| 1. |
- Akula, Murali K, et al.
(author)
-
Protein prenylation restrains innate immunity by inhibiting Rac1 effector interactions
- 2019
-
In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 10:1
-
Journal article (peer-reviewed)abstract
- Rho family proteins are prenylated by geranylgeranyltransferase type I (GGTase-I), which normally target proteins to membranes for GTP-loading. However, conditional deletion of GGIase-I in mouse macrophages increases GTP-loading of Rho proteins, leading to enhanced inflammatory responses and severe rheumatoid arthritis. Here we show that heterozygous deletion of the Rho family gene Rac1, but not Rhoa and Cdc42, reverses inflammation and arthritis in GGTase-I-deficient mice. Non-prenylated Rac1 has a high affinity for the adaptor protein Ras GTPase-activating-like protein 1 (Iqgap1), which facilitates both GTP exchange and ubiquitination-mediated degradation of Rac1. Consistently, inactivating lagapl normalizes Rac1 GTP-loading, and reduces inflammation and arthritis in GGTase-I-deficient mice, as well as prevents statins from increasing Rac1 GTP-loading and cytokine production in macrophages. We conclude that blocking prenylation stimulates Rac1 effector interactions and unleashes proinflammatory signaling. Our results thus suggest that prenylation normally restrains innate immune responses by preventing Rac1 effector interactions.
|
|
| 2. |
- Cutts, Briony, 1976, et al.
(author)
-
Nf1 deficiency cooperates with oncogenic K-RAS to induce acute myeloid leukemia in mice.
- 2009
-
In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 114:17, s. 3629-32
-
Journal article (peer-reviewed)abstract
- Hyperactive RAS signaling is caused by mutations in RAS genes or a deficiency of the neurofibromatosis gene (NF1) and is common in myeloid malignancies. In mice, expression of oncogenic K-RAS or inactivation of Nf1 in hematopoietic cells results in myeloproliferative disorders (MPDs) that do not progress to acute myeloid leukemia (AML). Because NF1 is a RAS-GTPase-activating protein it has been proposed that NF1 deficiency is functionally equivalent to an oncogenic RAS. It is not clear, however, whether Nf1 deficiency would be redundant in K-RAS-induced MPD development or whether the 2 mutations would cooperate in leukemogenesis. Here, we show that the simultaneous inactivation of Nf1 and expression of K-RAS(G12D) in mouse hematopoietic cells results in AML that was fatal in primary mice within 4 weeks and transplantable to sublethally irradiated secondary recipients. The data point to a strong cooperation between Nf1 deficiency and oncogenic K-RAS.
|
|
| 3. |
- Dalin, Martin, 1982, et al.
(author)
-
Myocardial KRASG12D expression does not cause cardiomyopathy in mice
- 2014
-
In: Cardiovascular Research. - : Oxford University Press (OUP). - 0008-6363 .- 1755-3245. ; 101:2, s. 229-235
-
Journal article (peer-reviewed)abstract
- AimsGerm-line mutations in genes encoding components of the RAS/mitogen-activated protein kinase (MAPK) pathway cause developmental disorders called RASopathies. Hypertrophic cardiomyopathy (HCM) is the most common myocardial pathology and a leading cause of death in RASopathy patients. KRAS mutations are found in Noonan and cardio-facio-cutaneous syndromes. KRAS mutations, unlike mutations of RAF1 and HRAS, are rarely associated with HCM. This has been attributed to the fact that germ-line KRAS mutations cause only a moderate up-regulation of the MAPK pathway. Highly bioactive KRAS mutations have been hypothesized to cause severe cardiomyopathy incompatible with life. The aim of this study was to define the impact of KRASG12D expression in the heart.Methods and resultsTo generate mice with endogenous cardiomyocyte-specific KRASG12D expression (cKRASG12D mice), we bred mice with a Cre-inducible allele expressing KRASG12D from its endogenous promoter (Kras2LSL) to mice expressing Cre under control of the cardiomyocyte-specific α-myosin heavy chain promoter (αMHC-Cre). cKRASG12D mice showed high levels of myocardial ERK and AKT signalling. However, surprisingly, cKRASG12D mice were born in Mendelian ratios, appeared healthy, and had normal function, size, and histology of the heart.ConclusionMice with cardiomyocyte-specific KRAS G12D expression do not develop heart pathology. These results challenge the view that the level of MAPK activation correlates with the severity of HCM in RASopathies and suggests that MAPK-independent strategies may be of interest in the development of new treatments for these syndromes. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2013.
|
|
| 4. |
|
|
| 5. |
- Khan, Omar M., 1980, et al.
(author)
-
Geranylgeranyltransferase type I (GGTase-I) deficiency hyperactivates macrophages and induces erosive arthritis in mice.
- 2011
-
In: The Journal of clinical investigation. - 1558-8238. ; 121:2, s. 628-39
-
Journal article (peer-reviewed)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.
|
|
| 6. |
- Khan, Omar M., 1980, et al.
