scholarly journals The primacy of affinity over clustering in regulation of adhesiveness of the integrin αLβ2

2004 ◽  
Vol 167 (6) ◽  
pp. 1241-1253 ◽  
Author(s):  
Minsoo Kim ◽  
Christopher V. Carman ◽  
Wei Yang ◽  
Azucena Salas ◽  
Timothy A. Springer
Keyword(s):  
Cell Adhesion ◽  
Ligand Binding ◽  
Immune Cell ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Intercellular Adhesion Molecule ◽  
Intercellular Adhesion Molecule 1 ◽  
Dynamic Regulation ◽  
Affinity Modulation ◽  
Leukocyte Function

Dynamic regulation of integrin adhesiveness is required for immune cell–cell interactions and leukocyte migration. Here, we investigate the relationship between cell adhesion and integrin microclustering as measured by fluorescence resonance energy transfer, and macroclustering as measured by high resolution fluorescence microscopy. Stimuli that activate adhesion through leukocyte function–associated molecule-1 (LFA-1) failed to alter clustering of LFA-1 in the absence of ligand. Binding of monomeric intercellular adhesion molecule-1 (ICAM-1) induced profound changes in the conformation of LFA-1 but did not alter clustering, whereas binding of ICAM-1 oligomers induced significant microclustering. Increased diffusivity in the membrane by cytoskeleton-disrupting agents was sufficient to drive adhesion in the absence of affinity modulation and was associated with a greater accumulation of LFA-1 to the zone of adhesion, but redistribution did not precede cell adhesion. Disruption of conformational communication within the extracellular domain of LFA-1 blocked adhesion stimulated by affinity-modulating agents, but not adhesion stimulated by cytoskeleton-disrupting agents. Thus, LFA-1 clustering does not precede ligand binding, and instead functions in adhesion strengthening after binding to multivalent ligands.

scholarly journals Patterns for RANTES Secretion and Intercellular Adhesion Molecule 1 Expression Mediate Transepithelial T Cell Traffic Based on Analyses In Vitro and In Vivo

1998 ◽  
Vol 187 (12) ◽  
pp. 1927-1940 ◽  
Author(s):  
Masahiko Taguchi ◽  
Deepak Sampath ◽  
Takeharu Koga ◽  
Mario Castro ◽  
Dwight C. Look ◽  
...  
Keyword(s):  
T Cells ◽  
Cell Adhesion ◽  
T Cell ◽  
Cell Surface ◽  
Immune Cell ◽  
Intercellular Adhesion Molecule ◽  
Airway Epithelial ◽  
Intercellular Adhesion Molecule 1 ◽  
Ifn Γ

Immune cell migration into and through mucosal barrier sites in general and airway sites in particular is a critical feature of immune and inflammatory responses, but the determinants of transepithelial (unlike transendothelial) immune cell traffic are poorly defined. Accordingly, we used primary culture airway epithelial cells and peripheral blood mononuclear cells to develop a cell monolayer system that allows for apical-to-basal and basal-to-apical T cell transmigration that can be monitored with quantitative immunofluorescence flow cytometry. In this system, T cell adhesion and subsequent transmigration were blocked in both directions by monoclonal antibodies (mAbs) against lymphocyte function-associated antigen 1 (LFA-1) or intercellular adhesion molecule 1 (ICAM-1) (induced by interferon γ [IFN-γ] treatment of epithelial cells). The total number of adherent plus transmigrated T cells was also similar in both directions, and this pattern fit with uniform presentation of ICAM-1 along the apical and basolateral cell surfaces. However, the relative number of transmigrated to adherent T cells (i.e., the efficiency of transmigration) was increased in the basal-to-apical relative to the apical-to-basal direction, so an additional mechanism was needed to mediate directional movement towards the apical surface. Screening for epithelial-derived β-chemokines indicated that IFN-γ treatment caused selective expression of RANTES (regulated upon activation, normal T cell expressed and secreted), and the functional significance of this finding was demonstrated by inhibition of epithelial–T cell adhesion and transepithelial migration by anti-RANTES mAbs. In addition, we found that epithelial (but not endothelial) cells preferentially secreted RANTES through the apical cell surface thereby establishing a chemical gradient for chemotaxis across the epithelium to a site where they may be retained by high levels of RANTES and apical ICAM-1. These patterns for epithelial presentation of ICAM-1 and secretion of RANTES appear preserved in airway epithelial tissue studied either ex vivo with expression induced by IFN-γ treatment or in vivo with endogenous expression induced by inflammatory disease (i.e., asthma). Taken together, the results define how the patterns for uniform presentation of ICAM-1 along the cell surface and specific apical sorting of RANTES may serve to mediate the level and directionality of T cell traffic through epithelium (distinct from endothelium) and provide a basis for how this process is precisely coordinated to route immune cells to the mucosal surface and maintain them there under normal and stimulated conditions.

