Inhibition Of Farnesylation Research Articles

Inhibition of farnesylation of Ras-GTPases ameliorates inflammation-induced loss of endothelial barrier integrity and leukocyte transmigration

Abstract Background and Aims The family of small GTPases (Rho- and Ras-GTPases) is known to regulate endothelial cytoskeleton dynamics and hence barrier integrity. The role of Rho GTPases (RhoA and Rac1) in endothelial barrier integrity is well characterized; however, little is known about the role of Ras-GTPases. The activity of small GTPases is regulated by several mechanisms, including post-translational prenylation (farnesylation or geranylgeranylation). The Ras-GTPases are preferentially post-translationally farnesylated by farnesyl transferases (FTs). The aim of the present study was to investigate whether inhibition of farnesylation of Ras-GTPases protects loss of endothelial barrier integrity induced by inflammatory mediators. Methods and Results Treatment of human primary endothelial cells (ECs; HUVEC and lung microvascular ECs) with pharmacological inhibitor of farnesyl transferases (FTIs), LB42708 (LB) and tipifarnib, stabilized basal endothelial barrier function (albumin-flux) and abrogated thrombin-induced hyperpermeability in a concentration- and time-dependent manner reaching maximum at a concentration of 2 mmol/L after 12 h of incubation. These concentrations of the FTIs reduced farnesylation of all the Ras isoforms but not the geranylgeranylation of Rho GTPases. Likewise, LB abrogated the TNFa-induced leucocyte transendothelial migration (Trans-well assay). Interestingly, FTIs treatment caused an enhanced translocation of VE-cadherin to cell-cell junctions (confocal microscopy) without exerting any effect on the actin cytoskeleton or endothelial contractile machinery; mainly regulated by Rho GTPases. The Ca2+-switch experiments demonstrated an inhibition of VE-cadherin internalization. These data were reproduced by lentiviral-mediated stable over-expression of the prenylation-dead mutants of Ras isoforms but not RhoA or Rac1. Conclusion The novel data of the present study demonstrate that FTIs protect endothelial barrier function against inflammatory mediator-induced endothelial hyperpermeability. We propose that FTIs are novel drug candidates for the treatment of edematous conditions (such as lung edema) where endothelial barrier integrity is compromised.

Abstract 1079: Combination of tipifarnib with KRAS G12C inhibitors to prevent adaptive resistance

Abstract Selective KRAS G12C inhibitors, including AMG510 (sotorasib) and MRTX849 (adagrasib), have exhibited clinical activity in patients with non-small cell lung cancer (NSCLC); however, drug resistance and relapse inevitably occur through various mechanisms, which limits the ability of these therapeutic agents to achieve durable responses. Resistance mechanisms include feedback reactivation of compensatory, oncogenic signaling pathways and the attainment of a drug-tolerant state, each of which allows cancer cells to survive the anti-tumor effects of these highly active drugs. Compensatory mechanisms ameliorating KRAS blockade include HRAS/NRAS and the PI3K-AKT-mTOR pathway. Tipifarnib is a clinical stage farnesyltransferase inhibitor known to inhibit multiple farnesylation-dependent proteins in tumor cells. We have recently shown that tipifarnib can prevent feedback-mediated adaptive resistance to the PI3Kα inhibitor, alpelisib, through inhibition of both HRAS and RHEB, allowing simultaneous blockade of two key nodes of the oncogenic MAPK- and PI3K-signaling pathways. In another example, tipifarnib has been demonstrated by others to inhibit the ability of tumor cells to enter a drug-tolerant state induced by the EGFR inhibitor, osimertinib, in EGFR-mutant NSCLC models. In these models, inhibition of farnesylation of certain RHO proteins appear to contribute to the death of drug-tolerant cells prior to the emergence of acquired resistance mutations. Building on these two mechanisms of how tipifarnib may prevent adaptive resistance, we propose that tipifarnib can be used as an effective partner drug to delay or prevent the onset of adaptive resistance to KRAS G12C inhibitors. We have conducted in vitro 2D and 3D viability and regrowth experiments using combinations of tipifarnib with KRAS G12C inhibitors and have observed synergistic, anti-proliferative effects in KRAS G12C NSCLC cell lines as well as enhanced activity of combination in a KRAS G12C NSCLC PDX model. We are currently expanding the scope of in vitro and in vivo combination studies to further evaluate the molecular mechanism(s) of resistance that tipifarnib targets when combined with KRAS G12C inhibitors. Citation Format: Hetika Vora Patel, Alison Smith, Stacia Chan, Linda Kessler, Francis Burrows, Shivani Malik. Combination of tipifarnib with KRAS G12C inhibitors to prevent adaptive resistance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1079.

