Regulation of γ-Secretase Activity in Alzheimer's Disease

Relevant Developments in the Use of Three-Component Reactions for the Total Synthesis of Natural Products. The last 15 Years

Multicomponent reactions (MCRs) offer a highly useful and valuable strategy that can fulfill an important role in synthesizing complex polysubstituted compounds, by simplifying otherwise long sequences and increasing their efficiency. The total synthesis of selected natural products employing three-component reactions as their common strategic MCR approach, is reviewed on a case-by-case basis with selected targets conquered during the last 15 years. The revision includes detailed descriptions of the selected successful sequences; relevant information on the isolation, and bioactivity of the different natural targets is also briefly provided.

Luteoloside inhibits Aβ1-42 fibrillogenesis, disintegrates preformed fibrils, and alleviates amyloid-induced cytotoxicity

Abnormal aggregation and fibrillogenesis of amyloid-β protein (Aβ) can cause Alzheimer's disease (AD). Thus, the discovery of effective drugs that inhibit Aβ fibrillogenesis in the brain is crucial for the treatment of AD. Luteoloside, as one of the polyphenolic compounds, is found to have a certain therapeutic effect on nervous system diseases. However, it remains unknown whether luteoloside is a potential drug for treating AD by modulating Aβ aggregation pathway. In this study, we performed diverse biophysical and biochemical methods to explore the inhibition of luteoloside on Aβ1-42 which is linked to AD. The results demonstrated that luteoloside efficiently prevented amyloid oligomerization and cross-β-sheet formation, reduced the rate of amyloid growth and the length of amyloid fibrils in a dose-dependent manner. Moreover, luteoloside was able to influence aggregation and conformation of Aβ1-42 during different fiber-forming phases, and it could disintegrate already preformed fibrils of Aβ1-42 and convert them into nontoxic aggregates. Furthermore, luteoloside protected cells from amyloid-induced cytotoxicity and hemolysis, and attenuated the level of reactive oxygen species (ROS). The molecular docking study showed that luteoloside interacted with Aβ1-42 mainly via Conventional Hydrogen Bond, Carbon Hydrogen Bond, Pi-Pi T-shaped, Pi-Alkyl and Pi-Anion, thereby possibly preventing it from forming the aggregates. These observations indicate that luteoloside, a natural anti-oxidant molecule, may be applicable as an effective inhibitor of Aβ, and promote further exploration of the therapeutic strategy against AD.

Mechanistic regulation of γ-secretase by their substrates

γ-Secretase (GS) is a transmembrane (TM) enzyme that plays important roles in the processing of approximately 90 substrates.

Cholesterol metabolites and plant sterols in cerebrospinal fluid are associated with Alzheimer's cerebral pathology and clinical disease progression

BACKGROUND AND PURPOSE

Altered cholesterol metabolism is associated with increased risk of neurodegeneration and in particular with the development of Alzheimer's disease (AD). Here, we investigate whether non-cholesterol sterols and oxysterols in the central nervous system are associated with (i) the presence of cerebral AD pathology, (ii) distinct aspects of AD pathology, i.e. amyloid pathology, neuronal injury, and tau pathology, and (iii) cognitive decline over time.

EXPERIMENTAL APPROACH

One hundred forty-two elder subjects with normal cognition, mild cognitive impairment, or mild dementia participating in a cohort study on cognitive decline and AD were included. Clinical and neuropsychological assessments were performed at inclusion and repeated at follow-up visits at 18 and 36 months. Concentrations of cholesterol, non-cholesterol sterols, and cholesterol metabolites were measured in cerebrospinal fluid (CSF), along with CSF beta-amyloid (Aβ)_1-42; Aβ_1-42/Aβ_1-40 ratio, total-tau (tau), and tau phosphorylated at threonine 181 (p-tau) as markers of amyloid pathology, neuronal injury and tau pathology, respectively. Cognitive decline was assessed by changes in Mini-Mental State Examination and Clinical Dementia Rating sum of boxes at follow-up visits.

KEY RESULTS

CSF 24S-hydroxycholesterol (24S-OHC) and the 24S-OHC/27-OHC ratio were higher in subjects with AD pathology. CSF desmosterol correlated with Aβ_1-42 levels. The 24S-OHC levels, the 24S-OHC/27-OHC ratio and the plant sterols campesterol and sitosterol were associated with the tau and p-tau levels. Both plant sterol concentrations along with the 24S-OHC/27-OHC ratio at baseline predicted cognitive decline at follow-up visits.

