Immune Complex-induced Integrin Activation and L-plastin Phosphorylation Require Protein Kinase A

Wang, Jun; Brown, Eric J.

doi:10.1074/jbc.274.34.24349

Cited by 54 publications

(72 citation statements)

References 51 publications

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“…It has previously been shown that Lpl is involved in the regulation of ␤2 integrin avidity and integrinmediated neutrophil adhesion (38). Consistent with a modulation of Lpl-associated leukocyte functions, ALP exhibited, beyond its effect on actin bundling, a marked suppressive effect on the conformational change of LFA-1 into its activated state upon stimulation with IgG-coated latex beads, as evidenced by fluorescenceactivated cell sorting staining with a conformationdependent LFA-1-specific mAb (26).…”

Section: Discussionmentioning

confidence: 71%

Antileukoproteinase: Modulation of neutrophil function and therapeutic effects on anti–type II collagen antibody–induced arthritis

Sehnert¹,

Cavcic²,

Böhm³

et al. 2004

Arthritis & Rheumatism

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Objective. Antileukoproteinase (ALP) is a physiologic inhibitor of granulocytic serine proteases. The present study was undertaken to investigate its therapeutic benefit in an antibody-transfer model of erosive polyarthritis and to elucidate its potential to interfere with immune complex-dependent inflammatory pathways.Methods. Arthritis development was induced in male (BALB/c ؋ B10.Q)F 1 mice by intravenous injection of two monoclonal antibodies specific for type II collagen and was quantified by clinical scoring and histopathology. Arthritis severity was assessed in a cohort of mice under systemic treatment with recombinant human ALP (daily doses of 0.1 mg for 5 days starting immediately after disease induction) in comparison with untreated controls. Concomitantly, functional assays (phagocytosis, oxidative burst, fluorescence-activated cell sorting analysis of integrin expression) were performed on neutrophils upon in vitro stimulation by IgG-coated latex beads.Results. ALP treatment reduced arthritis incidence and severity and had a protective effect against cartilage and bone erosion. ALP inhibited the conversion of the leukocyte ␤2 integrins into an active conformation upon Fc receptor stimulation of granulocytes. ALP bound to the actin-bundling protein L-plastin and down-modulated filamentous actin assembly in response to stimulation with IgG-coated latex beads in granulocytes. ALP exerted additional inhibitory effects on neutrophil functions associated with cytoskeletal reorganization, such as phagocytosis and oxidative burst.Conclusion. In addition to its antiprotease activity, ALP exerts a variety of blocking effects on neutrophil functions, probably due to modulation of cytoskeletal changes, that may contribute to this inhibitor's antiarthritis potential and qualify it as a multifunctional regulator of inflammatory responses.Antileukoproteinase (ALP), also named secretory leukocyte protease inhibitor for its presence in epithelial secretions and its ability to inhibit neutrophil serine protease, is a highly basic, acid-stable polypeptide. It comprises two mutually homologous highly disulfidebonded domains connected by a short linker (1). ALP circulates in blood, and experimental evidence indicates its physiologic expression by a variety of mucosal epithelial cells, by neutrophils (2), and by murine, but not human, macrophages (3). However, its low molecular weight (11 kd) and its cationic nature (pI Ͼ10) predispose ALP to leaving the circulation for specific accumulation in tissues, especially in cartilage (4,5).In addition to its antiproteolytic properties, ALP has been shown to exert a variety of antiinflammatory actions on macrophages and neutrophils (e.g., the suppression of lipopolysaccharide [LPS]-induced prostaglandin E 2 and matrix metalloproteinase production or

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Section: Discussionmentioning

confidence: 71%

Antileukoproteinase: Modulation of neutrophil function and therapeutic effects on anti–type II collagen antibody–induced arthritis

Sehnert¹,

Cavcic²,

Böhm³

et al. 2004

Arthritis & Rheumatism

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“…We next undertook a pharmacological approach to determine the signaling pathways that regulate L-plastin phosphorylation. L-plastin phosphorylation at Ser 5 was originally reported as being catalyzed via protein kinase A after FcgRIIA stimulation of neutrophils (29). We determined that pretreating T lymphocytes with H-89, an inhibitor of protein kinase A signaling, had no effect on SDF-1a-mediated L-plastin phosphorylation (Fig.…”

Section: Resultsmentioning

confidence: 81%

L-Plastin Regulates Polarization and Migration in Chemokine-Stimulated Human T Lymphocytes

