Electron cryo-tomography structure of axonemal doublet microtubule from Tetrahymena thermophila

Doublet microtubules (DMTs) provide a scaffold for axoneme assembly in motile cilia. Aside from α/β tubulins, the DMT comprises a large number of non-tubulin proteins in the luminal wall of DMTs, collectively named the microtubule inner proteins (MIPs). We used cryoET to study axoneme DMT isolated from Tetrahymena. We present the structures of DMT at nanometer and sub-nanometer resolution. The structures confirm that MIP RIB72A/B binds to the luminal wall of DMT by multiple DM10 domains. We found FAP115, an MIP-containing multiple EF-hand domains, located at the interface of four-tubulin dimers in the lumen of A-tubule. It contacts both lateral and longitudinal tubulin interfaces and playing a critical role in DMT stability. We observed substantial structure heterogeneity in DMT in an FAP115 knockout strain, showing extensive structural defects beyond the FAP115-binding site. The defects propagate along the axoneme. Finally, by comparing DMT structures from Tetrahymena and Chlamydomonas, we have identified a number of conserved MIPs as well as MIPs that are unique to each organism. This conservation and diversity of the DMT structures might be linked to their specific functions. Our work provides structural insights essential for understanding the roles of MIPs during motile cilium assembly and function, as well as their relationships to human ciliopathies.

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Electron Cryo-Tomography Structure of Axonemal Doublet Microtubule from Tetrahymena thermophila

10.1101/2021.07.13.452106 ◽

2021 ◽

Author(s):

Sam Li ◽

Jose-Jesus Fernandez ◽

Amy S Fabritius ◽

David Agard ◽

Mark Winey

Keyword(s):

Binding Site ◽

Structural Changes ◽

Tetrahymena Thermophila ◽

Critical Role ◽

Nanometer Resolution ◽

Ef Hand ◽

Motile Cilia ◽

And Function ◽

Structural Insights

Doublet microtubules (DMT) provide a scaffold for axoneme assembly in motile cilia. Aside from α/β tubulins, the DMT comprises a large number of non-tubulin proteins in the luminal wall of DMT, collectively named the microtubule inner proteins (MIPs). We used electron cryo-tomography to study axoneme DMT isolated from Tetrahymena thermophila. We present the structures of DMT at nanometer and sub-nanometer resolution. The structures confirm that MIP Rib72A/B binds to the luminal wall of the DMT by multiple DM10 domains, likely by recognizing the acetylated K40 residue of α-tubulin. We found Fap115, a MIP containing multiple EF-hand domains, located at the interface of four-tubulin dimers in the lumen of the A-tubule. It functions as a "molecular staple" stabilizing both lateral and longitudinal tubulin interfaces and playing a critical role in DMT stability. Defects caused by the depletion of Fap115 propagate along the axoneme due to extensive structural changes in the DMT at and beyond the Fap115 binding site. Finally, by comparing DMT structures from Tetrahymena and Chlamydomonas, we have identified a number of conserved MIPs as well as MIPs that are unique to each organism. This conservation and diversity of the DMT structures might be linked to their specific functions. Our work provides structural insights essential for understanding the roles of MIPs during motile cilium assembly and function, as well as their relationships to human ciliopathies.

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Structural insights into the Ca2+-dependent gating of the human mitochondrial calcium uniporter

eLife ◽

10.7554/elife.60513 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 7

Author(s):

Yan Wang ◽

Yan Han ◽

Ji She ◽

Nam X Nguyen ◽

Vamsi K Mootha ◽

...

Keyword(s):

Mitochondrial Calcium ◽

Dependent Manner ◽

Inner Mitochondrial Membrane ◽

Mitochondrial Calcium Uniporter ◽

Calcium Uniporter ◽

Ef Hand ◽

Conductive Channel ◽

And Function ◽

Structural Insights ◽

Mitochondrial Membrane Protein

Mitochondrial Ca2+ uptake is mediated by an inner mitochondrial membrane protein called the mitochondrial calcium uniporter. In humans, the uniporter functions as a holocomplex consisting of MCU, EMRE, MICU1 and MICU2, among which MCU and EMRE form a subcomplex and function as the conductive channel while MICU1 and MICU2 are EF-hand proteins that regulate the channel activity in a Ca2+-dependent manner. Here, we present the EM structures of the human mitochondrial calcium uniporter holocomplex (uniplex) in the presence and absence of Ca2+, revealing distinct Ca2+ dependent assembly of the uniplex. Our structural observations suggest that Ca2+ changes the dimerization interaction between MICU1 and MICU2, which in turn determines how the MICU1-MICU2 subcomplex interacts with the MCU-EMRE channel and, consequently, changes the distribution of the uniplex assemblies between the blocked and unblocked states.