CONCLUSIONS AND IMPLICATIONS

We show the importance of CSF levels of several non-cholesterol sterols and oxysterols to AD and core AD biomarkers. The plant sterols campesterol and sitosterol appear to be involved in tau pathology and neurodegeneration. CSF desmosterol level indicates CNS cholesterol synthesis and might be of relevance for clinical disease severity. Therefore these non-cholesterol sterols may represent intervention targets to slow down disease progression.

Potential Enzymatic Targets in Alzheimer's: A Comprehensive Review

Alzheimer's, a degenerative cause of the brain cells, is called as a progressive neurodegenerative disease and appears to have a heterogeneous etiology with main emphasis on amyloid-cascade and hyperphosphorylated tau-cascade hypotheses, that are directly linked with macromolecules called enzymes such as β- & γ-secretases, colinesterases, transglutaminases, and glycogen synthase kinase (GSK-3), cyclin-dependent kinase (cdk-5), microtubule affinity-regulating kinase (MARK). The catalytic activity of the above enzymes is the result of cognitive deficits, memory impairment and synaptic dysfunction and loss, and ultimately neuronal death. However, some other enzymes also lead to these dysfunctional events when reduced to their normal activities and levels in the brain, such as α- secretase, protein kinase C, phosphatases etc; metabolized to neurotransmitters, enzymes like monoamine oxidase (MAO), catechol-O-methyltransferase (COMT) etc. or these abnormalities can occur when enzymes act by other mechanisms such as phosphodiesterase reduces brain nucleotides (cGMP and cAMP) levels, phospholipase A2: PLA2 is associated with reactive oxygen species (ROS) production etc. On therapeutic fronts, several significant clinical trials are underway by targeting different enzymes for development of new therapeutics to treat Alzheimer's, such as inhibitors for β-secretase, GSK-3, MAO, phosphodiesterase, PLA2, cholinesterases etc, modulators of α- & γ-secretase activities and activators for protein kinase C, sirtuins etc. The last decades have perceived an increasing focus on findings and search for new putative and novel enzymatic targets for Alzheimer's. Here, we review the functions, pathological roles, and worth of almost all the Alzheimer's associated enzymes that address to therapeutic strategies and preventive approaches for treatment of Alzheimer's.

The role of extracellular matrix metalloproteinase inducer on the action of dihydrotestosterone against the cellular damage induced by Aβ42

Clinical studies have revealed that the risk of Alzheimer's disease (AD) in men is increased by age-related androgen depletion. The level of β-amyloid (Aβ) is elevated in the brains of AD patients, and Aβ is believed to play a critical role in the pathology of AD. Some studies have indicated that androgens affect AD risk by regulating the metabolism of Aβ by an unclear mechanism. In this study, we investigated the role of the extracellular matrix metalloproteinase inducer (CD147) in this action. Initially, we demonstrated that androgens positively regulate the expression of CD147 in adult male rats and SH-SY5Y cells. Furthermore, this regulation may involve androgen receptor (AR). Additionally, interference of CD147 expression decreased the clearance of Aβ in culture medium and reduced cell viability. It also affected the morphology of the cells and the expression of apoptosis-related proteins. Finally, we found that interference of CD147 expression blocked the dihydrotestosterone (DHT)-induced reduction in Aβ and the protection of cells. DHT regulates MMP-2's expression through CD147. Together, these results imply that androgen regulation of Aβ and cell protection may be affected by interfering with the expression of CD147.

Role of COX-2/PGE2 Mediated Inflammation in Oral Squamous Cell Carcinoma

A significant amount of research indicates that the cyclooxygenase/prostaglandin E2 (PGE2) pathway of inflammation contributes to the development and progression of a variety of cancers, including squamous cell carcinoma of the oral cavity and oropharynx (OSCC). Although there have been promising results from studies examining the utility of anti-inflammatory drugs in the treatment of OSCC, this strategy has been met with only variable success and these drugs are also associated with toxicities that make them inappropriate for some OSCC patients. Improved inflammation-targeting therapies require continued study of the mechanisms linking inflammation and progression of OSCC. In this review, a synopsis of OSCC biology will be provided, and recent insights into inflammation related mechanisms of OSCC pathobiology will be discussed. The roles of prostaglandin E2 and cluster of differentiation factor 147 (CD147) will be presented, and evidence for their interactions in OSCC will be explored. Through continued investigation into the protumourigenic pathways of OSCC, more treatment modalities targeting inflammation-related pathways can be designed with the hope of slowing tumour progression and improving patient prognosis in patients with this aggressive form of cancer.