Freeley

O’Dowd

Paul

et al. 2012

The Journal of Immunology

105

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Chemokines such as SDF-1α play a crucial role in orchestrating T lymphocyte polarity and migration via polymerization and reorganization of the F-actin cytoskeleton, but the role of actin-associated proteins in this process is not well characterized. In this study, we have investigated a role for L-plastin, a leukocyte-specific F-actin–bundling protein, in SDF-1α–stimulated human T lymphocyte polarization and migration. We found that L-plastin colocalized with F-actin at the leading edge of SDF-1α–stimulated T lymphocytes and was also phosphorylated at Ser5, a site that when phosphorylated regulates the ability of L-plastin to bundle F-actin. L-plastin phosphorylation was sensitive to pharmacological inhibitors of protein kinase C (PKC), and several PKC isoforms colocalized with L-plastin at the leading edge of SDF-1α–stimulated lymphocytes. However, PKC ζ, an established regulator of cell polarity, was the only isoform that regulated L-plastin phosphorylation. Knockdown of L-plastin expression with small interfering RNAs demonstrated that this protein regulated the localization of F-actin at the leading edge of chemokine-stimulated cells and was also required for polarization, lamellipodia formation, and chemotaxis. Knockdown of L-plastin expression also impaired the Rac1 activation cycle and Akt phosphorylation in response to SDF-1α stimulation. Furthermore, L-plastin also regulated SDF-1α–mediated lymphocyte migration on the integrin ligand ICAM-1 by influencing velocity and persistence, but in a manner that was independent of LFA-1 integrin activation or adhesion. This study, therefore, demonstrates an important role for L-plastin and the signaling pathways that regulate its phosphorylation in response to chemokines and adds L-plastin to a growing list of proteins implicated in T lymphocyte polarity and migration.

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“…1A). We replaced Ser5, its major phosphorylation site that is located in its regulatory headpiece domain (Lin et al, 1998;Shinomiya et al, 1995;Wang and Brown, 1999), with Ala (Lplastin Ser5Ala) or Glu (L-plastin Ser5Glu) to inactivate this site or to mimic constitutive phosphorylation, respectively. Although negatively charged residues and the phosphate group are chemically not identical, it is well documented that this approach can yield valuable information on the biological role of protein phosphorylation (Clarke et al, 2004;Gautreau et al, 2000;Huttelmaier et al, 1999).…”

Section: Resultsmentioning

confidence: 99%

“…L-plastin is phosphorylated on residues Ser5 and Ser7 in hematopoietic cells in vivo, but most likely on Ser5 exclusively in non-hematopoietic cells (Lin et al, 1998;Messier et al, 1993;Shinomiya et al, 1995). Whereas in vivo and in vitro phosphorylation of Ser5 by cAMP-dependent protein kinase A (PKA) is well documented (Lin et al, 1998;Wang and Brown, 1999), there is still controversy over which kinase(s) phosphorylate(s) Ser7.…”

Section: L-plastin a Malignant Transformation-associated Protein Ismentioning

confidence: 99%

Phosphorylation on Ser5 increases the F-actin-binding activity of L-plastin and promotes its targeting to sites of actin assembly in cells

Janji

Giganti

Corte

et al. 2006

Journal of Cell Science

157

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L-plastin, a malignant transformation-associated protein, is a member of a large family of actin filament cross-linkers. Here, we analysed how phosphorylation of L-plastin on Ser5 of the headpiece domain regulates its intracellular distribution and its interaction with F-actin in transfected cells and in in vitro assays. Phosphorylated wild-type L-plastin localised to the actin cytoskeleton in transfected Vero cells. Ser5Ala substitution reduced the capacity of L-plastin to localise with peripheral actin-rich membrane protrusions. Conversely, a Ser5Glu variant mimicking a constitutively phosphorylated state, accumulated in actin-rich regions and promoted the formation of F-actin microspikes in two cell lines. Similar to phosphorylated wild-type L-plastin, this variant remained associated with cellular F-actin in detergent-treated cells, whereas the Ser5Ala variant was almost completely extracted. When compared with non-phosphorylated protein, phosphorylated L-plastin and the Ser5Glu variant bound F-actin more efficiently in an in vitro assay. Importantly, expression of L-plastin elicited collagen invasion in HEK293T cells, in a manner dependent on Ser5 phosphorylation. Based on our findings, we propose that conversely to other calponin homology (CH)-domain family members, phosphorylation of L-plastin switches the protein from a low-activity to a high-activity state. Phosphorylated L-plastin might act as an integrator of signals controlling the assembly of the actin cytoskeleton and cell motility in a 3D-space.

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Immune Complex-induced Integrin Activation and L-plastin Phosphorylation Require Protein Kinase A

Cited by 54 publications

References 51 publications

Antileukoproteinase: Modulation of neutrophil function and therapeutic effects on anti–type II collagen antibody–induced arthritis

Antileukoproteinase: Modulation of neutrophil function and therapeutic effects on anti–type II collagen antibody–induced arthritis

L-Plastin Regulates Polarization and Migration in Chemokine-Stimulated Human T Lymphocytes

Phosphorylation on Ser5 increases the F-actin-binding activity of L-plastin and promotes its targeting to sites of actin assembly in cells

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