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Defective function of GABA-containing synaptic vesicles in mice lacking the AP-3B clathrin adaptor.

Nakatsu F, Okada M, Mori F, Kumazawa N, Iwasa H, Zhu G, Kasagi Y, Kamiya H, Harada A, Nishimura K, Takeuchi A, Miyazaki T, Watanabe M, Yuasa S, Manabe T, Wakabayashi K, Kaneko S, Saito T, Ohno H - J. Cell Biol. (2004)

Bottom Line: Although the physiological role of AP-3A has recently been elucidated, that of AP-3B remains unsolved.This facilitated the induction of long-term potentiation in the hippocampus and the abnormal propagation of neuronal excitability via the temporoammonic pathway.Thus, AP-3B plays a critical role in the normal formation and function of a subset of synaptic vesicles.

View Article: PubMed Central - PubMed

Affiliation: RIKEN Research Center for Allergy and Immunology, Kanagawa 230-0045, Japan.

ABSTRACT
AP-3 is a member of the adaptor protein (AP) complex family that regulates the vesicular transport of cargo proteins in the secretory and endocytic pathways. There are two isoforms of AP-3: the ubiquitously expressed AP-3A and the neuron-specific AP-3B. Although the physiological role of AP-3A has recently been elucidated, that of AP-3B remains unsolved. To address this question, we generated mice lacking mu3B, a subunit of AP-3B. mu3B-/- mice suffered from spontaneous epileptic seizures. Morphological abnormalities were observed at synapses in these mice. Biochemical studies demonstrated the impairment of gamma-aminobutyric acid (GABA) release because of, at least in part, the reduction of vesicular GABA transporter in mu3B-/- mice. This facilitated the induction of long-term potentiation in the hippocampus and the abnormal propagation of neuronal excitability via the temporoammonic pathway. Thus, AP-3B plays a critical role in the normal formation and function of a subset of synaptic vesicles. This work adds a new aspect to the pathogenesis of epilepsy.

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Ultrastructural analysis of synaptic terminals. (A–D) Electron micrographs of asymmetric (excitatory) terminals (A and B) and symmetric (inhibitory) terminals attaching to perikarya of CA1 pyramidal neurons (C and D) in the CA1 in wild-type (A and C) and μ3B−/−ΔNeo (B and D) mice at the age of 8 wk. Bar, 200 nm. (E–H) Developmental changes in the number of synaptic vesicles per unit area (E and F) and the diameter of synaptic vesicles (G and H) of excitatory (E and G) and inhibitory terminals (F and H) in μ3B−/−ΔNeo mice (open square) and wild-type mice (solid square). 30–50 areas (E and F) and >500 synaptic vesicles (G and H) from both genotypes (n = 3 each) were counted, respectively. Values are expressed as means ± SEM Student's or Welch's t test was used to determine the differences between μ3B−/−ΔNeo and wild-type mice (* indicates P < 0.05; ** indicates P < 0.01).
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fig3: Ultrastructural analysis of synaptic terminals. (A–D) Electron micrographs of asymmetric (excitatory) terminals (A and B) and symmetric (inhibitory) terminals attaching to perikarya of CA1 pyramidal neurons (C and D) in the CA1 in wild-type (A and C) and μ3B−/−ΔNeo (B and D) mice at the age of 8 wk. Bar, 200 nm. (E–H) Developmental changes in the number of synaptic vesicles per unit area (E and F) and the diameter of synaptic vesicles (G and H) of excitatory (E and G) and inhibitory terminals (F and H) in μ3B−/−ΔNeo mice (open square) and wild-type mice (solid square). 30–50 areas (E and F) and >500 synaptic vesicles (G and H) from both genotypes (n = 3 each) were counted, respectively. Values are expressed as means ± SEM Student's or Welch's t test was used to determine the differences between μ3B−/−ΔNeo and wild-type mice (* indicates P < 0.05; ** indicates P < 0.01).

Mentions: We next performed ultrastructural examination of the hippocampus. The number of synaptic vesicles per unit area was decreased in μ3B−/−ΔNeo mice. The density of synaptic vesicles in excitatory terminals was lower in μ3B−/−ΔNeo mice than in wild-type mice at the age of 4–16 wk (Fig. 3, A, B, and E). The density of synaptic vesicles in inhibitory terminals was also lower in μ3B−/−ΔNeo mice than in wild-type mice at the age of 2, 6, and 8 wk (Fig. 3, C, D, and F). In addition, the diameter of the synaptic vesicles in inhibitory synaptic terminals in μ3B−/−ΔNeo mice was evidently smaller than that in wild-type mice (Fig. 3, G and H). Thus, these results indicate that AP-3B is involved in the biogenesis of synaptic vesicles in hippocampus in vivo.


