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慶田城 迅大学院医学系研究科 医科学専攻助教
研究活動情報
■ 論文- Puncta adherentia junctions (PAJs) have been observed at glutamatergic excitatory synapses on glutamatergic excitatory neurons (E→E synapses) in the mouse hippocampus and are considered to be the mechanical adhesion sites between axon terminals and dendritic shafts. However, it remains unclear whether they are present at other types of synapses, such as glutamatergic synapses on GABAergic inhibitory neurons (E→I synapses) and GABAergic synapses on excitatory neurons (I→E synapses) and inhibitory neurons (I→I synapses). We showed here that the PAJ components, such as nectin-1, nectin-3, l-afadin, N-cadherin, β-catenin, and αN-catenin, were observed at all four types of synapses in cultured mouse hippocampal neurons. In the adult mouse hippocampus, these PAJ components were observed at a subset of I→I synapses on parvalbumin-positive GABAergic inhibitory neurons, similarly to their presence at E→E synapses in the CA1 and CA3 regions. In contrast, several PAJ components, including nectin-3, l-afadin, N-cadherin, β-catenin, and αN-catenin, were observed at E→I and I→E synapses, whereas nectin-1 was absent. These results indicate that the PAJs are formed at a subset of I→I synapses in addition to E→E synapses, where all examined PAJ components are present, whereas E→I and I→E synapses exhibit only partial localization of these components, reflecting molecular diversity among different synapses in the adult mouse hippocampus.2026年03月, The Journal of comparative neurology, 534(3) (3), e70152, 英語, 国際誌研究論文（学術雑誌）
- Neural networks comprise excitatory and inhibitory neurons, linked through excitatory and inhibitory synapses. Synaptic excitation/inhibition balance is controlled for brain development and functions, and its dysregulations are implicated in aging-dependent neuronal impairments. Here, we found that Necl-4/CADM4, an immunoglobulin superfamily cell adhesion molecule, is expressed in γ-aminobutyric acidergic (GABAergic) inhibitory neurons and localizes at GABAergic synapses on inhibitory neurons in cultured hippocampal neurons and the mouse hippocampus. Necl-4 genetic ablation induced neuronal loss with synaptic degenerations in the hippocampus, and cultured Necl-4-knockout (KO) hippocampal neurons were more susceptible to death. Prior to the neuronal death, the Necl-4-KO hippocampal neurons showed an increase in GABAergic synapse density on inhibitory neurons and in synaptic molecules at GABAergic synapses on inhibitory neurons, which were regulated by ErbB4 activation. Furthermore, electrophysiological analysis revealed that Necl-4 genetic ablation enhanced GABAergic synaptic currents on inhibitory neurons and induced high-frequency firing in dissociated hippocampal cultures composed of glutamatergic excitatory neurons and inhibitory neurons, contributing to excitotoxicity-mediated neuronal death. Thus, Necl-4 regulates GABAergic synaptic strength on inhibitory neurons via ErbB4 activation and prevents neuronal impairments.2025年12月, Molecular neurobiology, 62(12) (12), 15943 - 15968, 英語, 国際誌研究論文（学術雑誌）
- Mitophagy, a type of selective autophagy, specifically targets damaged mitochondria. The ULK complex regulates Parkin-mediated mitophagy, but the mechanism through which the ULK complex initiates mitophagosome formation remains unknown. The Rab7 GTPase (herein referring to Rab7a) is a key initiator of mitophagosome formation, and Ser-72 phosphorylation of Rab7 is important for this process. We have previously identified LRRK1 as a protein kinase responsible for Rab7 Ser-72 phosphorylation. In this study, we investigated the role of LRRK1 in mitophagy. We showed that LRRK1 functions downstream of ULK1 and ULK2 in Parkin-mediated mitophagy. Furthermore, we demonstrated that ectopic targeting of active LRRK1 to mitochondria is sufficient to induce the Ser-72 phosphorylation of Rab7, circumventing the requirement for ATG13, a component of the ULK complex. Thus, the ULK complex recruits LRRK1 to mitochondria by interacting with ATG13 to initiate mitophagosome formation. This study highlights the crucial role of the ULK complex-LRRK1 axis in the regulation of Parkin-mediated mitophagy.2022年12月, Journal of cell science, 135(23) (23), 英語, 国際誌研究論文（学術雑誌）
