Protein farnesyltransferase inhibitors and progeria

Use of Farnesyl Transferase Inhibitors in an Ageing Model in Drosophila

The presence of farnesylated proteins at the inner nuclear membrane (INM), such as the Lamins or Kugelkern in Drosophila, leads to specific changes in the nuclear morphology and accelerated ageing on the organismal level reminiscent of the Hutchinson-Gilford progeria syndrome (HGPS). Farnesyl transferase inhibitors (FTIs) can suppress the phenotypes of the nuclear morphology in cultured fibroblasts from HGPS patients and cultured cells overexpressing farnesylated INM proteins. Similarly, FTIs have been reported to suppress the shortened lifespan in model organisms. Here, we report an experimental system combining cell culture and Drosophila flies for testing the activity of substances on the HGPS-like nuclear morphology and lifespan, with FTIs as an experimental example. Consistent with previous reports, we show that FTIs were able to ameliorate the nuclear phenotypes induced by the farnesylated nuclear proteins Progerin, Kugelkern, or truncated Lamin B in cultured cells. The subsequent validation in Drosophila lifespan assays demonstrated the applicability of the experimental system: treating adult Drosophila with the FTI ABT-100 reversed the nuclear phenotypes and extended the lifespan of experimentally induced short-lived flies. Since kugelkern-expressing flies have a significantly shorter average lifespan, half the time is needed for testing substances in the lifespan assay.

Hutchinson-Gilford progeria patient-derived cardiomyocyte model of carrying LMNA gene variant c.1824 C > T

Cardiovascular diseases, atherosclerosis, and strokes are the most common causes of death in patients with Hutchinson-Gilford progeria syndrome (HGPS). The LMNA variant c.1824C > T accounts for ~ 90% of HGPS cases. The detailed molecular mechanisms of Lamin A in the heart remain elusive due to the lack of appropriate in vitro models. We hypothesize that HGPS patient's induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iCMCs) will provide a model platform to study the cardio-pathologic mechanisms associated with HGPS. To elucidate the effects of progerin in cardiomyocytes, we first obtained skin fibroblasts (SFs) from a de-identified HGPS patient (hPGP1, proband) and both parents from the Progeria Research Foundation. Through Sanger sequencing and restriction fragment length polymorphism, with the enzyme EciI, targeting Lamin A, we characterized hPGP1-SFs as heterozygous mutants for the LMNA variant c.1824 C > T. Additionally, we performed LMNA exon 11 bisulfite sequencing to analyze the methylation status of the progeria cells. Furthermore, we reprogrammed the three SFs into iPSCs and differentiated them into iCMCs, which gained a beating on day 7. Through particle image velocimetry analysis, we found that hPGP1-iCMCs had an irregular contractile function and decreased cardiac-specific gene and protein expressions by qRT-PCR and Western blot. Our progeria-patient-derived iCMCs were found to be functionally and structurally defective when compared to normal iCMCs. This in vitro model will help in elucidating the role of Lamin A in cardiac diseases and the cardio-pathologic mechanisms associated with progeria. It provides a new platform for researchers to study novel treatment approaches for progeria-associated cardiac diseases.

ZP3 and AIPL1 participate in GVBD of mouse oocytes by affecting the nuclear membrane localization and maturation of farnesylated prelamin A

The low maturation rate of oocytes is an important reason for female infertility and failure of assisted pregnancy. The germinal vesicle breakdown (GVBD) is a landmark event of oocyte maturation. In our previous studies, we found that zona pellucida 3 (ZP3) was strongly concentrated in the nuclear region of germinal vesicle (GV) oocytes and interacted with aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) and lamin A to promote GVBD. In the current study, we found that lamin A is mainly concentrated in the nuclear membrane. When ZP3 is knocked down, lamin A will be partially transferred to the nucleus of oocytes. The prelamin A is increased in both the nuclear membrane and nucleus, while phosphorylated lamin A (p-lamin A) is significantly reduced. AIPL1 was also proved to accumulate in the GV region of oocytes, and ZP3 deletion can significantly inhibit the aggregation of AIPL1 in the nuclear region. Similar to ZP3 knockdown, the absence of AIPL1 resulted in a decrease in the occurrence of GVBD, an increase in the amount of prelamin A, and a significant decrease in p-lamin A in oocytes developed in vitro. Finally, we propose the hypothesis that ZP3 can stabilize farnesylated prelamin A on the nuclear membrane of AIPL1, and promote its further processing into mature lamin A, therefore promoting the occurrence of GVBD. This study may be an important supplement for the mechanism of oocyte meiotic resumption and provide new diagnostic targets and treatment clues for infertility patients with oocyte maturation disorder.