A rapid synthesis of sphingosine from phytosphingosine

A simple and efficient protocol for the synthesis of a sphingosine starting from cost-effective phytosphingosine has been described. Two alternative synthetic pathway have been disclosed based on the use of two different kinds of protective groups for the protection of the amino group in the phytosphingosine. The protected phytosphingosine was subsequently transformed into sphingosine in 5 steps i.e. protection of the amine group, protection of 1,3-diol, leaving group insertion, elimination, and one-pot deprotection.

TMPyP Inhibits Amyloid-β Aggregation and Alleviates Amyloid-Induced Cytotoxicity

The aggregation or misfolding of amyloid-β (Aβ) is a major pathological hallmark of Alzheimer's disease (AD). The regulation of Aβ aggregation is thought to be an effective strategy for AD treatment. The capability of a water-soluble porphyrin, 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP), to inhibit Aβ aggregation and to lower Aβ-induced toxicity was demonstrated. As evidenced by surface plasmon resonance and circular dichroism, TMPyP can not only disrupt Aβ aggregation but also disassemble the preformed Aβ aggregates. The atomic force microscopy imaging proves that TMPyP inhibits the formation of both oligomers and fibrils. Molecular dynamic simulations provide an insight into the interaction between TMPyP and Aβ at the molecular level. The half-maximal inhibitory concentrations of TMPyP acting on the oligomers and fibrils were determined to be 0.6 and 0.43 μM, respectively. As a member of porphyrin family, TMPyP is of rather low cytotoxicity, and the cytotoxicity of the Aβ aggregates was also relieved upon coincubation with TMPyP. The excellent performance of TMPyP thus makes it a potential drug candidate for AD therapy.

Antiamyloidogenic Activity of Aβ42-Binding Peptoid in Modulating Amyloid Oligomerization

The oligomerization and aggregation of amyloid β (Aβ) play central role in the pathogenesis of Alzheimer's disease (AD). Molecular binding agents for modulating the formation of Aβ oligomers and fibrils have promising application potential in AD therapies. By screening a peptoid library using surface plasmon resonance imaging, amyloid inhibitory peptoid 1 (AIP1) that has high affinity to Aβ42 is identified. AIP1 is demonstrated to inhibit Aβ42 oligomerization and fibrillation and to rescue Aβ42-induced cytotoxicity through decreasing the content of Aβ42 oligomers that is related to cell membrane permeability. Molecular docking suggests that the binding sites of AIP1 may be at the N-terminus of Aβ42. The blood-brain barrier (BBB) permeability of AIP1 using an in vitro BBB model is also revealed. This work provides a strategy for the design and development of peptoid-based antiamyloidogenic agents. The obtained amyloid inhibitory peptoid shows prospects in the therapeutic application in AD.

GATA1-mediated transcriptional regulation of the γ-secretase activating protein increases Aβ formation in Down syndrome

Because of an extra copy of the Aβ precursor protein gene on chromosome 21, Down syndrome (DS) individuals develop high levels of Aβ peptides and Alzheimer disease-like brain amyloidosis early in life. Here we show that the γ-secretase activating protein (GSAP), a key enzyme in amyloidogenesis, is increased in DS brains and specifically regulated at the transcriptional level by GATA1 transcription factor. The discovery of this novel pathway has translational implications for DS, because pharmacological inhibition of GSAP is an attractive and viable Aβ-lowering therapeutic strategy for this disorder.

Tabersonine inhibits amyloid fibril formation and cytotoxicity of Aβ(1-42)

The misfolding and aggregation of amyloid beta (Aβ) peptides into amyloid fibrils are key events in the amyloid cascade hypothesis for the etiology of Alzheimer's disease (AD). Using thioflavin-T (ThT) fluorescence assay, atomic force microscopy, circular dichroism, size exclusion chromatography, surface plasmon resonance (SPR), and cytotoxicity tests, we demonstrate that tabersonine, an ingredient extracted from the bean of Voacanga africana, disrupts Aβ(1-42) aggregation and ameliorates Aβ aggregate-induced cytotoxicity. A small amount of tabersonine (e.g., 10 μM) can effectively inhibit the formation of Aβ(1-42) (e.g., 80 μM) fibrils or convert mature fibrils into largely innocuous amorphous aggregates. SPR results indicate that tabersonine binds to Aβ(1-42) oligomers in a dose-dependent way. Molecular dynamics (MD) simulations further confirm that tabersonine can bind to oligomers such as the pentamer of Aβ(1-42). Tabersonine preferentially interact with the β-sheet grooves of Aβ(1-42) containing aromatic and hydrophobic residues. The various binding sites and modes explain the diverse inhibitory effects of tabersonine on Aβ aggregation. Given that tabersonine is a natural product and a precursor for vincristine used in cancer chemotherapy, the biocompatibility and small size essential for permeating the blood-brain barrier make it a potential therapeutic drug candidate for treating AD.

