Figure 2
Enzymatic pathway for the modification of prenylated proteins.PFT attaches a farnesyl group to the C-terminal CaaX motif of specific cytosolic proteins. The farnesylated protein undergoes C-terminal aaX removal by the endoprotease Rce1p, and this is followed by S-adenosylmethionine (SAM)-dependent methylation of the COOH terminus by Imct; both modifications occur in the endoplasmic reticulum. Some proteins, such as N-Ras and H-Ras, are further modified after transfer to Golgi membranes by palmitoylation on one or two cysteines near the prenylated cysteine in a reaction catalyzed by DHHC9 and GCP16 in mammals (Erf2 and Erf4 in yeast endoplasmic reticulum membranes) and using palmitoyl coenzyme A (CoA) as the fatty-acid donor. After palmitoylation, fully lipidated N-Ras and H-Ras are transferred to the plasma membrane probably by vesicle transport. Other proteins, such as K-Ras, contain a polybasic region (KKKKKKSKTK) next to the prenylated C terminus that is thought to bind the protein to the cytosolic face of the plasma membrane through electrostatic interactions with acidic phospholipids. PPO, pyrophosphate. Farnesyl groups are shown in blue and palmitoyl groups are red.
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In eukaryotic cells, a specific set of proteins are modified by C-terminal attachment of 15-carbon farnesyl groups or 20-carbon geranylgeranyl groups that function both as anchors for fixing proteins to membranes and as molecular handles for facilitating binding of these lipidated proteins to other proteins. Additional modification of these prenyla...
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Context 1
... and X is one of a variety of amino acids. After attachment of the farnesyl group via a thioether linkage to the cysteine residue, the last three amino acids, aaX, are removed by a prenyl protein-specific endoprotease, and the α-carboxyl group of the newly exposed farnesylated cysteine is methylated by a prenyl protein-specific methyltransferase (Fig. 2). Some prenylated proteins such as H-Ras and N-Ras contain a second lipid chain, a 16-carbon palmitoyl group, that is thioester linked to the SH group of a cysteine that is close in protein sequence to the farnesylated-cysteine C terminus (Fig. 2). Known geranylgeranylated proteins include the γ subunit of heterotrimeric G proteins that ...
Context 2
... the newly exposed farnesylated cysteine is methylated by a prenyl protein-specific methyltransferase (Fig. 2). Some prenylated proteins such as H-Ras and N-Ras contain a second lipid chain, a 16-carbon palmitoyl group, that is thioester linked to the SH group of a cysteine that is close in protein sequence to the farnesylated-cysteine C terminus (Fig. 2). Known geranylgeranylated proteins include the γ subunit of heterotrimeric G proteins that function at the plasma membrane, and many small GTP-binding proteins such as the Rho proteins. The Rab subfamily of GTP-binding proteins contain a pair of geranylgeranyl groups on adjacent or nearly adjacent cysteines at the C terminus of the ...
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... far, three distinct protein prenyltransferases that attach prenyl groups to proteins have been identified. Protein farnesyltransferase (PFT) transfers the farnesyl group from farnesyl diphosphate to the cysteine SH of the CaaX motif at the C terminus of proteins ( Fig. 2). Protein geranylgeranyltransferase type I (PGGT-I) catalyzes a similar reaction using geranylgeranyl diphosphate as the prenyl donor. Protein geranylgeranyltransferase type II (also known as Rab geranylgeranyltransferase) catalyzes the transfer of both geranylgeranyl groups from geranylgeranyl diphosphate to two cysteine SH groups at ...
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... CaaX processing machinery includes the endoprotease Rce1p (and in some cases Ste24p, see below), which releases an intact aaX tripeptide from the newly prenylated CaaX protein, and isoprenylcysteine carboxylmethyltransferase (Icmt), which transfers a methyl group from S-adenosylmethionine to the α-carboxyl group of the prenyl cysteine (Fig. 2). Two important breakthroughs based on the discovery of the genes encoding these enzymes in S. cerevisiae were the identification of the genes' mammalian homologs and their recent targeted disruption in mice. Ras localization and transforming capacity was found to be markedly altered in mouse embryonic fibroblasts having null and ...
