Cryo-EM structures of human zinc transporter ZnT7 reveal the mechanism of Zn²⁺ uptake into the Golgi apparatus

クライオ電子顕微鏡により、ゴルジ体の亜鉛輸送体による亜鉛輸送機構の全容を解明 細胞の亜鉛恒常性維持機構の理解に大きな進展. 京都大学プレスリリース. 2023-08-29.Zinc ions (Zn²⁺) are vital to most cells, with the intracellular concentrations of Zn²⁺ being tightly regulated by multiple zinc transporters located at the plasma and organelle membranes. We herein present the 2.2-3.1 Å-resolution cryo-EM structures of a Golgi-localized human Zn²⁺/H+ antiporter ZnT7 (hZnT7) in Zn²⁺-bound and unbound forms. Cryo-EM analyses show that hZnT7 exists as a dimer via tight interactions in both the cytosolic and transmembrane (TM) domains of two protomers, each of which contains a single Zn²⁺-binding site in its TM domain. hZnT7 undergoes a TM-helix rearrangement to create a negatively charged cytosolic cavity for Zn²⁺ entry in the inward-facing conformation and widens the luminal cavity for Zn²⁺ release in the outward-facing conformation. An exceptionally long cytosolic histidine-rich loop characteristic of hZnT7 binds two Zn²⁺ ions, seemingly facilitating Zn²⁺ recruitment to the TM metal transport pathway. These structures permit mechanisms of hZnT7-mediated Zn²⁺ uptake into the Golgi to be proposed

Functional Analysis of MeCP2 Mutations Associated with Rett Syndrome Using Transient Expression Systems

レット症候群は生後半年から1歳半ころに発症する重度の精神発達遅滞を伴う疾患で女児の1万人から1万5千人に1人に発症する頻度の高い遺伝子疾患である。この疾患の原因遺伝子が最近MeCP2遺伝子であることが判明した。レット症候群の患者でみられる変異がMeCP2の本来の機能にどのような影響を及ぼすかを理解することは、レット症候群の病態を解明する上での手がかりになる。MeCP2は2つの機能ドメインを持ち、一つはメチル化CpGに結合するメチル化結合ドメイン(MBD)で、もう一つはヒストン脱アセチル化酵素をリクルートするSin3Aと結合する転写抑制ドメイン(TRD)である。報告されている変異の中でミスセンス変異の多くは、この二つのドメイン内でみられ、特にMBD内での変異の割合は多い。MBD内のミスセンス変異のMeCP2機能への影響を把握するため、培養細胞を用いた遺伝子導入発現系を開発して解析を行った

Functional Characterisation of MeCP2 Mutatiions Found in Male Patients with X Linked Mental Retardation

MeCP2の遺伝子変異は、Rett症候群以外の疾患の患者でも見つかり、X染色体性の精神発達遅滞を伴う男性患者においても報告された。これらの患者ではMBD内の変異として137番目のGluからGlyと140番目AlaからValのアミノ酸変異が確認された。これらの変異に関して、開発した二つの機能解析系を用いて解析を行ったところ、140番目の変異では、メチル化DNAに対しての転写抑制活性は完全に維持されており、137番目の変異ではわずかに転写抑制活性の低下がみられる程度であった。また、マウス細胞のヘテロクロマチン親和性についても140番と137番目の変異は共に明らかな点状の像を示し、親和性は維持されていた。これらの遺伝性の精神発達遅滞を伴う男性患者でのMeCP2の変異は、その機能への影響がレット症候群の場合と比較して軽度であるため、Rett症候群とは異なる病態を呈する成因となっている可能性が示唆された

Calaxin is required for cilia-driven determination of vertebrate laterality

Sasaki, K., Shiba, K., Nakamura, A. et al. Calaxin is required for cilia-driven determination of vertebrate laterality. Commun Biol 2, 226 (2019). https://doi.org/10.1038/s42003-019-0462-

Picosecond time-resolved fluorescence spectroscopy of hematoporphyrin derivative

The picosecond time-resolved fluorescence decays I(t) and spectra I(λ, t) for hematoporphyrin derivative (HPD) in a phosphate buffer saline aqueous solution at different concentrations (8.4 x 10^[-6] ～ 8.4 x 10^[-3] M) are measured by a two-dimensional synchroscan streak camera with a mode-locked CW dye laser, and a new emission band (which we call the Y-band) is found at high concentration. It is shown that the fluorescence decays composed of fast and slow components at high concentration are due to the Y-band (120 ps lifetime) from head-to-tail aggregates including equilibrium dimer and stable dimer, and the usual band (3.6 ns lifetime) from monomer, respectively, and the latter band is dynamically quenched by the Förster type resonance energy transfer from the monomer to the aggregate. Furthermore, the measurement of static fluorescence spectra from human gastric cancers and the surrounding in vivo after HPD injection shows that a band corresponding to the Y-band from the aggregate appears at only the cancerous cells