Regulation of gamma-secretase activating protein by the 5Lipoxygenase: in vitro and in vivo evidence

The formation of Aβ is directly controlled by the γ-secretase complex and its activator, γ-secretase activating protein (GSAP). GSAP derives from a C-terminal fragment of a larger precursor protein via a caspase-3 mediated cleavage. However, the mechanism regulating this process remains unknown. Here we provide in vitro experimental evidence that 5-Lipoxygenase (5LO) is as an endogenous regulator for GSAP formation, but not for other known γ-secretase modulators, by directly and specifically activating caspase-3. These results were confirmed in vivo by using transgenic mouse models of Alzheimer’s disease in which 5LO level and activity were modulated genetically or pharmacologically. Taken together, our findings demonstrate that GSAP cleavage via caspase-3 is regulated and depend upon the availability of 5LO further establishing this protein as an attractive and viable therapeutic target for Alzheimer’s disease.

Gamma secretase-activating protein is a substrate for caspase-3: implications for Alzheimer's disease

BACKGROUND

A major feature of Alzheimer's disease (AD) is the accumulation of amyloid-beta (Aβ), whose formation is regulated by the gamma-secretase complex and its activating protein (also known as GSAP). Because GSAP interacts with gamma-secretase without affecting the cleavage of Notch, it is an ideal target for a viable anti-Aβ therapy. However, despite much interest in this protein, the mechanisms involved in its neurobiology are unknown.

METHODS

Postmortem brain tissue samples from AD patients, transgenic mouse models of AD, and neuronal cells were used to investigate the molecular mechanism involved in GSAP formation and subsequent amyloidogenesis.

RESULTS

We identified a caspase-3 processing domain in the GSAP sequence and provide experimental evidence that this caspase is essential for GSAP activation and biogenesis of Aβ peptides. Furthermore, we demonstrated that caspase-3-dependent GSAP formation occurs in brains of individuals with AD and two different mouse models of AD and that the process is biologically relevant because its pharmacological blockade reduces Aβ pathology in vivo.

CONCLUSIONS

Our data, by identifying caspase-3 as the endogenous modulator of GSAP and Aβ production, establish caspase-3 as a novel, attractive and viable Aβ-lowering therapeutic target for AD.

Pathway-based analysis of genome-wide siRNA screens reveals the regulatory landscape of APP processing

The progressive aggregation of Amyloid-β (Aβ) in the brain is a major trait of Alzheimer's Disease (AD). Aβ is produced as a result of proteolytic processing of the β-amyloid precursor protein (APP). Processing of APP is mediated by multiple enzymes, resulting in the production of distinct peptide products: the non-amyloidogenic peptide sAPPα and the amyloidogenic peptides sAPPβ, Aβ40, and Aβ42. Using a pathway-based approach, we analyzed a large-scale siRNA screen that measured the production of different APP proteolytic products. Our analysis identified many of the biological processes/pathways that are known to regulate APP processing and have been implicated in AD pathogenesis, as well as revealing novel regulatory mechanisms. Furthermore, we also demonstrate that some of these processes differentially regulate APP processing, with some mechanisms favouring production of certain peptide species over others. For example, synaptic transmission having a bias towards regulating Aβ40 production over Aβ42 as well as processes involved in insulin and pancreatic biology having a bias for sAPPβ production over sAPPα. In addition, some of the pathways identified as regulators of APP processing contain genes (CLU, BIN1, CR1, PICALM, TREM2, SORL1, MEF2C, DSG2, EPH1A) recently implicated with AD through genome wide association studies (GWAS) and associated meta-analysis. In addition, we provide supporting evidence and a deeper mechanistic understanding of the role of diabetes in AD. The identification of these processes/pathways, their differential impact on APP processing, and their relationships to each other, provide a comprehensive systems biology view of the “regulatory landscape” of APP.

