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The Arf GAP SMAP2 is necessary for organized vesicle budding from the trans-Golgi network and subsequent acrosome formation in spermiogenesis.

Funaki T, Kon S, Tanabe K, Natsume W, Sato S, Shimizu T, Yoshida N, Wong WF, Ogura A, Ogawa T, Inoue K, Ogonuki N, Miki H, Mochida K, Endoh K, Yomogida K, Fukumoto M, Horai R, Iwakura Y, Ito C, Toshimori K, Watanabe T, Satake M - Mol. Biol. Cell (2013)

Bottom Line: In the present study, SMAP2 is detected on the TGN in the pachytene spermatocyte to the round spermatid stages of spermatogenesis.Furthermore, syntaxin2, a component of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, is not properly concentrated at the site of acrosome formation.Thus this study reveals a link between SMAP2 and CALM/syntaxin2 in clathrin-coated vesicle formation from the TGN and subsequent acrosome formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Immunology, Department of Pathology, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan.

ABSTRACT
The trans-Golgi network (TGN) functions as a hub organelle in the exocytosis of clathrin-coated membrane vesicles, and SMAP2 is an Arf GTPase-activating protein that binds to both clathrin and the clathrin assembly protein (CALM). In the present study, SMAP2 is detected on the TGN in the pachytene spermatocyte to the round spermatid stages of spermatogenesis. Gene targeting reveals that SMAP2-deficient male mice are healthy and survive to adulthood but are infertile and exhibit globozoospermia. In SMAP2-deficient spermatids, the diameter of proacrosomal vesicles budding from TGN increases, TGN structures are distorted, acrosome formation is severely impaired, and reorganization of the nucleus does not proceed properly. CALM functions to regulate vesicle sizes, and this study shows that CALM is not recruited to the TGN in the absence of SMAP2. Furthermore, syntaxin2, a component of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, is not properly concentrated at the site of acrosome formation. Thus this study reveals a link between SMAP2 and CALM/syntaxin2 in clathrin-coated vesicle formation from the TGN and subsequent acrosome formation. SMAP2-deficient mice provide a model for globozoospermia in humans.

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Acrosome formation and SMAP2. (A) Germ cells were prepared from wild-type testes as in Figure 3 and processed for immunofluorescence staining as indicated. Each row represents a stage of acrosome formation (Golgi, cap, acrosome, and maturation phases). The marker for the acrosomal components is sp56. (B) Germ cells were prepared from SMAP2(−/−) testes and processed for sp56 staining. See the text for details of observed abnormalities. Bars, 5 μm.
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Figure 4: Acrosome formation and SMAP2. (A) Germ cells were prepared from wild-type testes as in Figure 3 and processed for immunofluorescence staining as indicated. Each row represents a stage of acrosome formation (Golgi, cap, acrosome, and maturation phases). The marker for the acrosomal components is sp56. (B) Germ cells were prepared from SMAP2(−/−) testes and processed for sp56 staining. See the text for details of observed abnormalities. Bars, 5 μm.

Mentions: We examined the relationship between SMAP2 residing on the TGN and acrosome formation. Acrosome formation occurs in the round and elongated spermatid stages and is divided into the following four phases: a Golgi phase, a cap phase, an acrosome phase, and a maturation phase (Figure 4A). Each phase is characterized by distinct staining patterns of the acrosomal component sp56 (Kim et al., 2001). SMAP2 fluorescence at the TGN was detected in the Golgi and cap phases, and sp56 fluorescence was detected near the nucleus, whereas SMAP2 fluorescence was relatively distant from the nucleus. SMAP2 and sp56 fluorescence did not overlap. This relative localization is consistent with the known spatial orientation of the TGN and the acrosome. SMAP2 fluorescence was not detected in the acrosome and maturation phases. Therefore TGN-associated SMAP2 was detected in the early phases of acrosome formation when acrosomal components are synthesized. The disappearance of SMAP2 probably reflects the shedding of the TGN and other organelles during spermiogenesis (Susi et al., 1971).


The Arf GAP SMAP2 is necessary for organized vesicle budding from the trans-Golgi network and subsequent acrosome formation in spermiogenesis.