(author)
-
Targeting GGTase-I Activates RHOA, Increases Macrophage Reverse Cholesterol Transport, and Reduces Atherosclerosis in Mice
- 2013
-
In: Circulation. - : Ovid Technologies (Wolters Kluwer Health). - 0009-7322 .- 1524-4539. ; 127:7, s. 782-790
-
Journal article (peer-reviewed)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
|
|
| 7. |
- Le Gal, Kristell, et al.
(author)
-
Antioxidants can increase melanoma metastasis in mice.
- 2015
-
In: Science Translational Medicine. - : American Association for the Advancement of Science (AAAS). - 1946-6242 .- 1946-6234. ; 7:308
-
Journal article (peer-reviewed)abstract
- Antioxidants in the diet and supplements are widely used to protect against cancer, but clinical trials with antioxidants do not support this concept. Some trials show that antioxidants actually increase cancer risk and a study in mice showed that antioxidants accelerate the progression of primary lung tumors. However, little is known about the impact of antioxidant supplementation on the progression of other types of cancer, including malignant melanoma. We show that administration of N-acetylcysteine (NAC) increases lymph node metastases in an endogenous mouse model of malignant melanoma but has no impact on the number and size of primary tumors. Similarly, NAC and the soluble vitamin E analog Trolox markedly increased the migration and invasive properties of human malignant melanoma cells but did not affect their proliferation. Both antioxidants increased the ratio between reduced and oxidized glutathione in melanoma cells and in lymph node metastases, and the increased migration depended on new glutathione synthesis. Furthermore, both NAC and Trolox increased the activation of the small guanosine triphosphatase (GTPase) RHOA, and blocking downstream RHOA signaling abolished antioxidant-induced migration. These results demonstrate that antioxidants and the glutathione system play a previously unappreciated role in malignant melanoma progression.
|
|
| 8. |
- Liu, Meng, 1976, et al.
(author)
-
Targeting the protein prenyltransferases efficiently reduces tumor development in mice with K-RAS-induced lung cancer
- 2010
-
In: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 107:14, s. 6471-6476
-
Journal article (peer-reviewed)abstract
- RAS and RHO proteins, which contribute to tumorigenesis and metastasis, undergo posttranslational modification with an isoprenyl lipid by protein farnesyltransferase (FTase) or protein geranylgeranyltransferase-I (GGTase-I). Inhibitors of FTase and GGTase-I were developed to block RAS-induced malignancies, but their utility has been difficult to evaluate because of off-target effects, drug resistance, and toxicity. Moreover, the impact of FTase deficiency and combined FTase/GGTase-I deficiency has not been evaluated with genetic approaches. We found that inactivation of FTase eliminated farnesylation of HDJ2 and H-RAS, prevented H-RAS targeting to the plasma membrane, and blocked proliferation of primary and K-RAS(G12D)-expressing fibroblasts. FTase inactivation in mice with K-RAS-induced lung cancer reduced tumor growth and improved survival, similar to results obtained previously with inactivation of GGTase-I. Simultaneous inactivation of FTase and GGTase-I markedly reduced lung tumors and improved survival without apparent pulmonary toxicity. These data shed light on the biochemical and therapeutic importance of FTase and suggest that simultaneous inhibition of FTase and GGTase-I could be useful in cancer therapeutics.
|
|
| 9. |
|
|
| 10. |
- Staffas, Anna, 1982, et al.
(author)
-
Wild-type KRAS inhibits oncogenic KRAS-induced T-all in mice.
- 2015
-
In: Leukemia. - : Springer Science and Business Media LLC. - 1476-5551 .- 0887-6924. ; 29, s. 1032-1040
-
Journal article (peer-reviewed)abstract
- The role of hyperactive RAS signaling is well established in myeloid malignancies but less clear in T-cell malignancies. The Kras2LSLMx1-Cre (KM) mouse model expresses endogenous KRASG12D in hematopoietic cells and is widely used to study mechanisms and treatment of myeloproliferative neoplasms (MPN). The model displays an intriguing shift from MPN to acute T-cell leukemia (T-ALL) after transplantation to wild-type mice but the mechanisms underlying this lineage shift is unknown. Here, we show that KRASG12D increases proliferation of both myeloid and T-cell progenitors, but whereas myeloid cells differentiate, T-cell differentiation is inhibited at early stages. Secondary mutations in the expanded pool of T-cell progenitors accompany T-ALL development, and our results indicate that the shift from myeloid to T-lymphoid malignancy after transplantation is explained by the increased likelihood for secondary mutations when the tumor life-span is increased. We demonstrate that tumor life span increases after transplantation because primary KM mice die rapidly, not from MPN, but from KRASG12D expression in nonhematopoietic cells which causes intestinal bleeding and severe anemia. We also identify loss of the wild-type KRAS allele as a secondary mutation in all T-ALL cells and provide evidence that wild-type KRAS acts as a tumor suppressor in the T-cell lineage in mice.Leukemia accepted article preview online, 05 November 2014. doi:10.1038/leu.2014.315.
|
|
