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1.
Eur J Cell Biol ; 101(2): 151222, 2022 Apr.
Article in English | MEDLINE | ID: covidwho-1881962

ABSTRACT

Clathrin-mediated endocytosis (CME) is the major route through which cells internalise various substances and recycle membrane components. Via the coordinated action of many proteins, the membrane bends and invaginates to form a vesicle that buds off-along with its contents-into the cell. The contribution of the actin cytoskeleton to this highly dynamic process in mammalian cells is not well understood. Unlike in yeast, where there is a strict requirement for actin in CME, the significance of the actin cytoskeleton to mammalian CME is variable. However, a growing number of studies have established the actin cytoskeleton as a core component of mammalian CME, and our understanding of its contribution has been increasing at a rapid pace. In this review, we summarise the state-of-the-art regarding our understanding of the endocytic cytoskeleton, its physiological significance, and the questions that remain to be answered.


Subject(s)
Actin Cytoskeleton , Clathrin , Actin Cytoskeleton/metabolism , Actins/metabolism , Animals , Cell Membrane/metabolism , Clathrin/metabolism , Cytoskeleton/metabolism , Endocytosis/physiology , Mammals/metabolism , Saccharomyces cerevisiae/metabolism
2.
Elife ; 112022 01 25.
Article in English | MEDLINE | ID: covidwho-1662829

ABSTRACT

The human proteome is replete with short linear motifs (SLiMs) of four to six residues that are critical for protein-protein interactions, yet the importance of the sequence surrounding such motifs is underexplored. We devised a proteomic screen to examine the influence of SLiM sequence context on protein-protein interactions. Focusing on the EVH1 domain of human ENAH, an actin regulator that is highly expressed in invasive cancers, we screened 36-residue proteome-derived peptides and discovered new interaction partners of ENAH and diverse mechanisms by which context influences binding. A pocket on the ENAH EVH1 domain that has diverged from other Ena/VASP paralogs recognizes extended SLiMs and favors motif-flanking proline residues. Many high-affinity ENAH binders that contain two proline-rich SLiMs use a noncanonical site on the EVH1 domain for binding and display a thermodynamic signature consistent with the two-motif chain engaging a single domain. We also found that photoreceptor cilium actin regulator (PCARE) uses an extended 23-residue region to obtain a higher affinity than any known ENAH EVH1-binding motif. Our screen provides a way to uncover the effects of proteomic context on motif-mediated binding, revealing diverse mechanisms of control over EVH1 interactions and establishing that SLiMs can't be fully understood outside of their native context.


Subject(s)
Actins/metabolism , Binding Sites , DNA-Binding Proteins/metabolism , Microfilament Proteins/metabolism , Proline/metabolism , Cell Adhesion Molecules/metabolism , HEK293 Cells , Humans , Proteomics
3.
Int J Mol Sci ; 23(1)2021 Dec 24.
Article in English | MEDLINE | ID: covidwho-1580700

ABSTRACT

Acute respiratory distress syndrome (ARDS) followed by repair with lung remodeling is observed in COVID-19. These findings can lead to pulmonary terminal fibrosis, a form of irreversible sequelae. There is evidence that TGF-ß is intimately involved in the fibrogenic process. When activated, TGF-ß promotes the differentiation of fibroblasts into myofibroblasts and regulates the remodeling of the extracellular matrix (ECM). In this sense, the present study evaluated the histopathological features and immunohistochemical biomarkers (ACE-2, AKT-1, Caveolin-1, CD44v6, IL-4, MMP-9, α-SMA, Sphingosine-1, and TGF-ß1 tissue expression) involved in the TGF-ß1 signaling pathways and pulmonary fibrosis. The study consisted of 24 paraffin lung samples from patients who died of COVID-19 (COVID-19 group), compared to 10 lung samples from patients who died of H1N1pdm09 (H1N1 group) and 11 lung samples from patients who died of different causes, with no lung injury (CONTROL group). In addition to the presence of alveolar septal fibrosis, diffuse alveolar damage (DAD) was found to be significantly increased in the COVID-19 group, associated with a higher density of Collagen I (mature) and III (immature). There was also a significant increase observed in the immunoexpression of tissue biomarkers ACE-2, AKT-1, CD44v6, IL-4, MMP-9, α-SMA, Sphingosine-1, and TGF-ß1 in the COVID-19 group. A significantly lower expression of Caveolin-1 was also found in this group. The results suggest the participation of TGF-ß pathways in the development process of pulmonary fibrosis. Thus, it would be plausible to consider therapy with TGF-ß inhibitors in those patients recovered from COVID-19 to mitigate a possible development of pulmonary fibrosis and its consequences for post-COVID-19 life quality.


