Mcl-1 Is Essential for the Survival of Synovial Fibroblasts in Rheumatoid Arthritis

Liu, Hongtao; Eksarko, Polikseni; Temkin, Vladislav; Haines, G. Kenneth; Perlman, Harris; Koch, Alisa E.; Thimmapaya, Bayar; Pope, Richard M.

doi:10.4049/jimmunol.175.12.8337

Cited by 82 publications

(70 citation statements)

References 57 publications

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“…The primary human macrophages used in this study were differentiated in vitro for 7 days from monocytes, which were purified by elutriation from the PB of healthy donors, as previously described (32)(33)(34)(35)(36)(37). Purified monocytes were suspended in medium without fetal bovine serum (FBS) and allowed to adhere to cell culture dishes for 1 hour.…”

Section: Methodsmentioning

confidence: 99%

“…Purified monocytes were suspended in medium without fetal bovine serum (FBS) and allowed to adhere to cell culture dishes for 1 hour. Afterward, medium was changed to RPMI 1640 supplemented with 20% FBS, 100 units penicillin, 100 g/ml streptomycin, and 1 g/ml polymyxin B. Adherent cells were allowed to differentiate into normal control macrophages, as previously described (32)(33)(34)(35)(36)(37).…”

Section: Methodsmentioning

confidence: 99%

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Increased macrophage activation mediated through toll‐like receptors in rheumatoid arthritis

Huang

Adebayo

et al. 2007

Arthritis & Rheumatism

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170

157

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Increased macrophage activation mediated through toll‐like receptors in rheumatoid arthritis

Huang

Adebayo

et al. 2007

Arthritis & Rheumatism

Self Cite

170

157

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“…The purified peripheral monocytes were suspended in serum-free RPMI 1640 medium, and allowed to adhere to cell culture dishes at 37°C in 5% CO 2 for 1 h before change to medium containing 20% fetal bovine serum (FBS), 100 g/ml penicillin, 50 g/ml streptomycin, and 1 g/ml of polymyxin B. The adherent cells were allowed to differentiate into macrophages in culture for up to 7 days as described previously (27)(28)(29)(30)(31)(32)(33).…”

Section: Methodsmentioning

confidence: 99%

Role of H2-calponin in Regulating Macrophage Motility and Phagocytosis

Huang

Hossain

et al. 2008

Journal of Biological Chemistry

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108

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The actin cytoskeleton plays a major role in cell motility that is essential for the function of phagocytes. Calponin is an actinassociated regulatory protein. Here we report the finding of significant levels of the h2 isoform of calponin in peripheral blood cells of myeloid lineage. To study the functional significance, h2-calponin gene (Cnn2) interrupted mice were constructed. Germ line transmission of the Cnn2-flox-neo allele was obtained in chimeras from two independent clones of targeted embryonic stem cells. The insertion of the neo R cassette into intron 2 of the Cnn2 gene resulted in a significant knockdown of h2-calponin expression. Removing the frt-flanked neo R cassette by FLP1 recombinase rescued the knockdown effect. Cre recombinaseinduced deletion of the loxP-flanked exon 2 eliminated the expression of h2-calponin protein. H2-calponin-free mice showed reduced numbers of peripheral blood neutrophils and monocytes. H2-calponin-free macrophages demonstrated a higher rate of proliferation and faster migration than that of h2-calponin-positive cells, consistent with a faster diapedesis of peripheral monocytes and neutrophils. H2-calponin-free macrophages showed reduced spreading in adhesion culture together with decreased tropomyosin in the actin cytoskeleton. The lack of h2-calponin also significantly increased macrophage phagocytotic activity, suggesting a novel mechanism to regulate phagocyte functions.Leukocytes are mobile cells and their actin cytoskeleton plays a central role in the locomotion, transmigration, and phagocytosis. These activities are essential for the function of myeloid cells, including neutrophils, monocytes, and macrophages, in defensive and autoimmune responses (1). Despite the significant biological and medical importance, the regulation of actin cytoskeleton in myeloid cells is not well understood.Calponin is an actin filament-associated protein of 34 -37 kDa (292-330 amino acids) found in smooth muscle (2) as well as non-muscle cells (3,4). Through high affinity binding to F-actin, calponin inhibits the actin-activated myosin MgATPase (5-8) and motor activity (9 -11). The association of calponin with actin filaments and its regulatory function have led to a model wherein calponin may represent a thin filament regulatory mechanism modulating smooth muscle contraction (12).Three isoforms of calponin (h1, h2, and acidic) have been identified in higher vertebrates as the products of three homologous genes (13-17). The three isoforms of calponin have distinct theoretical isoelectric points (pI values): H1-calponin is basic (pI 9.4), h2-calponin is near neutral (pI 7.5), whereas the acidic calponin has a lower pI of 5.2. H1-calponin is the predominant isoform specifically expressed in differentiated smooth muscle cells and its role in regulating smooth muscle contractility (9) is a focus of ongoing research. The majority of previous structural and functional studies of calponin were obtained from chicken gizzard calponin that is equivalent to the mammalian h1-calponin. The acidic c...