- Primary cilia are antenna-like organelles that regulate growth and development via extracellular signals. However, the molecular mechanisms underlying cilia dynamics, particularly those regulating their disassembly, are not well understood. Here, we show that leucine-rich repeat kinase 1 (LRRK1) plays a role in regulating cilia disassembly. The depletion of LRRK1 impairs primary cilia resorption following serum stimulation in cultured cells. Polo-like kinase 1 (PLK1) plays an important role in this process. During ciliary resorption, PLK1 phosphorylates LRRK1 at the primary cilia base, resulting in its activation. We identified nuclear distribution protein nudE-like 1 (NDEL1), which is known to positively regulate cilia disassembly, as a target of LRRK1 phosphorylation. Whereas LRRK1 phosphorylation of NDEL1 on Ser-155 promotes NDEL1 interaction with the intermediate chains of cytoplasmic dynein-2, it is also crucial for triggering ciliary resorption through dynein-2-driven retrograde intraflagellar transport. These findings provide evidence that a novel PLK1-LRRK1-NDEL1 pathway regulates cilia disassembly.2022年11月, Journal of cell science, 135(21) (21), 英語, 国際誌研究論文（学術雑誌）
- Multilayered proliferation in an adherent culture as well as proliferation in a suspension culture is a characteristic feature of cancer cells. We previously showed using T47D human mammary cancer cells that nectin-4, upregulated in many cancer cells, cis-interacts with ErbB2 and its trastuzumab-resistant splice variants, p95-ErbB2 and ErbB2ΔEx16, and enhances DNA synthesis mainly through the PI3K-AKT pathway in an adherent culture. We showed here that only the combination of nectin-4 and p95-ErbB2, but not that of nectin-4 and ErbB2 or that of nectin-4 and ErbB2ΔEx16, cooperatively enhanced multilayered T47D cell proliferation through the Hippo pathway-mediated SOX2 gene expression in an adherent culture. T47D cells expressed the components of the apical junctional complex (AJC) consisting of adherens junctions (AJs) and tight junctions and cell polarity molecules, but not the AJ component afadin. The AJC and apicobasal polarity were disorganized in T47D cells in a monolayer and T47D cells stably expressing both nectin-4 and p95-ErbB2 in multilayers. These results indicate that nectin-4 and p95-ErbB2 play a stimulatory role in multilayered proliferation in an adherent culture.2022年04月, Genes to cells : devoted to molecular & cellular mechanisms, 英語, 国際誌研究論文（学術雑誌）
- Nectin-4, upregulated in various cancer cells, cis-interacts with ErbB2 and its trastuzumab-resistant splice variants, p95-ErbB2 and ErbB2∆Ex16, enhancing DNA synthesis through the PI3K-AKT signaling in human breast cancer T47D cells in an adherent culture. We found here that nectin-4 and p95-ErbB2, but not nectin-4 and either ErbB2 or ErbB2∆Ex16, cooperatively enhanced SOX2 gene expression and cell proliferation in a suspension culture. This enhancement of T47D cell proliferation in a suspension culture by nectin-4 and p95-ErbB2 was dependent on the SOX2 gene expression. In T47D cells, nectin-4 and any one of p95-ErbB2, ErbB2, or ErbB2∆Ex16 cooperatively activated the PI3K-AKT signaling, known to induce the SOX2 gene expression, to similar extents. However, only a combination of nectin-4 and p95-ErbB2, but not that of nectin-4 and either ErbB2 or ErbB2∆Ex16, cooperatively enhanced the SOX2 gene expression. Detailed studies revealed that only nectin-4 and p95-ErbB2 cooperatively activated the Hippo signaling. YAP inhibited the SOX2 gene expression in this cell line and thus the MST1/2-LATS1/2 signaling-mediated YAP inactivation increased the SOX2 gene expression. These results indicate that only the combination of nectin-4 and p95-ErbB2, but not that of nectin-4 and either ErbB2 or ErbB2∆Ex16, cooperatively regulates the Hippo signaling-dependent SOX2 gene expression, enhancing anchorage-independent T47D cell proliferation.2021年04月, Scientific reports, 11(1) (1), 7344 - 7344, 英語, 国際誌研究論文（学術雑誌）
