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Type XVII collagen regulates lamellipod stability, cell motility, and signaling to Rac1 by targeting bullous pemphigoid antigen 1e to alpha6beta4 integrin.

ABSTRACT: Rac1 activity, polarity, lamellipodial dynamics, and directed motility are defective in keratinocytes exhibiting deficiency in ?4 integrin or knockdown of the plakin protein Bullous Pemphigoid Antigen 1e (BPAG1e). The activity of Rac, formation of stable lamellipodia, and directed migration are restored in ?4 integrin-deficient cells by inducing expression of a truncated form of ?4 integrin, which lacks binding sites for BPAG1e and plectin. In these same cells, BPAG1e, the truncated ?4 integrin, and type XVII collagen (Col XVII), a transmembrane BPAG1e-binding protein, but not plectin, colocalize along the substratum-attached surface. This finding suggested to us that Col XVII mediates the association of BPAG1e and ?6?4 integrin containing the truncated ?4 subunit and supports directed migration. To test these possibilities, we knocked down Col XVII expression in keratinocytes expressing both full-length and truncated ?4 integrin proteins. Col XVII-knockdown keratinocytes exhibit a loss in BPAG1e-?6?4 integrin interaction, a reduction in lamellipodial stability, an impairment in directional motility, and a decrease in Rac1 activity. These defects are rescued by a mutant Col XVII protein truncated at its carboxyl terminus. In summary, our results suggest that in motile cells Col XVII recruits BPAG1e to ?6?4 integrin and is necessary for activation of signaling pathways, motile behavior, and lamellipodial stability.

SUBMITTER: Hamill KJ

PROVIDER: S-EPMC3143638 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature

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Type XVII collagen regulates lamellipod stability, cell motility, and signaling to Rac1 by targeting bullous pemphigoid antigen 1e to alpha6beta4 integrin.

Hamill Kevin J KJ Hopkinson Susan B SB Jonkman Marcel F MF Jones Jonathan C R JC

The Journal of biological chemistry 20110603 30

Rac1 activity, polarity, lamellipodial dynamics, and directed motility are defective in keratinocytes exhibiting deficiency in β4 integrin or knockdown of the plakin protein Bullous Pemphigoid Antigen 1e (BPAG1e). The activity of Rac, formation of stable lamellipodia, and directed migration are restored in β4 integrin-deficient cells by inducing expression of a truncated form of β4 integrin, which lacks binding sites for BPAG1e and plectin. In these same cells, BPAG1e, the truncated β4 integrin, ...[more]

PMID: 21642434

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Project description:Bullous pemphigoid (BP), the most common autoimmune blistering disease, is induced by autoantibodies to type XVII collagen (COL17). Previous studies demonstrated that COL17 harbors several epitopes targeted by autoreactive T and B cells and that the target epitopes change sequentially during the disease course. To elucidate the details of the humoral immune response to COL17, we used an active BP mouse model in which BP is induced by the adoptive transfer of spleen cells from wild-type mice immunized with human COL17-expressing skin grafting to immunodeficient COL17-humanized (Rag-2-/-, mouse Col17-/-, human COL17+) mice. By immunoblot analysis, antibodies to the NC16A domain and other extracellular domains (ECDs) of COL17 were detected earlier than antibodies to intracellular domains (ICDs) in the active BP model. Time course analysis by enzyme-linked immunosorbent assay demonstrated a delayed peak of antibodies to ICD epitopes in active BP model. The blockade of CD40-CD40 ligand interaction soon after the adoptive transfer suppressed the production of antibodies to the non-collagenous 16A (NC16A) domain but not to an ICD epitope, suggesting the sequential activation from T and B cells against the ECD epitopes including the NC16A domain to those against ICD epitopes in vivo. Both wild-type mice immunized with a fragment of the NC16A domain and the recipients of those spleen cells produced IgG antibodies to ICD and ECD epitopes, showing intramolecular epitope spreading from the NC16A domain to other epitopes of COL17. Furthermore, we found that a portion of the active BP model mice show intermolecular epitope spreading from human COL17 to murine BP230. The appearance of antibodies to ICD epitopes of COL17 or of antibodies to murine BP230 did not correlate with the skin changes in the mice, suggesting that those antibodies have low pathogenicity. These results suggest that the immune response to the ECD epitopes of COL17, especially to the NC16A domain, triggers intramolecular, and intermolecular epitope spreading to ICD epitopes of COL17 and to murine BP230. These novel findings provide insight into the mechanism of epitope spreading in organ-specific, antibody-mediated autoimmune disorders.