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“…The apoptotic profile was determined by flow cytometry utilizing a Beckman-Coulter EpicsXL flow cytometer and system 2 software, as described (27,31,32). The hypodiploid DNA peak (Ͻ2 N DNA) immediately adjacent to the G 0 /G 1 peak (2 N DNA) represented apoptotic cells and was quantified by histogram analyses.…”

Section: Methodsmentioning

confidence: 99%

“…The amplification program was: 50°C for 2 min, 95°C for 10 min, followed by 40 cycles of 95°C for 15 s, and 60°C for 1 min. Quantitative values were derived from the threshold cycle number (C t ) (11,32). The experiments were normalized to glyceraldehyde-3-phosphate dehydrogenase.…”

Section: Methodsmentioning

confidence: 99%

Activation-induced Degradation of FLIPL Is Mediated via the Phosphatidylinositol 3-Kinase/Akt Signaling Pathway in Macrophages

Shi

Tran

Sobkoviak

et al. 2009

Journal of Biological Chemistry

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Cellular FLIP (Flice-like inhibitory protein) negatively modulates the caspase 8-dependent apoptotic cascade triggered by the activation of death receptors, such as the tumor necrosis factor (TNF) 2 receptor-1 and Fas (1-3). Although the flip gene is expressed as multiple splice variants in many tissues (1, 4), it produces two major isoforms at the protein level, FLIP long (FLIP L ) and FLIP short (FLIP S ). Both isoforms contain two death effector domains in the N terminus that allow for interaction with the adapter molecule Fas-associated death domain. FLIP L , the more abundantly expressed isoform in most cell types, additionally contains an nonfunctional caspase activation-like domain in its C terminus (1). The increased expression of FLIP renders tumor cells and macrophages from the joints of patients with rheumatoid arthritis resistant to death receptor and chemotherapeutic drug-mediated apoptosis (5-8), whereas the level of FLIP correlates with tumor progression and patient outcomes (9).To date, the transcriptional and post-transcription regulation of FLIP has not been fully elucidated. NF-B strongly upregulates the expression of FLIP L and FLIP S (10), and TNF␣ and LPS, which activate NF-B, are known to induce FLIP (11,12). Additionally, Akt has been implicated in the induction of FLIP (13-16). Post-transcriptionally, FLIP L and FLIP S are regulated by ubiquitin-proteasome pathway (17-20). As reported recently (21), the TNF␣-accelerated FLIP L turnover in mouse hepatocytes and mouse embryonic fibroblasts was mediated through JNK activation that occurs when NF-B activation is suppressed. The JNK-mediated phosphorylation of E3 ubiquitin ligase Itch results in the ubiquitination and degradation of FLIP L . However, the role of TNF␣ in the post-transcriptional regulation of FLIP in the absence of NF-B inhibition or the prolonged activation of JNK is not known.The dysregulation of macrophage function contributes to the pathogenesis of rheumatoid arthritis, inflammatory bowel disease, atherosclerosis, and chronic obstructive pulmonary disease (22)(23)(24)(25)(26). Our prior observations demonstrate that FLIP is critical for the protection of macrophages against death receptor-mediated apoptosis in rheumatoid arthritis (8, 27); however, knowledge of the mechanisms that regulate FLIP in macrophages is incomplete. While characterizing the expression of FLIP in macrophages, in contrast to expectations, we noticed that activation with TNF␣ or LPS actually reduced the protein levels of FLIP L , but not FLIP S , at 1 and 2 h, even though the mRNA of both isoforms was increased. The activation-induced reduction of FLIP L resulted in the increased activation of caspase 8, which promoted the activation of NF-B and the expression of FLIP mRNA. Our observations also demonstrate that the PI3K/Akt-1 (Akt) pathway mediates the activationinduced reduction of FLIP L by the phosphorylation of FLIP L at serine 273. These observations identify a novel pathway regulating the decision for life and death of the macrophage following ...

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Mcl-1 Is Essential for the Survival of Synovial Fibroblasts in Rheumatoid Arthritis

Cited by 82 publications

References 57 publications

Increased macrophage activation mediated through toll‐like receptors in rheumatoid arthritis

Increased macrophage activation mediated through toll‐like receptors in rheumatoid arthritis

Role of H2-calponin in Regulating Macrophage Motility and Phagocytosis

Activation-induced Degradation of FLIPL Is Mediated via the Phosphatidylinositol 3-Kinase/Akt Signaling Pathway in Macrophages

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