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... reversible post-translational modification 54 . In the Ras superfamily, H-Ras and N-Ras are examples of proteins that are both prenylated and palmitoylated 55 . Palmitoylation of the C terminus of these Ras proteins occurs after the farnesylation of the C-terminal cysteine and at cysteine residues slightly upstream of the farnesylated cysteine ( Fig. 2). Although inhibitors of Ras palmitoylation are known (2-bromopalmitate 56 and cerulenin analogs 57,58 , for example), the mechanisms and selectivity steering this palmitoylation process are still unclear. Several palmitoylation motifs have been found in different classes of proteins and have been reviewed 52 . We focus on the recent ...
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... K-Ras protein contains eight lysine residues just upstream of the farnesylated C terminus (Fig. 2). It is has been suggested that these cationic lysines form favorable electrostatic interactions with the cytosolic face of the plasma membrane; anionic phospholipids including phosphatidylserine and phosphatidylinositol are present at relatively high abundances on this membrane leaflet. An electrostatic basis for targeting of K-Ras to ...
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... Post-translational lipid modifications, including N-myristoylation, palmitoylation, prenylation, glycosylphosphatidy linositol (GPI) anchor addition, and cholesterol attachment, expand the functional and structural diversity of the eukaryotic proteome (1,2). The chemical and physical properties, activities, and cellular distribution of proteins are significantly modified by the covalent attachment of a non-peptidic hydrophobic moiety to a protein. ...
... The chemical and physical properties, activities, and cellular distribution of proteins are significantly modified by the covalent attachment of a non-peptidic hydrophobic moiety to a protein. These post-translational modifications of proteins, including prenylation, allow their interactions with cellular membranes, a crucial requirement for proper cell signaling and functions (2). Prenylation includes both farnesylation and geranylgeranylation and is an irreversible covalent modification found in all eukaryotic cells. ...
Prenylation is an irreversible post-translational modification that supports membrane interactions of proteins involved in various cellular processes, including migration, proliferation, and survival. Dysregulation of prenylation contributes to multiple disorders, including cancers and vascular and neurodegenerative diseases. Prenyltransferases tether isoprenoid lipids to proteins via a thioether linkage during prenylation. Pharmacological inhibition of the lipid synthesis pathway by statins is a therapeutic approach to control hyperlipidemia. Building on our previous finding that statins inhibit membrane association of G protein γ (Gγ) in a subtype-dependent manner, we investigated the molecular reasoning for this differential inhibition. We examined the prenylation of carboxy-terminus (Ct) mutated Gγ in cells exposed to Fluvastatin and prenyl transferase inhibitors and monitored the subcellular localization of fluorescently tagged Gγ subunits and their mutants using live-cell confocal imaging. Reversible optogenetic unmasking-masking of Ct residues was used to probe their contribution to prenylation and membrane interactions of the prenylated proteins. Our findings suggest that specific Ct residues regulate membrane interactions of the Gγ polypeptide, statin sensitivity, and extent of prenylation. Our results also show a few hydrophobic and charged residues at the Ct are crucial determinants of a protein’s prenylation ability, especially under suboptimal conditions. Given the cell and tissue-specific expression of different Gγ subtypes, our findings indicate a plausible mechanism allowing for statins to differentially perturb heterotrimeric G protein signaling in cells depending on their Gγ-subtype composition. Our results may also provide molecular reasoning for repurposing statins as Ras oncogene inhibitors and the failure of using prenyltransferase inhibitors in cancer treatment.
... Post-translational lipid modifications, including N-myristoylation, palmitoylation, prenylation, glycosylphosphatidylinositol (GPI) anchor addition, and cholesterol attachment, expand the functional and structural diversity of the eukaryotic proteome (1,2). The chemical and physical properties, activities, and cellular distribution of proteins are significantly modified by the covalent attachment of a non-peptidic hydrophobic moiety to a protein. ...
... The chemical and physical properties, activities, and cellular distribution of proteins are significantly modified by the covalent attachment of a non-peptidic hydrophobic moiety to a protein. This results in the interaction of post-translationally modified proteins with cellular membranes and facilitates multiple cellular signaling pathways (2). Protein prenylation has been studied extensively due to its significance in the proper cellular activity of numerous proteins. ...