Plasma Progerin in Patients With Hutchinson-Gilford Progeria Syndrome: Immunoassay Development and Clinical Evaluation.

Hutchinson-Gilford progeria syndrome (HGPS) is an ultrarare, fatal, premature aging disease caused by a toxic protein called progerin. Circulating progerin has not been previously detected, precluding research using readily available biological samples. This study aimed to develop a plasma progerin assay to evaluate progerin's quantity, response to progerin-targeted therapy, and relationship to patient survival. Biological samples were collected by The Progeria Research Foundation Cell and Tissue Bank from a non-HGPS cohort cross-sectionally and a HGPS cohort longitudinally. HGPS donations occurred at baseline and intermittently while treated with farnesylation inhibitors lonafarnib±pravastatin and zoledronate, within 3 sequential open-label clinical trials at Boston Children's Hospital totaling >10 years of treatment. An ultrasensitive single-molecule counting progerin immunoassay was developed with prespecified performance parameters. Intra- and interpatient group statistics were descriptive. The relationship between progerin and survival was assessed by using joint modeling with time-dependent slopes parameterization. The assay's dynamic detection range was 59 to 30 000 pg/mL (R2=0.9987). There was no lamin A cross-reactivity. Mean plasma progerin in non-HGPS participants (n=69; 39 male, 30 female; age, 0.2-71.3 years) was 351±251 pg/mL, and in drug-naive participants with HGPS (n=74; 37 female, 37 male; age, 2.1-17.5 years) was 33 261±12 346 pg/mL, reflecting a 95-fold increase in affected children (P<0.0001). Progerin levels did not differ by sex (P=0.99). Lonafarnib treatment resulted in an average per-visit progerin decrease from baseline of between 35% to 62% (all P<0.005); effects were not augmented by adding pravastatin and zoledronate. Progerin levels fell within 4 months of therapy and remained lower for up to 10 years. The magnitude of progerin decrease positively associated with patient survival (P<0.0001; ie, 15 000 pg/mL decrease yields a 63.9% decreased risk of death). For any given decrease in progerin, life expectancy incrementally increased with longer treatment duration. A sensitive, quantitative immunoassay for progerin was developed and used to demonstrate high progerin levels in HGPS plasma that decreased with lonafarnib therapy. The extent of improved survival was associated with both the magnitude of progerin decrease and duration at lower levels. Thus, plasma progerin is a biomarker for HGPS whose reduction enables short- and long-term assessment of progerin-targeted treatment efficacy. URL: https://www. gov. Unique identifiers: NCT00879034 and NCT00916747.

NRas activity is regulated by dynamic interactions with nanoscale signaling clusters at the plasma membrane

SummaryNRas is a key mediator of the mitogenic pathway in normal cells and in cancer cells. Its dynamics and nanoscale organization at the plasma membrane (PM) facilitate its signaling. Here, we used two-color photoactivated localization microscopy to resolve the organization of individual NRas and associated signaling proteins in live melanoma cells, with resolution down to ∼20 nm. Upon EGF activation, a fraction of NRas and BRAF (dis)assembled synchronously at the PM in co-clusters. NRas and BRAF clusters associated with GPI-enriched domains, serving as possible nucleation sites for these clusters. NRas and BRAF association in mutual clusters was reduced by the NRas farnesylation inhibitor lonafarnib, yet enhanced by the BRAF inhibitor vemurafenib. Surprisingly, dispersed NRas molecules associated with the periphery of self-clusters of either Grb2 or NF1. Thus, NRas-mediated signaling, which is critical in health and disease, is regulated by dynamic interactions with functional clusters of BRAF or other related proteins at the PM.

