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FMRP mediates mGluR5-dependent translation of amyloid precursor protein.

Westmark CJ, Malter JS - PLoS Biol. (2007)

Bottom Line: Amyloid precursor protein (APP) facilitates synapse formation in the developing brain, while beta-amyloid (Abeta) accumulation, which is associated with Alzheimer disease, results in synaptic loss and impaired neurotransmission.APP mRNA coimmunoprecipitated with FMRP in resting synaptoneurosomes, but the interaction was lost shortly after DHPG treatment.Our data indicate that postsynaptic FMRP binds to and regulates the translation of APP mRNA through metabotropic glutamate receptor activation and suggests a possible link between Alzheimer disease and fragile X syndrome.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Laboratory Medicine, Waisman Center for Developmental Disabilities, University of Wisconsin, Madison, Wisconsin, United States of America. westmark@facstaff.wisc.edu

ABSTRACT
Amyloid precursor protein (APP) facilitates synapse formation in the developing brain, while beta-amyloid (Abeta) accumulation, which is associated with Alzheimer disease, results in synaptic loss and impaired neurotransmission. Fragile X mental retardation protein (FMRP) is a cytoplasmic mRNA binding protein whose expression is lost in fragile X syndrome. Here we show that FMRP binds to the coding region of APP mRNA at a guanine-rich, G-quartet-like sequence. Stimulation of cortical synaptoneurosomes or primary neuronal cells with the metabotropic glutamate receptor agonist DHPG increased APP translation in wild-type but not fmr-1 knockout samples. APP mRNA coimmunoprecipitated with FMRP in resting synaptoneurosomes, but the interaction was lost shortly after DHPG treatment. Soluble Abeta40 or Abeta42 levels were significantly higher in multiple strains of fmr-1 knockout mice compared to wild-type controls. Our data indicate that postsynaptic FMRP binds to and regulates the translation of APP mRNA through metabotropic glutamate receptor activation and suggests a possible link between Alzheimer disease and fragile X syndrome.

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Related in: MedlinePlus

FMRP Binds to a G-Rich Sequence in APP mRNA(A) Relative positions of the G-rich, predicted G-quartet and 29 base elements in nucleotides 446-2500 of APP (top). FMRP IPs digested with ribonuclease T1, analyzed by RTqPCR, and plotted as a percentage of APP mRNA699–796 (bottom).(B) FMRP IPs analyzed by the modified CLIP method and plotted as a percentage of APP699–796 mRNA.
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pbio-0050052-g007: FMRP Binds to a G-Rich Sequence in APP mRNA(A) Relative positions of the G-rich, predicted G-quartet and 29 base elements in nucleotides 446-2500 of APP (top). FMRP IPs digested with ribonuclease T1, analyzed by RTqPCR, and plotted as a percentage of APP mRNA699–796 (bottom).(B) FMRP IPs analyzed by the modified CLIP method and plotted as a percentage of APP699–796 mRNA.

Mentions: FMRP is a component of large RNP complexes [38]. The data presented here demonstrate that APP mRNA is also associated with this RNP. To determine the likely interaction site, in vitro RNase protection assays were performed on FMRP IPs from whole-cortex lysates. Residual APP mRNA was mapped by RTqPCR with primers immediately surrounding the predicted G-quartet (Figure 7A). Surprisingly, the G-rich area immediately preceding the G-quartet (nt 699–796) was approximately 4-fold more protected from nuclease digestion than fragments containing the predicted G-quartet (825–846). Although this protected area does not contain a canonical G-quartet motif, the sequence is very G-rich and contains several closely spaced DWGG repeats. The smallest amplicon (nt 774–871) containing the predicted G-quartet motif amplified a 98-base fragment, of which 46 nucleotides were guanines (47% G-rich; Table S1). Although this is the most G-rich amplicon of those tested, and T1 ribonuclease cuts 3′ of single-stranded G-residues, the 98-nt protected fragment (amplicon 699–796) was 40% G-rich, providing nearly equivalent numbers of targets for digestion. Thus, nucleotides 699–796 in the coding region of APP mRNA possess a G-rich sequence that is protected from nuclease digestion by an RNP complex containing FMRP.


