scholarly journals DSL ligand endocytosis physically dissociates Notch1 heterodimers before activating proteolysis can occur

2007 ◽  
Vol 176 (4) ◽  
pp. 445-458 ◽  
Author(s):  
James T. Nichols ◽  
Alison Miyamoto ◽  
Samantha L. Olsen ◽  
Brendan D'Souza ◽  
Christine Yao ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Cell Surface ◽  
Ligand Binding ◽  
Extracellular Domain ◽  
Intramolecular Interactions ◽  
Mechanical Forces ◽  
Mature Cell ◽  
Intracellular Domain ◽  
Notch Activation ◽  
Transduction Current

Cleavage of Notch by furin is required to generate a mature, cell surface heterodimeric receptor that can be proteolytically activated to release its intracellular domain, which functions in signal transduction. Current models propose that ligand binding to heterodimeric Notch (hNotch) induces a disintegrin and metalloprotease (ADAM) proteolytic release of the Notch extracellular domain (NECD), which is subsequently shed and/or endocytosed by DSL ligand cells. We provide evidence for NECD release and internalization by DSL ligand cells, which, surprisingly, did not require ADAM activity. However, losses in either hNotch formation or ligand endocytosis significantly decreased NECD transfer to DSL ligand cells, as well as signaling in Notch cells. Because endocytosis-defective ligands bind hNotch, but do not dissociate it, additional forces beyond those produced through ligand binding must function to disrupt the intramolecular interactions that keep hNotch intact and inactive. Based on our findings, we propose that mechanical forces generated during DSL ligand endocytosis function to physically dissociate hNotch, and that dissociation is a necessary step in Notch activation.

Contributions of extracellular and intracellular domains of full length and chimeric cadherin molecules to junction assembly in epithelial cells

1998 ◽  
Vol 111 (9) ◽  
pp. 1305-1318 ◽  
Author(s):  
S.M. Norvell ◽  
K.J. Green
Keyword(s):  
Epithelial Cells ◽  
Cell Surface ◽  
Extracellular Domain ◽  
Full Length ◽  
Intracellular Domain ◽  
Epithelial Junctions ◽  
Intracellular Domains ◽  
E Cadherin ◽  
Cell Cell

The integrity of cell-cell junctions in epithelial cells depends on functional interactions of both extracellular and intracellular domains of cadherins with other junction proteins. To examine the roles of the different domains of E-cadherin and desmoglein in epithelial junctions, we stably expressed full length desmoglein 1 and chimeras of E-cadherin and desmoglein 1 in A431 epithelial cells. Full length desmoglein 1 was able to incorporate into or disrupt endogenous desmosomes depending on expression level. Each of the chimeric cadherin molecules exhibited distinct localization patterns at the cell surface. A chimera of the desmoglein 1 extracellular domain and the E-cadherin intracellular domain was distributed diffusely at the cell surface while the reverse chimera, comprising the E-cadherin extracellular domain and the desmoglein 1 intracellular domain, localized in large, sometimes contiguous patches at cell-cell interfaces. Nevertheless, both constructs disrupted desmosome assembly. Expression of constructs containing the desmoglein 1 cytoplasmic domain resulted in approximately a 3-fold decrease in E-cadherin bound to plakoglobin and a 5- to 10-fold reduction in the steady-state levels of the endogenous desmosomal cadherins, desmoglein 2 and desmocollin 2, possibly contributing to the dominant negative effect of the desmoglein 1 tail. In addition, biochemical analysis of protein complexes in the stable lines revealed novel in vivo protein interactions. Complexes containing beta-catenin and desmoglein 1 were identified in cells expressing constructs containing the desmoglein 1 tail. Furthermore, interactions were identified between endogenous E-cadherin and the chimera containing the E-cadherin extracellular domain and the desmoglein 1 intracellular domain providing in vivo evidence for previously predicted lateral interactions of E-cadherin extracellular domains.

scholarly journals Fibronectin type III and intracellular domains of Toll-like receptor 4 interactor with leucine-rich repeats (Tril) are required for developmental signaling

2017 ◽  
Author(s):  
Hyung-Seok Kim ◽  
Autumn McKnite ◽  
Yuanyuan Xie ◽  
Jan L. Christian
Keyword(s):  
Embryonic Development ◽  
Cell Surface ◽  
Extracellular Domain ◽  
Toll Like Receptor ◽  
Toll Like Receptor 4 ◽  
Intracellular Domain ◽  
Fibronectin Type Iii ◽  
Leucine Rich Repeats ◽  
Fibronectin Type

