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The nuclear import of Frizzled2-C by Importins-beta11 and alpha2 promotes postsynaptic development.

Mosca TJ, Schwarz TL - Nat. Neurosci. (2010)

Bottom Line: The mechanism of nuclear import is unknown and the developmental consequences of this translocation are uncertain.We found that Fz2-C localization to muscle nuclei required the nuclear import factors Importin-beta11 and Importin-alpha2 and that this pathway promoted the postsynaptic development of the subsynaptic reticulum (SSR), an elaboration of the postsynaptic plasma membrane. importin-beta11 (imp-beta11) and dfz2 mutants had less SSR, and some boutons lacked the postsynaptic marker Discs Large.Thus, Wnt-activated growth of the postsynaptic membrane is mediated by the synapse-to-nucleus translocation and active nuclear import of Fz2-C via a selective Importin-beta11/alpha2 pathway.

View Article: PubMed Central - PubMed

Affiliation: The F.M. Kirby Neurobiology Center, Children's Hospital Boston, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.

ABSTRACT
Synapse-to-nucleus signaling is critical for synaptic development and plasticity. In Drosophila, the ligand Wingless causes the C terminus of its Frizzled2 receptor (Fz2-C) to be cleaved and translocated from the postsynaptic density to nuclei. The mechanism of nuclear import is unknown and the developmental consequences of this translocation are uncertain. We found that Fz2-C localization to muscle nuclei required the nuclear import factors Importin-beta11 and Importin-alpha2 and that this pathway promoted the postsynaptic development of the subsynaptic reticulum (SSR), an elaboration of the postsynaptic plasma membrane. importin-beta11 (imp-beta11) and dfz2 mutants had less SSR, and some boutons lacked the postsynaptic marker Discs Large. These developmental defects in imp-beta11 mutants could be overcome by expression of Fz2-C fused to a nuclear localization sequence that can bypass Importin-beta11. Thus, Wnt-activated growth of the postsynaptic membrane is mediated by the synapse-to-nucleus translocation and active nuclear import of Fz2-C via a selective Importin-beta11/alpha2 pathway.

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Importins-β11 and -α2 are Expressed in Drosophila Muscle NucleiRepresentative confocal images of wild-type (y,w; FRT42D; +; +) muscles (a-f, I, j) or importin-α2  mutant (y,w; imp-α2D14; +; +) nuclei (g,h) stained with antibodies to an importin (magenta) and to the nuclear marker nonA (green). (a,b) Anti-Importin-β11 staining is observed at the nuclear envelope and within the nucleus. (c,d) Anti-Importin-α1 nonspecifically labels Z-bands but is undetectable in the nucleus. (e,f) Anti-Importin-α2 staining is observed within the nucleus. (g,h) In Importin-α2  mutant nuclei anti-Importin-α2 does not label muscle nuclei, indicating that the nuclear staining in e and f is specific for importin-α2. Nonspecific puncta in the cytoplasm persist, however in the mutant. (i,j) Wild-type muscle was not immunoreactive for anti-Importin-α3 although the antibody did recognize Importin-α3 in neuronal tissues known to express Importin-α3 (data not shown). Scale bar = 10 µm.
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Figure 1: Importins-β11 and -α2 are Expressed in Drosophila Muscle NucleiRepresentative confocal images of wild-type (y,w; FRT42D; +; +) muscles (a-f, I, j) or importin-α2 mutant (y,w; imp-α2D14; +; +) nuclei (g,h) stained with antibodies to an importin (magenta) and to the nuclear marker nonA (green). (a,b) Anti-Importin-β11 staining is observed at the nuclear envelope and within the nucleus. (c,d) Anti-Importin-α1 nonspecifically labels Z-bands but is undetectable in the nucleus. (e,f) Anti-Importin-α2 staining is observed within the nucleus. (g,h) In Importin-α2 mutant nuclei anti-Importin-α2 does not label muscle nuclei, indicating that the nuclear staining in e and f is specific for importin-α2. Nonspecific puncta in the cytoplasm persist, however in the mutant. (i,j) Wild-type muscle was not immunoreactive for anti-Importin-α3 although the antibody did recognize Importin-α3 in neuronal tissues known to express Importin-α3 (data not shown). Scale bar = 10 µm.

Mentions: Nuclear import can proceed via an importin-α and -β acting jointly, or by an importin-β alone3. Our previous work determined that Importin-β11 was expressed in muscle nuclei (Fig. 1a,b)16, but importin-α expression in these muscles was not examined. Of the three Drosophila importin-α homologues17, neither Importin-α1 nor -α3 could be detected immunocytochemically in muscle nuclei (Fig. 1c,d and i,j ). Importin-α2 immunoreactivity, however, was present in wild-type but not importin-α2 mutant nuclei (Fig. 1e,f,g,h). Non-specific immunoreactivity was seen at the NMJ of both wild-type and importin-α2 larvae (not shown), which prevented determining if Importin-α2 was also at the synapse.


The nuclear import of Frizzled2-C by Importins-beta11 and alpha2 promotes postsynaptic development.

