The Role of Phosphatidylinositol 4,5 Bisphosphate Breakdown in Cell-Surface Receptor Activation

Abstract To defend against microbial invaders but also to establish symbiotic programs, plants need to detect the presence of microbes through the perception of molecular signatures characteristic of a whole class of microbes. Among these molecular signatures, extracellular glycans represent a structurally complex and diverse group of biomolecules that has a pivotal role in the molecular dialog between plants and microbes. Secreted glycans and glycoconjugates such as symbiotic lipochitooligosaccharides or immunosuppressive cyclic β-glucans act as microbial messengers that prepare the ground for host colonization. On the other hand, microbial cell surface glycans are important indicators of microbial presence. They are conserved structures normally exposed and thus accessible for plant hydrolytic enzymes and cell surface receptor proteins. While the immunogenic potential of bacterial cell surface glycoconjugates such as lipopolysaccharides and peptidoglycan has been intensively studied in the past years, perception of cell surface glycans from filamentous microbes such as fungi or oomycetes is still largely unexplored. To date, only few studies have focused on the role of fungal-derived cell surface glycans other than chitin, highlighting a knowledge gap that needs to be addressed. The objective of this review is to give an overview on the biological functions and perception of microbial extracellular glycans, primarily focusing on their recognition and their contribution to plant–microbe interactions.

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CYRI-A regulates macropinocytic cup maturation and mediates integrin uptake, limiting invasive migration

10.1101/2020.12.04.411645 ◽

2020 ◽

Author(s):

Anh Hoang Le ◽

Tamas Yelland ◽

Nikki Paul ◽

Loic Fort ◽

Savvas Nikolaou ◽

...

Keyword(s):

Plasma Membrane ◽

Cell Surface ◽

Ewing Sarcoma ◽

Negative Regulator ◽

Cell Surface Receptor ◽

Actin Dynamics ◽

Surface Receptor ◽

Sarcoma Cells ◽

Wave Complex

The Scar/WAVE complex is the major driver of actin nucleation at the plasma membrane, resulting in lamellipodia and membrane ruffles. While lamellipodia aid migration, membrane ruffles can generate macropinosomes - cup-like structures - important for nutrient uptake and regulation of cell surface receptor levels. How macropinosomes are formed and the role of the actin machinery in their formation and resolution is still not well understood. Mammalian CYRI-B is a recently described negative regulator of the Scar/WAVE complex by RAC1 sequestration, but its other paralogue, CYRI-A has not been characterised. Here we implicate CYRI-A as a key regulator of macropinocytosis maturation and integrin internalisation from the cell surface. We find that CYRI-A is recruited to nascent macropinosomes in a transient but distinct burst, downstream of PIP3-mediated RAC1 activation to regulate actin polymerisation. CYRI-A precedes RAB5A recruitment to engulfed macropinocytic cups and departs as RAB5A is recruited, consistent with a role for CYRI-A as a local suppressor of actin dynamics, enabling the resolution of the macropinocytic cup. The suppression of integrin a5b1 uptake caused by the co-depletion of CYRI-A and B in Ewing sarcoma cells, leads to an enhancement of surface integrin levels and enhanced invasion and anchorage-independent growth in 3D. Thus CYRI-A is a dynamic regulator of integrin uptake via macropinocytosis, functioning together with CYRI-B to regulate integrin homeostasis on the cell surface.

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The emerging role of cell surface receptor and protein binding radiopharmaceuticals in cancer diagnostics and therapy

Nuclear Medicine and Biology ◽

10.1016/j.nucmedbio.2020.06.005 ◽

2020 ◽

Cited By ~ 1

Author(s):

Luigi Aloj ◽

Bala Attili ◽

Doreen Lau ◽

Corradina Caraco ◽

Laura M. Lechermann ◽

...

Keyword(s):

Cell Surface ◽

Protein Binding ◽

Cancer Diagnostics ◽

Cell Surface Receptor ◽

Surface Receptor ◽

Diagnostics And Therapy

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Role of Asparagine-Linked Glycosylation in Cell Surface Expression and Function of the Human Adrenocorticotropin Receptor (Melanocortin 2 Receptor) in 293/FRT Cells

Endocrinology ◽

10.1210/en.2009-0826 ◽

2010 ◽

Vol 151 (2) ◽

pp. 660-670 ◽

Cited By ~ 27

Author(s):

Simon Roy ◽

Benoît Perron ◽

Nicole Gallo-Payet

Keyword(s):