MEK inhibition exerts temporal and myeloid cell-specific effects in the pathogenesis of neurofibromatosis type 1 arteriopathy

Mutations in the NF1 tumor suppressor gene are linked to arteriopathy. Nf1 heterozygosity (Nf1+/–) results in robust neointima formation, similar to humans, and myeloid-restricted Nf1+/– recapitulates this phenotype via MEK-ERK activation. Here we define the contribution of myeloid subpopulations to NF1 arteriopathy. Neutrophils from WT and Nf1+/– mice were functionally assessed in the presence of MEK and farnesylation inhibitors in vitro and neutrophil recruitment to lipopolysaccharide was assessed in WT and Nf1+/– mice. Littermate 12–15 week-old male wildtype and Nf1+/– mice were subjected to carotid artery ligation and provided either a neutrophil depleting antibody (1A8), liposomal clodronate to deplete monocytes/macrophages, or PD0325901 and neointima size was assessed 28 days after injury. Bone marrow transplant experiments assessed monocyte/macrophage mobilization during neointima formation. Nf1+/– neutrophils exhibit enhanced proliferation, migration, and adhesion via p21Ras activation of MEK in vitro and in vivo. Neutrophil depletion suppresses circulating Ly6Clow monocytes and enhances neointima size, while monocyte/macrophage depletion and deletion of CCR2 in bone marrow cells abolish neointima formation in Nf1+/– mice. Taken together, these findings suggest that neurofibromin-MEK-ERK activation in circulating neutrophils and monocytes during arterial remodeling is nuanced and points to important cross-talk between these populations in the pathogenesis of NF1 arteriopathy.

Patterns of neuronal Rhes as a novel hallmark of tauopathies.

The farnesyltransferase inhibitor, Lonafarnib, reduces tau inclusions and associated atrophy in familial tauopathy models through activation of autophagy, mediated by the inhibition of farnesylation of the Ras GTPase, Rhes. While hinting at a role of Rhes in tau aggregation, it is unclear how translatable these results are for sporadic forms of tauopathy. We examined histological slides of allocortex and neocortex from multiple postmortem cases in five different tauopathies, FTLD-TDP, and healthy controls using immunofluorescence for Rhes, several tau post-translational modifications, and phospho-TDP-43. Single nucleus RNA data suggest that Rhes is found in all cortical neuron subpopulations but not in glia. Histologic investigation showed that nearly all neurons in control brains display a pattern of diffuse cytoplasmic Rhes positivity. However, in the presence of abnormal tau, but not abnormal TDP-43, the patterns of neuronal cytoplasmic Rhes tend to present as either punctiform or entirely absent. This observation reinforces the relevance of findings that link Rhes changes and tau pathology from the in vivo and in vitro models of tauopathy. The results here support a potential clinical application of Lonafarnib to tauopathies.

Metabolic labeling with an alkyne probe reveals similarities and differences in the prenylomes of several brain-derived cell lines and primary cells

Protein prenylation involves the attachment of one or two isoprenoid group(s) onto cysteine residues positioned near the C-terminus. This modification is essential for many signal transduction processes. In this work, the use of the probe C15AlkOPP for metabolic labeling and identification of prenylated proteins in a variety of cell lines and primary cells is explored. Using a single isoprenoid analogue, 78 prenylated protein groups from the three classes of prenylation substrates were identified including three novel prenylation substrates in a single experiment. Applying this method to three brain-related cell lines including neurons, microglia, and astrocytes showed substantial overlap (25%) in the prenylated proteins identified. In addition, some unique prenylated proteins were identified in each type. Eight proteins were observed exclusively in neurons, five were observed exclusively in astrocytes and three were observed exclusively in microglia, suggesting their unique roles in these cells. Furthermore, inhibition of farnesylation in primary astrocytes revealed the differential responses of farnesylated proteins to an FTI. Importantly, these results provide a list of 19 prenylated proteins common to all the cell lines studied here that can be monitored using the C15AlkOPP probe as well as a number of proteins that were observed in only certain cell lines. Taken together, these results suggest that this chemical proteomic approach should be useful in monitoring the levels and exploring the underlying role(s) of prenylated proteins in various diseases.