FMRP mediates mGluR5-dependent translation of amyloid precursor protein.

Westmark CJ, Malter JS - PLoS Biol. (2007)

FMRP Binds to a G-Rich Sequence in APP mRNA(A) Relative positions of the G-rich, predicted G-quartet and 29 base elements in nucleotides 446-2500 of APP (top). FMRP IPs digested with ribonuclease T1, analyzed by RTqPCR, and plotted as a percentage of APP mRNA699–796 (bottom).(B) FMRP IPs analyzed by the modified CLIP method and plotted as a percentage of APP699–796 mRNA.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC1808499&req=5

pbio-0050052-g007: FMRP Binds to a G-Rich Sequence in APP mRNA(A) Relative positions of the G-rich, predicted G-quartet and 29 base elements in nucleotides 446-2500 of APP (top). FMRP IPs digested with ribonuclease T1, analyzed by RTqPCR, and plotted as a percentage of APP mRNA699–796 (bottom).(B) FMRP IPs analyzed by the modified CLIP method and plotted as a percentage of APP699–796 mRNA.
Mentions: FMRP is a component of large RNP complexes [38]. The data presented here demonstrate that APP mRNA is also associated with this RNP. To determine the likely interaction site, in vitro RNase protection assays were performed on FMRP IPs from whole-cortex lysates. Residual APP mRNA was mapped by RTqPCR with primers immediately surrounding the predicted G-quartet (Figure 7A). Surprisingly, the G-rich area immediately preceding the G-quartet (nt 699–796) was approximately 4-fold more protected from nuclease digestion than fragments containing the predicted G-quartet (825–846). Although this protected area does not contain a canonical G-quartet motif, the sequence is very G-rich and contains several closely spaced DWGG repeats. The smallest amplicon (nt 774–871) containing the predicted G-quartet motif amplified a 98-base fragment, of which 46 nucleotides were guanines (47% G-rich; Table S1). Although this is the most G-rich amplicon of those tested, and T1 ribonuclease cuts 3′ of single-stranded G-residues, the 98-nt protected fragment (amplicon 699–796) was 40% G-rich, providing nearly equivalent numbers of targets for digestion. Thus, nucleotides 699–796 in the coding region of APP mRNA possess a G-rich sequence that is protected from nuclease digestion by an RNP complex containing FMRP.

Bottom Line: Amyloid precursor protein (APP) facilitates synapse formation in the developing brain, while beta-amyloid (Abeta) accumulation, which is associated with Alzheimer disease, results in synaptic loss and impaired neurotransmission.APP mRNA coimmunoprecipitated with FMRP in resting synaptoneurosomes, but the interaction was lost shortly after DHPG treatment.Our data indicate that postsynaptic FMRP binds to and regulates the translation of APP mRNA through metabotropic glutamate receptor activation and suggests a possible link between Alzheimer disease and fragile X syndrome.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Laboratory Medicine, Waisman Center for Developmental Disabilities, University of Wisconsin, Madison, Wisconsin, United States of America. westmark@facstaff.wisc.edu

ABSTRACT
Amyloid precursor protein (APP) facilitates synapse formation in the developing brain, while beta-amyloid (Abeta) accumulation, which is associated with Alzheimer disease, results in synaptic loss and impaired neurotransmission. Fragile X mental retardation protein (FMRP) is a cytoplasmic mRNA binding protein whose expression is lost in fragile X syndrome. Here we show that FMRP binds to the coding region of APP mRNA at a guanine-rich, G-quartet-like sequence. Stimulation of cortical synaptoneurosomes or primary neuronal cells with the metabotropic glutamate receptor agonist DHPG increased APP translation in wild-type but not fmr-1 knockout samples. APP mRNA coimmunoprecipitated with FMRP in resting synaptoneurosomes, but the interaction was lost shortly after DHPG treatment. Soluble Abeta40 or Abeta42 levels were significantly higher in multiple strains of fmr-1 knockout mice compared to wild-type controls. Our data indicate that postsynaptic FMRP binds to and regulates the translation of APP mRNA through metabotropic glutamate receptor activation and suggests a possible link between Alzheimer disease and fragile X syndrome.

Show MeSH
Related in: MedlinePlus