Subject(s)
COVID-19/metabolism , Pulmonary Fibrosis/metabolism , Signal Transduction , Transforming Growth Factor beta/metabolism , Actins/metabolism , Adrenal Cortex Hormones/therapeutic use , Adult , Aged , Aged, 80 and over , Angiotensin-Converting Enzyme 2/metabolism , COVID-19/complications , COVID-19/drug therapy , COVID-19/pathology , Caveolin 1/metabolism , Collagen Type I/metabolism , Collagen Type III/metabolism , Female , Humans , Hyaluronan Receptors/metabolism , Immunohistochemistry , Influenza A Virus, H1N1 Subtype/metabolism , Influenza, Human/metabolism , Influenza, Human/pathology , Interleukin-4/metabolism , Male , Matrix Metalloproteinase 9/metabolism , Middle Aged , Proto-Oncogene Proteins c-akt/metabolism , Pulmonary Fibrosis/complications , Pulmonary Fibrosis/drug therapy , Pulmonary Fibrosis/pathology , Retrospective Studies , Transforming Growth Factor beta1/metabolism
4.
Neurobiol Dis ; 161: 105561, 2021 12.
Article in English | MEDLINE | ID: covidwho-1510138

ABSTRACT

Coronavirus disease 19 (COVID-19) is a respiratory illness caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). COVID-19 pathogenesis causes vascular-mediated neurological disorders via elusive mechanisms. SARS-CoV-2 infects host cells via the binding of viral Spike (S) protein to transmembrane receptor, angiotensin-converting enzyme 2 (ACE2). Although brain pericytes were recently shown to abundantly express ACE2 at the neurovascular interface, their response to SARS-CoV-2 S protein is still to be elucidated. Using cell-based assays, we found that ACE2 expression in human brain vascular pericytes was increased upon S protein exposure. Pericytes exposed to S protein underwent profound phenotypic changes associated with an elongated and contracted morphology accompanied with an enhanced expression of contractile and myofibrogenic proteins, such as α-smooth muscle actin (α-SMA), fibronectin, collagen I, and neurogenic locus notch homolog protein-3 (NOTCH3). On the functional level, S protein exposure promoted the acquisition of calcium (Ca2+) signature of contractile ensheathing pericytes characterized by highly regular oscillatory Ca2+ fluctuations. Furthermore, S protein induced lipid peroxidation, oxidative and nitrosative stress in pericytes as well as triggered an immune reaction translated by activation of nuclear factor-kappa-B (NF-κB) signaling pathway, which was potentiated by hypoxia, a condition associated with vascular comorbidities that exacerbate COVID-19 pathogenesis. S protein exposure combined to hypoxia enhanced the production of pro-inflammatory cytokines involved in immune cell activation and trafficking, namely macrophage migration inhibitory factor (MIF). Using transgenic mice expressing the human ACE2 that recognizes S protein, we observed that the intranasal infection with SARS-CoV-2 rapidly induced hypoxic/ischemic-like pericyte reactivity in the brain of transgenic mice, accompanied with an increased vascular expression of ACE2. Moreover, we found that SARS-CoV-2 S protein accumulated in the intranasal cavity reached the brain of mice in which the nasal mucosa is deregulated. Collectively, these findings suggest that SARS-CoV-2 S protein impairs the vascular and immune regulatory functions of brain pericytes, which may account for vascular-mediated brain damage. Our study provides a better understanding for the mechanisms underlying cerebrovascular disorders in COVID-19, paving the way to develop new therapeutic interventions.


Subject(s)
Angiotensin-Converting Enzyme 2/metabolism , Brain/metabolism , COVID-19/metabolism , Hypoxia-Ischemia, Brain/metabolism , Hypoxia/metabolism , Inflammation/metabolism , Pericytes/metabolism , SARS-CoV-2/metabolism , Spike Glycoprotein, Coronavirus/metabolism , Actins/metabolism , Angiotensin-Converting Enzyme 2/drug effects , Angiotensin-Converting Enzyme 2/genetics , Animals , Brain/blood supply , COVID-19/physiopathology , Calcium Signaling , Collagen Type I/metabolism , Fibronectins/metabolism , Humans , Hypoxia-Ischemia, Brain/physiopathology , Lipid Peroxidation/drug effects , Lipid Peroxidation/genetics , Macrophage Migration-Inhibitory Factors/drug effects , Macrophage Migration-Inhibitory Factors/metabolism , Mice , Mice, Transgenic , Muscle, Smooth, Vascular/cytology , Muscle, Smooth, Vascular/metabolism , Myocytes, Smooth Muscle/cytology , Myocytes, Smooth Muscle/metabolism , Myofibroblasts , NF-kappa B/drug effects , NF-kappa B/metabolism , Nasal Mucosa , Nitrosative Stress , Oxidative Stress , Pericytes/cytology , Pericytes/drug effects , Phenotype , Receptor, Notch3/metabolism , Receptors, Coronavirus/drug effects , Receptors, Coronavirus/genetics , Receptors, Coronavirus/metabolism , Spike Glycoprotein, Coronavirus/pharmacology
5.
Phys Rev E ; 104(2-1): 024417, 2021 Aug.
Article in English | MEDLINE | ID: covidwho-1393562

ABSTRACT

In several pathological conditions, such as coronavirus infections, multiple sclerosis, Alzheimer's and Parkinson's diseases, the physiological shape of axons is altered and a periodic sequence of bulges appears. Experimental evidences suggest that such morphological changes are caused by the disruption of the microtubules composing the cytoskeleton of the axon. In this paper, we develop a mathematical model of damaged axons based on the theory of continuum mechanics and nonlinear elasticity. The axon is described as a cylinder composed of an inner passive part, called axoplasm, and an outer active cortex, composed mainly of F-actin and able to contract thanks to myosin-II motors. Through a linear stability analysis we show that, as the shear modulus of the axoplasm diminishes due to the disruption of the cytoskeleton, the active contraction of the cortex makes the cylindrical configuration unstable to axisymmetric perturbations, leading to a beading pattern. Finally, the nonlinear evolution of the bifurcated branches is investigated through finite element simulations.