Abolishing the prelamin A ZMPSTE24 cleavage site leads to progeroid phenotypes with near-normal longevity in mice

The zinc metalloprotease ZMPSTE24 removes the last 15 amino acids of prelamin A, including a farnesylated cysteine, to produce mature lamin A. The premature aging disorder Hutchinson–Gilford progeria syndrome is caused by a permanently farnesylated prelamin A variant lacking the ZMPSTE24 cleavage site. ZMPSTE24 loss of function leads to the accumulation of farnesylated prelamin A and causes progeroid disorders. Some studies have implicated prelamin A in physiological aging. We describe mice with an amino acid substitution in prelamin A that blocks the ZMPSTE24-catalyzed cleavage. These mice develop progeroid phenotypes but, in contrast to those modeling Hutchinson–Gilford progeria syndrome or ZMPSTE24 deficiency, have near-normal lifespans, thus providing a model to study the effects of farnesylated prelamin A during aging.

Prelamin A is a farnesylated precursor of lamin A, a nuclear lamina protein. Accumulation of the farnesylated prelamin A variant progerin, with an internal deletion including its processing site, causes Hutchinson–Gilford progeria syndrome. Loss-of-function mutations in ZMPSTE24, which encodes the prelamin A processing enzyme, lead to accumulation of full-length farnesylated prelamin A and cause related progeroid disorders. Some data suggest that prelamin A also accumulates with physiological aging. Zmpste24^−/− mice die young, at ∼20 wk. Because ZMPSTE24 has functions in addition to prelamin A processing, we generated a mouse model to examine effects solely due to the presence of permanently farnesylated prelamin A. These mice have an L648R amino acid substitution in prelamin A that blocks ZMPSTE24-catalyzed processing to lamin A. The Lmna^L648R/L648R mice express only prelamin and no mature protein. Notably, nearly all survive to 65 to 70 wk, with ∼40% of male and 75% of female Lmna^L648R/L648R mice having near-normal lifespans of 90 wk (almost 2 y). Starting at ∼10 wk of age, Lmna^L648R/L648R mice of both sexes have lower body masses than controls. By ∼20 to 30 wk of age, they exhibit detectable cranial, mandibular, and dental defects similar to those observed in Zmpste24^−/− mice and have decreased vertebral bone density compared to age- and sex-matched controls. Cultured embryonic fibroblasts from Lmna^L648R/L648R mice have aberrant nuclear morphology that is reversible by treatment with a protein farnesyltransferase inhibitor. These novel mice provide a model to study the effects of farnesylated prelamin A during physiological aging.

Potential of Farnesyl Transferase Inhibitors in Combination Regimens in Squamous Cell Carcinomas

Current therapies for recurrent and metastatic SCC are associated with poor outcomes, and options for later lines of treatment are limited. Insights into potential therapeutic targets, as well as mechanisms of resistance to available therapies, have begun to be elucidated, creating the basis for exploration of combination approaches to drive better patient outcomes. Tipifarnib, a farnesyl transferase inhibitor (FTI), is a small molecule drug that has demonstrated encouraging clinical activity in a genetically-defined subset of head and neck squamous cell carcinoma (HNSCC)-specifically, tumors that express a mutation in the HRAS protooncogene. More recently, bioinformatic analyses and results from patient-derived xenograft modeling indicate that HRAS pathway dependency may extend to a broader subpopulation of SCCs beyond HRAS mutants in the context of combination with agents such as cisplatin, cetuximab, or alpelisib. In addition, tipifarnib can also inactivate additional farnesylated proteins implicated in resistance to approved therapies, including immunotherapies, through a variety of distinct mechanisms, suggesting that tipifarnib could serve as an anchor for combination regimens in SCCs and other tumor types.

