Natural Polyketides to Prevent Cardiovascular Disease
Catherina Caballero-George in Natural Products and Cardiovascular Health, 2018
Additionally, there are pleiotropic effects that the inhibition of the mevalonate pathway may incur as a result of this pathway’s role in the production of a number of key isoprenoid intermediaries. The effect is due to the role that prenylation, the addition of hydrophobic molecules to a protein, plays in protein trafficking and cellular signaling by facilitating protein-membrane interactions. First, farnesyl pyrophosphate signals protein transport to the lumen of the endoplasmic reticulum for further modification and is implicated in interactions involving Ras family proteins. Second, geranylgeranyl pyrophosphate plays a role in the modulation of the RhoA, Rac and Cdc signaling pathways. These are integral GTPase proteins for cellular growth, proliferation and migration that are employed ubiquitously across normal cell types and are often the subject of mutation in tumorigenic cells (Liao and Laufs, 2005).
Guanosine Triphosphate-Binding Proteins
Enrique Pimentel in Handbook of Growth Factors, 2017
Ras proteins are involved in the complex mechanisms of signal transduction across the membrane in many different biological systems. They are associated with various cellular proteins of 50 to 150 kDa.159 c-Ras proteins are synthesized as cytosolic precursors that are proteolytically processed to mature forms that localize to the plasma membrane. Association of Ras proteins with the membrane require posttranslational modifications at the carboxyl-terminal region, including prenylation, removal of three carboxyl-terminal residues and carboxyl methylation, and palmitoylation (addition of palmitic acid residues).160 Anchorage of Ras to the membrane is associated with prenylation, the covalent addition of a farnesyl moiety (polyisoprenoid group) to the sulfur of a cysteine in the carboxyl-terminal part of the Ras molecule.161-165 The donor of farnesyl residues required for prenylation is farnesyl pyrophosphate, and the farnesyl residue transfer is effected by the heterodimeric enzyme, famesyltransferase.166,167 Farnesyl, a polyisoprenoid derived from mevalonic acid, is an intermediate of the cholesterol biosynthetic pathway. Isoprenoid addition to the Ras protein is critical for both Ras membrane association and transforming activity.168 By contrast, nonpalmitoylated Ras derivatives containing myristic acid at their amino termini show efficient membrane association and display transforming activity even in their nonmutated, normal forms.169
Small-Molecule Targeted Therapies
David E. Thurston, Ilona Pysz in Chemistry and Pharmacology of Anticancer Drugs, 2021
Both normal and mutated Ras proteins need to anchor to the cell membrane for signal transduction to occur (Figure 6.54). Attachment to the membrane occurs through several post-translational modifications, in particular the transfer of a 15-carbon isoprenoid group to the carboxy-terminal of the Ras protein, a process known as prenylation. This isoprenoid group ensures that Ras can attach to its correct intracellular membrane-bound location. Thus, the membrane-bound Ras protein represents a “molecular switch” that allows transport of a signal (e.g., a growth factor) from the external environment of a cell to its nucleus. The first stage of this process involves an extracellular ligand stimulating a monomeric receptor kinase (RTK) that then dimerizes. Next, Grb2, an initial adaptor protein, identifies and interacts with a binding site, which in turn allows recruitment of “Son of Sevenless” (SoS), a second adaptor protein. The latter causes the inactive GDP-carrying Ras to become active by substituting GDP for GTP. After this, the signal can be transmitted downstream by the activated Ras to other effectors, such as Raf. In the MAPK signaling pathway, the Raf protein is the first kinase in the signaling chain.
Choroideremia: molecular mechanisms and development of AAV gene therapy
Published in Expert Opinion on Biological Therapy, 2018
Maria I Patrício, Alun R Barnard, Kanmin Xue, Robert E MacLaren
Choroideremia has a prevalence of about 1:50,000 [4]. It is caused by mutations in the CHM gene (OMIM Gene/Locus MIM number: 300390), located on the X chromosome at position Xq21.2, which encodes Rab escort protein-1 (REP1). The cloning of the CHM gene was completed in 1990 [8], but it took a bit longer to uncover its function as an escort of Rab proteins [9]. The mRNA spans 15 exons with a coding sequence of 1962 bp. It is expressed ubiquitously and encodes a 653-amino acid-long protein, REP1. REP1 plays a key role as part of the prenylation machinery. Prenylation is a type of post-transcriptional modification necessary for membrane association and protein–protein interactions, in which REP1 acts as an escort of Rab proteins [10]. The mechanism how CHM mutations affect the prenylation process and its impact on cell homeostasis are explored in detail in the next section. Below we discuss the clinical and genetic diagnosis of choroideremia, as well as the genotype-phenotype correlations evidenced to date.
High-throughput tool to discriminate effects of NMs (Cu-NPs, Cu-nanowires, CuNO3, and Cu salt aged): transcriptomics in Enchytraeus crypticus
Published in Nanotoxicology, 2018
Susana I. L. Gomes, Carlos P. Roca, Natália Pegoraro, Tito Trindade, Janeck J. Scott-Fordsmand, Mónica J. B. Amorim
In addition to the protein modifications affected for all Cu forms except CuNO3 (as discussed above), Cu-Nwires and Cu salt-aged are involved in protein lipidation, geranylgeranylation, and neddylation. Geranylgeranylation is a type of lipidation (or prenylation) that adds hydrophobic groups to a protein, and plays an important role in protein–protein and protein–membrane interactions. In the current study, both protein lipidation and the most specific protein geranylgeranylation are being affected, since different genes were involved in the two biological processes. Lipidation processes, together with membrane budding and membrane docking (also affected by Cu-Nwires and Cu salt-aged) might be associated with endocytosis. The inhibition of both protein geranylgeranylation and protein neddylation has been associated with increase in apoptosis (Li et al. 2002; Wang et al. 2015). In our case, however, the genes involved in these processes (e.g. protein geranylgeranyltransferase type beta subunit and nedd8 activating enzyme e1 subunit 1) were up-regulated, indicating induction and not inhibition, for which posteriori effects are unknown.
Progress in the development of novel therapies for choroideremia
Published in Expert Review of Ophthalmology, 2019
Jasmina Cehajic Kapetanovic, Maria I Patrício, Robert E MacLaren
The levels of REP1 in peripheral blood mononuclear cells can be measured in vitro by immunoblot assays. The absence or reduced levels of REP1 can be used to support the diagnosis of choroideremia. Moreover, the detection of reduced prenylation activity can further aid the diagnosis. These premises led to the investigation of a method to test the biological activity of AAV vector carrying CHM gene currently under trial for choroideremia. We recently developed a robust in vitro prenylation assay using a biotinylated lipid donor to test the REP1 activity following the transduction of HEK293 cells with AAV2-REP1 [17]. Specifically, two Rab proteins, RAB27A and RAB6A, were used as substrates in a prenylation reaction in which a biotinylated lipid donor was incorporated. The amount of biotinylated lipid donor detected was proportional to the amount of AAV2-REP1 present in the reaction. We also found that the prenylation of RAB6A is more sensitive to REP1 protein expression compared to RAB27A. This method was found to be robust and reproducible in several cell lines. This assay can be used to test the biological activity of AAV vectors in choroideremia gene therapy clinical trials.
Related Knowledge Centers
- Biomolecule
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- Lamin
- Protein
- Cell Membrane
- Lipid-Anchored Protein
- Glycosylphosphatidylinositol
- Geranylgeranylation