Project description:BackgroundBullous pemphigoid (BP) is the most common autoimmune blistering disease in the West. Oral steroids are the standard treatment.This is an update of the review published in 2005.ObjectivesTo assess treatments for bullous pemphigoid.Search strategyIn August 2010 we updated our searches of the Cochrane Skin Group Specialised Register, the Cochrane Central Register of Controlled Trials (Clinical Trials), MEDLINE, EMBASE, and the Ongoing Trials registers.Selection criteriaRandomised controlled trials of treatments for participants with immunofluorescence-confirmed bullous pemphigoid.Data collection and analysisAt least two authors evaluated the studies for the inclusion criteria, and extracted data independently.Main resultsWe included 10 randomised controlled trials (with a total of 1049 participants) of moderate to high risk of bias. All studies involved different comparisons, none had a placebo group. In 1 trial plasma exchange plus prednisone gave significantly better disease control at 1 month (0.3 mg/kg: RR 18.78, 95% CI 1.20 to 293.70) than prednisone alone (1.0 mg/kg: RR 1.79, 95% CI 1.11 to 2.90), while another trial showed no difference in disease control at 6 months.No differences in disease control were seen for different doses or formulations of prednisolone (one trial each), for azathioprine plus prednisone compared with prednisone alone (one trial), for prednisolone plus azathioprine compared with prednisolone plus plasma exchange (one trial), for prednisolone plus mycophenolate mofetil or plus azathioprine (one trial), for tetracycline plus nicotinamide compared with prednisolone (one trial). Chinese traditional medicine plus prednisone was not effective in one trial.There were no significant differences in healing in a comparison of a standard regimen of topical steroids (clobetasol) with a milder regimen (RR 1.00, 95% 0.97 to 1.03) in one trial. In another trial, clobetasol showed significantly more disease control than oral prednisolone in people with extensive and moderate disease (RR 1.09, 95% CI 1.02 to 1.17), with significantly reduced mortality and adverse events (RR 1.06, 95% CI 1.00 to 1.12).Authors' conclusionsVery potent topical steroids are effective and safe treatments for BP, but their use in extensive disease may be limited by side-effects and practical factors. Milder regimens (using lower doses of steroids) are safe and effective in moderate BP. Starting doses of prednisolone greater than 0.75 mg/kg/day do not give additional benefit, lower doses may be adequate to control disease and reduce the incidence and severity of adverse reactions. The effectiveness of adding plasma exchange, azathioprine or mycophenolate mofetil to corticosteroids, and combination treatment with tetracycline and nicotinamide needs further investigation.