Five Surfactin Isomers Produced during Cheonggukjang Fermentation by Bacillus pumilus HY1 and Their Properties

The cyclic lipopeptide produced from Bacillus pumilus strain HY1 was isolated from Korean soybean sauce cheonggukjang. The chemical structures of the surfactin isomers were analyzed using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and electrospray ionization tandem mass spectrometry (ESI-MS/MS). The five potential surfactin isoforms were detected with protonated masses of m/z 994.7, 1008.7, 1022.7, 1036.7, and 1050.7 and different structures in combination with Na+, K+, and Ca2+ ions. ESI-MS/MS analysis revealed that the isolated surfactin possessed the precise amino acid sequence LLVDLL and hydroxyl fatty acids with 12 to 16 carbons. The surfactin content during cheonggukjang fermentation increased from 0.3 to 51.2 mg/kg over 60 h of fermentation. The mixture of five surfactin isoforms of cheonggukjang inhibited the growth of two cancer cell lines. The growth of both MCF-7 and Caco-2 cells was strongly inhibited with 100 μg/μL of surfactin. This study is the first-time report of five surfactin isomers of Bacillus pumilus strain HY1 during Korean soybean sauce cheonggukjang fermentation, which has cytotoxic properties.

Accumulation of prelamin A induces premature aging through mTOR overactivation

Hutchinson-Gilford progeria syndrome (HGPS) arises when a truncated form of farnesylated prelamin A accumulates at the nuclear envelope, leading to misshapen nuclei. Previous studies of adult Zmpste24-deficient mice, a mouse model of progeria, have reported a metabolic response involving inhibition of the mTOR (mammalian target of rapamycin) kinase and activation of autophagy. However, exactly how mTOR or autophagy is involved in progeria remains unclear. Here, we investigate this question by crossing Zmpste24^+/- mice with mice hypomorphic in mTOR (mTOR^△/+ ), or mice heterozygous in autophagy-related gene 7 (Atg7^+/- ). We find that accumulation of prelamin A induces premature aging through mTOR overactivation and impaired autophagy in newborn Zmpste24^-/- mice. Zmpste24^-/- mice with genetically reduced mTOR activity, but not heterozygosity in Atg7, show extended lifespan. Moreover, mTOR inhibition partially restores autophagy and S6K1 activity. We also show that progerin interacts with the Akt phosphatase to promote full activation of the Akt/mTOR signaling pathway. Finally, although we find that genetic reduction of mTOR postpones premature aging in Zmpste24 KO mice, frequent embryonic lethality occurs. Together, our findings show that over-activated mTOR contributes to premature aging in Zmpste24^-/- mice, and suggest a potential strategy in treating HGPS patients with mTOR inhibitors.

Long term breeding of the Lmna G609G progeric mouse: Characterization of homozygous and heterozygous models

The transgenic Lmna^G609G progeric mouse represents an outstanding animal model for studying the human Hutchinson-Gilford Progeria Syndrome (HGPS) caused by a mutation in the LMNA gene, coding for the nuclear envelope protein Lamin A/C, and, as an important, more general scope, for studying the complex process governing physiological aging in humans. Here we give a comprehensive description of the peculiarities related to the breeding of Lmna^G609G mice over a prolonged period of time, and of many features observed in a large colony for a 2-years period. We describe the breeding and housing conditions underlining the possible interference of the genetic background on the phenotype expression. This information represents a useful tool when planning and interpreting studies on the Lmna^G609G mouse model, complementing any specific data already reported in the literature about this model since its production. It is also particularly relevant for the heterozygous mouse, which mirrors the genotype of the human pathology however requires an extended time to manifest symptoms and to be carefully studied.