The differential statin effect on cytokine production of monocytes or macrophages is mediated by differential geranylgeranylation-dependent Rac1 activation

Monocytes and macrophages contribute to pathogenesis of various inflammatory diseases, including auto-inflammatory diseases, cancer, sepsis, or atherosclerosis. They do so by production of cytokines, the central regulators of inflammation. Isoprenylation of small G-proteins is involved in regulation of production of some cytokines. Statins possibly affect isoprenylation-dependent cytokine production of monocytes and macrophages differentially. Thus, we compared statin-dependent cytokine production of lipopolysaccharide (LPS)-stimulated freshly isolated human monocytes and macrophages derived from monocytes by overnight differentiation. Stimulated monocytes readily produced tumor necrosis factor-α, interleukin-6, and interleukin-1β. Statins did not alter cytokine production of LPS-stimulated monocytes. In contrast, monocyte-derived macrophages prepared in the absence of statin lost the capacity to produce cytokines, whereas macrophages prepared in the presence of statin still produced cytokines. The cells expressed indistinguishable nuclear factor-kB activity, suggesting involvement of separate, statin-dependent regulation pathways. The presence of statin was necessary during the differentiation phase of the macrophages, indicating that retainment-of-function rather than costimulation was involved. Reconstitution with mevalonic acid, farnesyl pyrophosphate, or geranylgeranyl pyrophosphate blocked the retainment effect, whereas reconstitution of cholesterol synthesis by squalene did not. Inhibition of geranylgeranylation by GGTI-298, but not inhibition of farnesylation or cholesterol synthesis, mimicked the retainment effect of the statin. Inhibition of Rac1 activation by the Rac1/TIAM1-inhibitor NSC23766 or by Rac1-siRNA (small interfering RNA) blocked the retainment effect. Consistent with this finding, macrophages differentiated in the presence of statin expressed enhanced Rac1-GTP-levels. In line with the above hypothesis that monocytes and macrophages are differentially regulated by statins, the CD14/CD16-, merTK-, CX3CR1-, or CD163-expression (M2-macrophage-related) correlated inversely to the cytokine production. Thus, monocytes and macrophages display differential Rac1-geranylgeranylation-dependent functional capacities, that is, statins sway monocytes and macrophages differentially.

C-Terminal Farnesylation of UCH-L1 Plays a Role in Transport of Epstein-Barr Virus Primary Oncoprotein LMP1 to Exosomes.

Increasing evidence shows that exosomes are key regulators in cancer cell-to-cell communication. Several reports on Epstein-Barr virus (EBV)-related malignancies demonstrate that latent membrane protein 1 (LMP1) secreted by exosomes derived from EBV- or LMP1-positive cells can promote cancer progression and metastasis. However, the mechanism by which LMP1 is loaded into exosomes is still poorly understood. Here, we examined whether the process of LMP1 loading into exosomes is linked to the multifunctional molecule of the ubiquitin system-ubiquitin C-terminal hydrolase-L1 (UCH-L1). For the first time, we demonstrate that LMP1 is physically associated with UCH-L1 and that directing of LMP1 to exosomes is mediated by C-terminal farnesylation of UCH-L1. Additionally, we found that the FTI-277 farnesyltransferase inhibitor reduces motility- and anchorage-independent growth of EBV-positive cells in functional assays. On the basis of our results, we conclude that C-terminal farnesylation of UCH-L1 is one of the key mechanisms by which LMP1 is sorted to exosomes. We hypothesize that inhibition of farnesylation with specific small-molecule inhibitors blocks exosome-mediated transfer of prometastatic molecules such as LMP1 during cancer cell-to-cell communications and thereby impedes the process of cancer invasion. IMPORTANCE Exosomes are small vesicles that cells secrete into the extracellular space, and there is increasing evidence that they have pivotal roles in cell-to-cell communication in malignancy. It is reported also that EBV-associated malignant cells, including those derived from nasopharyngeal carcinoma (NPC) and B-cell lymphoma, secrete exosomes. These EBV-related exosomes may contain viral products such as latent membrane protein 1 (LMP1) and may contribute to cancer progression. The aim of this study was to investigate the mechanism by which those viral products are loaded in exosomes. In this study, we show for the first time that ubiquitin C-terminal hydrolase-L1 (UCH-L1) and its C-terminal farnesylation, a posttranslational lipid modification, contribute to this mechanism. Our results also suggest that inhibition of UCH-L1 farnesylation is a potential therapeutic target against cancer metastasis and invasion.

Simvastatin inhibits the expression of stemness‑related genes and the metastatic invasion of human cancer cells via destruction of the cytoskeleton.