Picosecond time-resolved fluorescence spectroscopy of hematoporphyrin derivative

The picosecond time-resolved fluorescence decays I(t) and spectra I(λ, t) for hematoporphyrin derivative (HPD) in a phosphate buffer saline aqueous solution at different concentrations (8.4 x 10^[-6] ～ 8.4 x 10^[-3] M) are measured by a two-dimensional synchroscan streak camera with a mode-locked CW dye laser, and a new emission band (which we call the Y-band) is found at high concentration. It is shown that the fluorescence decays composed of fast and slow components at high concentration are due to the Y-band (120 ps lifetime) from head-to-tail aggregates including equilibrium dimer and stable dimer, and the usual band (3.6 ns lifetime) from monomer, respectively, and the latter band is dynamically quenched by the Förster type resonance energy transfer from the monomer to the aggregate. Furthermore, the measurement of static fluorescence spectra from human gastric cancers and the surrounding in vivo after HPD injection shows that a band corresponding to the Y-band from the aggregate appears at only the cancerous cells

Experimental Study on Evaporation Characteristics of Light Cycle Oil Droplet under Various Ambient Conditions

The authors conducted droplet evaporation experiments of light cycle oil (LCO) at various ambient temperatures and pressures. Five kinds of LCO and three kinds of arranged fuels were used. We investigated the evaporation characteristics of LCO and the relationships between the evaporation characteristics and the cetane index. In addition to that, a surrogate fuel composed of four chemical species, which can simulate the droplet evaporation characteristics of LCO, was suggested. Experimental results show that the differences in droplet lifetime between fuel species become larger with decreasing ambient temperature. This is because the low volatile component made the evaporation rate outstandingly slow at a low ambient temperature. It was found that the relationship between droplet lifetime and the late-stage distillation temperature becomes stronger at low ambient temperature and high ambient pressure. By an analysis employing the properties of chemical species in LCO surrogate fuel, it is clarified that the mass evaporation rate becomes smaller than the internal diffusion, which is the condition similar to that in the distillation test. Finally, the relationship between the droplet lifetime and the cetane index was investigated. It can be concluded that the droplet lifetime is independent of the cetane index under all conditions tested in this study. The experimental data obtained by this research can be utilized for the validation of multicomponent fuel droplet evaporation models in the future

Mini-laparoscopic surgery versus conventional laparoscopic surgery for patients with endometriosis

Objective: To compare mini-laparoscopic surgery and conventional laparoscopic surgery in patients with endometriosis that was conducted to determine the superiority of mini-laparoscopic surgical technique. Design: Retrospective analysis. Settings: Osaka Medical College Hospital, Hokusetsu General Hospital, and Daiichi-Towakai Hospital, Osaka, Japan. Patients: Forty-six patients with endometriosis who underwent conventional or mini-laparoscopic surgery between November 2009 and October 2012. Intervention: Patients were divided into three groups. Group A underwent conventional surgery with one 12-mm port for a 10-mm laparoscope and three 5-mm ports. Groups B and C underwent mini-laparoscopic surgery with one 5-mm port for a 5-mm laparoscope and one 5-mm port as well as two 3-mm ports (Group B) or two 2.3-mm ports for the Mini-Lap Grasper (Group C). Measurements and main results: Operating time was significantly longer in Group C than in Group B (p = 0.01). Serum C-reactive protein levels 1 day after surgery were significantly lower in Groups B and C than in Group A (p < 0.001). In Groups B and C, C-reactive protein levels 1 day after surgery were similar, but rescue analgesic requirements were significantly higher in Group B (p = 0.003). Conclusion: Mini-laparoscopic surgery for patients with endometriosis is safe. Group C exhibited decreased postoperative incisional pain, and the procedure used was less invasive and produced superior cosmetic results. However, operating time in Group C was significantly longer. The procedure that Group B underwent was also minimally invasive with a similar operating time and improved cosmetic appearance

Functional Analysis of MeCP2 Mutations Associated with Rett Syndrome Using Transient Expression Systems

レット症候群は生後半年から1歳半ころに発症する重度の精神発達遅滞を伴う疾患で女児の1万人から1万5千人に1人に発症する頻度の高い遺伝子疾患である。この疾患の原因遺伝子が最近MeCP2遺伝子であることが判明した。レット症候群の患者でみられる変異がMeCP2の本来の機能にどのような影響を及ぼすかを理解することは、レット症候群の病態を解明する上での手がかりになる。MeCP2は2つの機能ドメインを持ち、一つはメチル化CpGに結合するメチル化結合ドメイン(MBD)で、もう一つはヒストン脱アセチル化酵素をリクルートするSin3Aと結合する転写抑制ドメイン(TRD)である。報告されている変異の中でミスセンス変異の多くは、この二つのドメイン内でみられ、特にMBD内での変異の割合は多い。MBD内のミスセンス変異のMeCP2機能への影響を把握するため、培養細胞を用いた遺伝子導入発現系を開発して解析を行った