All-trans retinoic acid and rapamycin normalize Hutchinson Gilford progeria fibroblast phenotype

Hutchinson Gilford progeria syndrome is a fatal disorder characterized by accelerated aging, bone resorption and atherosclerosis, caused by a LMNA mutation which produces progerin, a mutant lamin A precursor. Progeria cells display progerin and prelamin A nuclear accumulation, altered histone methylation pattern, heterochromatin loss, increased DNA damage and cell cycle alterations. Since the LMNA promoter contains a retinoic acid responsive element, we investigated if all-trans retinoic acid administration could lower progerin levels in cultured fibroblasts. We also evaluated the effect of associating rapamycin, which induces autophagic degradation of progerin and prelamin A. We demonstrate that all-trans retinoic acid acts synergistically with low-dosage rapamycin reducing progerin and prelamin A, via transcriptional downregulation associated with protein degradation, and increasing the lamin A to progerin ratio. These effects rescue cell dynamics and cellular proliferation through recovery of DNA damage response factor PARP1 and chromatin-associated nuclear envelope proteins LAP2α and BAF. The combined all-trans retinoic acid-rapamycin treatment is dramatically efficient, highly reproducible, represents a promising new approach in Hutchinson-Gilford Progeria therapy and deserves investigation in ageing-associated disorders.

Enhanced SRSF5 Protein Expression Reinforces Lamin A mRNA Production in HeLa Cells and Fibroblasts of Progeria Patients

The Hutchinson Gilford Progeria Syndrome (HGPS) is a rare genetic disease leading to accelerated aging. Three mutations of the LMNA gene leading to HGPS were identified. The more frequent ones, c.1824C>T and c.1822G>A, enhance the use of the intron 11 progerin 5'splice site (5'SS) instead of the LMNA 5'SS, leading to the production of the truncated dominant negative progerin. The less frequent c.1868C>G mutation creates a novel 5'SS (LAΔ35 5'SS), inducing the production of another truncated LMNA protein (LAΔ35). Our data show that the progerin 5'SS is used at low yield in the absence of HGPS mutation, whereas utilization of the LAΔ35 5'SS is dependent upon the presence of the c.1868C>G mutation. In the perspective to correct HGPS splicing defects, we investigated whether SR proteins can modify the relative yields of utilization of intron 11 5'SSs. By in cellulo and in vitro assays, we identified SRSF5 as a direct key regulator increasing the utilization of the LMNA 5'SS in the presence of the HGPS mutations. Enhanced SRSF5 expression in dermal fibroblasts of HGPS patients as well as PDGF-BB stimulation of these cells decreased the utilization of the progerin 5'SS, and improves nuclear morphology, opening new therapeutic perspectives for premature aging.

Prenylome profiling reveals S-farnesylation is crucial for membrane targeting and antiviral activity of ZAP long-isoform

S-prenylation is an important lipid modification that targets proteins to membranes for cell signaling and vesicle trafficking in eukaryotes. As S-prenylated proteins are often key effectors for oncogenesis, congenital disorders, and microbial pathogenesis, robust proteomic methods are still needed to biochemically characterize these lipidated proteins in specific cell types and disease states. Here, we report that bioorthogonal proteomics of macrophages with an improved alkyne-isoprenoid chemical reporter enables large-scale profiling of prenylated proteins, as well as the discovery of unannotated lipidated proteins such as isoform-specific S-farnesylation of zinc-finger antiviral protein (ZAP). Notably, S-farnesylation was crucial for targeting the long-isoform of ZAP (ZAPL/PARP-13.1/zc3hav1) to endolysosomes and enhancing the antiviral activity of this immune effector. These studies demonstrate the utility of isoprenoid chemical reporters for proteomic analysis of prenylated proteins and reveal a role for protein prenylation in host defense against viral infections.

Hip pathology in Hutchinson-Gilford progeria syndrome: a report of two children

Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder. The estimated incidence is one in 4 million births. Orthopaedic manifestations include abnormality of the hips occurring early in the disease process. Severe coxa valga can be apparent by the age of 2 years. We report two cases of HGPS, one in a 7-year-old girl with avascular necrosis of the left hip and the second in a 13-year-old girl with recurrent traumatic hip dislocations. We demonstrate the pathoanatomical changes in the hip with HGPS using a combination of imaging modalities including radiographic, computed tomographic and MRI scans. These include coxa magna, coxa valga and acetabular dysplasia. We also comment on how these would affect the surgical management of this high-risk group of patients.