Statins are a class of drugs that inhibit the rate-limiting steps in the cholesterol biosynthesis pathway. They act by inhibiting 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase, which catalyzes the conversion of HMG-CoA to mevalonate. Blocking of mevalonate synthesis leads to inhibition of the farnesylation and geranylgeranylation of several functional proteins, such as RhoA and other small guanosine triphosphate-binding proteins, that are important in maintaining the undifferentiated status of the cells. In the present study, we hypothesized that simvastatin, likely through the inhibition of farnesylation and geranylgeranylation of Rac1, Cd42 and RhoA, induces a destruction/restructuration of the cytoskeleton that decreases mechanical strain transfer to the nuclei, inducing the loss of transmission of regulatory signals from the cytoskeleton to the nucleoskeleton. Although this remains at present a hypothesis and is not easy to define if the de-structuration of the cytoskeleton is a secondary effect of simvastatin treatment or the inhibition of post-translational protein modification have a precise role in the structuration of actin cytoskeleton, we speculate that these signal variations could inhibit the expression of certain stemness genes, which could therefore be considered nucleoskeleton-associated and mechanically regulated genes. On the other hand, the restructuration of the cytoskeleton inhibits the formation of lamellipodia and filopodia, which likely decreases the capability of cancer cells to invade the extracellular matrix, thereby modulating the equilibrium between proliferation, differentiation and metastatic invasion in human cancer cells. On the basis of our results we think that simvastatin, alone or in combination with conventional drugs, may have a possible role in cancer therapy.

Prelamin A processing, accumulation and distribution in normal cells and laminopathy disorders

ABSTRACTLamin A is part of a complex structural meshwork located beneath the nuclear envelope and is involved in both structural support and the regulation of gene expression. Lamin A is initially expressed as prelamin A, which contains an extended carboxyl terminus that undergoes a series of post-translational modifications and subsequent cleavage by the endopeptidase ZMPSTE24 to generate lamin A. To facilitate investigations of the role of this cleavage in normal and disease states, we developed a monoclonal antibody (PL-1C7) that specifically recognizes prelamin A at the intact ZMPSTE24 cleavage site, ensuring prelamin A detection exclusively. Importantly, PL-1C7 can be used to determine prelamin A localization and accumulation in cells where lamin A is highly expressed without the use of exogenous fusion proteins. Our results show that unlike mature lamin A, prelamin A accumulates as discrete and localized foci at the nuclear periphery. Furthermore, whereas treatment with farnesylation inhibitors of cells overexpressing a GFP-prelamin A fusion protein results in the formation of large nucleoplasmic clumps, these aggregates are not observed upon similar treatment of cells expressing endogenous prelamin A or in cells lacking ZMPSTE24 expression and/or activity. Finally, we show that specific laminopathy-associated mutations exhibit both positive and negative effects on prelamin A accumulation, indicating that these mutations affect prelamin A processing efficiency in different manners.

Permanent farnesylation of lamin A mutants linked to progeria impairs its phosphorylation at serine 22 during interphase.

Mutants of lamin A cause diseases including the Hutchinson-Gilford progeria syndrome (HGPS) characterized by premature aging. Lamin A undergoes a series of processing reactions, including farnesylation and proteolytic cleavage of the farnesylated C-terminal domain. The role of cleavage is unknown but mutations that affect this reaction lead to progeria. Here we show that interphase serine 22 phosphorylation of endogenous mutant lamin A (progerin) is defective in cells from HGPS patients. This defect can be mimicked by expressing progerin in human cells and prevented by inhibition of farnesylation. Furthermore, serine 22 phosphorylation of non-farnesylated progerin was enhanced by a mutation that disrupts lamin A head to tail interactions. The phosphorylation of lamin A or non-farnesylated progerin was associated to the formation of spherical intranuclear lamin A droplets that accumulate protein kinases of the CDK family capable of phosphorylating lamin A at serine 22. CDK inhibitors compromised the turnover of progerin, accelerated senescence of HGPS cells and reversed the effects of FTI on progerin levels. We discuss a model of progeria where faulty serine 22 phosphorylation compromises phase separation of lamin A polymers, leading to accumulation of functionally impaired lamin A structures.

