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Interaction of Cupidin/Homer2 with two actin cytoskeletal regulators, Cdc42 small GTPase and Drebrin, in dendritic spines.

Shiraishi-Yamaguchi Y, Sato Y, Sakai R, Mizutani A, Knöpfel T, Mori N, Mikoshiba K, Furuichi T - BMC Neurosci (2009)

Bottom Line: Overexpression of CPDDelta191-230 decreased the number of synapses and reduced the amplitudes of miniature excitatory postsynaptic currents in hippocampal neurons.CPDDelta191-230 overexpression decreased Drebrin clustering in the dendritic spines of hippocampal neurons.These results indicate that Cupidin/Homer2 interacts with the dendritic spine actin regulators Cdc42 and Drebrin via its C-terminal and N-terminal domains, respectively, and that it may be involved in spine morphology and synaptic properties.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan. f1966@cc.nagasaki-u.ac.jp

ABSTRACT

Background: Homer is a postsynaptic scaffold protein that links various synaptic signaling proteins, including the type I metabotropic glutamate receptor subunits 1alpha and 5, the inositol 1,4,5-trisphosphate receptor, Shank and Cdc42 small GTPase. Overexpression of Homer induces changes in dendritic spine morphology in cultured hippocampal neurons. However, the molecular basis underpinning Homer-mediated spine morphogenesis remains unclear. In this study, we aimed to elucidate the structural and functional properties of the interaction between Cupidin/Homer2 and two actin-cytoskeletal regulators, Cdc42 small GTPase and Drebrin.

Results: Cupidin/Homer2 interacted with activated Cdc42 small GTPase via the Cdc42-binding domain that resides around amino acid residues 191-283, within the C-terminal coiled-coil domain. We generated a Cupidin deletion mutant lacking amino acids 191-230 (CPDDelta191-230), which showed decrease Cdc42-binding ability but maintained self-multimerization ability. Cupidin suppressed Cdc42-induced filopodia-like protrusion formation in HeLa cells, whereas CPDDelta191-230 failed to do so. In cultured hippocampal neurons, Cupidin was targeted to dendritic spines, whereas CPDDelta191-230 was distributed in dendritic shafts as well as spines. Overexpression of CPDDelta191-230 decreased the number of synapses and reduced the amplitudes of miniature excitatory postsynaptic currents in hippocampal neurons. Cupidin interacted with a dendritic spine F-actin-binding protein, Drebrin, which possesses two Homer ligand motifs, via the N-terminal EVH-1 domain. CPDDelta191-230 overexpression decreased Drebrin clustering in the dendritic spines of hippocampal neurons.

Conclusion: These results indicate that Cupidin/Homer2 interacts with the dendritic spine actin regulators Cdc42 and Drebrin via its C-terminal and N-terminal domains, respectively, and that it may be involved in spine morphology and synaptic properties.

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Cupidin/Homer scaffolds for actin cytoskeleton modulators and postsynaptic proteins. Cupidin/Homer2 acts as a scaffold tethering postsynaptic signalling proteins (such as mGluR1α/5, IP3R, and Shank) as well as the dendritic actin-binding protein Drebrin, a spine actin modulator, via the N-terminal EVH-1 domain, which recognizes the PPxxF consensus motif. It also links the GTP-bound, activated Cdc42 small GTPase, which is known to regulate filopodia formation, via the C-terminal CBD (Cdc42-binding domain) and forms a tetrameric scaffold complex via the C-terminal coiled-coil (CC) and Leu zipper motif (LZA and LZB) regions. The Homer scaffold complex is implicated in the facilitation of signalling crosstalk among tethered synapse proteins and regulation of the actin-based morphology of dendritic spines.
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Figure 7: Cupidin/Homer scaffolds for actin cytoskeleton modulators and postsynaptic proteins. Cupidin/Homer2 acts as a scaffold tethering postsynaptic signalling proteins (such as mGluR1α/5, IP3R, and Shank) as well as the dendritic actin-binding protein Drebrin, a spine actin modulator, via the N-terminal EVH-1 domain, which recognizes the PPxxF consensus motif. It also links the GTP-bound, activated Cdc42 small GTPase, which is known to regulate filopodia formation, via the C-terminal CBD (Cdc42-binding domain) and forms a tetrameric scaffold complex via the C-terminal coiled-coil (CC) and Leu zipper motif (LZA and LZB) regions. The Homer scaffold complex is implicated in the facilitation of signalling crosstalk among tethered synapse proteins and regulation of the actin-based morphology of dendritic spines.