Dynamic Regulation of Src by Csk in Integrin α IIb β 3 Mediated Signalling.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 2661-2661
Author(s):  
Martin Vielreicher ◽  
Ralf Steinmeyer ◽  
Gregory Harms ◽  
Ulrich Walter ◽  
Achim Obergfell
Keyword(s):  
Cell Adhesion ◽  
Tyrosine Kinases ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Src Family Kinases ◽  
Dynamic Regulation ◽  
Fibrinogen Binding ◽  
Normal Hemostasis ◽  
Rapid Activation ◽  
Adhesion Process

Abstract When platelets adhere to fibrinogen, they undergo profound actin rearragements and spreading. These responses require signals triggered by aIIbb3, a process known as outside-in signalling. Although aIIbb3 signaling is required for normal hemostasis, its molecular basis is incompletely understood. Recently we demonstrated by coimmunoprecipitation techniques that several Src family kinases are constitutively associated with aIIbb3 in platelets. Fibrinogen binding to aIIbb3 leads to rapid activation of Src and recruitement and activation of the Syk tyrosine kinase. Theses interactions are significant because murine platelets defiecient in multiple Src kinases or Syk fail to spread on fibrinogen. One of the earliest events upon binding of fibrinogen to the receptor is the assembly of a multimolecular protein complex inculding the tyrosine kinases Src and Syk. Phosphorylation of Src at Tyrosine 418 leads to Src activation, phosphorylation of Tyrosine 529 to inactivation. The inactivation of Src is mediated by Csk. Previous studies have shown that in resting platelets Csk forms a complex with integrin α IIb β3 and Src. After fibrinogen binding Csk leaves this complex. The aim of this study is to elucidate the dynamics of Src inactivation and the interaction with Csk in this process by using Fluorescence Resonance Energy Transfer (FRET). A5 CHO cells stably expressing integrin α IIb β3 were transfected with Csk-YFP and various Src mutatnts in a GFP vector. After cell adhesion on fibrinogen, a strong FRET signal could be observed at the edges of nascent lamellipodia of the spreading cell. The FRET signal was dynamic since it was transported in waves inside the cell within seconds. After completion of the adhesion process a weak FRET signal remained visible inside the cell. A different pattern could be observed when cells were transfected with Csk and the active Src mutant Y529F. The observed FRET signal was much weaker and less dynamic after cells were allowed to spread on fibrinogen suggesting that the muation of Tyrosine 529 to Phenylalanine inhibited Csk binding and inactivation of Src. This was not due to a spreading defect since the cells appeared to spread on fibrinogen normally. The use of the inactive Src mutant K295R revealed a FRET signal comparable to WT Src. These studies suggest that Src inactivation is dynamically regulated within seconds after cell adhesion on fibrinogen and that Tyrosine 529 is required for the interaction of Csk with Src in this process.

Permissive transmembrane helix heterodimerization is required for the expression of a functional integrin

2008 ◽  
Vol 410 (3) ◽  
pp. 495-502 ◽  
Author(s):  
Ardcharaporn Vararattanavech ◽  
Man-Li Tang ◽  
Hoi-Yeung Li ◽  
Chi-Hang Wong ◽  
S. K. Alex Law ◽  
...  
Keyword(s):  
Transmembrane Helix ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Protein S ◽  
Intercellular Adhesion Molecule ◽  
State Transitions ◽  
Transmembrane Helices ◽  
Intercellular Adhesion Molecule 1 ◽  
Cytoplasmic Tails ◽  
Β2 Integrins