Subject(s)
Axons/pathology , Elasticity , Models, Neurological , Actins/metabolism , Axons/metabolism , Biomechanical Phenomena
7.
Int J Mol Sci ; 21(22)2020 Nov 10.
Article in English | MEDLINE | ID: covidwho-917002

ABSTRACT

Pro-inflammatory cytokines like interleukin-1ß (IL-1ß) are upregulated during early responses to tissue damage and are expected to transiently compromise the mechanical microenvironment. Fibroblasts are key regulators of tissue mechanics in the lungs and other organs. However, the effects of IL-1ß on fibroblast mechanics and functions remain unclear. Here we treated human pulmonary fibroblasts from control donors with IL-1ß and used Atomic Force Microscopy to unveil that IL-1ß significantly reduces the stiffness of fibroblasts concomitantly with a downregulation of filamentous actin (F-actin) and alpha-smooth muscle (α-SMA). Likewise, COL1A1 mRNA was reduced, whereas that of collagenases MMP1 and MMP2 were upregulated, favoring a reduction of type-I collagen. These mechanobiology changes were functionally associated with reduced proliferation and enhanced migration upon IL-1ß stimulation, which could facilitate lung repair by drawing fibroblasts to sites of tissue damage. Our observations reveal that IL-1ß may reduce local tissue rigidity by acting both intracellularly and extracellularly through the downregulation of fibroblast contractility and type I collagen deposition, respectively. These IL-1ß-dependent mechanical effects may enhance lung repair further by locally increasing pulmonary tissue compliance to preserve normal lung distension and function. Moreover, our results support that IL-1ß provides innate anti-fibrotic protection that may be relevant during the early stages of lung repair.


Subject(s)
Interleukin-1beta/physiology , Lung/physiology , Actins/metabolism , Adolescent , Adult , Biomechanical Phenomena , Cell Movement/drug effects , Cell Movement/physiology , Cell Proliferation/drug effects , Cell Proliferation/physiology , Cells, Cultured , Collagen Type I/genetics , Collagen Type I/metabolism , Collagen Type III/genetics , Collagen Type III/metabolism , Cyclooxygenase 2/metabolism , Elasticity/drug effects , Elasticity/physiology , Female , Fibroblasts/cytology , Fibroblasts/drug effects , Fibroblasts/physiology , Humans , Interleukin-1beta/pharmacology , Lung/cytology , Lung/drug effects , Male , Microscopy, Atomic Force , RNA, Messenger/genetics , RNA, Messenger/metabolism , Regeneration/genetics , Regeneration/physiology , Wound Healing/drug effects , Wound Healing/genetics , Wound Healing/physiology , Young Adult
9.
FASEB J ; 34(3): 4653-4669, 2020 03.
Article in English | MEDLINE | ID: covidwho-832736

ABSTRACT

Transmissible gastroenteritis virus (TGEV) is a swine enteropathogenic coronavirus that causes significant economic losses in swine industry. Current studies on TGEV internalization mainly focus on viral receptors, but the internalization mechanism is still unclear. In this study, we used single-virus tracking to obtain the detailed insights into the dynamic events of the TGEV internalization and depict the whole sequential process. We observed that TGEVs could be internalized through clathrin- and caveolae-mediated endocytosis, and the internalization of TGEVs was almost completed within ~2 minutes after TGEVs attached to the cell membrane. Furthermore, the interactions of TGEVs with actin and dynamin 2 in real time during the TGEV internalization were visualized. To our knowledge, this is the first report that single-virus tracking technique is used to visualize the entire dynamic process of the TGEV internalization: before the TGEV internalization, with the assistance of actin, clathrin, and caveolin 1 would gather around the virus to form the vesicle containing the TGEV, and after ~60 seconds, dynamin 2 would be recruited to promote membrane fission. These results demonstrate that TGEVs enter ST cells via clathrin- and caveolae-mediated endocytic, actin-dependent, and dynamin 2-dependent pathways.


Subject(s)
Gastroenteritis, Transmissible, of Swine/metabolism , Gastroenteritis, Transmissible, of Swine/virology , Transmissible gastroenteritis virus/pathogenicity , Actins/metabolism , Animals , Caveolae/metabolism , Caveolin 1/metabolism , Cell Line , Cell Membrane/metabolism , Cell Membrane/physiology , Cell Membrane/virology , Clathrin/metabolism , Dynamin II/metabolism , Endocytosis/physiology , Membrane Fusion/physiology , Swine , Virus Internalization
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