Funaki T, Kon S, Tanabe K, Natsume W, Sato S, Shimizu T, Yoshida N, Wong WF, Ogura A, Ogawa T, Inoue K, Ogonuki N, Miki H, Mochida K, Endoh K, Yomogida K, Fukumoto M, Horai R, Iwakura Y, Ito C, Toshimori K, Watanabe T, Satake M - Mol. Biol. Cell (2013)

Acrosome formation and SMAP2. (A) Germ cells were prepared from wild-type testes as in Figure 3 and processed for immunofluorescence staining as indicated. Each row represents a stage of acrosome formation (Golgi, cap, acrosome, and maturation phases). The marker for the acrosomal components is sp56. (B) Germ cells were prepared from SMAP2(−/−) testes and processed for sp56 staining. See the text for details of observed abnormalities. Bars, 5 μm.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756916&req=5

Figure 4: Acrosome formation and SMAP2. (A) Germ cells were prepared from wild-type testes as in Figure 3 and processed for immunofluorescence staining as indicated. Each row represents a stage of acrosome formation (Golgi, cap, acrosome, and maturation phases). The marker for the acrosomal components is sp56. (B) Germ cells were prepared from SMAP2(−/−) testes and processed for sp56 staining. See the text for details of observed abnormalities. Bars, 5 μm.
Mentions: We examined the relationship between SMAP2 residing on the TGN and acrosome formation. Acrosome formation occurs in the round and elongated spermatid stages and is divided into the following four phases: a Golgi phase, a cap phase, an acrosome phase, and a maturation phase (Figure 4A). Each phase is characterized by distinct staining patterns of the acrosomal component sp56 (Kim et al., 2001). SMAP2 fluorescence at the TGN was detected in the Golgi and cap phases, and sp56 fluorescence was detected near the nucleus, whereas SMAP2 fluorescence was relatively distant from the nucleus. SMAP2 and sp56 fluorescence did not overlap. This relative localization is consistent with the known spatial orientation of the TGN and the acrosome. SMAP2 fluorescence was not detected in the acrosome and maturation phases. Therefore TGN-associated SMAP2 was detected in the early phases of acrosome formation when acrosomal components are synthesized. The disappearance of SMAP2 probably reflects the shedding of the TGN and other organelles during spermiogenesis (Susi et al., 1971).

Bottom Line: In the present study, SMAP2 is detected on the TGN in the pachytene spermatocyte to the round spermatid stages of spermatogenesis.Furthermore, syntaxin2, a component of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, is not properly concentrated at the site of acrosome formation.Thus this study reveals a link between SMAP2 and CALM/syntaxin2 in clathrin-coated vesicle formation from the TGN and subsequent acrosome formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Immunology, Department of Pathology, Institute of Development, Aging and Cancer, Tohoku University, Sendai 980-8575, Japan.

ABSTRACT
The trans-Golgi network (TGN) functions as a hub organelle in the exocytosis of clathrin-coated membrane vesicles, and SMAP2 is an Arf GTPase-activating protein that binds to both clathrin and the clathrin assembly protein (CALM). In the present study, SMAP2 is detected on the TGN in the pachytene spermatocyte to the round spermatid stages of spermatogenesis. Gene targeting reveals that SMAP2-deficient male mice are healthy and survive to adulthood but are infertile and exhibit globozoospermia. In SMAP2-deficient spermatids, the diameter of proacrosomal vesicles budding from TGN increases, TGN structures are distorted, acrosome formation is severely impaired, and reorganization of the nucleus does not proceed properly. CALM functions to regulate vesicle sizes, and this study shows that CALM is not recruited to the TGN in the absence of SMAP2. Furthermore, syntaxin2, a component of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex, is not properly concentrated at the site of acrosome formation. Thus this study reveals a link between SMAP2 and CALM/syntaxin2 in clathrin-coated vesicle formation from the TGN and subsequent acrosome formation. SMAP2-deficient mice provide a model for globozoospermia in humans.

Show MeSH
Related in: MedlinePlus