Oxidative stress and cell membranes in the pathogenesis of Alzheimer's disease

Amyloid β proteins and oxidative stress are believed to have central roles in the development of Alzheimer's disease. Lipid membranes are among the most vulnerable cellular components to oxidative stress, and membranes in susceptible regions of the brain are compositionally distinct from those in other tissues. This review considers the evidence that membranes are either a source of neurotoxic lipid oxidation products or the target of pathogenic processes involving amyloid β proteins that cause permeability changes or ion channel formation. Progress toward a comprehensive theory of Alzheimer's disease pathogenesis is discussed in which lipid membranes assume both roles and promote the conversion of monomeric amyloid β proteins into fibrils, the pathognomonic histopathological lesion of the disease.

Affinity pulldown of γ-secretase and associated proteins from human and rat brain

γ-Secretase is a transmembrane protease complex responsible for the processing of a multitude of type 1 transmembrane proteins, including amyloid precursor protein (APP) and Notch. A functional complex is dependent on the assembly of four proteins: presenilin (PS), nicastrin, Aph-1 and Pen-2. Little is known about how the substrates are selected by γ-secretase, but it has been suggested that γ-secretase associated proteins (GSAPs) could be of importance. For instance, it was recently reported from studies in cell lines that TMP21, a transmembrane protein involved in trafficking, binds to γ-secretase and regulates the processing of APP-derived substrates without affecting Notch cleavage. Here, we present an efficient and selective method for purification and analysis of γ-secretase and GSAPs. Microsomal membranes were prepared from rat or human brain and incubated with a γ-secretase inhibitor coupled to biotin via a long linker and a S-S bridge. After pulldown using streptavidin beads, bound proteins were eluted under reducing conditions and digested by trypsin. The tryptic peptides were subjected to LC-MS/MS analysis, and proteins were identified by sequence data from MS/MS spectra. All of the known γ-secretase components were identified. Interestingly, TMP21 and the PS associated protein syntaxin1 were associated to γ-secretase in rat brain. We suggest that the present method can be used for further studies on the composition of the γ-secretase complex.

A general and concise asymmetric synthesis of sphingosine, safingol and phytosphingosines via tethered aminohydroxylation

A novel, practical and efficient enantioselective synthesis of sphingoid bases, l-threo-[2S,3S]-sphinganine (safingol), l-threo-[2S,3S]-sphingosine, l-arabino-[2R,3S,4R] and l-xylo-[2R,3S,4S]-C(18)-phytosphingosine is described. The synthetic strategy features the Sharpless kinetic resolution and tethered aminohydroxylation (TA) as the key steps.

BACE and gamma-secretase characterization and their sorting as therapeutic targets to reduce amyloidogenesis

Secretases are named for enzymes processing amyloid precursor protein (APP), a prototypic type-1 membrane protein. This led directly to discovery of novel Aspartyl proteases (beta-secretases or BACE), a tetramer complex gamma-secretase (gamma-SC) containing presenilins, nicastrin, aph-1 and pen-2, and a new role for metalloprotease(s) of the ADAM family as a alpha-secretases. Recent advances in defining pathways that mediate endosomal-lysosomal-autophagic-exosomal trafficking now provide targets for new drugs to attenuate abnormal production of fibril forming products characteristic of AD. A key to success includes not only characterization of relevant secretases but mechanisms for sorting and transport of key metabolites to abnormal vesicles or sites for assembly of fibrils. New developments we highlight include an important role for an 'early recycling endosome' coated in retromer complex containing lipoprotein receptor LRP-II (SorLA) for switching APP to a non-amyloidogenic pathway for alpha-secretases processing, or to shuttle APP to a 'late endosome compartment' to form Abeta or AICD. LRP11 (SorLA) is of particular importance since it decreases in sporadic AD whose etiology otherwise is unknown.