Cell Surface ◽

Fold Increase ◽

Surface Expression ◽

Site Directed Mutagenesis ◽

Cell Surface Receptor ◽

Cell Surface Expression ◽

Camp Production ◽

Glycosylation Sites ◽

Surface Receptor

Asparagine-linked glycosylation (N-glycosylation) of G protein-coupled receptors may be necessary for functions ranging from agonist binding, folding, maturation, stability, and internalization. Human melanocortin 2 receptor (MC2R) possesses putative N-glycosylation sites in its N-terminal extracellular domain; however, to date, the role of MC2R N-glycosylation has yet to be investigated. The objective of the present study is to examine whether N-glycosylation is essential or not for cell surface expression and cAMP production in native and MC2R accessory protein (MRAPα, -β, or -dCT)-expressing cells using 293/FRT transfected with Myc-MC2R. Western blot analyses performed with or without endoglycosidase H, peptide:N-glycosidase F or tunicamycin treatments and site-directed mutagenesis revealed that MC2R was glycosylated in the N-terminal domain at its two putative N-glycosylation sites (Asn12-Asn13-Thr14 and Asn17-Asn18-Ser19). In the absence of human MRAP coexpression, N-glycosylation of at least one of the two sites was necessary for MC2R cell surface expression. However, when MRAP was present, cell surface expression of MC2R mutants was either rescued entirely with the N17-18Q (QQNN) and N12-13Q (NNQQ) mutants or partially with the unglycosylated N12-13, 17-18Q (QQQQ) mutant. Functional and expression analyses revealed a discrepancy between wild-type (WT) and QQQQ cell surface receptor levels and maximal cAMP production with a 4-fold increase in EC50 values. Taken together, these results indicate that the absence of MC2R N-glycosylation abrogates to a large extent MC2R cell surface expression in the absence of MRAPs, whereas when MC2R is N-glycosylated, it can be expressed at the plasma membrane without MRAP assistance.

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Heterogeneity in VEGF Receptor-2 mobility and organization on the endothelial cell surface leads to diverse activation models by VEGF

10.1101/800946 ◽

2019 ◽

Author(s):

Bruno da Rocha-Azevedo ◽

Sungsoo Lee ◽

Aparajita Dasgupta ◽

Anthony R. Vega ◽

Luciana R. de Oliveira ◽

...

Keyword(s):

Cell Surface ◽

Single Molecule ◽

Receptor Activation ◽

Cell Surface Receptor ◽

Vegf Receptor ◽

Surface Receptors ◽

Endothelial Cell Surface ◽

Heterogeneous Nature ◽

Surface Receptor ◽

Complex Relationships

SummaryThe nanoscale organization of cell surface receptors plays an important role in signaling. We determined this organization and its relation to receptor activation for VEGF Receptor-2 (VEGFR-2), a critical receptor tyrosine kinase in endothelial cells (ECs), by combining live-cell single-molecule imaging of endogenous VEGFR-2 with rigorous computational analysis. We found that surface VEGFR-2 can be mobile or immobile/confined, and monomeric or non-monomeric, with a complex interplay between the two. The mobility and interaction heterogeneity of VEGFR-2 in the basal state led to heterogeneity in the sequence of steps leading to VEGFR-2 activation by VEGF. Specifically, we found that VEGF can bind to both monomeric and non-monomeric VEGFR-2, and, when binding to monomeric VEGFR-2, promotes dimer formation but only for immobile/confined receptors. Overall, our study highlights the dynamic and heterogeneous nature of cell surface receptor organization and its complex relationships with receptor activation and signaling.

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Lyn controls chemotaxis and motility of CLL cells via phosphorylation of ROR1

10.1101/2020.05.29.124156 ◽

2020 ◽

Author(s):

Zankruti Dave ◽

Olga Vondálová Blanářová ◽

Štěpán Čada ◽

Pavlína Janovská ◽

Nikodém Zezula ◽

...

Keyword(s):

Cell Surface ◽

Cell Receptor ◽

Kinase Domain ◽

Lymphocytic Leukemia ◽

Cell Surface Receptor ◽

Surface Dynamics ◽

Lyn Kinase ◽

Mantle Cell ◽

Surface Receptor

AbstractChronic lymphocytic leukemia (CLL) and mantle cell lymphoma (MCL) are malignancies characterized by the dependence on B-cell receptor (BCR) signaling and by the high expression of the cell surface receptor ROR1. Both, BCR and ROR1 are therapeutic targets in these diseases and the understanding of their mutual cross talk is thus of direct therapeutic relevance. In this study we analyzed the role of Lyn, a kinase from the Src family, as a mediator of the BCR-ROR1 crosstalk. We confirm the functional interaction between Lyn and ROR1 and demonstrate that Lyn kinase efficiently phosphorylates ROR1 in its kinase domain and aids the recruitment of an E3 ligase c-CBL. The absence of Lyn in Lyn KO Maver-1 cells produced by CRISPR-Cas9 resulted in the increased ROR1 cell surface levels and deregulated migratory properties. Similar correlations between ROR1 surface dynamics, levels of active Lyn and chemotactic properties were confirmed in primary CLL samples. Our data establish Lyn-mediated phosphorylation of ROR1 as a point of crosstalk between BCR and ROR1 signaling pathways.

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