AbstractToll-like receptor 4 interactor with leucine-rich repeats (Tril) is a transmembrane protein that functions as a coreceptor for Toll-like receptors (Tlrs) to mediate innate immune responses in the adult brain. Tril also triggers degradation of the Bmp inhibitor, Smad7, during early embryonic development to allow for normal blood formation. Tril most likely plays additional, yet to be discovered, roles during embryogenesis. In the current studies, we performed a structure-function analysis, which indicated that the extracellular domain, including the fibronectin type III (FN) domain, and the intracellular domain of Tril are required to trigger Smad7 degradation in the early Xenopus embryo. Furthermore, we found that a Tril deletion mutant lacking the FN domain (TrilΔFN) can dominantly inhibit signaling by endogenous Tril when overexpressed in vivo. This finding raises the intriguing possibility that the FN domain functions to bind endogenous Tril/Tlr4 ligands, perhaps including extracellular matrix molecules. We also show that Tril normally cycles between the cell surface and endosomes, and that the Tril extracellular domain is required to retain Tril at the cell surface, while the intracellular domain is required for Tril internalization in Xenopus ectodermal explants. Using a CHO cell aggregation assay, we further show that, unlike other transmembrane proteins that contain leucine rich repeats in the extracellular domain, Tril is not sufficient to mediate homophilic adhesion. Our findings identify TrilΔFN as a valuable tool that can be used to block the function of endogenous Tril in vivo in order to discover additional roles during embryonic development.

Mutations in the WSAWSE and cytosolic domains of the erythropoietin receptor affect signal transduction and ligand binding and internalization

1992 ◽  
Vol 12 (10) ◽  
pp. 4553-4561
Author(s):  
D E Quelle ◽  
F W Quelle ◽  
D M Wojchowski
Keyword(s):  
Signal Transduction ◽  
Cell Surface ◽  
Ligand Binding ◽  
Erythropoietin Receptor ◽  
Cell Surface Receptor ◽  
Erythroid Progenitor ◽  
Epo Receptor ◽  
Cytosolic Domain ◽  
Cytosolic Domains ◽  
Surface Receptor

The terminal development of erythroid progenitor cells is promoted in part through the interaction of erythropoietin (EPO) with its cell surface receptor. This receptor and a growing family of related cytokine receptors share homologous extracellular features, including a well-conserved WSXWS motif. To explore the functional significance of this motif in the murine EPO receptor, five WSAWSE mutants were prepared and their signal-transducing, ligand binding, and endocytotic properties were compared. EPO receptors mutated at tryptophan residues (W-232, W-235----G; W-235----G; W-235----F) failed to mediate EPO-induced growth or pp100 phosphorylation, while S-236----T and E-237----K mutants exhibited partial to full activity (50 to 100% of wild-type growth and induced phosphorylation). Ligand affinity was reduced for mutant receptors (two- to fivefold), yet expression at the cell surface for all receptors was nearly equivalent. Also, the ability of mutated receptors to internalize ligand was either markedly reduced or abolished (W-235----F), indicating a role for the WSAWSE region in hormone internalization. Interestingly, receptor forms lacking 97% of the cytosolic domain (no signal-transducing capacity; binding affinity reduced two- to threefold) internalized EPO efficiently. This and all WSAWSE receptor forms studied also mediated specific cross-linking of 125I-EPO to three accessory membrane proteins (M(r)s, 120,000, 105,000, and 93,000). These findings suggest that the WSAWSE domain of the EPO receptor is important for EPO-induced signal transduction and ligand internalization. In contrast, although the cytosolic domain is required for growth signaling, it appears nonessential for efficient endocytosis.

scholarly journals Mutations in the WSAWSE and cytosolic domains of the erythropoietin receptor affect signal transduction and ligand binding and internalization.

1992 ◽  
Vol 12 (10) ◽  
pp. 4553-4561 ◽  
Author(s):  
D E Quelle ◽  
F W Quelle ◽  
D M Wojchowski
Keyword(s):  
Signal Transduction ◽  
Cell Surface ◽  
Ligand Binding ◽  
Erythropoietin Receptor ◽  
Cell Surface Receptor ◽  
Erythroid Progenitor ◽  
Epo Receptor ◽  
Cytosolic Domain ◽  
Cytosolic Domains ◽  
Surface Receptor

The terminal development of erythroid progenitor cells is promoted in part through the interaction of erythropoietin (EPO) with its cell surface receptor. This receptor and a growing family of related cytokine receptors share homologous extracellular features, including a well-conserved WSXWS motif. To explore the functional significance of this motif in the murine EPO receptor, five WSAWSE mutants were prepared and their signal-transducing, ligand binding, and endocytotic properties were compared. EPO receptors mutated at tryptophan residues (W-232, W-235----G; W-235----G; W-235----F) failed to mediate EPO-induced growth or pp100 phosphorylation, while S-236----T and E-237----K mutants exhibited partial to full activity (50 to 100% of wild-type growth and induced phosphorylation). Ligand affinity was reduced for mutant receptors (two- to fivefold), yet expression at the cell surface for all receptors was nearly equivalent. Also, the ability of mutated receptors to internalize ligand was either markedly reduced or abolished (W-235----F), indicating a role for the WSAWSE region in hormone internalization. Interestingly, receptor forms lacking 97% of the cytosolic domain (no signal-transducing capacity; binding affinity reduced two- to threefold) internalized EPO efficiently. This and all WSAWSE receptor forms studied also mediated specific cross-linking of 125I-EPO to three accessory membrane proteins (M(r)s, 120,000, 105,000, and 93,000). These findings suggest that the WSAWSE domain of the EPO receptor is important for EPO-induced signal transduction and ligand internalization. In contrast, although the cytosolic domain is required for growth signaling, it appears nonessential for efficient endocytosis.

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