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Matrix valency regulates integrin-mediated lymphoid adhesion via Syk kinase.

Stupack DG, Li E, Silletti SA, Kehler JA, Geahlen RL, Hahn K, Nemerow GR, Cheresh DA - J. Cell Biol. (1999)

Bottom Line: Nonactivated lymphoid cells attach preferentially to polymerized ECM proteins yet are unable to attach to monomeric forms or fragments of these proteins without previous activation.Adhesion of nonactivated lymphoid cells to polymeric ECM components results in activation of the antigen receptor-associated Syk kinase that accumulates in adhesion-promoting podosomes.In fact, activation of Syk by antigen or agonists, as well as expression of an activated Syk mutant in lymphoid cells, facilitates their adhesion to monomeric ECM proteins or their fragments.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA.

ABSTRACT
Lymphocytes accumulate within the extracellular matrix (ECM) of tumor, wound, or inflammatory tissues. These tissues are largely comprised of polymerized adhesion proteins such as fibrin and fibronectin or their fragments. Nonactivated lymphoid cells attach preferentially to polymerized ECM proteins yet are unable to attach to monomeric forms or fragments of these proteins without previous activation. This adhesion event depends on the appropriate spacing of integrin adhesion sites. Adhesion of nonactivated lymphoid cells to polymeric ECM components results in activation of the antigen receptor-associated Syk kinase that accumulates in adhesion-promoting podosomes. In fact, activation of Syk by antigen or agonists, as well as expression of an activated Syk mutant in lymphoid cells, facilitates their adhesion to monomeric ECM proteins or their fragments. These results reveal a cooperative interaction between signals emanating from integrins and antigen receptors that can serve to regulate stable lymphoid cell adhesion and retention within a remodeling ECM.

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Inhibition of LCL binding by piceatannol. Increasing  concentration of LY294002 or piceatannol were incubated with  LCL for 15 min. Cells were then assessed for adhesion as described above. LY294002 caused visible decreases in LCL  spreading at concentrations as low as 2.5 μM (asterisk), and inhibited PI(3)K activity, (inset), but did not block attachment at  concentrations below 100 μM. The derived IC50 for piceatannol  inhibition of adhesion was ∼5 μM. Inhibition of Syk (> 90%),  but not the related src family kinase Lyn (18 ± 11%) was assessed by autokinase activity (inset).
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Figure 7: Inhibition of LCL binding by piceatannol. Increasing concentration of LY294002 or piceatannol were incubated with LCL for 15 min. Cells were then assessed for adhesion as described above. LY294002 caused visible decreases in LCL spreading at concentrations as low as 2.5 μM (asterisk), and inhibited PI(3)K activity, (inset), but did not block attachment at concentrations below 100 μM. The derived IC50 for piceatannol inhibition of adhesion was ∼5 μM. Inhibition of Syk (> 90%), but not the related src family kinase Lyn (18 ± 11%) was assessed by autokinase activity (inset).

Mentions: As an initial approach to testing whether Syk was involved in regulating adhesion to the ECM, LCL were allowed to bind to PB in the presence of either pharmacological inhibitors known to inhibit Syk (piceatannol) or PI(3)K (LY294002 and wortmannin). Adhesion of the LCL to PB was blocked by piceatannol (IC50 ∼5 mM), but was only slightly impacted by the PI(3)K inhibitor LY294002 (Fig. 7). Although LY294002 treated cells attached, they exhibited reduced PI(3)K activity (Fig. 7, inset), failed to spread (data not shown), and were more susceptible to shear force during washing, resulting in an apparent slight inhibition of adhesion. Similar results were obtained with an alternative inhibitor of PI(3)K, wortmannin (increasing effect from 70–80 nM, data not shown). Although selective for the kinase Syk, piceatannol has pleiotropic effects on cells, including the blockade of src family kinases at increased concentrations. However, no significant inhibition of the related src family kinase Lyn (the major src kinase in LCL) was found in these studies at the concentrations of piceatannol used (Fig. 7, inset).