Project description:Bullous pemphigoid (BP) is a rare autoimmune skin blistering disease, characterized by the presence of autoantibodies against hemidesmosomal autoantigens. Cytokine expression is altered in BP patients, and several of these differently expressed cytokines, including IL-1α, IL-1β, IL-8, and TNF-α, contribute to disease pathogenesis. Since genetic polymorphisms in the genes of these cytokines might be implicated in susceptibility to BP disease, we aimed at testing this implication in susceptibility to BP in an Iranian cohort. Blood samples were collected from the subjects and genomic DNA was extracted. To detect the single nucleotide polymorphisms (SNPs), IL-1α (rs1800587), IL-1β (rs1143627, rs16944, rs1143634), IL-8 (rs4073), and TNF-α (rs1799964, rs1800630, rs1799724, and rs361525) genes were genotyped in BP patients and healthy controls as well as IL-8 (rs4073) in pemphigus vulgaris (PV) patients. Quantitative gene expression was evaluated by RT-PCR analysis. A significant difference was observed in the distribution of genotypes or alleles of IL-8 SNP between the BP patients and controls. The A-allele of IL-8 SNP is significantly more prevalent in the control individuals compared to the BP patient. To further validate this observation, we included PV patients as an additional control. Again, the A-allele of IL-8 SNP is significantly more prevalent in the PV compared to the BP patients. While we observed a trend toward significant differences regarding alleles of TNF-α rs1799724 as well as alleles of TNF-α rs1799964, this difference was, however, not evident after correction for multiple analysis. There was no significant difference in all other studied SNPs. In contrast to IL-1α, IL-1β, and TNF-α, IL-8 gene expression levels were significantly higher in the patients than that of controls. The minor allele in IL-8 SNP might play a protective role in susceptibility to BP in Iranian patients. Although higher expression levels of IL-8 gene was found in the patients compared with healthy controls, these levels, however, suggest no association with the examined polymorphism. Moreover, further investigation revealed an elevation in gene expression between wild and polymorphic genotypes of IL-1α rs1800587 and TNF-α rs361525 in the patient group and these SNPs are therefore associated with altering the levels of gene expression.

Project description:Bullous pemphigoid antigen 180 (BP180) is a component of hemidesmosomes, i.e., cell-substrate adhesion complexes. To determine the function of specific sequences of BP180 to its incorporation in hemidesmosomes, we have transfected 804G cells with cDNA-constructs encoding wild-type and deletion mutant forms of human BP180. The results show that the cytoplasmic domain of BP180 contains sufficient information for the recruitment of the protein into hemidesmosomes because removal of the extracellular and transmembrane domains does not abolish targeting. Expression of chimeric proteins, which consist of the membrane targeting sequence of K-Ras fused to the cytoplasmic domain of BP180 with increasing internal deletions or lacking the NH2 terminus, indicates that the localization of BP180 in hemidesmosomes is mediated by a segment that spans 265 amino acids. This segment comprises two important regions located within the central part and at the NH2 terminus of the cytoplasmic domain of BP180. To investigate the effect of the alpha6beta4 integrin on the subcellular distribution of BP180, we have transfected COS-7 cells, which lack alpha6beta4 and BP180, with cDNAs for BP180 as well as for human alpha6A and beta4. We provide evidence that a mutant form of BP180 lacking the collagenous extracellular domain as well as a chimeric protein, which contains the entire cytoplasmic domain of BP180, are colocalized with alpha6beta4. In contrast, when cells were transfected with cDNAs for alpha6A and mutant forms of beta4, either lacking the cytoplasmic COOH-terminal half or carrying phenylalanine substitutions in the tyrosine activation motif of the cytoplasmic domain, the recombinant BP180 molecules were mostly not colocalized with alpha6beta4, but remained diffusely distributed at the cell surface. Moreover, in cells transfected with cDNAs for alpha6A and a beta4/beta1 chimera, in which the cytoplasmic domain of beta4 was replaced by that of the beta1 integrin subunit, BP180 was not colocalized with the alpha6beta4/beta1 chimera in focal adhesions, but remained again diffusely distributed. These results indicate that sequences within the cytoplasmic domain of beta4 determine the subcellular distribution of BP180.

Dataset Information

Type XVII collagen regulates lamellipod stability, cell motility, and signaling to Rac1 by targeting bullous pemphigoid antigen 1e to alpha6beta4 integrin.

Publications

Type XVII collagen regulates lamellipod stability, cell motility, and signaling to Rac1 by targeting bullous pemphigoid antigen 1e to alpha6beta4 integrin.

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