Farnesyltransferase inhibitor treatment restores chromosome territory positions and active chromosome dynamics in Hutchinson-Gilford progeria syndrome cells

Background

Hutchinson-Gilford progeria syndrome (HGPS) is a premature ageing syndrome that affects children leading to premature death, usually from heart infarction or strokes, making this syndrome similar to normative ageing. HGPS is commonly caused by a mutation in the A-type lamin gene, LMNA (G608G). This leads to the expression of an aberrant truncated lamin A protein, progerin. Progerin cannot be processed as wild-type pre-lamin A and remains farnesylated, leading to its aberrant behavior during interphase and mitosis. Farnesyltransferase inhibitors prevent the accumulation of farnesylated progerin, producing a less toxic protein.

Results

We have found that in proliferating fibroblasts derived from HGPS patients the nuclear location of interphase chromosomes differs from control proliferating cells and mimics that of control quiescent fibroblasts, with smaller chromosomes toward the nuclear interior and larger chromosomes toward the nuclear periphery. For this study we have treated HGPS fibroblasts with farnesyltransferase inhibitors and analyzed the nuclear location of individual chromosome territories. We have found that after exposure to farnesyltransferase inhibitors mis-localized chromosome territories were restored to a nuclear position akin to chromosomes in proliferating control cells. Furthermore, not only has this treatment afforded chromosomes to be repositioned but has also restored the machinery that controls their rapid movement upon serum removal. This machinery contains nuclear myosin 1β, whose distribution is also restored after farnesyltransferase inhibitor treatment of HGPS cells.

Conclusions

This study not only progresses the understanding of genome behavior in HGPS cells but demonstrates that interphase chromosome movement requires processed lamin A.

Protein farnesylation inhibitors cause donut-shaped cell nuclei attributable to a centrosome separation defect

Despite the success of protein farnesyltransferase inhibitors (FTIs) in the treatment of certain malignancies, their mode of action is incompletely understood. Dissecting the molecular pathways affected by FTIs is important, particularly because this group of drugs is now being tested for the treatment of Hutchinson-Gilford progeria syndrome. In the current study, we show that FTI treatment causes a centrosome separation defect, leading to the formation of donut-shaped nuclei in nontransformed cell lines, tumor cell lines, and tissues of FTI-treated mice. Donut-shaped nuclei arise during chromatin decondensation in late mitosis; subsequently, cells with donut-shaped nuclei exhibit defects in karyokinesis, develop aneuploidy, and are often binucleated. Binucleated cells proliferate slowly. We identified lamin B1 and proteasome-mediated degradation of pericentrin as critical components in FTI-induced "donut formation" and binucleation. Reducing pericentrin expression or ectopic expression of nonfarnesylated lamin B1 was sufficient to elicit donut formation and binucleated cells, whereas blocking proteasomal degradation eliminated FTI-induced donut formation. Our studies have uncovered an important role of FTIs on centrosome separation and define pericentrin as a (indirect) target of FTIs affecting centrosome position and bipolar spindle formation, likely explaining some of the anticancer effects of these drugs.

Absence of progeria-like disease phenotypes in knock-in mice expressing a non-farnesylated version of progerin

Hutchinson-Gilford progeria syndrome (HGPS) is caused by a mutant prelamin A, progerin, that terminates with a farnesylcysteine. HGPS knock-in mice (Lmna(HG/+)) develop severe progeria-like disease phenotypes. These phenotypes can be ameliorated with a protein farnesyltransferase inhibitor (FTI), suggesting that progerin's farnesyl lipid is important for disease pathogenesis and raising the possibility that FTIs could be useful for treating humans with HGPS. Subsequent studies showed that mice expressing non-farnesylated progerin (Lmna(nHG/+) mice, in which progerin's carboxyl-terminal -CSIM motif was changed to -SSIM) also develop severe progeria, raising doubts about whether any treatment targeting protein prenylation would be particularly effective. We suspected that those doubts might be premature and hypothesized that the persistent disease in Lmna(nHG/+) mice could be an unanticipated consequence of the cysteine-to-serine substitution that was used to eliminate farnesylation. To test this hypothesis, we generated a second knock-in allele yielding non-farnesylated progerin (Lmna(csmHG)) in which the carboxyl-terminal -CSIM motif was changed to -CSM. We then compared disease phenotypes in mice harboring the Lmna(nHG) or Lmna(csmHG) allele. As expected, Lmna(nHG/+) and Lmna(nHG/nHG) mice developed severe progeria-like disease phenotypes, including osteolytic lesions and rib fractures, osteoporosis, slow growth and reduced survival. In contrast, Lmna(csmHG/+) and Lmna(csmHG/csmHG) mice exhibited no bone disease and displayed entirely normal body weights and survival. The frequencies of misshapen cell nuclei were lower in Lmna(csmHG/+) and Lmna(csmHG/csmHG) fibroblasts. These studies show that the ability of non-farnesylated progerin to elicit disease depends on the carboxyl-terminal mutation used to eliminate protein prenylation.