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The Laryngeal Epithelium in Reflux

Perspectives on Voice and Voice Disorders ◽

10.1044/vvd21.3.112 ◽

2011 ◽

Vol 21 (3) ◽

pp. 112-117 ◽

Cited By ~ 2

Author(s):

Elizabeth Erickson-Levendoski ◽

Mahalakshmi Sivasankar

Keyword(s):

Laryngopharyngeal Reflux ◽

Critical Role ◽

Structure And Function ◽

Laryngeal Disease ◽

Health And Disease ◽

And Function ◽

The Impact

The epithelium plays a critical role in the maintenance of laryngeal health. This is evident in that laryngeal disease may result when the integrity of the epithelium is compromised by insults such as laryngopharyngeal reflux. In this article, we will review the structure and function of the laryngeal epithelium and summarize the impact of laryngopharyngeal reflux on the epithelium. Research investigating the ramifications of reflux on the epithelium has improved our understanding of laryngeal disease associated with laryngopharyngeal reflux. It further highlights the need for continued research on the laryngeal epithelium in health and disease.

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Faculty Opinions recommendation of Critical role of cyclophilin A and its prolyl-peptidyl isomerase activity in the structure and function of the hepatitis C virus replication complex.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1162955.623591 ◽

2009 ◽

Author(s):

Teresa Compton

Keyword(s):

Hepatitis C Virus ◽

Hepatitis C ◽

Virus Replication ◽

Critical Role ◽

Cyclophilin A ◽

Structure And Function ◽

Replication Complex ◽

Isomerase Activity ◽

And Function

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Faculty Opinions recommendation of A critical role for GluN2B-containing NMDA receptors in cortical development and function.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.13407968.14778067 ◽

2011 ◽

Author(s):

Hisashi Umemori ◽

Erin Johnson-Venkatesh

Keyword(s):

Nmda Receptors ◽

Critical Role ◽

Cortical Development ◽

And Function

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The lung–gut axis during viral respiratory infections: the impact of gut dysbiosis on secondary disease outcomes

Mucosal Immunology ◽

10.1038/s41385-020-00361-8 ◽

2021 ◽

Author(s):

Valentin Sencio ◽

Marina Gomes Machado ◽

François Trottein

Keyword(s):

Gut Microbiota ◽

Bacterial Infections ◽

Respiratory Infections ◽

Critical Role ◽

Good Health ◽

Disease Outcomes ◽

And Function ◽

Viral Respiratory Infections ◽

The Impact ◽

Viral Respiratory

AbstractBacteria that colonize the human gastrointestinal tract are essential for good health. The gut microbiota has a critical role in pulmonary immunity and host’s defense against viral respiratory infections. The gut microbiota’s composition and function can be profoundly affected in many disease settings, including acute infections, and these changes can aggravate the severity of the disease. Here, we discuss mechanisms by which the gut microbiota arms the lung to control viral respiratory infections. We summarize the impact of viral respiratory infections on the gut microbiota and discuss the potential mechanisms leading to alterations of gut microbiota’s composition and functions. We also discuss the effects of gut microbial imbalance on disease outcomes, including gastrointestinal disorders and secondary bacterial infections. Lastly, we discuss the potential role of the lung–gut axis in coronavirus disease 2019.