Prenylation is a universal and irreversible post-translational modification that supports membrane interactions of proteins involved in various cellular processes, including migration, proliferation, and survival. Thus, dysregulation of prenylation contributes to multiple disorders, including cancers, vascular diseases, and neurodegenerative diseases. During prenylation, prenyltransferase enzymes tether metabolically produced isoprenoid lipids to proteins via a thioether linkage. Pharmacological inhibition of the lipid synthesis pathway by statins has long been a therapeutic approach to control hyperlipidemia. Building on our previous finding that statins inhibit membrane association of G protein γ (Gγ) in a subtype-dependent manner, we investigated the molecular reasoning for this differential. We examined the prenylation efficacy of carboxy terminus (Ct) mutated Gγ in cells exposed to Fluvastatin and prenyl transferase inhibitors and monitored the subcellular localization of fluorescently tagged Gγ subunits and their mutants using live-cell confocal imaging. Reversible optogenetic unmasking-masking of Ct residues was used to probe their contribution to the prenylation process and membrane interactions of the prenylated proteins. Our findings suggest that specific Ct residues regulate membrane interactions of the Gγ polypeptide statin sensitivity, and prenylation efficacy. Our results also show that a few hydrophobic and charged residues at the Ct are crucial determinants of a protein’s prenylation ability, especially under suboptimal conditions. Given the cell and tissue-specific expression of different Gγ subtypes, our findings explain how and why statins differentially perturb heterotrimeric G protein signaling in specific cells and tissues. Our results may provide molecular reasoning for repurposing statins as Ras oncogene inhibitors and the failure of using prenyltransferase inhibitors in cancer treatment.
... [3] Prenylation regulates protein subcellular localization and interactions with other proteins. [4] Dysregulation of prenylation is involved in various disorders, including cardiovascular and cerebrovascular diseases, cancers, bone diseases, infectious diseases, progeria, and neurodegenerative diseases including Alzheimer's disease (AD). [5] For example, dysregulated isoprenoid synthesis and prenylation of small GTPases have been associated with multiple processes of AD pathology, including amyloid-β precursor protein processing, tau phosphorylation, neuroinflammation, and cognitive function. ...
Protein lipidation is a widespread modification that regulates protein subcellular localization, structure and function. Dysregulation of protein lipidation has been implicated in various human diseases, including neurological disorders, infectious diseases and cancers. Thus lipid‐modifying enzymes and their substrate proteins are emerging as attractive drug targets. The development of small‐molecule modulators of protein lipidation has remarkably impacted our understanding of lipid‐modification biology and potential therapeutics. In this review, we summarize recent progress in small‐molecule targeting of protein lipidation and highlight therapeutic opportunities.
... Heterocyclic molecules, whether of synthetic or natural origin, play a very important role in life processes and appear as a particularly interesting support in a wide variety of fields such as (pharmacy, medicine, industry, etc.). [1][2][3][4][5] One of the major challenges in organic chemistry research is the deployment of new processes for the preparation of heterocycles, allowing better combinations of functional groups and higher degrees of molecular complexity to be obtained cost-effectively and rapidly, under mild reaction conditions, and from readily available starting materials. For these reasons, the scientific community has devoted a great effort to finding effective synthesis methods for a wide variety of heterocyclic compounds. ...
... While exploring the mechanism of action of FTS, that was reported to inhibit RAS function, it was determined that it releases RAS from the membrane, displacing it into the cytosol, indicating that the major site of action of the FTS is at the anchoring point in the membrane [51]. The PTMs pathway is vital for the functions of most small GTPases where it is essential for their membrane binding and localization which is an essential step in their activation [61]. These modifications facilitate the proteins' association with the inner surfaces of the plasma membranes, where they interact with upstream activators and downstream effectors in various signaling pathways [57]. ...
Finding effective therapies against cancers driven by mutant and/or overexpressed hyperactive G-proteins remains an area of active research. Polyisoprenylated cysteinyl amide inhibitors (PCAIs) are agents that mimic the essential posttranslational modifications of G-proteins. It is hypothesized that PCAIs work as anticancer agents by disrupting polyisoprenylation-dependent functional interactions of the G-Proteins. This study tested this hypothesis by determining the effect of the PCAIs on the levels of RAS and related monomeric G-proteins. Following 48 h exposure, we found significant decreases in the levels of KRAS, RHOA, RAC1, and CDC42 ranging within 20-66% after NSL-YHJ-2-27 (5 μM) treatment in all four cell lines tested, A549, NCI-H1299, MDA-MB-231, and MDA-MB-468. However, no significant difference was observed on the G-protein, RAB5A. Interestingly, 38 and 44% decreases in the levels of the farnesylated and acylated NRAS were observed in the two breast cancer cell lines, MDA-MB-231, and MDA-MB-468, respectively, while HRAS levels showed a 36% decrease only in MDA-MB-468 cells. Moreover, after PCAIs treatment, migration, and invasion of A549 cells were inhibited by 72 and 70%, respectively while the levels of vinculin and fascin dropped by 33 and 43%, respectively. These findings implicate the potential role of PCAIs as anticancer agents through their direct interaction with monomeric G-proteins.