Matrix valency regulates integrin-mediated lymphoid adhesion via Syk kinase.

Stupack DG, Li E, Silletti SA, Kehler JA, Geahlen RL, Hahn K, Nemerow GR, Cheresh DA - J. Cell Biol. (1999)

Inhibition of LCL binding by piceatannol. Increasing  concentration of LY294002 or piceatannol were incubated with  LCL for 15 min. Cells were then assessed for adhesion as described above. LY294002 caused visible decreases in LCL  spreading at concentrations as low as 2.5 μM (asterisk), and inhibited PI(3)K activity, (inset), but did not block attachment at  concentrations below 100 μM. The derived IC50 for piceatannol  inhibition of adhesion was ∼5 μM. Inhibition of Syk (> 90%),  but not the related src family kinase Lyn (18 ± 11%) was assessed by autokinase activity (inset).
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Related In: Results  -  Collection

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Figure 7: Inhibition of LCL binding by piceatannol. Increasing concentration of LY294002 or piceatannol were incubated with LCL for 15 min. Cells were then assessed for adhesion as described above. LY294002 caused visible decreases in LCL spreading at concentrations as low as 2.5 μM (asterisk), and inhibited PI(3)K activity, (inset), but did not block attachment at concentrations below 100 μM. The derived IC50 for piceatannol inhibition of adhesion was ∼5 μM. Inhibition of Syk (> 90%), but not the related src family kinase Lyn (18 ± 11%) was assessed by autokinase activity (inset).
Mentions: As an initial approach to testing whether Syk was involved in regulating adhesion to the ECM, LCL were allowed to bind to PB in the presence of either pharmacological inhibitors known to inhibit Syk (piceatannol) or PI(3)K (LY294002 and wortmannin). Adhesion of the LCL to PB was blocked by piceatannol (IC50 ∼5 mM), but was only slightly impacted by the PI(3)K inhibitor LY294002 (Fig. 7). Although LY294002 treated cells attached, they exhibited reduced PI(3)K activity (Fig. 7, inset), failed to spread (data not shown), and were more susceptible to shear force during washing, resulting in an apparent slight inhibition of adhesion. Similar results were obtained with an alternative inhibitor of PI(3)K, wortmannin (increasing effect from 70–80 nM, data not shown). Although selective for the kinase Syk, piceatannol has pleiotropic effects on cells, including the blockade of src family kinases at increased concentrations. However, no significant inhibition of the related src family kinase Lyn (the major src kinase in LCL) was found in these studies at the concentrations of piceatannol used (Fig. 7, inset).

Bottom Line: Nonactivated lymphoid cells attach preferentially to polymerized ECM proteins yet are unable to attach to monomeric forms or fragments of these proteins without previous activation.Adhesion of nonactivated lymphoid cells to polymeric ECM components results in activation of the antigen receptor-associated Syk kinase that accumulates in adhesion-promoting podosomes.In fact, activation of Syk by antigen or agonists, as well as expression of an activated Syk mutant in lymphoid cells, facilitates their adhesion to monomeric ECM proteins or their fragments.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA.

ABSTRACT
Lymphocytes accumulate within the extracellular matrix (ECM) of tumor, wound, or inflammatory tissues. These tissues are largely comprised of polymerized adhesion proteins such as fibrin and fibronectin or their fragments. Nonactivated lymphoid cells attach preferentially to polymerized ECM proteins yet are unable to attach to monomeric forms or fragments of these proteins without previous activation. This adhesion event depends on the appropriate spacing of integrin adhesion sites. Adhesion of nonactivated lymphoid cells to polymeric ECM components results in activation of the antigen receptor-associated Syk kinase that accumulates in adhesion-promoting podosomes. In fact, activation of Syk by antigen or agonists, as well as expression of an activated Syk mutant in lymphoid cells, facilitates their adhesion to monomeric ECM proteins or their fragments. These results reveal a cooperative interaction between signals emanating from integrins and antigen receptors that can serve to regulate stable lymphoid cell adhesion and retention within a remodeling ECM.

Show MeSH
Related in: MedlinePlus