Mosca TJ, Schwarz TL - Nat. Neurosci. (2010)

Importins-β11 and -α2 are Expressed in Drosophila Muscle NucleiRepresentative confocal images of wild-type (y,w; FRT42D; +; +) muscles (a-f, I, j) or importin-α2  mutant (y,w; imp-α2D14; +; +) nuclei (g,h) stained with antibodies to an importin (magenta) and to the nuclear marker nonA (green). (a,b) Anti-Importin-β11 staining is observed at the nuclear envelope and within the nucleus. (c,d) Anti-Importin-α1 nonspecifically labels Z-bands but is undetectable in the nucleus. (e,f) Anti-Importin-α2 staining is observed within the nucleus. (g,h) In Importin-α2  mutant nuclei anti-Importin-α2 does not label muscle nuclei, indicating that the nuclear staining in e and f is specific for importin-α2. Nonspecific puncta in the cytoplasm persist, however in the mutant. (i,j) Wild-type muscle was not immunoreactive for anti-Importin-α3 although the antibody did recognize Importin-α3 in neuronal tissues known to express Importin-α3 (data not shown). Scale bar = 10 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2913881&req=5

Figure 1: Importins-β11 and -α2 are Expressed in Drosophila Muscle NucleiRepresentative confocal images of wild-type (y,w; FRT42D; +; +) muscles (a-f, I, j) or importin-α2 mutant (y,w; imp-α2D14; +; +) nuclei (g,h) stained with antibodies to an importin (magenta) and to the nuclear marker nonA (green). (a,b) Anti-Importin-β11 staining is observed at the nuclear envelope and within the nucleus. (c,d) Anti-Importin-α1 nonspecifically labels Z-bands but is undetectable in the nucleus. (e,f) Anti-Importin-α2 staining is observed within the nucleus. (g,h) In Importin-α2 mutant nuclei anti-Importin-α2 does not label muscle nuclei, indicating that the nuclear staining in e and f is specific for importin-α2. Nonspecific puncta in the cytoplasm persist, however in the mutant. (i,j) Wild-type muscle was not immunoreactive for anti-Importin-α3 although the antibody did recognize Importin-α3 in neuronal tissues known to express Importin-α3 (data not shown). Scale bar = 10 µm.
Mentions: Nuclear import can proceed via an importin-α and -β acting jointly, or by an importin-β alone3. Our previous work determined that Importin-β11 was expressed in muscle nuclei (Fig. 1a,b)16, but importin-α expression in these muscles was not examined. Of the three Drosophila importin-α homologues17, neither Importin-α1 nor -α3 could be detected immunocytochemically in muscle nuclei (Fig. 1c,d and i,j ). Importin-α2 immunoreactivity, however, was present in wild-type but not importin-α2 mutant nuclei (Fig. 1e,f,g,h). Non-specific immunoreactivity was seen at the NMJ of both wild-type and importin-α2 larvae (not shown), which prevented determining if Importin-α2 was also at the synapse.

Bottom Line: The mechanism of nuclear import is unknown and the developmental consequences of this translocation are uncertain.We found that Fz2-C localization to muscle nuclei required the nuclear import factors Importin-beta11 and Importin-alpha2 and that this pathway promoted the postsynaptic development of the subsynaptic reticulum (SSR), an elaboration of the postsynaptic plasma membrane. importin-beta11 (imp-beta11) and dfz2 mutants had less SSR, and some boutons lacked the postsynaptic marker Discs Large.Thus, Wnt-activated growth of the postsynaptic membrane is mediated by the synapse-to-nucleus translocation and active nuclear import of Fz2-C via a selective Importin-beta11/alpha2 pathway.

View Article: PubMed Central - PubMed

Affiliation: The F.M. Kirby Neurobiology Center, Children's Hospital Boston, Department of Neurobiology, Harvard Medical School, Boston, Massachusetts, USA.

ABSTRACT
Synapse-to-nucleus signaling is critical for synaptic development and plasticity. In Drosophila, the ligand Wingless causes the C terminus of its Frizzled2 receptor (Fz2-C) to be cleaved and translocated from the postsynaptic density to nuclei. The mechanism of nuclear import is unknown and the developmental consequences of this translocation are uncertain. We found that Fz2-C localization to muscle nuclei required the nuclear import factors Importin-beta11 and Importin-alpha2 and that this pathway promoted the postsynaptic development of the subsynaptic reticulum (SSR), an elaboration of the postsynaptic plasma membrane. importin-beta11 (imp-beta11) and dfz2 mutants had less SSR, and some boutons lacked the postsynaptic marker Discs Large. These developmental defects in imp-beta11 mutants could be overcome by expression of Fz2-C fused to a nuclear localization sequence that can bypass Importin-beta11. Thus, Wnt-activated growth of the postsynaptic membrane is mediated by the synapse-to-nucleus translocation and active nuclear import of Fz2-C via a selective Importin-beta11/alpha2 pathway.

Show MeSH
Related in: MedlinePlus