Reversal of age-dependent nuclear morphology by inhibition of prenylation does not affect lifespan in Caenorhabditis elegans

Fibroblasts derived from Hutchinson-Gilford progeria syndrome (HGPS) patients and dermal cells derived from healthy old humans in culture display age-dependent progressive changes in nuclear architecture due to accumulation of farnesylated lamin A. Treating human HGPS cells or mice expressing farnesylated lamin A with farnesyl transferase inhibitors (FTIs) reverses nuclear phenotypes and extends lifespan. Aging adult Caenorhabditis elegans show changes in nuclear architecture resembling those seen in HGPS fibroblasts, as well as a decline in motility, phenotypes which are also inhibited by the FTI gliotoxin. However, it was not clear whether these effects were due to loss of farnesylation or to side effects of this drug. Here, we used a different FTI, manumycin or downregulated polyprenyl synthetase with RNAi to test the roles of farnesylation in C. elegans aging. Our results show that the age-dependent changes in nuclear morphology depend on farnesylation. We also demonstrate that inhibition of farnesylation does not affect motility or lifespan, suggesting that the effects of blocking protein prenylation on nuclear morphology could be separated from their effects on motility and lifespan. These results provide further understanding of the role of lamin and farnesylation in the normal aging process and in HGPS.

Prediction and evaluation of protein farnesyltransferase inhibition by commercial drugs

The similarity ensemble approach (SEA) relates proteins based on the set-wise chemical similarity among their ligands. It can be used to rapidly search large compound databases and to build cross-target similarity maps. The emerging maps relate targets in ways that reveal relationships one might not recognize based on sequence or structural similarities alone. SEA has previously revealed cross talk between drugs acting primarily on G-protein coupled receptors (GPCRs). Here we used SEA to look for potential off-target inhibition of the enzyme protein farnesyltransferase (PFTase) by commercially available drugs. The inhibition of PFTase has profound consequences for oncogenesis, as well as a number of other diseases. In the present study, two commercial drugs, Loratadine and Miconazole, were identified as potential ligands for PFTase and subsequently confirmed as such experimentally. These results point toward the applicability of SEA for the prediction of not only GPCR-GPCR drug cross talk but also GPCR-enzyme and enzyme-enzyme drug cross talk.

Gliotoxin reverses age-dependent nuclear morphology phenotypes, ameliorates motility, but fails to affect lifespan of adult Caenorhabditis elegans

Specific mutations in human LMNA or loss of ZMPSTE26 activity cause abnormal processing of lamin A and early aging diseases, including Hutchinson Gilford progeria syndrome (HGPS). HGPS fibroblasts in culture undergo age-dependent progressive changes in nuclear architecture. Treating these cells with farnesyl transferase inhibitors (FTIs) reverse these nuclear phenotypes and also extend lifespan of mice HGPS models. Dermal cells derived from healthy old humans also accumulate the abnormally processed lamin A. However, the effect of FTIs on normal aging cells was not tested. Aging adult C. elegans cells show changes in nuclear architecture similar to HGPS fibroblasts and down regulating lamin expression in adult C. elegans reduces their lifespan. Here, we show that nuclei of adult C. elegans, in which lamin is down-regulated, have similar phenotypes to normal aging nuclei, but at an earlier age. We further show that treating adult C. elegans with the FTI gliotoxin reverses nuclear phenotypes and improves motility of aging worms. However, the average lifespan of the gliotoxin-treated animals was similar to that of untreated animals. These results suggest that lamins are involved in the process of normal aging in C. elegans.