Defective function of GABA-containing synaptic vesicles in mice lacking the AP-3B clathrin adaptor.

Nakatsu F, Okada M, Mori F, Kumazawa N, Iwasa H, Zhu G, Kasagi Y, Kamiya H, Harada A, Nishimura K, Takeuchi A, Miyazaki T, Watanabe M, Yuasa S, Manabe T, Wakabayashi K, Kaneko S, Saito T, Ohno H - J. Cell Biol. (2004)

Ultrastructural analysis of synaptic terminals. (A–D) Electron micrographs of asymmetric (excitatory) terminals (A and B) and symmetric (inhibitory) terminals attaching to perikarya of CA1 pyramidal neurons (C and D) in the CA1 in wild-type (A and C) and μ3B−/−ΔNeo (B and D) mice at the age of 8 wk. Bar, 200 nm. (E–H) Developmental changes in the number of synaptic vesicles per unit area (E and F) and the diameter of synaptic vesicles (G and H) of excitatory (E and G) and inhibitory terminals (F and H) in μ3B−/−ΔNeo mice (open square) and wild-type mice (solid square). 30–50 areas (E and F) and >500 synaptic vesicles (G and H) from both genotypes (n = 3 each) were counted, respectively. Values are expressed as means ± SEM Student's or Welch's t test was used to determine the differences between μ3B−/−ΔNeo and wild-type mice (* indicates P < 0.05; ** indicates P < 0.01).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172536&req=5

fig3: Ultrastructural analysis of synaptic terminals. (A–D) Electron micrographs of asymmetric (excitatory) terminals (A and B) and symmetric (inhibitory) terminals attaching to perikarya of CA1 pyramidal neurons (C and D) in the CA1 in wild-type (A and C) and μ3B−/−ΔNeo (B and D) mice at the age of 8 wk. Bar, 200 nm. (E–H) Developmental changes in the number of synaptic vesicles per unit area (E and F) and the diameter of synaptic vesicles (G and H) of excitatory (E and G) and inhibitory terminals (F and H) in μ3B−/−ΔNeo mice (open square) and wild-type mice (solid square). 30–50 areas (E and F) and >500 synaptic vesicles (G and H) from both genotypes (n = 3 each) were counted, respectively. Values are expressed as means ± SEM Student's or Welch's t test was used to determine the differences between μ3B−/−ΔNeo and wild-type mice (* indicates P < 0.05; ** indicates P < 0.01).
Mentions: We next performed ultrastructural examination of the hippocampus. The number of synaptic vesicles per unit area was decreased in μ3B−/−ΔNeo mice. The density of synaptic vesicles in excitatory terminals was lower in μ3B−/−ΔNeo mice than in wild-type mice at the age of 4–16 wk (Fig. 3, A, B, and E). The density of synaptic vesicles in inhibitory terminals was also lower in μ3B−/−ΔNeo mice than in wild-type mice at the age of 2, 6, and 8 wk (Fig. 3, C, D, and F). In addition, the diameter of the synaptic vesicles in inhibitory synaptic terminals in μ3B−/−ΔNeo mice was evidently smaller than that in wild-type mice (Fig. 3, G and H). Thus, these results indicate that AP-3B is involved in the biogenesis of synaptic vesicles in hippocampus in vivo.

Bottom Line: Although the physiological role of AP-3A has recently been elucidated, that of AP-3B remains unsolved.This facilitated the induction of long-term potentiation in the hippocampus and the abnormal propagation of neuronal excitability via the temporoammonic pathway.Thus, AP-3B plays a critical role in the normal formation and function of a subset of synaptic vesicles.

View Article: PubMed Central - PubMed

Affiliation: RIKEN Research Center for Allergy and Immunology, Kanagawa 230-0045, Japan.

ABSTRACT
AP-3 is a member of the adaptor protein (AP) complex family that regulates the vesicular transport of cargo proteins in the secretory and endocytic pathways. There are two isoforms of AP-3: the ubiquitously expressed AP-3A and the neuron-specific AP-3B. Although the physiological role of AP-3A has recently been elucidated, that of AP-3B remains unsolved. To address this question, we generated mice lacking mu3B, a subunit of AP-3B. mu3B-/- mice suffered from spontaneous epileptic seizures. Morphological abnormalities were observed at synapses in these mice. Biochemical studies demonstrated the impairment of gamma-aminobutyric acid (GABA) release because of, at least in part, the reduction of vesicular GABA transporter in mu3B-/- mice. This facilitated the induction of long-term potentiation in the hippocampus and the abnormal propagation of neuronal excitability via the temporoammonic pathway. Thus, AP-3B plays a critical role in the normal formation and function of a subset of synaptic vesicles. This work adds a new aspect to the pathogenesis of epilepsy.

Show MeSH
Related in: MedlinePlus