Search results for "Cell Surface"

In situ structural analysis of SARS-CoV-2 spike reveals flexibility mediated by three hinges

2020

Flexible spikes The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein enables viral entry into host cells by binding to the angiotensin-converting enzyme 2 (ACE2) receptor and is a major target for neutralizing antibodies. About 20 to 40 spikes decorate the surface of virions. Turoňová et al. now show that the spike is flexibly connected to the viral surface by three hinges that are well protected by glycosylation sites. The flexibility imparted by these hinges may explain how multiple spikes act in concert to engage onto the flat surface of a host cell. Science, this issue p. 203

In situ structural analysis of SARS-CoV-2 spike reveals flexibility mediated by three hinges

2020

AbstractThe spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is required for cell entry and is the major focus for vaccine development. We combine cryo electron tomography, subtomogram averaging and molecular dynamics simulations to structurally analyze Sin situ. Compared to recombinant S, the viral S is more heavily glycosylated and occurs predominantly in a closed pre-fusion conformation. We show that the stalk domain of S contains three hinges that give the globular domain unexpected orientational freedom. We propose that the hinges allow S to scan the host cell surface, shielded from antibodies by an extensive glycan coat. The structure of native S contr…

Differential TNF-Signaling in Chronic Inflammatory Disorders

2004

TNF-alpha is a pleiotropic cytokine with strong proinflammatory and immunomodulatory properties. TNF-alpha plays a critical role in many acute or chronic inflammatory diseases and anti-TNF-strategies have proven to be clinically effective. Two TNF-specific cell surface receptors TNF-R1 and TNF-R2 have been identified and the function of these receptors and the downstream intracellular signal transduction pathways have been extensively studied in vitro. For a long time TNF-R1 was considered to be the predominant mediator of TNF-signaling, whereas TNF-R2 was ascribed only auxilliary function. However, there is increasing clinical and experimental evidence for an important independent role of …

Binding analyses of Cry1Ab and Cry1Ac with membrane vesicles from Bacillus thuringiensis-resistant and -susceptible Ostrinia nubilalis.

2004

The binding properties of Bacillus thuringiensis toxins to brush border membrane vesicles of Dipel-resistant and -susceptible Ostrinia nubilalis larvae were compared using ligand-toxin immunoblot analysis, surface plasmon resonance (SPR), and radiolabeled toxin binding assays. In ligand-toxin immunoblot analysis, the number of Cry1Ab or Cry1Ac toxin binding proteins and the relative toxin binding intensity were similar in vesicles from resistant and susceptible larvae. Surface plasmon resonance with immobilized activated Cry1Ab toxin indicated that there were no significant differences in binding with fluid-phase vesicles from resistant and susceptible larvae. Homologous competition assays …

Ligands and receptors: common theme in insect storage protein transport.

1999

The passage of macromolecules through biological membranes is an essential process for all multicellular organisms. Insects have developed a mechanism different from that known for all other eukaryotes investigated so far. This review discusses the function and evolution of this mechanism. Insect pupae do not feed during metamorphosis. Therefore they depend on material that has been accumulated during the larval life. At the end of this period, shortly before pupariation, a rise in titer of ecdysteroid hormones induces the incorporation of a large fraction of storage proteins (hexamerins) from the body fluid into the fat body cells. The transport of hexamerins across the cell-membrane is me…

β1D Integrin Inhibits Cell Cycle Progression in Normal Myoblasts and Fibroblasts

1998

Integrins are alphabeta heterodimeric transmembrane receptors involved in the regulation of cell growth and differentiation. The beta1 integrin subunit is widely expressed in vivo and is represented by four alternatively spliced cytoplasmic domain isoforms. beta1D is a muscle-specific variant of beta1 integrin and a predominant beta1 isoform in striated muscles. In the present study we showed that expression of the exogenous beta1D integrin in C2C12 myoblasts and NIH 3T3 or REF 52 fibroblasts inhibited cell proliferation. Unlike the case of the common beta1A isoform, adhesion of beta1D-transfected C2C12 myoblasts specifically via the expressed integrin did not activate mitogen-activated pro…

2018

Oncogenic human papillomaviruses (HPV) are small DNA viruses that infect keratinocytes. After HPV binding to cell surface receptors, a cascade of molecular interactions mediates the infectious cellular internalization of virus particles. Aside from the virus itself, important molecular players involved in virus entry include the tetraspanin CD151 and the epidermal growth factor receptor (EGFR). To date, it is unknown how these components are coordinated in space and time. Here, we studied plasma membrane dynamics of CD151 and EGFR and the HPV16 capsid during the early phase of infection. We find that the proteinase ADAM17 activates the extracellular signal-regulated kinases (ERK1/2) pathway…

Kultivācijas apstākļu ietekme uz etanolveidojošo un pienskābes baktēriju virsmas īpašībām un fizioloģisko noturību

2013

Elektroniskā versija nesatur pielikumus

Increased expression of leptin and the leptin receptor as a marker of breast cancer progression: possible role of obesity-related stimuli.

2006

Abstract Purpose: Recent in vitro studies suggested that the autocrine leptin loop might contribute to breast cancer development by enhancing cell growth and survival. To evaluate whether the leptin system could become a target in breast cancer therapy, we examined the expression of leptin and its receptor (ObR) in primary and metastatic breast cancer and noncancer mammary epithelium. We also studied whether the expression of leptin/ObR in breast cancer can be induced by obesity-related stimuli, such as elevated levels of insulin, insulin-like growth factor-I (IGF-I), estradiol, or hypoxic conditions. Experimental Design: The expression of leptin and ObR was examined by immunohistochemistry…

Paracrine dialogue in implantation

2002

We know that the implantation process requires a functionally normal embryo at the blastocyst stage and a receptive endometrium, but also a communication link between them is needed. This paracrine dialogue between the embryo, endometrium and the corpus luteum are known to occur in ruminants and primates, more specifically endometrial-embryonic interactions have been reported in rodents and primates but not in humans. This process is a highly regulated mechanism and many molecules take part in this cross-talk. Here, we present updated information in humans on the embryonic regulation of endometrial epithelial molecules such as chemokines, adhesion and anti-adhesion molecules, and leptin dur…