Mentions: Our study demonstrates the structural and functional interaction of Cupidin/Homer2 with two dendritic spine F-actin modulators, Cdc42 small GTPase, via the C-terminal region, and Drebrin, via the N-terminal EVH1 domain. Cdc42 regulates actin polymerization and is involved in filopodia formation [24] and dendritic spine morphogenesis [18-20]. Over-expression of Drebrin increases spine length [21] and promotes synaptic clustering of PSD-95 and F-actin [22]. Homer also interacts with Shank, another postsynaptic scaffold protein that binds to the GKAP/PSD-95/NMDA receptor complex [9]. Overexpression of Shank together with Homer induces enlargement of spine heads [13] and increases the level of the βPIX guanine nucleotide exchange factor (GEF) for Cdc42 in the PSD [13,25]. Moreover, oligophrenin-1 (Ophn-1), a Rho GTPase activating protein (GAP) that is involved in non-specific X-linked mental retardation and binds Homer1b/c, changes spine morphology in hippocampal neurons [26]. Taken together, these lines of evidence suggest that postsynaptic Homer-mediated scaffolding is involved in the regulation of dendritic spine morphology by interacting with the actin organization signaling molecules Cdc42 and Drebrin, as well as synaptic signaling molecules including the NMDA receptor complex, mGluR1α/5 subunits and InsP3R (Fig. 7).


Interaction of Cupidin/Homer2 with two actin cytoskeletal regulators, Cdc42 small GTPase and Drebrin, in dendritic spines.

Shiraishi-Yamaguchi Y, Sato Y, Sakai R, Mizutani A, Knöpfel T, Mori N, Mikoshiba K, Furuichi T - BMC Neurosci (2009)

Cupidin/Homer scaffolds for actin cytoskeleton modulators and postsynaptic proteins. Cupidin/Homer2 acts as a scaffold tethering postsynaptic signalling proteins (such as mGluR1α/5, IP3R, and Shank) as well as the dendritic actin-binding protein Drebrin, a spine actin modulator, via the N-terminal EVH-1 domain, which recognizes the PPxxF consensus motif. It also links the GTP-bound, activated Cdc42 small GTPase, which is known to regulate filopodia formation, via the C-terminal CBD (Cdc42-binding domain) and forms a tetrameric scaffold complex via the C-terminal coiled-coil (CC) and Leu zipper motif (LZA and LZB) regions. The Homer scaffold complex is implicated in the facilitation of signalling crosstalk among tethered synapse proteins and regulation of the actin-based morphology of dendritic spines.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2666743&req=5

