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- Khan, Omar M., 1980, et al.
(författare)
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Geranylgeranyltransferase type I (GGTase-I) deficiency hyperactivates macrophages and induces erosive arthritis in mice.
- 2011
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Ingår i: The Journal of clinical investigation. - 1558-8238. ; 121:2, s. 628-39
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Tidskriftsartikel (refereegranskat)abstract
- RHO family proteins are important for the function of inflammatory cells. They are modified with a 20-carbon geranylgeranyl lipid in a process catalyzed by protein geranylgeranyltransferase type I (GGTase-I). Geranylgeranylation is viewed as essential for the membrane targeting and activity of RHO proteins. Consequently, inhibiting GGTase-I to interfere with RHO protein activity has been proposed as a strategy to treat inflammatory disorders. However, here we show that mice lacking GGTase-I in macrophages develop severe joint inflammation resembling erosive rheumatoid arthritis. The disease was initiated by the GGTase-I-deficient macrophages and was transplantable and reversible in bone marrow transplantation experiments. The cells accumulated high levels of active GTP-bound RAC1, CDC42, and RHOA, and RAC1 remained associated with the plasma membrane. Moreover, GGTase-I deficiency activated p38 and NF-κB and increased the production of proinflammatory cytokines. The results challenge the view that geranylgeranylation is essential for the activity and localization of RHO family proteins and suggest that reduced geranylgeranylation in macrophages can initiate erosive arthritis.
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| 2. |
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| 3. |
- Ibrahim, Mohamed X, et al.
(författare)
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Genetic Analyses of the CAAX Protein Prenyltransferases in Mice
- 2011
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Ingår i: The Enzymes. - 1874-6047. ; 29, s. 259-274
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The RAS and RHO family proteins, the nuclear lamins, and other socalled CAAX proteins undergo three sequential posttranslational processing steps: prenylation, endoproteolysis, and carboxyl methylation. These steps are mediated by four different enzymes: farnesyltransferase (FTase) or geranylgeranyltransferase type I (GGTase-I), RAS converting enzyme 1 (RCE1), and isoprenylcysteine carboxyl methyltransferase (ICMT). Over the past 20 years, there has been an intense interest in understanding the biological significance of CAAX protein processing and its impact on CAAX protein stability, membrane targeting, protein–protein interactions, signaling, and function. Perhaps, the greatest interest has stemmed from the efforts of targeting the CAAX protein prenyltransferases FTase and GGTase-I as a strategy to interfere with the activity of disease-causing mutants of CAAX proteins such as RAS and prelamin A in the treatment of cancer and progeroid disorders. Mice with targeted conditional knockout alleles for FTase and GGTase-I have been used to shed light on those topics. Here, we review the genetic studies that have provided new information on the biochemical and medical importance of CAAX protein prenylation.
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| 4. |
- Khan, Omar M., 1980
(författare)
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Defining the Role of GGTase-I in the Development of Rheumatoid Arthritis and Atherosclerosis
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- RHO family proteins control cell movement and intracellular signaling by cycling between active GTP-bound and inactive GDP-bound states. Aberrant signaling of RHO GTPases has been implicated in many diseases including cancer and inflammation. Geranylgeranyltransferase type I (GGTase-I) attaches a 20-carbon geranylgeranyl lipid to a carboxyl-terminal CAAX motif of most RHO family proteins. Geranylgeranylation is viewed as essential for membrane targeting and activation of RHO proteins. Consequently, inhibiting GGTase-I to interfere with RHO protein lipidation and activity has been proposed as a strategy to treat cancer and inflammatory disorders. Moreover, statins – widely prescribed cholesterol-lowering drugs – possess anti-inflammatory properties that are independent of their cholesterol-lowering effects. These pleiotropic statin effects are thought to be mediated by reduced synthesis of geranylgeranyl lipids and reduced geranylgeranylation and inhibition of RHO family proteins. Despite the therapeutic interest in GGTase-I, no studies have yet defined the impact of inactivating GGTase-I in mouse models of inflammation using genetic strategies. Paper I of this thesis shows that mice lacking GGTase-I in macrophages develop joint inflammation and bone erosions similar to rheumatoid arthritis. The disease was initiated by GGTase-I-deficient macrophages which accumulated high levels of GTPbound RAC1, CDC42, and RHOA, and RAC1 remained associated with the plasma membrane. Moreover, GGTase-I deficiency led to robust activation of p38 MAPK and NF-κB, and increased production of proinflammatory cytokines. This effect was caused by non-geranylgeranylated GTP-bound RAC1. Thus, rather than being an anti-inflammatory drug target, GGTase-I protects mice from inflammation and arthritis development. In Paper II, we tested if GGTase-I deficiency in macrophages would affect the development of atherosclerosis in LDL receptor–deficient mice. We hypothesized that aortic lesions would be enhanced due to local and systemic inflammation and the presence of rheumatoid arthritis – a disease that carries a high risk of atherosclerosis development in humans. Contrary to our expectations, GGTase-I deficiency markedly reduced atherosclerosis development. Cellular analyses revealed impaired foam cell formation due to high levels of cholesterol efflux. Molecular analyses revealed increased COX2 and PPARγ activity and expression of the scavenger receptors CD36 and SR-B1. The pathway was triggered by RHOA which accumulated in the active GTP-bound state in the GGTase-I-deficient macrophages. This thesis challenges the current dogma that geranylgeranylation is essential for RHO protein activation and suggest that this posttranslational modification may actually inhibit RHO protein function. The thesis also sheds new light on the role of RHO family proteins in macrophage inflammatory signaling and cholesterol homeostasis and mechanisms underlying pleiotropic statin effects.
