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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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Tissue specificity of aczonin mRNA and protein expression. (A) Chicken aczonin mRNA (10 μg poly(A)+ RNA per lane). (B) Human aczonin mRNA (2 μg poly(A)+ RNA per lane). (C) Mouse aczonin protein (80 μg of tissue homogenate protein per lane). Tissue abbreviations are: A, adrenal gland; AC, adrenal cortex; AM, adrenal medulla; B, brain; BS, brain stem; C, cerebellum; FB, forebrain; H, heart; I, small intestine; K, kidney; Li, liver; Lu, lung; M, muscle; O, ovary; Pa, pancreas; Pl, placenta; Sp, spleen; St, stomach; Te, testis; Tm, thymus; and Tr, thyroid. Smears are attributed to partial degradation of these very long mRNA and protein molecules. Long exposures are shown to illustrate tissue specificity.
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Figure 3: Tissue specificity of aczonin mRNA and protein expression. (A) Chicken aczonin mRNA (10 μg poly(A)+ RNA per lane). (B) Human aczonin mRNA (2 μg poly(A)+ RNA per lane). (C) Mouse aczonin protein (80 μg of tissue homogenate protein per lane). Tissue abbreviations are: A, adrenal gland; AC, adrenal cortex; AM, adrenal medulla; B, brain; BS, brain stem; C, cerebellum; FB, forebrain; H, heart; I, small intestine; K, kidney; Li, liver; Lu, lung; M, muscle; O, ovary; Pa, pancreas; Pl, placenta; Sp, spleen; St, stomach; Te, testis; Tm, thymus; and Tr, thyroid. Smears are attributed to partial degradation of these very long mRNA and protein molecules. Long exposures are shown to illustrate tissue specificity.

Mentions: Northern blot analysis of RNAs from various chicken and human tissues showed that aczonin mRNA, which is very large and therefore partially degraded, is most highly expressed in the brain and detectable at low abundance in several endocrine glands but in none of the other tissues analyzed (Fig. 3A and Fig. B). In both species, testis mRNA gave a unique band pattern, with smaller molecular sizes than in the other tissues. Antisera were raised against recombinant aczonin partial sequences and employed for Western blot analysis of mouse tissue homogenates. A very large protein far above the 206-kD marker, apparently partially degraded, was detected in different brain regions and, after longer exposure, very weakly in stomach but in none of the other tissues analyzed, including adrenal gland, testis, and pancreas (Fig. 3 C). In endocrine cells, aczonin protein may be poorly translated from the mRNA or rapidly degraded. Aczonin mRNA and protein are found in similar abundances in forebrain, cerebellum, and brainstem (Fig. 3A and Fig. C), indicating expression throughout the brain.


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)

Tissue specificity of aczonin mRNA and protein expression. (A) Chicken aczonin mRNA (10 μg poly(A)+ RNA per lane). (B) Human aczonin mRNA (2 μg poly(A)+ RNA per lane). (C) Mouse aczonin protein (80 μg of tissue homogenate protein per lane). Tissue abbreviations are: A, adrenal gland; AC, adrenal cortex; AM, adrenal medulla; B, brain; BS, brain stem; C, cerebellum; FB, forebrain; H, heart; I, small intestine; K, kidney; Li, liver; Lu, lung; M, muscle; O, ovary; Pa, pancreas; Pl, placenta; Sp, spleen; St, stomach; Te, testis; Tm, thymus; and Tr, thyroid. Smears are attributed to partial degradation of these very long mRNA and protein molecules. Long exposures are shown to illustrate tissue specificity.
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Related In: Results  -  Collection

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Figure 3: Tissue specificity of aczonin mRNA and protein expression. (A) Chicken aczonin mRNA (10 μg poly(A)+ RNA per lane). (B) Human aczonin mRNA (2 μg poly(A)+ RNA per lane). (C) Mouse aczonin protein (80 μg of tissue homogenate protein per lane). Tissue abbreviations are: A, adrenal gland; AC, adrenal cortex; AM, adrenal medulla; B, brain; BS, brain stem; C, cerebellum; FB, forebrain; H, heart; I, small intestine; K, kidney; Li, liver; Lu, lung; M, muscle; O, ovary; Pa, pancreas; Pl, placenta; Sp, spleen; St, stomach; Te, testis; Tm, thymus; and Tr, thyroid. Smears are attributed to partial degradation of these very long mRNA and protein molecules. Long exposures are shown to illustrate tissue specificity.
Mentions: Northern blot analysis of RNAs from various chicken and human tissues showed that aczonin mRNA, which is very large and therefore partially degraded, is most highly expressed in the brain and detectable at low abundance in several endocrine glands but in none of the other tissues analyzed (Fig. 3A and Fig. B). In both species, testis mRNA gave a unique band pattern, with smaller molecular sizes than in the other tissues. Antisera were raised against recombinant aczonin partial sequences and employed for Western blot analysis of mouse tissue homogenates. A very large protein far above the 206-kD marker, apparently partially degraded, was detected in different brain regions and, after longer exposure, very weakly in stomach but in none of the other tissues analyzed, including adrenal gland, testis, and pancreas (Fig. 3 C). In endocrine cells, aczonin protein may be poorly translated from the mRNA or rapidly degraded. Aczonin mRNA and protein are found in similar abundances in forebrain, cerebellum, and brainstem (Fig. 3A and Fig. C), indicating expression throughout the brain.

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