Drug screening on Hutchinson Gilford progeria pluripotent stem cells reveals aminopyrimidines as new modulators of farnesylation

Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder characterized by a dramatic appearance of premature aging. HGPS is due to a single-base substitution in exon 11 of the LMNA gene (c.1824C>T) leading to the production of a toxic form of the prelamin A protein called progerin. Because farnesylation process had been shown to control progerin toxicity, in this study we have developed a screening method permitting to identify new pharmacological inhibitors of farnesylation. For this, we have used the unique potential of pluripotent stem cells to have access to an unlimited and relevant biological resource and test 21 608 small molecules. This study identified several compounds, called monoaminopyrimidines, which target two key enzymes of the farnesylation process, farnesyl pyrophosphate synthase and farnesyl transferase, and rescue in vitro phenotypes associated with HGPS. Our results opens up new therapeutic possibilities for the treatment of HGPS by identifying a new family of protein farnesylation inhibitors, and which may also be applicable to cancers and diseases associated with mutations that involve farnesylated proteins.

LMNA mutations resulting in lipodystrophy and HIV protease inhibitors trigger vascular smooth muscle cell senescence and calcification: Role of ZMPSTE24 downregulation

BackgroundSome LMNA mutations responsible for lipodystrophies, and some HIV-protease inhibitors (PIs) induce accumulation of farnesylated prelamin A and premature senescence in some cell types. Patients with LMNA mutations or under PI-based therapy suffer from early atherosclerosis. The metalloprotease ZMPSTE24 is the key enzyme in prelamin A maturation. AimWe studied whether altered expression of ZMPSTE24 could contribute to vascular cell dysfunction in response to LMNA mutations or PI treatments. MethodsProtein expression of prelamin A and ZMPSTE24 were evaluated in patients' cells and in human cultured VSMCs. Oxidative stress, inflammation, senescence and transdifferentiation/calcification were evaluated in VSMCs. ResultsFibroblasts from LMNA-mutated lipodystrophic patients (mutations R482W, D47Y or R133L) and peripheral blood mononuclear cells from PI-treated-HIV-infected patients expressed increased prelamin A and decreased ZMPSTE24, which was also observed in VSMCs overexpressing mutant LMNA or treated with PIs. These alterations correlated with oxidative stress, inflammation, senescence and calcification (all p < 0.05). ZMPSTE24 silencing in native VSMCs recapitulated the mutant LMNA- and PI-induced accumulation of farnesylated prelamin A, oxidative stress, inflammation, senescence and calcification. A negative regulator of ZMPSTE24, miRNA-141-3p, was enhanced in LMNA-mutated or PI-treated VSMCs. The farnesylation inhibitors pravastatin and FTI-277, or the antioxidant N-acetyl cysteine, partly restored ZMPSTE24 expression, and concomitantly decreased oxidative stress, inflammation, senescence, and calcification of PI-treated VSCMs. ConclusionsZMPSTE24 downregulation is a major contributor in VSMC dysfunctions resulting from LMNA mutations or PI treatments that could translate in early atherosclerosis at the clinical level. These novel pathophysiological mechanisms could open new therapeutic perspectives for cardiovascular aging.

Abstract 230: Protein Farnesylation Inhibitor Tipifarnib Prevents Development of Chronic Hypoxia-induced Pulmonary Hypertension

Study objectives: Small GTPase RhoB contributes to pulmonary vascular remodelling in pulmonary hypertension. Farnesylation of RhoB augments cell proliferation while geranylgeranylation of RhoB is believed to be pro-apoptotic. We hypothesized that farnesyltransferase inhibitors may prevent vascular pathology in pulmonary hypertension. We studied the effects of farnesyltransferase inhibitor Tipifarnib on pulmonary vascular remodelling and vasoreactivity in chronically hypoxic pulmonary hypertensive mice and cultured human pulmonary artery endothelial cells (HPAECs). Chemical proteomics was used to characterise Tipifarnib-induced changes in protein prenylation while label- free quantitative proteomics was used to characterise changes induced by overexpression of RhoB prenylation mutants: farnesylated-only or geranlygeranylated-only RhoB in HPAECs. The effects of Tipifarnib on Ras and Rho GTPases expression and activity, filamentous and globular actin levels and eNOS pathway, were also studied. Results: Oral administration of Tipifarnib significantly attenuated chronic hypoxia-induced pulmonary hypertension in mice. This protective effect was associated with a marked improvement of endothelium-dependent vasodilatation, reduction in pulmonary vascular muscularization and a decrease in the right ventricular systolic pressure. Tipifarnib reduced farnesylation and increased geranyl-geranylation of several proteins, including Rho GTPases and Ras and reduced their activity in vitro and in vivo. Tipifarnib-induced changes in cultured cells were associated with a decrease in cell proliferation, decreased polymerization of actin and increased eNOS mRNA and protein levels. Proteomic analysis of HPAECs overexpressing prenylation mutants of RhoB suggests that protective effects of Tipifarnib may result, at least in part, from inhibition of RhoB farnesylation. Conclusions: We demonstrate protective effects of farnesyltransferase inhibitor Tipifarnib in chronic hypoxia-induced pulmonary hypertension. The effects of Tipifarnib may result from inhibition of small GTPases activity and increase in NO signalling.