... Well-known farnesylated proteins are the small GTPases of the Ras-superfamily including Rab, Ran, Ras, Rho and Arf, influencing cellular processes like cell differentiation and inflammation (Song et al., 2019). Members of the Ras-family are known to play a crucial role in tumorgenesis, explaining the extensive research on the drug class of FTIs and its member Manumycin A (Zhang and Casey, 1996;Gelb et al., 2006). ...
Manumycin A is postulated to be a specific inhibitor against the farnesyltransferase (FTase) since this effect has been shown in 1993 for yeast FTase. Since then, plenty of studies investigated Manumycin A in human cells as well as in model organisms like Caenorhabditis elegans. Some studies pointed to additional targets and pathways involved in Manumycin A effects like apoptosis. Therefore, these studies created doubt whether the main mechanism of action of Manumycin A is FTase inhibition. For some of these alternative targets half maximal inhibitory concentrations (IC50) of Manumycin A are available, but not for human and C. elegans FTase. So, we aimed to 1) characterize missing C. elegans FTase kinetics, 2) elucidate the IC50 and Ki values of Manumycin A on purified human and C. elegans FTase 3) investigate Manumycin A dependent expression of FTase and apoptosis genes in C. elegans. C. elegans FTase has its temperature optimum at 40°C with KM of 1.3 µM (farnesylpyrophosphate) and 1.7 µM (protein derivate). Whilst other targets are inhibitable by Manumycin A at the nanomolar level, we found that Manumycin A inhibits cell-free FTase in micromolar concentrations (Ki human 4.15 μM; Ki C. elegans 3.16 μM). Furthermore, our gene expression results correlate with other studies indicating that thioredoxin reductase 1 is the main target of Manumycin A. According to our results, the ability of Manumycin A to inhibit the FTase at the micromolar level is rather neglectable for its cellular effects, so we postulate that the classification as a specific FTase inhibitor is no longer valid.
... The mevalonate pathway intermediates FPP (farnesyl diphosphate) and GGPP (geranylgeranyl diphosphate) that are essential enzymes for prenylation pathways. 8 Statins are HMG-CoA reductase inhibitors commonly used for the treatment of patients with hypercholesterolemia and prevention of cardiovascular diseases. 9 Due to their ability in blocking HMG-CoA reductase, an enzyme catalyzing the synthesis of mevalonate which is a critical precursor in mevalonate pathway, statins also inhibit protein prenylation and functions of many prenylation-dependent oncogenic proteins in cancer cells. ...
The resistance of glioblastoma to chemotherapy remains a significant clinical problem. Targeting alternative pathways such as protein prenylation is known to be effective against many cancers. Fluvastatin is a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl- CoA (HMG-CoA) reductase, thereby inhibits prenylation. We demonstrate that fluvastatin alone effectively inhibits proliferation and induces apoptosis in multiple human glioblastoma cell lines. The combination index analysis shows that fluvastatin acts synergistically with common chemotherapy drugs for glioblastoma: temozolomide and irinotecan. We further show that fluvastatin acts on glioblastoma through inhibiting prenylation-dependent Ras activation. The combination of fluvastatin and low dose temozolomide resulted in remarkable inhibition of glioblastoma tumor in mice throughout the whole treatment duration without causing toxicity. Such combinatorial effects provide the basis for utilizing these FDA-approved drugs as a potential clinical approach in overcoming resistance and improving glioblastoma treatment.
... Prelamin A (664 amino acids), the precursor of lamin A, has 98 unique carboxyl-terminal amino acids that contain a CAAX motif Hennekes & Nigg, 1994). The CAAX motif of lamin A is modified by farnesylation and is important for targeting the inner nuclear membrane (Gelb et al, 2006). The functional diversification of A-and B-type lamins has been interpreted through their differences in protein structure, expression, localization patterns, and biochemical properties (Rober et al, 1989;Lammerding et al, 2006;Adam & Goldman, 2012;Nmezi et al, 2019). ...