ZMPSTE24, an integral membrane zinc metalloprotease with a connection to progeroid disorders

ZMPSTE24 is an integral membrane zinc metalloprotease originally discovered in yeast as an enzyme (called Ste24p) required for maturation of the mating pheromone a-factor. Surprisingly, ZMPSTE24 has recently emerged as a key protease involved in human progeroid disorders. ZMPSTE24 has only one identified mammalian substrate, the precursor of the nuclear scaffold protein lamin A. ZMPSTE24 performs a critical endoproteolytic cleavage step that removes the hydrophobic farnesyl-modified tail of prelamin A. Failure to do so has drastic consequences for human health and longevity. Here, we discuss the discovery of the yeast and mammalian ZMPSTE24 orthologs and review the unexpected connection between ZMPSTE24 and premature aging.

Nuclear lamins: key regulators of nuclear structure and activities

The nuclear lamina is a proteinaceous structure located underneath the inner nuclear membrane (INM), where it associates with the peripheral chromatin. It contains lamins and lamin-associated proteins, including many integral proteins of the INM, chromatin modifying proteins, transcriptional repressors and structural proteins. A fraction of lamins is also present in the nucleoplasm, where it forms stable complexes and is associated with specific nucleoplasmic proteins. The lamins and their associated proteins are required for most nuclear activities, mitosis and for linking the nucleoplasm to all major cytoskeletal networks in the cytoplasm. Mutations in nuclear lamins and their associated proteins cause about 20 different diseases that are collectively called laminopathies'. This review concentrates mainly on lamins, their structure and their roles in DNA replication, chromatin organization, adult stem cell differentiation, aging, tumorogenesis and the lamin mutations leading to laminopathic diseases.

Molecular ageing in progeroid syndromes: Hutchinson-Gilford progeria syndrome as a model

Hutchinson-Gilford progeria syndrome (HGPS) is a rare premature aging disorder that belongs to a group of conditions called laminopathies which affect nuclear lamins. Mutations in two genes, LMNA and ZMPSTE24, have been found in patients with HGPS. The p.G608G LMNA mutation is the most commonly reported mutation. The aim of this work was to compile a comprehensive literature review of the clinical features and genetic mutations and mechanisms of this syndrome as a contribution to health care workers. This review shows the necessity of a more detailed clinical identification of Hutchinson-Gilford progeria syndrome and the need for more studies on the pharmacologic and pharmacogenomic approach to this syndrome.

Increasing the length of progerin's isoprenyl anchor does not worsen bone disease or survival in mice with Hutchinson-Gilford progeria syndrome

Hutchinson-Gilford progeria syndrome (HGPS) is caused by the synthesis of a truncated prelamin A, commonly called progerin, that contains a carboxyl-terminal farnesyl lipid anchor. The farnesyl lipid anchor helps to target progerin to membrane surfaces at the nuclear rim, where it disrupts the integrity of the nuclear lamina and causes misshapen nuclei. Several lines of evidence have suggested that progerin's farnesyl lipid anchor is crucial for the emergence of disease phenotypes. Because a geranylgeranyl lipid is approximately 45-fold more potent than a farnesyl lipid in anchoring proteins to lipid membranes, we hypothesized that a geranylgeranylated version of progerin might be more potent in eliciting disease phenotypes. To test this hypothesis, we used gene targeting to create mice expressing geranylgeranylated progerin (Lmna(ggHG/+)). We then compared Lmna(ggHG/+) mice, side-by-side, with otherwise identical mice expressing farnesylated progerin (Lmna(HG/+)). Geranylgeranylation of progerin in Lmna(ggHG/+) cells and farnesylation of progerin in Lmna(HG/+) cells was confirmed by metabolic labeling. Contrary to our expectations, Lmna(ggHG/+) mice survived longer than Lmna(HG/+) mice. The Lmna(ggHG/+) mice also exhibited milder bone disease. The steady-state levels of progerin, relative to lamin C, were lower in Lmna(ggHG/+) mice than in Lmna(HG/+) mice, providing a potential explanation for the milder disease in Lmna(ggHG/+) mice.

