Ultrastructural analysis of the functional domains in FMRP using primary hippocampal mouse neurons

Levenga, Josien; Buijsen, Ronald A.M.; Rifé, M.; Moine, Hervé; Nelson, David L.; Oostra, Ben A.; Willemsen, Rob; Vrij, Femke M.S. de

doi:10.1016/j.nbd.2009.05.004

Cited by 23 publications

(19 citation statements)

References 45 publications

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“…1B-D). The cellular distribution of FXR2P [217] is qualitatively similar to that previously observed for heterologously-expressed FXR2P (Levenga et al, 2009;; see also Stackpole et al, 2014). Taken together, these data indicate that FXR2P with EGFP inserted within N-terminal domains organizes into granular assemblages within neurons.…”

Section: Egfp Fusions In the Amino Terminal Half Of Fxr2p Form Granulsupporting

confidence: 76%

The FXR2P low complexity domain drives assembly of multiple fibril types with differing ribosome association in neurons

Stackpole

Akins

Ivshina

et al. 2018

Preprint

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Section: Egfp Fusions In the Amino Terminal Half Of Fxr2p Form Granulsupporting

confidence: 76%

The FXR2P low complexity domain drives assembly of multiple fibril types with differing ribosome association in neurons

Stackpole

Akins

Ivshina

et al. 2018

Preprint

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“…2); and 5) as observed for other RNA binding proteins expressed in neurons, both wild type and mutant FXR2P formed granules (Figs. 3, 4; Köhrmann et al, 1999; Davidovic et al, 2007; Levenga et al, 2009). Taken together, these results indicate that myristoylation is important for regulating FXR2P localization within the axonal arbor.…”

Section: Discussionmentioning

confidence: 99%

N-myristoylation regulates the axonal distribution of the Fragile X-related protein FXR2P

Stackpole

Akins

Fallon

2014

Molecular and Cellular Neuroscience

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Fragile X Syndrome, the leading cause of inherited intellectual disability and autism, is caused by loss of function of Fragile X mental retardation protein (FMRP). FMRP is an RNA binding protein that regulates local protein synthesis in the somatodendritic compartment. However, emerging evidence also indicates important roles for FMRP in axonal and presynaptic function. In particular, FMRP and its homolog FXR2P localize axonally and presynaptically to discrete endogenous structures in the brain termed Fragile X granules (FXGs). FXR2P is a component of all FXGs and is necessary for the axonal and presynaptic localization of FMRP to these structures. We therefore sought to identify and characterize structural features of FXR2P that regulate its axonal localization. Sequence analysis reveals that FXR2P harbors a consensus N-terminal myristoylation sequence (MGXXXS) that is absent in FMRP. Using click chemistry with wild type and an unmyristoylatable G2A mutant we demonstrate that FXR2P is N-myristoylated on glycine 2, establishing it as a lipid-modified RNA binding protein. To investigate the role of FXR2P N-myristoylation in neurons we generated fluorescently tagged wild type and unmyristoylatable FXR2P (WT and G2A, respectively) and expressed them in primary cortical cultures. Both FXR2PWT and FXR2PG2A are expressed at equivalent overall levels and are capable of forming FMRP-containing axonal granules. However, FXR2PWT granules are largely restricted to proximal axonal segments while granules formed with unmyristoylatable FXR2PG2A are localized throughout the axonal arbor, including in growth cones. These studies indicate that N-terminal myristoylation of the RNA binding protein FXR2P regulates its localization within the axonal arbor. Moreover, since FMRP localization within axonal domains requires its association with FXR2P, these findings suggest that FXR2P lipid modification is a control point for the axonal and presynaptic distribution of FMRP.

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“…This is not surprising, as neither FMRP(I304N) nor FMRPΔRGG is expected to act as a dominant negative in this context. FMRP(I304N) is able to heterodimerize with wild-type FMRP and subsequently be recruited to RNA granules (Laggerbauer et al, 2001; Levenga et al, 2009), and FMRPΔRGG is unable to bind G-quartet RNA, and thus should not interfere with endogenous FMRP regulation of these transcripts.…”

Section: Discussionmentioning

confidence: 99%

Fragile X Protein FMRP Is Required for Homeostatic Plasticity and Regulation of Synaptic Strength by Retinoic Acid

Soden

Chen²

2010

J. Neurosci.

169

180

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Homeostatic synaptic plasticity adjusts the strength of synapses during global changes in neural activity, thereby stabilizing the overall activity of neural networks. Suppression of synaptic activity increases synaptic strength by inducing synthesis of retinoic acid (RA), which activates postsynaptic synthesis of AMPA-type glutamate receptors (AMPARs) in dendrites and promotes synaptic insertion of newly synthesized AMPARs. Here, we show that fragile X mental retardation protein (FMRP), an RNA-binding protein that regulates dendritic protein synthesis, is essential for increases in synaptic strength induced by RA or by blockade of neural activity in the mouse hippocampus. Although activity-dependent RA synthesis is maintained in Fmr1 knock-out neurons, RA-dependent dendritic translation of GluR1-type AMPA receptors is impaired. Intriguingly, FMRP is only required for the form of homeostatic plasticity that is dependent on both RA signaling and local protein synthesis. Postsynaptic expression of wild-type or mutant FMRP(I304N) in knock-out neurons reduced the total, surface, and synaptic levels of AMPARs, implying a role for FMRP in regulating AMPAR abundance. Expression of FMRP lacking the RGG box RNA-binding domain had no effect on AMPAR levels. Importantly, postsynaptic expression of wild-type FMRP, but not FMRP(I304N) or FMRP⌬RGG, restored synaptic scaling when expressed in knock-out neurons. Together, these findings identify an unanticipated role for FMRP in regulating homeostatic synaptic plasticity downstream of RA. Our results raise the possibility that at least some of the symptoms of fragile X syndrome reflect impaired homeostatic plasticity and impaired RA signaling.

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Ultrastructural analysis of the functional domains in FMRP using primary hippocampal mouse neurons

Cited by 23 publications

References 45 publications

The FXR2P low complexity domain drives assembly of multiple fibril types with differing ribosome association in neurons

The FXR2P low complexity domain drives assembly of multiple fibril types with differing ribosome association in neurons

N-myristoylation regulates the axonal distribution of the Fragile X-related protein FXR2P

Fragile X Protein FMRP Is Required for Homeostatic Plasticity and Regulation of Synaptic Strength by Retinoic Acid

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