The current paradigm is that integrin is activated via inside-out signalling when its cytoplasmic tails and TMs (transmembrane helices) are separated by specific cytosolic protein(s). Perturbations of the helical interface between the α- and β-TMs of an integrin, as a result of mutations, affect its function. Previous studies have shown the requirement for specific pairing between integrin subunits by ectodomain-exchange analyses. It remains unknown whether permissive α/β-TM pairing of an integrin is also required for pairing specificity and the expression of a functionally regulated receptor. We performed scanning replacement of integrin β2-TM with a TM of other integrin β-subunits. With the exception of β4 substitution, others presented β2-integrins with modified phenotypes, either in their expression or ligand-binding properties. Subsequently, we adopted αLβ2 for follow-on experiments because its conformation and affinity-state transitions have been well defined as compared with other members of the β2-integrins. Replacement of β2- with β3-TM generated a chimaeric αLβ2 of an intermediate affinity that adhered to ICAM-1 (intercellular adhesion molecule 1) but not to ICAM-3 constitutively. Replacing αL-TM with αIIb-TM, forming a natural αIIb/β3-TM pair, reversed the phenotype of the chimaera to that of wild-type αLβ2. Interestingly, the replacement of αLβ2- with β3-TM showed neither an extended conformation nor the separation of its cytoplasmic tails, which are well-reported hallmarks of an activated αLβ2, as determined by reporter mAb (monoclonal antibody) KIM127 reactivity and FRET (fluorescence resonance energy transfer) measurements respectively. Collectively, our results suggest that TM pairing specificity is required for the expression of a functionally regulated integrin.

Local Delivery of Ibuprofen via Controlled-release Polymers Prevents Angiographic Vasospasm in a Monkey Model of Subarachnoid Hemorrhage

2005 ◽  
Vol 57 (suppl_1) ◽  
pp. 184-190 ◽  
Author(s):  
Gustavo Pradilla ◽  
Quoc-Anh Thai ◽  
Federico G. Legnani ◽  
Richard E. Clatterbuck ◽  
Philippe Gailloud ◽  
...  
Keyword(s):  
Cell Adhesion ◽  
Subarachnoid Hemorrhage ◽  
Controlled Release ◽  
Adhesion Molecule ◽  
Subarachnoid Space ◽  
Intercellular Adhesion Molecule ◽  
Intercellular Adhesion Molecule 1 ◽  
Cynomolgus Monkeys ◽  
Monkey Model ◽  
Angiographic Vasospasm

Abstract OBJECTIVE: Adhesion and migration of leukocytes into the periadventitial space play a role in the pathophysiology of vasospasm after subarachnoid hemorrhage (SAH). Intercellular adhesion molecule-1 is a determinant cell adhesion molecule involved in this process. Ibuprofen has been shown to inhibit intercellular adhesion molecule-1 upregulation and prevent vasospasm in animal models of SAH. In this study, we report the toxicity and efficacy of locally delivered ibuprofen incorporated into controlled-release polymers to prevent vasospasm in a monkey model of SAH. METHODS: Ibuprofen was incorporated into ethylene-vinyl acetate (EVAc) polymers at 45% loading (wt:wt). For the toxicity study, cynomolgus monkeys (n = 5) underwent surgical implantation of either blank/EVAc polymers (n = 3) or 45% ibuprofen/EVAc polymers (n = 2) in the subarachnoid space, were followed up for 13 weeks, and were killed for histopathological analysis. For the efficacy study, cynomolgus monkeys (n = 14) underwent cerebral angiography 7 days before and 7 days after surgery and SAH and were randomized to receive either a 45% ibuprofen/EVAc polymer (n = 7; mean dose of ibuprofen, 6 mg/kg) or blank EVAc polymers (n = 7) in the subarachnoid space. Angiographic vasospasm was determined by digital image analysis. Student's t test was used for analysis. RESULTS: Animals implanted with ibuprofen polymers showed no signs of local or systemic toxicity. Animals treated with ibuprofen polymers had 91 ± 9% lumen patency of the middle cerebral artery, compared with 53 ± 11% of animals treated with blank/EVAc polymers (P < 0.001). CONCLUSION: Ibuprofen polymers are safe and prevent angiographic vasospasm after SAH in the monkey model. These findings support the role of cell adhesion molecules and inflammation in the pathophysiology of vasospasm.

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