Eliminating the synthesis of mature lamin A reduces disease phenotypes in mice carrying a Hutchinson-Gilford progeria syndrome allele

Hutchinson-Gilford progeria syndrome is caused by the synthesis of a mutant form of prelamin A, which is generally called progerin. Progerin is targeted to the nuclear rim, where it interferes with the integrity of the nuclear lamina, causes misshapen cell nuclei, and leads to multiple aging-like disease phenotypes. We created a gene-targeted allele yielding exclusively progerin (Lmna HG) and found that heterozygous mice (Lmna HG/+) exhibit many phenotypes of progeria. In this study, we tested the hypothesis that the phenotypes elicited by the Lmna HG allele might be modulated by compositional changes in the nuclear lamina. To explore this hypothesis, we bred mice harboring one Lmna HG allele and one Lmna LCO allele (a mutant allele that produces lamin C but no lamin A). We then compared the phenotypes of Lmna HG/LCO mice (which produce progerin and lamin C) with littermate Lmna HG/+ mice (which produce lamin A, lamin C, and progerin). Lmna HG/LCO mice exhibited improved HG/LCO fibroblasts had fewer misshapen nuclei than Lmna HG/+ fibroblasts (p < 0.0001). A likely explanation for these differences was uncovered; the amount of progerin in Lmna HG/LCO fibroblasts and tissues was lower than in Lmna HG/+ fibroblasts and tissues. These studies suggest that compositional changes in the nuclear lamina can influence both the steady-state levels of progerin and the severity of progeria-like disease phenotypes.

Treatment with a farnesyltransferase inhibitor improves survival in mice with a Hutchinson-Gilford progeria syndrome mutation

Hutchinson-Gilford progeria syndrome (HGPS) is a progeroid syndrome characterized by multiple aging-like disease phenotypes. We recently reported that a protein farnesyltransferase inhibitor (FTI) improved several disease phenotypes in mice with a HGPS mutation (Lmna(HG/+)). Here, we investigated the impact of an FTI on the survival of Lmna(HG/+) mice. The FTI significantly improved the survival of both male and female Lmna(HG/+) mice. Treatment with the FTI also improved body weight curves and reduced the number of spontaneous rib fractures. This study provides further evidence for a beneficial effect of an FTI in HGPS.

Farnesyl diphosphate analogues with omega-bioorthogonal azide and alkyne functional groups for protein farnesyl transferase-catalyzed ligation reactions

Eleven farnesyl diphosphate analogues, which contained omega-azide or alkyne substituents suitable for bioorthogonal Staudinger and Huisgen [3 + 2] cycloaddition coupling reactions, were synthesized. The analogues were evaluated as substrates for the alkylation of peptide cosubstrates by yeast protein farnesyl transferase. Five of the diphosphates were good alternative substrates for farnesyl diphosphate (FPP). Steady-state kinetic constants were measured for the active compounds, and the products were characterized by HPLC and LC-MS. Two of the analogues gave steady-state kinetic parameters (kcat and Km) very similar to those of the natural substrate.

New approaches to progeria

Progeria (Hutchinson-Gilford progeria syndrome) is a rare genetic disorder that offers considerable insight into the biology of premature aging. This review summarizes the clinical characteristics of this disease and the underlying mutation in the lamin A (LMNA) gene that results in this phenotype. Modifications in the processing of prelamin A through alterations in farnesylation are detailed, because this pathway offers a possible drug target. Finally, discussion of an ongoing clinical trial for these children, including possible parameters for evaluation, are discussed. In the span of less than a decade, this disease has progressed from an interesting phenotype to one in which the gene defect has been identified, animal models have been created and tested with drugs that target the primary disease pathway, and significant clinical baseline data for the support of a clinical trial have been obtained.

Surfactin from Bacillus subtilis displays anti-proliferative effect via apoptosis induction, cell cycle arrest and survival signaling suppression

The effect of surfactin on the proliferation of LoVo cells, a human colon carcinoma cell line, was examined. Surfactin strongly blocked the proliferation of LoVo cells by inducing pro-apoptotic activity and arresting the cell cycle, according to several lines of evidence on DNA fragmentation, Annexin V staining, and altered levels of poly (ADP-ribose) polymerase, caspase-3, p21(WAF1/Cip1), p53, CDK2 and cyclin E. The anti-proliferative activity of surfactin was mediated by inhibiting extracellular-related protein kinase and phosphoinositide 3-kinase/Akt activation, as assessed by phosphorylation levels. Therefore, our data suggest that surfactin may have anti-cancer properties as a result of its ability to downregulate the cell cycle and suppress its survival.