Lamins form the nuclear lamina, which is important for nuclear structure and activity. Although posttranslational modifications, in particular serine phosphorylation, have been shown to be important for structural properties and functions of lamins, little is known about the role of tyrosine phosphorylation in this regard. In this study, we found that the constitutively active Src Y527F mutant caused the disassembly of lamin A/C. We demonstrate that Src directly phosphorylates lamin A mainly at Tyr45 both in vitro and in intact cells. The phosphomimetic Y45D mutant was diffusively distributed in the nucleoplasm and failed to assemble into the nuclear lamina. Depletion of lamin A/C in HeLa cells induced nuclear dysmorphia and genomic instability as well as increased nuclear plasticity for cell migration, all of which were partially restored by re-expression of lamin A, but further promoted by the Y45D mutant. Together, our results reveal a novel mechanism for regulating the assembly of nuclear lamina through Src and suggest that aberrant phosphorylation of lamin A by Src may contribute to nuclear dysmorphia, genomic instability, and nuclear plasticity.
... Prenylation, the modification of proteins by isoprenoids, is known to control the localization and activity of several proteins, with a broad impact on cell regulation [65][66][67]. Most prenylated proteins, among them Rho GTPases, contain the CAAX target motif (where C represents the acceptor cysteine, A is an aliphatic amino acid and X is any terminal amino acid). ...
Cells and tissues are continuously exposed to both chemical and physical stimuli and dynamically adapt and respond to this variety of external cues to ensure cellular homeostasis, regulated development and tissue-specific differentiation. Alterations of these pathways promote disease progression-a prominent example being cancer. Rho GTPases are key regulators of the re-modeling of cytoskeleton and cell membranes and their coordination and integration with different biological processes, including cell polarization and motility, as well as other signaling networks such as growth signaling and proliferation. Apart from the control of GTP-GDP cycling, Rho GTPase activity is spatially and temporally regulated by post-translation modifications (PTMs) and their assembly onto specific protein complexes, which determine their controlled activity at distinct cellular compartments. Although Rho GTPases were traditionally conceived as targeted from the cytosol to the plasma membrane to exert their activity, recent research demonstrates that active pools of different Rho GTPases also localize to endomembranes and the nucleus. In this review, we discuss how PTM-driven modulation of Rho GTPases provides a versatile mechanism for their com-partmentalization and functional regulation. Understanding how the subcellular sorting of active small GTPase pools occurs and what its functional significance is could reveal novel therapeutic opportunities.
... One example of such post-translational modifications is protein farnesylation, a type of protein prenylation. This modification makes a significant contribution to the functions of a certain group of proteins that are involved in many biological regulations in eukaryotic cells (Zhang and Casey, 1996;Gelb et al., 2006). Accumulated evidence suggests that disruption of farnesylation is highly associated with various human diseases, especially cancers. ...
... But the petioles of era1 are shorter than those of WT. This inconsistency possibly results from the fact that farnesylation can affect many different processes in addition to its roles in the BR signaling pathway (Zhang and Casey, 1996;Gelb et al., 2006). In other words, the observed phenotype of era1 is a cumulative effect of many abolished farnesylation related processes. ...
Brassinosteroids (BRs) are a group of steroidal phytohormones, playing critical roles in almost all physiological aspects during the life span of a plant. In Arabidopsis, BRs are perceived at the cell surface, triggering a reversible phosphorylation‐based signaling cascade that leads to the activation and nuclear accumulation of a family of transcription factors, represented by BES1 and BZR1. Protein farnesylation is a type of post‐translational modification, functioning in many important cellular processes. Previous studies demonstrated a role of farnesylation in BR biosynthesis via regulating the endoplasmic reticulum localization of a key bassinolide (BL) biosynthetic enzyme BR6ox2. Whether such a process is also involved in BR signaling is not understood. Here, we demonstrate that protein farnesylation is involved in mediating BR signaling in Arabidopsis. A loss‐of‐function mutant of ENHANCED RESPONSE TO ABA 1 (ERA1), encoding a β subunit of the protein farnesyl transferase holoenzyme, can alter the BL sensitivity of bak1‐4 from a reduced to a hypersensitive level. era1 can partially rescue the BR defective phenotype of a heterozygous mutant of bin2‐1, a gain‐of‐function mutant of BIN2 which encodes a negative regulator in the BR signaling. Our genetic and biochemical analyses revealed that ERA1 plays a significant role in regulating the protein stability of BES1.