CD147, a gamma-secretase associated protein is upregulated in Alzheimer's disease brain and its cellular trafficking is affected by presenilin-2

Gamma-secretase activity has been extensively investigated due to its role in Alzheimer's disease. Here, we studied the association of CD147, a transmembrane glycoprotein belonging to the immunoglobulin family, with gamma-secretase and its expression in Alzheimer's disease and control tissues. Subcellular fractionation of postmitochondrial supernatant from rat brain on step iodixanol gradient in combination with co-immunoprecipitation using an anti-nicastrin antibody showed association of limited amount of CD147 to gamma-secretase. By immunoblotting of postnuclear pellets from Alzheimer's disease and control human brain tissues we showed that CD147 with molecular weight 75 kDa is upregulated in frontal cortex and thalamus of the Alzheimer's disease brains. Immunohistochemistry of brain tissues from Alzheimer's disease and control revealed specific upregulation of CD147 in neurons, axons and capillaries of Alzheimer's disease frontal cortex and thalamus. The effect of presenilin-1 and -2, which are the catalytic subunits of gamma-secretase, on CD147 expression and subcellular localization was analyzed by confocal microscopy in combination with flow cytometry and showed that PS2 affected the subcellular localization of CD147 in mouse embryonic fibroblast cells. We suggest that a small fraction of CD147 present in the brain is associated with the gamma-secretase, and can be involved in mechanisms dysregulated in Alzheimer's disease brain.

Upregulation of HAb18G/CD147 in activated human umbilical vein endothelial cells enhances the angiogenesis

Previous studies demonstrated that CD147 molecule, highly expressed on the surface of various malignant tumor cells, significantly correlated with the malignancy of these cancers; however, the role of HAb18G/CD147 in endothelial cells has yet to be established. In this study, we found that the expression of HAb18G/CD147 was significantly upregulated in activated HUVECs. The inhibition of HAb18G/CD147 expression by specific siRNA led to significantly decreased angiogenesis in vitro. Our data indicate that HAb18G/CD147 may regulate angiogenesis via several mechanisms including proliferation, survival, migration, MMPs secretion, and PI3K/Akt activation. Our findings for the first time suggest that upregulation of HAb18G/CD147 in activated HUVECs might play an important role in angiogenesis.

An efficient and general enantioselective synthesis of sphingosine, phythosphingosine, and 4-substituted derivatives

A general and efficient protocol for the enantioselective synthesis of sphingosine, phythosphingosine, and 4-substituted derivatives was established. These compounds were obtained from a common intermediate prepared from butadiene monoepoxide by a synthetic sequence involving enantioselective allylic substitution, cross-metathesis, and dihydroxylation.

The interaction of beta-amyloid protein with cellular membranes stimulates its own production

Gradual changes in steady-state levels of beta amyloid peptides (Abeta) in brain are considered an initial step in the amyloid cascade hypothesis of Alzheimer's disease. Abeta is a product of the secretase cleavage of amyloid precursor protein (APP). There is evidence that the membrane lipid environment may modulate secretase activity and alters its function. Cleavage of APP strongly depends on membrane properties. Since Abeta perturbs cell membrane fluidity, the cell membrane may be the location where the neurotoxic cascade of Abeta is initiated. Therefore, we tested effects of oligomeric Abeta on membrane fluidity of whole living cells, the impact of exogenous and cellular Abeta on the processing of APP and the role of GM-1 ganglioside. We present evidence that oligoAbeta((1-40)) stimulates the amyloidogenic processing of APP by reducing membrane fluidity and complexing with GM-1 ganglioside. This dynamic action of Abeta may start a vicious circle, where endogenous Abeta stimulates its own production. Based on our novel findings, we propose that oligoAbeta((1-40)) accelerates the proteolytic cleavage of APP by decreasing membrane fluidity.

CD147 immunoglobulin superfamily receptor function and role in pathology

The immunoglobulin superfamily member CD147 plays an important role in fetal, neuronal, lymphocyte and extracellular matrix development. Here we review the current understanding of CD147 expression and protein interactions with regard to CD147 function and its role in pathologic conditions including heart disease, Alzheimer's disease, stroke and cancer. A model linking hypoxic conditions found within the tumor microenvironment to upregulation of CD147 expression and tumor progression is introduced.

Towards individualized medicine: flies lead the way

While the search for the genetic foundation of complex diseases receives a great deal of attention in the popular scientific press, it is merely the first step in a very long journey from gene identification to therapeutic options. Unexpectedly, even diseases that are caused by mutations in a single gene have a collection of diverse possible symptoms that variably affect each patient. What is becoming more obvious is the need to correlate specific endophenotypes, or subsets of disease symptoms, with specific genetic and/or environmental factors that differ from patient to patient. Surprisingly, Drosophila melanogaster, the common fruit fly, may be a key player in making these assignments, and in the drug-discovery process that necessarily follows. In this review, we discuss the issues that are emerging in neurological disease research, and why Drosophila’s role in the pathway towards pharmacological solutions is likely to increase.