- The hypothalamus plays a central role in homeostasis and aging. The hypothalamic arcuate nucleus (ARC) controls homeostasis of food intake and energy expenditure and retains adult neural stem cells (NSCs)/progenitor cells. Aging induces the loss of NSCs and the enhancement of inflammation, including the activation of glial cells in the ARC, but aging-associated alterations of the hypothalamic cells remain obscure. Here, we identified Sox2 and NeuN double-positive cells in a subpopulation of cells in the mouse ARC. These cells were reduced in number with aging, although NeuN-positive neuronal cells were unaltered in the total number. Diet-induced obesity mice fed with high-fat diet presented a similar hypothalamic alteration to aged mice. This study provides a new insight into aging-induced changes in the hypothalamus.2020年, Frontiers in aging neuroscience, 12, 609911 - 609911, 英語, 国際誌研究論文（学術雑誌）
- Nectin-4 cell adhesion molecule and ErbB2 tyrosine kinase receptor are upregulated in many cancers, including breast cancer, and promote cancer cell proliferation and metastasis. Using human breast cancer cell lines T47D and SUM190-PT, in which both nectin-4 and ErbB2 were upregulated, we showed here that nectin-4 cis-interacted with ErB2 and enhanced its dimerization and activation, followed by the activation of the phosphoinositide 3-kinase-AKT signalling pathway for DNA synthesis. The third immunoglobulin-like domain of nectin-4 cis-interacted with domain IV of ErbB2. This region differs from the trastuzumab-interacting region but is included in the trastuzumab-resistant splice variants of ErbB2, p95-ErbB2 and ErbB2ΔEx16. Nectin-4 also cis-interacted with these trastuzumab-resistant splice variants and enhanced the activation of the phosphoinositide 3-kinase-AKT signalling pathway for DNA synthesis. In addition, nectin-4 enhanced the activation of the p95-ErbB2-induced JAK-STAT3 signalling pathway, but not the ErbB2- or ErbB2ΔEx16-induced JAK-STAT3 signalling pathway. These results indicate that nectin-4 cis-interacts with ErbB2 and its trastuzumab-resistant splice variants and enhances the activation of these receptors and downstream signalling pathways in a novel mechanism.2019年12月, Scientific reports, 9(1) (1), 18997 - 18997, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- Blackwell Publishing Ltd, 2018年03月, Genes to cells : devoted to molecular & cellular mechanisms, 23(3) (3), 214 - 224, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- 2017年09月, Scientific reports, 7(1) (1), 11375 - 11375, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- Cell-surface cytokine receptors are regulated by their cis-interacting stimulatory and inhibitory co-receptors. We previously showed that the Ig-like cell-adhesion molecule nectin-4 cis-interacts with the prolactin receptor through the extracellular region and stimulates prolactin-induced prolactin receptor activation and signaling, resulting in alveolar development in the mouse mammary gland. However, it remains unknown how this interaction stimulates these effects. We show here that the cis-interaction of the extracellular region of nectin-4 with the prolactin receptor was not sufficient for eliciting these effects and that the cytoplasmic region of nectin-4 was also required for this interaction. The cytoplasmic region of nectin-4 directly interacted with suppressor of cytokine signaling 1 (SOCS1), but not SOCS3, JAK2, or STAT5a, and inhibited the interaction of SOCS1 with JAK2, eventually resulting in the increased phosphorylation of STAT5a. The juxtamembrane region of nectin-4 interacted with the Src homology 2 domain of SOCS1. Both the interaction of nectin-4 with the extracellular region of the prolactin receptor and the interaction of SOCS1 with the cytoplasmic region of nectin-4 were required for the stimulatory effect of nectin-4 on the prolactin-induced prolactin receptor activation. The third