Figure 7: Cupidin/Homer scaffolds for actin cytoskeleton modulators and postsynaptic proteins. Cupidin/Homer2 acts as a scaffold tethering postsynaptic signalling proteins (such as mGluR1α/5, IP3R, and Shank) as well as the dendritic actin-binding protein Drebrin, a spine actin modulator, via the N-terminal EVH-1 domain, which recognizes the PPxxF consensus motif. It also links the GTP-bound, activated Cdc42 small GTPase, which is known to regulate filopodia formation, via the C-terminal CBD (Cdc42-binding domain) and forms a tetrameric scaffold complex via the C-terminal coiled-coil (CC) and Leu zipper motif (LZA and LZB) regions. The Homer scaffold complex is implicated in the facilitation of signalling crosstalk among tethered synapse proteins and regulation of the actin-based morphology of dendritic spines.
Mentions: Our study demonstrates the structural and functional interaction of Cupidin/Homer2 with two dendritic spine F-actin modulators, Cdc42 small GTPase, via the C-terminal region, and Drebrin, via the N-terminal EVH1 domain. Cdc42 regulates actin polymerization and is involved in filopodia formation [24] and dendritic spine morphogenesis [18-20]. Over-expression of Drebrin increases spine length [21] and promotes synaptic clustering of PSD-95 and F-actin [22]. Homer also interacts with Shank, another postsynaptic scaffold protein that binds to the GKAP/PSD-95/NMDA receptor complex [9]. Overexpression of Shank together with Homer induces enlargement of spine heads [13] and increases the level of the βPIX guanine nucleotide exchange factor (GEF) for Cdc42 in the PSD [13,25]. Moreover, oligophrenin-1 (Ophn-1), a Rho GTPase activating protein (GAP) that is involved in non-specific X-linked mental retardation and binds Homer1b/c, changes spine morphology in hippocampal neurons [26]. Taken together, these lines of evidence suggest that postsynaptic Homer-mediated scaffolding is involved in the regulation of dendritic spine morphology by interacting with the actin organization signaling molecules Cdc42 and Drebrin, as well as synaptic signaling molecules including the NMDA receptor complex, mGluR1α/5 subunits and InsP3R (Fig. 7).

Bottom Line: Overexpression of CPDDelta191-230 decreased the number of synapses and reduced the amplitudes of miniature excitatory postsynaptic currents in hippocampal neurons.CPDDelta191-230 overexpression decreased Drebrin clustering in the dendritic spines of hippocampal neurons.These results indicate that Cupidin/Homer2 interacts with the dendritic spine actin regulators Cdc42 and Drebrin via its C-terminal and N-terminal domains, respectively, and that it may be involved in spine morphology and synaptic properties.

View Article: PubMed Central - HTML - PubMed

Affiliation: Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan. f1966@cc.nagasaki-u.ac.jp

ABSTRACT

Background: Homer is a postsynaptic scaffold protein that links various synaptic signaling proteins, including the type I metabotropic glutamate receptor subunits 1alpha and 5, the inositol 1,4,5-trisphosphate receptor, Shank and Cdc42 small GTPase. Overexpression of Homer induces changes in dendritic spine morphology in cultured hippocampal neurons. However, the molecular basis underpinning Homer-mediated spine morphogenesis remains unclear. In this study, we aimed to elucidate the structural and functional properties of the interaction between Cupidin/Homer2 and two actin-cytoskeletal regulators, Cdc42 small GTPase and Drebrin.

Results: Cupidin/Homer2 interacted with activated Cdc42 small GTPase via the Cdc42-binding domain that resides around amino acid residues 191-283, within the C-terminal coiled-coil domain. We generated a Cupidin deletion mutant lacking amino acids 191-230 (CPDDelta191-230), which showed decrease Cdc42-binding ability but maintained self-multimerization ability. Cupidin suppressed Cdc42-induced filopodia-like protrusion formation in HeLa cells, whereas CPDDelta191-230 failed to do so. In cultured hippocampal neurons, Cupidin was targeted to dendritic spines, whereas CPDDelta191-230 was distributed in dendritic shafts as well as spines. Overexpression of CPDDelta191-230 decreased the number of synapses and reduced the amplitudes of miniature excitatory postsynaptic currents in hippocampal neurons. Cupidin interacted with a dendritic spine F-actin-binding protein, Drebrin, which possesses two Homer ligand motifs, via the N-terminal EVH-1 domain. CPDDelta191-230 overexpression decreased Drebrin clustering in the dendritic spines of hippocampal neurons.

Conclusion: These results indicate that Cupidin/Homer2 interacts with the dendritic spine actin regulators Cdc42 and Drebrin via its C-terminal and N-terminal domains, respectively, and that it may be involved in spine morphology and synaptic properties.

Show MeSH
Related in: MedlinePlus