmodulin-dependent kinase II (CaMKII). In line with this we show that reduced m6A levels impair synaptic protein-synthesis of CAMKII. Our results suggest that N6-RNA-methylation is an important mechanism to control synaptic protein synthesis which is affected early in cognitive diseases. This data submission just includes mouse data.
Project description:Regulator of G Protein Signaling 14 (RGS14) is a complex scaffolding protein with an unusual domain structure that allows it to integrate G protein and mitogen-activated protein kinase (MAPK) signaling pathways. RGS14 mRNA and protein are enriched in brain tissue of rodents and primates. In the adult mouse brain, RGS14 is predominantly expressed in postsynaptic dendrites and spines of hippocampal CA2 pyramidal neurons where it naturally inhibits synaptic plasticity and hippocampus-dependent learning and memory. However, the signaling proteins that RGS14 natively interacts with in neurons to regulate plasticity are unknown. Here, we show that RGS14 exists as a component of a high molecular weight protein complex in brain. To identify RGS14 neuronal interacting partners, endogenous RGS14 isolated from mouse brain was subjected to mass spectrometry and proteomic analysis. We find that RGS14 interacts with key postsynaptic proteins that regulate neuronal plasticity. Gene ontology analysis reveals that the most enriched RGS14 interacting proteins have functional roles in actin-binding, calmodulin(CaM)-binding, and CaM-dependent protein kinase (CaMK) activity. We validate these proteomics findings using biochemical assays that identify interactions between RGS14 and two previously unknown binding partners: CaM and CaMKII. We report that RGS14 directly interacts with CaM in a calcium-dependent manner and is phosphorylated by CaMKII in vitro. Lastly, we detect that RGS14 associates with CaMKII and with CaM in hippocampal CA2 neurons by proximity ligation assays in mouse brain sections. Taken together, these findings demonstrate that RGS14 is a novel CaM effector and CaMKII phosphorylation substrate thereby providing new insight into cellular mechanisms by which RGS14 controls plasticity in CA2 neurons.
Project description:Calmodulin sits at the center of molecular mechanisms underlying learning and memory. Its complex, and sometimes opposite, influences via the binding to various proteins are yet to be fully understood. Calcium/calmodulin-dependent protein kinase II (CaMKII) and calcineurin (CaN) both bind open calmodulin, favoring Long-term-potentiation (LTP) or depression (LTD) respectively. Neurogranin binds to the closed conformation of calmodulin and its impact on synaptic plasticity is less clear. We set up a mechanistic computational model based on allosteric principles to simulate calmodulin state transitions and its interaction with calcium ions and the three binding partners mentioned above. We simulated calcium spikes at various frequencies and show that neurogranin regulates synaptic plasticity along three modalities. At low spike frequencies, neurogranin inhibits the onset of LTD by limiting CaN activation. At intermediate frequencies, neurogranin limits LTP by precluding binding of CaMKII with calmodulin. Finally, at high spike frequencies, neurogranin promotes LTP by enhancing CaMKII autophosphorylation. While neurogranin might act as a calmodulin buffer, it does not significantly preclude the calmodulin opening by calcium. On the contrary, neurogranin synchronizes the opening of calmodulin's two lobes and promotes their activation at specific frequencies, increasing the chance of CaMKII trans-autophosphorylation. Importantly, the positive effect of neurogranin on CaMKII activation is mediated via CaN, and too few or too much CaN will abolish this effect. Furthermore, the amount of neurogranin itself differentially regulates the levels of CaN and CaMKII activities, as well as the frequencies at which the balance switch from one to the other.
Project description:Li2012 Calcium mediated synaptic
plasticity
This model is an extension of
BIOMD0000000183.
This model is described in the article:
Calcium input frequency,
duration and amplitude differentially modulate the relative
activation of calcineurin and CaMKII.
Li L, Stefan MI, Le Novère
N.
PLoS ONE 2012; 7(9): e43810
Abstract:
NMDA receptor dependent long-term potentiation (LTP) and
long-term depression (LTD) are two prominent forms of synaptic
plasticity, both of which are triggered by post-synaptic
calcium elevation. To understand how calcium selectively
stimulates two opposing processes, we developed a detailed
computational model and performed simulations with different
calcium input frequencies, amplitudes, and durations. We show
that with a total amount of calcium ions kept constant, high
frequencies of calcium pulses stimulate calmodulin more
efficiently. Calcium input activates both calcineurin and
Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) at all
frequencies, but increased frequencies shift the relative
activation from calcineurin to CaMKII. Irrespective of
amplitude and duration of the inputs, the total amount of
calcium ions injected adjusts the sensitivity of the system to
calcium input frequencies. At a given frequency, the quantity
of CaMKII activated is proportional to the total amount of
calcium. Thus, an input of a small amount of calcium at high
frequencies can induce the same activation of CaMKII as a
larger amount, at lower frequencies. Finally, the extent of
activation of CaMKII signals with high calcium frequency is
further controlled by other factors, including the availability
of calmodulin, and by the potency of phosphatase
inhibitors.
This model is hosted on
BioModels Database
and identified by:
BIOMD0000000628.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
Project description:Here, we use a novel technique for locating regions of N6-adenosine methylation (m6A) throughout the transcriptome and present a profile of m6A sites in the mouse brain. Our use of methylated RNA immunoprecipitation combined with RNA-seq (MeRIP-Seq) identifies thousands of RNAs which contain m6A sites. In addition, we find that regions of m6A formation are particularly enriched near stop codons, which might provide clues into the potential funciton of this highly prevalent RNA modificaiton. Examination of m6A sites in murine brain RNA.