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Mechanosensation and Mechanotransduction by Lymphatic Endothelial Cells Act as Important Regulators of Lymphatic Development and Function

International Journal of Molecular Sciences ◽

10.3390/ijms22083955 ◽

2021 ◽

Vol 22 (8) ◽

pp. 3955

Author(s):

László Bálint ◽

Zoltán Jakus

Keyword(s):

Endothelial Cells ◽

Endothelial Cell ◽

Cell Fate ◽

Molecular Mechanisms ◽

Critical Role ◽

Mechanical Forces ◽

Lymphatic Endothelial Cells ◽

Lymphatic Development ◽

And Function ◽

The Impact

Our understanding of the function and development of the lymphatic system is expanding rapidly due to the identification of specific molecular markers and the availability of novel genetic approaches. In connection, it has been demonstrated that mechanical forces contribute to the endothelial cell fate commitment and play a critical role in influencing lymphatic endothelial cell shape and alignment by promoting sprouting, development, maturation of the lymphatic network, and coordinating lymphatic valve morphogenesis and the stabilization of lymphatic valves. However, the mechanosignaling and mechanotransduction pathways involved in these processes are poorly understood. Here, we provide an overview of the impact of mechanical forces on lymphatics and summarize the current understanding of the molecular mechanisms involved in the mechanosensation and mechanotransduction by lymphatic endothelial cells. We also discuss how these mechanosensitive pathways affect endothelial cell fate and regulate lymphatic development and function. A better understanding of these mechanisms may provide a deeper insight into the pathophysiology of various diseases associated with impaired lymphatic function, such as lymphedema and may eventually lead to the discovery of novel therapeutic targets for these conditions.

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Negative Strain Rate Sensitivity Induced by Structure Heterogeneity in Zr64.13Cu15.75Ni10.12Al10 Bulk Metallic Glass

Metals ◽

10.3390/met11020339 ◽

2021 ◽

Vol 11 (2) ◽

pp. 339

Author(s):

Xiang Wang ◽

Zhi Qiang Ren ◽

Wei Xiong ◽

Si Nan Liu ◽

Ying Liu ◽

...

Keyword(s):

Metallic Glass ◽

Strain Rate ◽

Bulk Metallic Glass ◽

Strain Rate Sensitivity ◽

Critical Role ◽

Rate Sensitivity ◽

Confined Compression ◽

Negative Strain Rate Sensitivity ◽

Cast Specimen ◽

Structure Heterogeneity

The negative strain rate sensitivity (SRS) of metallic glasses is frequently observed. However, the physical essence involved is still not well understood. In the present work, small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM) reveal the strong structure heterogeneity at nanometer and tens of nanometer scales, respectively, in bulk metallic glass (BMG) Zr64.13Cu15.75Ni10.12Al10 subjected to fully confined compression processing. A transition of SRS of stress, from 0.012 in the as-cast specimen to −0.005 in compression processed specimen, was observed through nanoindentation. A qualitative formulation clarifies the critical role of internal stress induced by structural heterogeneity in this transition. It reveals the physical origin of this negative SRS frequently reported in structurally heterogeneous BMG alloys and its composites.

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Expression and function of Smad7 in autoimmune and inflammatory diseases

Journal of Molecular Medicine ◽

10.1007/s00109-021-02083-1 ◽

2021 ◽

Author(s):

Yiping Hu ◽

Juan He ◽

Lianhua He ◽

Bihua Xu ◽

Qingwen Wang

Keyword(s):

Posttranscriptional Regulation ◽

Molecular Mechanisms ◽

Transforming Growth Factor ◽

Inflammatory Diseases ◽

Kidney Diseases ◽

Critical Role ◽

Transforming Growth Factor Β ◽

Negative Regulator ◽

Signaling Mechanism ◽

And Function

AbstractTransforming growth factor-β (TGF-β) plays a critical role in the pathological processes of various diseases. However, the signaling mechanism of TGF-β in the pathological response remains largely unclear. In this review, we discuss advances in research of Smad7, a member of the I-Smads family and a negative regulator of TGF-β signaling, and mainly review the expression and its function in diseases. Smad7 inhibits the activation of the NF-κB and TGF-β signaling pathways and plays a pivotal role in the prevention and treatment of various diseases. Specifically, Smad7 can not only attenuate growth inhibition, fibrosis, apoptosis, inflammation, and inflammatory T cell differentiation, but also promotes epithelial cells migration or disease development. In this review, we aim to summarize the various biological functions of Smad7 in autoimmune diseases, inflammatory diseases, cancers, and kidney diseases, focusing on the molecular mechanisms of the transcriptional and posttranscriptional regulation of Smad7.

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