A novel role of farnesylation in targeting a mitotic checkpoint protein, human Spindly, to kinetochores.

Kinetochore (KT) localization of mitotic checkpoint proteins is essential for their function during mitosis. hSpindly KT localization is dependent on the RZZ complex and hSpindly recruits the dynein-dynactin complex to KTs during mitosis, but the mechanism of hSpindly KT recruitment is unknown. Through domain-mapping studies we characterized the KT localization domain of hSpindly and discovered it undergoes farnesylation at the C-terminal cysteine residue. The N-terminal 293 residues of hSpindly are dispensable for its KT localization. Inhibition of farnesylation using a farnesyl transferase inhibitor (FTI) abrogated hSpindly KT localization without affecting RZZ complex, CENP-E, and CENP-F KT localization. We showed that hSpindly is farnesylated in vivo and farnesylation is essential for its interaction with the RZZ complex and hence KT localization. FTI treatment and hSpindly knockdown displayed the same mitotic phenotypes, indicating that hSpindly is a key FTI target in mitosis. Our data show a novel role of lipidation in targeting a checkpoint protein to KTs through protein-protein interaction.

Laminopathies: clinical presentations and management

The number of laminopathies is large, and the variability is equally wide. OMIM mentions 10 different entities, but there are several additional reports of individuals with a lamin A/C mutation who have phenotypes that are still at variance of these. This variability can be explained in two ways. One is the widespread dissemination of the lamin A/C protein within our bodies and indeed within individual cells and the many functions that is has. The function of providing firmness to the nuclear envelop is a major function. A lack of that firmness due to the abnormal protein causes all structures and proteins in the envelope potentially to be disturbed. These have all kind of functions, sometimes also completely unrelated, and all can be disturbed by the abnormal lamin A/C only. The other explanation is the variability between individuals with changes in the same gene in general. Even brothers and sisters with exactly the same mutation in exactly the same gene can still show very different phenotypes. The background is that it will not be a single gene that explains the phenotype but also the background of genetic information of each person, and the exogenous influences on this, are important. Indeed, “monogenic disorder do not exist”[1]. So variability should in fact be expected and also explained to patients. One can evaluate all laminopathies for their major manifestations, which are the heart, muscles, nerves, joints, fat tissue, skin, bone, morphology of the face, growth and endocrine functioning. Some laminopathies are explained by mainly heart and muscle abnormalities, other mainly by bone, fat, skin, growth and face abnormalities. However, it may be this distinction is artificial. It may be that in fact (almost) all laminopathies show signs or symptoms in all of the above tissues, but we fail to recognize this either because we haven't looked carefully enough, or because patients die for one particularly affected tissue and therefore don't have the time to show the other manifestations in other tissues. This can be important in evaluating patients with the various laminopathies, in providing optimal care to them, and in considerations if a management if applied for one of the consequences of an lamin A/C, as one cannot exclude others will then arise that have been unknown until then. Some may argue that this means in fact all patients with a laminopathy might be better put under a single diagnosis. That seems not right. Detailed discussions about this are available in literature[2]. In addition, the WHO has decided in the development of the upcoming new International Classification of Diseases that what really counts is what a patient experiences from an entity. And surely it does make a difference if one has an entity that leads to demise already around birth (restrictive dermopathy), leads to significant problems that will be fatal in puberty (Hutchinson-Gilford progeria), or allow you to live well into adulthood at least with only limited restrictions in well-being (mandibulo-acral dysostosis). So grouping all disorders under the umbrella laminopathy is very useful for our insights, but for patients subdivision into individual entities is still essential. The grouping into laminopathy has also advantages in considering various management strategies. In a very basic way one can divide management into influencing the abnormal DNA (gene therapy), influencing the abnormal RNA (mainly through morpholinos and other small molecules), decreasing the amount of abnormal protein and/or increasing the amount of normal protein (by farnesylation inhibition or increasing turnover of proteins), and by influencing the consequences on a cell or tissue level (for instance by statins). Gradually it becomes clear that the most effective way must be influencing the abnormal RNA as the other ways are either undesirable (gene therapy) or lack true, curative effectivity (FTIs and statins). The advantage by working in this way is that studies for one laminopathy might have benefits for the other laminopathies as well, and in the end also for all patients.