Ig-like domain of nectin-4 and the second fibronectin type III domain of the prolactin receptor were involved in this cis-interaction, and both the extracellular and transmembrane regions of nectin-4 and the prolactin receptor were required for this direct interaction. These results indicate that nectin-4 serves as a stimulatory co-receptor for the prolactin receptor by regulating the feedback inhibition of SOCS1 in the JAK2-STAT5a signaling pathway.2017年04月, The Journal of biological chemistry, 292(17) (17), 6895 - 6909, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- 2015年08月, Nature cell biology, 17(8) (8), 1024 - 35, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- 2015年02月, Journal of cell science, 128(4) (4), 829 - 829, 英語, 国際誌[査読有り]
- 2015年01月, Journal of cell science, 128(2) (2), 385 - 96, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- Activation of the epidermal growth factor receptor (EGFR) not only initiates multiple signal-transduction pathways, including the MAP kinase (MAPK) pathway, but also triggers trafficking events that relocalize receptors from the cell surface to intracellular endocytic compartments. In this paper, we demonstrate that leucine-rich repeat kinase LRRK1, which contains a MAPKKK-like kinase domain, forms a complex with activated EGFR through an interaction with Grb2. Subsequently, LRRK1 and epidermal growth factor (EGF) are internalized and co-localized in early endosomes. LRRK1 regulates EGFR transport from early to late endosomes and regulates the motility of EGF-containing early endosomes in a manner dependent on its kinase activity. Furthermore, LRRK1 serves as a scaffold facilitating the interaction of EGFR with the endosomal sorting complex required for transport-0 complex, thus enabling efficient sorting of EGFR to the inner vesicles of multivesicular bodies. Our findings provide the first evidence that a MAPKKK-like protein regulates the endosomal trafficking of EGFR.2011年01月, Nature communications, 2(158) (158), 158 - 158, 英語, 国際誌[査読有り]研究論文（学術雑誌）
- 2017年度生命科学系学会合同年次大会, 2017年12月, 日本語, 日本分子生物学会・日本生化学会, 神戸, 国内会議ネクチン-4はSOCS1によるフィードバック阻害を抑制することで乳腺分化におけるプロラクチン受容体シグナル伝達を促進するポスター発表
- 第64回日本生化学会 近畿支部例会, 2017年05月, 日本語, 日本生化学会, 豊中, 国内会議乳腺分化における細胞間接着分子ネクチンの機能口頭発表（一般）
- 日本学術振興会, 科学研究費助成事業, 基盤研究(C), 神戸大学, 2026年04月01日 - 2029年03月31日アミロイドβによるスパイン退縮とシナプス減少に起因する神経細胞障害機構の解析
- 日本学術振興会, 科学研究費助成事業, 基盤研究(C), 神戸大学, 2021年04月01日 - 2022年03月31日細胞接着分子と膜受容体が制御するがん細胞の増殖と停止、その再開のスイッチ機構本研究では、がんの発症と転移の過程におけるがん細胞の増殖・運動の停止・再開のスイッチ機構を解明することを目的とし、細胞接着分子ネクチン－４、成長因子受容体ErbB2、ErbB2のバリアントであるp95-ErbB2この機構に果たす機能の解析を行い、本年度は以下の結果が得られた。 （１）乳がん細胞の増殖・運動の停止・再開のスイッチ機構、および新たな生存機構：がん細胞の増殖・運動の停止・再開のスイッチ機構を解明するため、乳がん細胞で上記の分子の発現や相互作用、増殖・運動に関わるシグナル伝達分子の活性化を検討した。その結果、ネクチン－４がErbB2のバリアントであるp95-ErbB2と結合した場合にのみ、Hippo経路を介して転写因子SOX2の発現を促進した。また、SOX2はがん細胞の非接着状態の増殖を促進した。これらの結果を論文として発表した。 （２）乳がん細胞の増殖・運動の停止・再開のスイッチ機構、および新たな生存機構：がん細胞の増殖・運動の停止・再開のスイッチ機構を解明するため、がん細胞を観察している際、新たな表現型を発見した。ネクチン－４がErbB2のバリアントであるp95-ErbB2と結合した場合にのみ、がん細胞の多層化が認められた。この多層化は、Hippo経路を介したSOX2の発現が必要であることが明らかとなった。また、アドへレンスジャンクションやタイトジャンクションに局在する細胞接着分子、がん細胞のアピカル側やベーサル側に局在する極性分子などの局在場所も変化していた。これらの結果を論文として発表した。
- 日本学術振興会, 科学研究費助成事業 若手研究, 若手研究, 神戸大学, 2019年04月01日 - 2021年03月31日細胞接着分子ネクチンによるがん細胞の増殖と運動の停止と再開のスイッチ機構がん細胞は、原発巣では増殖し運動するが、血中循環中は増殖や運動を停止し、転移巣では増殖や運動を再開する。しかし、この増殖・運動の停止・再開のスイッチ機構は不明である。本研究では、がんの発症と転移の過程におけるがん細胞の増殖・運動の停止・再開のスイッチ機構を解明することを目的とし、ネクチン－４、ErbB2、インテグリンα6β4がこの機構に果たす機能の解析を行い、本年度は以下の結果が得られた。 （１）乳がん細胞の増殖・運動の停止・再開のスイッチ機構、及び新たな生存機構：乳がん細胞では、増殖・運動と生存は、ネクチン－４やErbB2、インテグリンα6β4の相互作用により制御されると考えられている。そこで、これら分子の発現や増殖・運動に関わるシグナル伝達分子の活性化を、原発巣を模した接着状態、血中循環中を模した非接着状態で比較検討した。その結果、非接着状態では増殖に重要なErbB2の発現量が減少していた。また、生存に重要なSrcの活性化が認められた。予想外に、STAT3の活性化も検出された。現在、これら分子の変動と上記分子の関係、これらが制御すると期待される増殖・運動の停止・再開のスイッチ機構や生存機構を解析している。 （2）がん細胞の転移過程におけるエキソソームの作用機構：インテグリンα6β4やネクチン－４、ErbB2を含むエキソソームによるがん細胞の転移や増殖・運動の停止・再開のスイッチ機構への関与、また、エキソソームの具体的な標的細胞/ECM、それを介したがん細胞定着機構は不明である。これらを解明するために、まず乳がん細胞から精製したエキソソームにインテグリンα6β4やネクチン－４、ErbB2が含まれることを確認した。また、乳がん細胞の転移先の一つである脳から血管を採取した。現在、採取した脳血管に精製エキソソームを処理し、エキソソームが脳血管のどの部位に検出されるか検討している。
- 学術研究助成基金助成金／若手研究(B), 2017年04月 - 2019年03月, 研究代表者競争的資金