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| 5. |
- Khan, Omar M., 1980, et al.
(författare)
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Targeting GGTase-I Activates RHOA, Increases Macrophage Reverse Cholesterol Transport, and Reduces Atherosclerosis in Mice
- 2013
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Ingår i: Circulation. - : Ovid Technologies (Wolters Kluwer Health). - 0009-7322 .- 1524-4539. ; 127:7, s. 782-790
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Tidskriftsartikel (refereegranskat)abstract
- Background-Statins have antiinflammatory and antiatherogenic effects that have been attributed to inhibition of RHO protein geranylgeranylation in inflammatory cells. The activity of protein geranylgeranyltransferase type I (GGTase-I) is widely believed to promote membrane association and activation of RHO family proteins. However, we recently showed that knockout of GGTase-I in macrophages activates RHO proteins and proinflammatory signaling pathways, leading to increased cytokine production and rheumatoid arthritis. In this study, we asked whether the increased inflammatory signaling of GGTase-I-deficient macrophages would influence the development of atherosclerosis in low-density lipoprotein receptor-deficient mice. Methods and Results-Aortic lesions in mice lacking GGTase-I in macrophages (Pggt1b Delta/Delta) contained significantly more T lymphocytes than the lesions in controls. Surprisingly, however, mean atherosclerotic lesion area in Pggt1b Delta/Delta mice was reduced by approximate to 60%. GGTase-I deficiency reduced the accumulation of cholesterol esters and phospholipids in macrophages incubated with minimally modified and acetylated low-density lipoprotein. Analyses of GGTase-I-deficient macrophages revealed upregulation of the cyclooxygenase 2-peroxisome proliferator-activated-gamma pathway and increased scavenger receptor class B type I-and CD36-mediated basal and high-density lipoprotein-stimulated cholesterol efflux. Lentivirus-mediated knockdown of RHOA, but not RAC1 or CDC42, normalized cholesterol efflux. The increased cholesterol efflux in cultured cells was accompanied by high levels of macrophage reverse cholesterol transport and slightly reduced plasma lipid levels in vivo. Conclusions-Targeting GGTase-I activates RHOA and leads to increased macrophage reverse cholesterol transport and reduced atherosclerosis development despite a significant increase in inflammation
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| 6. |
- Sayin, Volkan I., 1983, et al.
(författare)
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Loss of One Copy of Zfp148 Reduces Lesional Macrophage Proliferation and Atherosclerosis in Mice by Activating p53
- 2014
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Ingår i: Circulation Research. - : Ovid Technologies (Wolters Kluwer Health). - 0009-7330 .- 1524-4571. ; 115:9, s. 781-791
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Tidskriftsartikel (refereegranskat)abstract
- Rationale: Cell proliferation and cell cycle control mechanisms are thought to play central roles in the pathogenesis of atherosclerosis. The transcription factor Zinc finger protein 148 (Zfp148) was shown recently to maintain cell proliferation under oxidative conditions by suppressing p53, a checkpoint protein that arrests proliferation in response to various stressors. It is established that inactivation of p53 accelerates atherosclerosis, but whether increased p53 activation confers protection against the disease remains to be determined. Objective: We aimed to test the hypothesis that Zfp148 deficiency reduces atherosclerosis by unleashing p53 activity. Methods and Results: Mice harboring a gene-trap mutation in the Zfp148 locus (Zfp148(gt/+)) were bred onto the apolipoprotein E (Apoe)(-/-) genetic background and fed a high-fat or chow diet. Loss of 1 copy of Zfp148 markedly reduced atherosclerosis without affecting lipid metabolism. Bone marrow transplantation experiments revealed that the effector cell is of hematopoietic origin. Peritoneal macrophages and atherosclerotic lesions from Zfp148(gt/+)Apoe(-/-) mice showed increased levels of phosphorylated p53 compared with controls, and atherosclerotic lesions contained fewer proliferating macrophages. Zfp148(gt/+) Apoe(-/-) mice were further crossed with p53-null mice (Trp53(-/-) [the gene encoding p53]). There was no difference in atherosclerosis between Zfp148(gt/+) Apoe(-/-) mice and controls on a Trp53(+/-) genetic background, and there was no difference in levels of phosphorylated p53 or cell proliferation. Conclusions: Zfp148 deficiency increases p53 activity and protects against atherosclerosis by causing proliferation arrest of lesional macrophages, suggesting that drugs targeting macrophage proliferation may be useful in the treatment of atherosclerosis.
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