Correction: Driven to Death: Inhibition of Farnesylation Increases Ras Activity in Osteosarcoma and Promotes Growth Arrest and Cell Death

Correction: Driven to Death: Inhibition of Farnesylation Increases Ras Activity in Osteosarcoma and Promotes Growth Arrest and Cell Death

Impact of farnesylation inhibitors on survival in Hutchinson-Gilford progeria syndrome.

Hutchinson-Gilford progeria syndrome is an ultrarare segmental premature aging disease resulting in early death from heart attack or stroke. There is no approved treatment, but starting in 2007, several recent single-arm clinical trials administered inhibitors of protein farnesylation aimed at reducing toxicity of the disease-producing protein progerin. No study assessed whether treatments influence patient survival. The key elements necessary for this analysis are a robust natural history of survival and comparison with a sufficiently large patient population that has been treated for a sufficient time period with disease-targeting medications. We generated Kaplan-Meier survival analyses for the largest untreated Hutchinson-Gilford progeria syndrome cohort to date. Mean survival was 14.6 years. Comparing survival for treated versus age- and sex-matched untreated cohorts, hazard ratio was 0.13 (95% confidence interval, 0.04-0.37; P<0.001) with median follow-up of 5.3 years from time of treatment initiation. There were 21 of 43 deaths in untreated versus 5 of 43 deaths among treated subjects. Treatment increased mean survival by 1.6 years. This study provides a robust untreated disease survival profile that can be used for comparisons now and in the future to assess changes in survival with treatments for Hutchinson-Gilford progeria syndrome. The current comparisons estimating increased survival with protein farnesylation inhibitors provide the first evidence of treatments influencing survival for this fatal disease. http://www.clinicaltrials.gov. Unique Indentifiers: NCT00425607, NCT00879034, and NCT00916747.

Simvastatin Treatment Enhances NMDAR-Mediated Synaptic Transmission by Upregulating the Surface Distribution of the GluN2B Subunit

The ramifications of statins on plasma cholesterol and coronary heart disease have been well documented. However, there is increasing evidence that inhibition of the mevalonate pathway may provide independent neuroprotective and procognitive pleiotropic effects, most likely via inhibition of isoprenoids, mainly farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP). FPP and GGPP are the major donors of prenyl groups for protein prenylation. Modulation of isoprenoid availability impacts a slew of cellular processes including synaptic plasticity in the hippocampus. Our previous work has demonstrated that simvastatin (SV) administration improves hippocampus-dependent spatial memory, rescuing memory deficits in a mouse model of Alzheimer's disease. Treatment of hippocampal slices with SV enhances long-term potentiation (LTP), and this effect is dependent on the activation of Akt (protein kinase B). Further studies showed that SV-induced enhancement of hippocampal LTP is driven by depletion of FPP and inhibition of farnesylation. In the present study, we report the functional consequences of exposure to SV at cellular/synaptic and molecular levels. While application of SV has no effect on intrinsic membrane properties of CA1 pyramidal neurons, including hyperpolarization-activated cyclic-nucleotide channel-mediated sag potentials, the afterhyperpolarization (AHP), and excitability, SV application potentiates the N-methyl D-aspartate receptor (NMDAR)-mediated contribution to synaptic transmission. In mouse hippocampal slices and human neuronal cells, SV treatment increases the surface distribution of the GluN2B subunit of the NMDAR without affecting cellular cholesterol content. We conclude that SV-induced enhancement of synaptic plasticity in the hippocampus is likely mediated by augmentation of synaptic NMDAR components that are largely responsible for driving synaptic plasticity in the CA1 region.