Project description:Here, we use a novel technique for locating regions of N6-adenosine methylation (m6A) throughout the transcriptome and present a profile of m6A sites in the mouse brain. Our use of methylated RNA immunoprecipitation combined with RNA-seq (MeRIP-Seq) identifies thousands of RNAs which contain m6A sites. In addition, we find that regions of m6A formation are particularly enriched near stop codons, which might provide clues into the potential funciton of this highly prevalent RNA modificaiton. Examination of m6A sites in murine brain RNA and human embryonic kidney cells.
Project description:Benzodiazepine (BZ) drugs treat seizures, anxiety, insomnia, and alcohol withdrawal by potentiating γ2 subunit containing GABA type A receptors (GABAARs). BZ clinical use is hampered by tolerance and withdrawal symptoms, which include heightened seizure susceptibility, panic, and sleep disturbances. Here, we undergo a comprehensive investigation of inhibitory GABAergic and excitatory glutamatergic plasticity in mice tolerant to benzodiazepine sedation. Using quantitative proteomics approaches, we reveal cortex neuroadaptations of key pro-excitatory mediators and synaptic plasticity pathways, highlighted by Ca2+/calmodulin-dependent protein kinase II (CAMKII), MAPK, and PKC signaling.
Project description:N6-methyladenosine (m6A) is the most abundant modified base in eukaryotic mRNA and has been linked to diverse effects on mRNA fate and function. Current m6A mapping approaches rely on immunoprecipitation of m6A-containing RNA fragments to identify regions of transcripts that contain m6A. This approach localizes m6A residues to 100-200 nt-long regions of transcripts. The precise position of m6A in mRNAs cannot be identified on a transcriptome-wide level because there are no chemical methods to distinguish between m6A and adenosine. Here we show that anti-m6A antibodies can induce specific mutational signatures at m6A residues after ultraviolet light-induced antibody-RNA crosslinking and reverse transcription. Similarly, we find these antibodies induce mutational signatures at N6, 2’-O-dimethyladenosine (m6Am), a nucleotide found at the first encoded position of certain mRNAs. Using these mutational signatures, we map m6A and m6Am at single-nucleotide resolution in human and mouse mRNA and identify snoRNAs as a novel class of m6A-containing ncRNAs. UV-crosslinking and immunoprecipitation with m6A-specific antibodies was used to map m6A and m6Am in cellular RNA with single nucleotide resolution.
Project description:Stefan2008 - calmodulin allostery
An allosteric model for calmodulin activation, in which binding to calcium facilitates the transition between a low-affinity [tense (T)] and a high-affinity [relaxed (R)] state.
This model is described in the article:
An allosteric model of calmodulin explains differential activation of PP2B and CaMKII.
Stefan MI, Edelstein SJ, Le Novère N
Proc. Natl. Acad. Sci. U.S.A. 2008 Aug; 105(31): 10768-10773
Abstract:
Calmodulin plays a vital role in mediating bidirectional synaptic plasticity by activating either calcium/calmodulin-dependent protein kinase II (CaMKII) or protein phosphatase 2B (PP2B) at different calcium concentrations. We propose an allosteric model for calmodulin activation, in which binding to calcium facilitates the transition between a low-affinity [tense (T)] and a high-affinity [relaxed (R)] state. The four calcium-binding sites are assumed to be nonidentical. The model is consistent with previously reported experimental data for calcium binding to calmodulin. It also accounts for known properties of calmodulin that have been difficult to model so far, including the activity of nonsaturated forms of calmodulin (we predict the existence of open conformations in the absence of calcium), an increase in calcium affinity once calmodulin is bound to a target, and the differential activation of CaMKII and PP2B depending on calcium concentration.
This model is hosted on BioModels Database and identified by: BIOMD0000000183.
To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models.
To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.
Project description:N6-Methyladenosine (m6A) and N6,2'-O-dimethyladenosine (m6Am) are abundant mRNA modifications that regulate transcript processing and translation. The role of both, here termed m6A/m, in the stress response in the adult brain in vivo are currently unknown. Here, we provide a detailed analysis of the stress-epitranscriptome using m6A/m-Seq, global and gene-specific m6A/m measurements. We show that stress exposure and glucocorticoids region- and time-specifically alter m6A/m and its regulatory network. We demonstrate that deletion of the methyltransferase Mettl3 or the demethylase Fto in adult neurons alter the m6A/m epitranscriptome, increase fear memory, alter the transcriptome response to fear and synaptic plasticity. Moreover, we report that regulation of m6A/m is impaired in major depressive disorder (MDD) patients following glucocorticoid stimulation. Our findings indicate that brain m6A/m represents a novel layer of complexity in gene expression regulation after stress and that dysregulation of the m6A/m-response may contribute to the pathophysiology of stress-related psychiatric disorders.
Project description:N6-methyl-adenosine (m6A) is the most abundant modification on messenger RNAs and is linked to human diseases, but its functions in mammalian development are poorly understood. Here we reveal the evolutionary conservation and function of m6A by mapping the m6A methylome in mouse and human embryonic stem cells. Thousands of messenger and long noncoding RNAs show conserved m6A modification, including transcripts encoding core pluripotency transcription factors. m6A is enriched over 3M-bM-^@M-^Y untranslated regions at defined sequence motifs, and marks unstable transcripts, including transcripts turned over upon differentiation. Genetic inactivation or depletion of mouse and human Mettl3, one of the m6A methylases, led to m6A erasure on select target genes, prolonged Nanog expression upon differentiation, and impaired ESCM-bM-^@M-^Ys exit from self-renewal towards differentiation into several lineages in vitro and in vivo. Thus, m6A is a mark of transcriptome flexibility required for stem cells to differentiate to specific lineages. Examing m6A modification differences in two different cell types