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Aczonin, a 550-kD putative scaffolding protein of presynaptic active zones, shares homology regions with Rim and Bassoon and binds profilin.

Wang X, Kibschull M, Laue MM, Lichte B, Petrasch-Parwez E, Kilimann MW - J. Cell Biol. (1999)

Bottom Line: We report the identification and initial characterization of aczonin, a neuron-specific 550-kD protein concentrated at the presynaptic active zone and associated with a detergent-resistant cytoskeletal subcellular fraction.Aczonin binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics.Large parts of aczonin, including the zinc finger, PDZ, and C2 domains, are homologous to Rim or to Bassoon, two other proteins concentrated in presynaptic active zones.

View Article: PubMed Central - PubMed

Affiliation: Institut für Physiologische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.

ABSTRACT
Neurotransmitter exocytosis is restricted to the active zone, a specialized area of the presynaptic plasma membrane. We report the identification and initial characterization of aczonin, a neuron-specific 550-kD protein concentrated at the presynaptic active zone and associated with a detergent-resistant cytoskeletal subcellular fraction. Analysis of the amino acid sequences of chicken and mouse aczonin indicates an organization into multiple domains, including two pairs of Cys(4) zinc fingers, a polyproline tract, and a PDZ domain and two C2 domains near the COOH terminus. The second C2 domain is subject to differential splicing. Aczonin binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics. Large parts of aczonin, including the zinc finger, PDZ, and C2 domains, are homologous to Rim or to Bassoon, two other proteins concentrated in presynaptic active zones. We propose that aczonin is a scaffolding protein involved in the organization of the molecular architecture of synaptic active zones and in the orchestration of neurotransmitter vesicle trafficking.

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Immunohisto-chemical localization of aczonin in rat brain. Light microscopic inspection of the cerebellar cortex (A) shows finely punctate staining of the molecular layer (m), and ring-shaped or patchy immunopositive structures in the granule cell layer (g), whereas the medulla (md) is immunonegative. p indicates Purkinje cell layer. Electron microscopy shows that immunoperoxidase reaction product is restricted to the presynaptic active zones (B) of an asymmetric synapse with a dendritic spine in the molecular layer of the dentate gyrus or (C) of a mossy fiber terminal in a cerebellar glomerulus. In B, note that aczonin immunoreactivity is focused to the two junctional zones of the perforated synaptic specialization. Bar: 115 μm (A); 0.33 μm (B); or 1 μm (C).
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Figure 4: Immunohisto-chemical localization of aczonin in rat brain. Light microscopic inspection of the cerebellar cortex (A) shows finely punctate staining of the molecular layer (m), and ring-shaped or patchy immunopositive structures in the granule cell layer (g), whereas the medulla (md) is immunonegative. p indicates Purkinje cell layer. Electron microscopy shows that immunoperoxidase reaction product is restricted to the presynaptic active zones (B) of an asymmetric synapse with a dendritic spine in the molecular layer of the dentate gyrus or (C) of a mossy fiber terminal in a cerebellar glomerulus. In B, note that aczonin immunoreactivity is focused to the two junctional zones of the perforated synaptic specialization. Bar: 115 μm (A); 0.33 μm (B); or 1 μm (C).

Mentions: Immunohistochemical procedures for light and electron microscopical analysis of rat brain were as described previously (Kutzleb et al. 1998). Identical results were obtained with affinity-purified antibodies against two different aczonin sequence regions (see above). Images shown in Fig. 4 were obtained with serum 2. Preimmune antibodies and preincubation of the immune antibodies with an excess of the recombinant antigen were employed as controls.


Aczonin, a 550-kD putative scaffolding protein of presynaptic active zones, shares homology regions with Rim and Bassoon and binds profilin.

Wang X, Kibschull M, Laue MM, Lichte B, Petrasch-Parwez E, Kilimann MW - J. Cell Biol. (1999)

Immunohisto-chemical localization of aczonin in rat brain. Light microscopic inspection of the cerebellar cortex (A) shows finely punctate staining of the molecular layer (m), and ring-shaped or patchy immunopositive structures in the granule cell layer (g), whereas the medulla (md) is immunonegative. p indicates Purkinje cell layer. Electron microscopy shows that immunoperoxidase reaction product is restricted to the presynaptic active zones (B) of an asymmetric synapse with a dendritic spine in the molecular layer of the dentate gyrus or (C) of a mossy fiber terminal in a cerebellar glomerulus. In B, note that aczonin immunoreactivity is focused to the two junctional zones of the perforated synaptic specialization. Bar: 115 μm (A); 0.33 μm (B); or 1 μm (C).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2164979&req=5

Figure 4: Immunohisto-chemical localization of aczonin in rat brain. Light microscopic inspection of the cerebellar cortex (A) shows finely punctate staining of the molecular layer (m), and ring-shaped or patchy immunopositive structures in the granule cell layer (g), whereas the medulla (md) is immunonegative. p indicates Purkinje cell layer. Electron microscopy shows that immunoperoxidase reaction product is restricted to the presynaptic active zones (B) of an asymmetric synapse with a dendritic spine in the molecular layer of the dentate gyrus or (C) of a mossy fiber terminal in a cerebellar glomerulus. In B, note that aczonin immunoreactivity is focused to the two junctional zones of the perforated synaptic specialization. Bar: 115 μm (A); 0.33 μm (B); or 1 μm (C).
Mentions: Immunohistochemical procedures for light and electron microscopical analysis of rat brain were as described previously (Kutzleb et al. 1998). Identical results were obtained with affinity-purified antibodies against two different aczonin sequence regions (see above). Images shown in Fig. 4 were obtained with serum 2. Preimmune antibodies and preincubation of the immune antibodies with an excess of the recombinant antigen were employed as controls.

Bottom Line: We report the identification and initial characterization of aczonin, a neuron-specific 550-kD protein concentrated at the presynaptic active zone and associated with a detergent-resistant cytoskeletal subcellular fraction.Aczonin binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics.Large parts of aczonin, including the zinc finger, PDZ, and C2 domains, are homologous to Rim or to Bassoon, two other proteins concentrated in presynaptic active zones.

View Article: PubMed Central - PubMed

Affiliation: Institut für Physiologische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.

ABSTRACT
Neurotransmitter exocytosis is restricted to the active zone, a specialized area of the presynaptic plasma membrane. We report the identification and initial characterization of aczonin, a neuron-specific 550-kD protein concentrated at the presynaptic active zone and associated with a detergent-resistant cytoskeletal subcellular fraction. Analysis of the amino acid sequences of chicken and mouse aczonin indicates an organization into multiple domains, including two pairs of Cys(4) zinc fingers, a polyproline tract, and a PDZ domain and two C2 domains near the COOH terminus. The second C2 domain is subject to differential splicing. Aczonin binds profilin, an actin-binding protein implicated in actin cytoskeletal dynamics. Large parts of aczonin, including the zinc finger, PDZ, and C2 domains, are homologous to Rim or to Bassoon, two other proteins concentrated in presynaptic active zones. We propose that aczonin is a scaffolding protein involved in the organization of the molecular architecture of synaptic active zones and in the orchestration of neurotransmitter vesicle trafficking.

Show MeSH
Related in: MedlinePlus