Role of neuroproteomics in CNS drug discovery

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▼ ‘Neuroproteomics’ is the term used for theapplication of proteomics to the study of theCNS and disorders of the CNS. The knowledgegained from neuroproteomics can be appliedto the development of diagnostics and thera-peutics for neurological disorders. The drugdiscovery process is viewed in the context ofthe overall management of neurological disor-ders, which should be based on an under-standing of the pathomechanism of theparticular disease and of matching drugs tothe needs of individual patients – so-called‘personalized medicine’. This requires aninnovative approach to drug discovery.Proteomic technologies are providing anopportunity to integrate information from thegenome, expressed mRNAs (see Glossary) andtheir respective proteins, as well a subcellularlocalization. This approach would enable thedetection of genes that encode for proteinsexpressed in specific tissues at low abundance,thereby permitting the rapid identificationof proteins that are likely to be targets fortherapeutic and diagnostic development.Proteomic approaches are particularly valu-able for molecular dissection of diseases of theCNS from postmortem specimens, wheredecay limits mRNA expression-based analyses.

Various proteomic technologies have beendescribed in a special report on this topic [1].

Study of neurological diseases at protein levelProtein pathology is a salient feature in sev-eral neurological disorders. Understandingthe pathology of these diseases is an impor-tant step in rational drug discovery. Neuro-degenerative diseases are proteinopathieswith a specific proteins playing a role in the pathogenesis; for example, β-amyloid inAlzheimer’s disease, α-synuclein in Parkinson’sdisease and PrP protein in prion diseases.Various biomarkers of neurological disorderscan serve as drug targets; they can also formthe basis from which to develop diagnostictests. Protein-based diagnostic tests for neuro-logical disorders using body fluids − CSF andblood − are important in the development oftherapies linked to diagnostics. Loss of neuronsand disturbances of neurotransmission canresult in disease-specific alterations of neur-onal and CSF proteins, which are suitable forproteomic analysis.

The function of the brain can be defined interms of the number, type and location ofmultiprotein complexes [2]. A comprehensivelist of these complexes would provide a basisfor maps of interactions or functional connec-tions between complexes. Ascertaining the

Role of neuroproteomics in CNS drugdiscoveryKewal K. Jain

Kewal K. JainJain PharmaBiotech, CH-4057

Basel, Switzerland.e-mail: [email protected]

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TARGETS Vol. 1, No. 03 September 2002

Neuroproteomics is the application of proteomics to the study of the CNS

and its disorders. Proteomic technologies can be applied to the discovery

of targets for drugs to treat neurological disorders. Diseases that are

particularly suitable for this approach are those with protein pathology,such

as Alzheimer’s disease.Important receptors for CNS drugs include proteins

such as G-protein-coupled receptors, N-methyl-d-aspartate receptors and

protein kinases. Molecular diagnostics can be based on proteins detected

in the cerebrospinal fluid and these same proteins can serve as drug targets.

Proteomics complements pharmacogenomics and will facilitate the

development of personalized medicines for neurological disorders.

www.drugdiscoverytoday.com

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Glossary

5-HT: 5-hydroxytryptamine (serotonin)CNS: central nervous systemCSF: cerebrospinal fluidGPCR: G-protein-coupled-receptormRNA: messenger ribonucleic acidPET: positron emission tomographySPECT: single photon emission tomography

function of the complexes in the brain will require acombination of integrated approaches. To claim that acomplex is important in any particular function, it will benecessary to demonstrate that interference with many ofits individual proteins (by genetic or pharmacological intervention) interferes with the overall common functionof the complex. Proteomics tools offer new ways to analyzenetworks of proteins that control important neurobiologicalphenomena. Intracellular pathways underlying gene expression in the CNS are shown in Fig. 1.

Application of proteomic technologies in neurosciencesVarious proteomic technologies have been applied to thestudy of the CNS. CNS proteomics can identify cell typesand tissues contributing to the disease phenotype.However, because the proteome of a cell or tissue is not asimple reflection of its transcriptome, direct protein-basedanalysis is needed. Proteomics is also applied to resolutionof in silico gene prediction uncertainties by direct open-reading-frame verification [3].

The most common proteomic technologies are based ontwo-dimensional gel electrophoresis (2D GE) of proteins in

a complex mixture and their isola-tion/identification by mass spectrom-etry (MS). Proteomic analysis of braintissue has been done as an extensionof the study of CSF proteins. Thesestudies are further facilitated by theavailability of a 2D map of 180 brain-specific proteins from the parietal lobecortex [4]. Optimal application of MSin combination with 2D polyacry-lamide gel electrophoresis (PAGE) ofhuman CSF can enable the identifi-cation of new potential biologicalmarkers of neurological disorders [5].

Techniques for the analysis of mem-brane proteins and cell signallingpathways are most valuable for CNS

drug discovery. About 50% of drug targets are membraneproteins that play key roles in the function and diseases ofthe CNS. 2D GE is not adequate for this class of proteinsbut liquid phase isoelectric focusing in combination withone-dimensional electrophoresis and followed by massspectrometry and database searches, has been found to bean important tool for identifying low-abundant proteinsin human CSF and membrane proteins in human frontalcortex [6]. In another method, called the mass westernexperiment, membrane protein extracts are labelled withcustom isotope-coded affinity tag reagents and digested,and the labelled peptides are analyzed by liquid chro-matography-tandem mass spectrometry [7]. This appli-cation of ion trap selective reaction monitoring maximizessensitivity, enabling the analysis of peptides that wouldotherwise go undetected.

New developments in membrane protein microarrayswill facilitate the drug discovery process. Corning, Inc. hasdemonstrated direct pin-printing of membrane proteinsand ligand-binding assays on biochips [8]. Various applica-tions of protein microarrays/biochips in studies relevant toCNS drug discovery are shown in Box 1.

Laser capture microdissection (LCM) is an importantadjunct to the study of CNS tissues. LCM has been used onpostmortem brain tissue, which can yield good-qualitymRNA and intact protein antigens, enabling the successfulapplication of molecular profiling techniques. The tech-nique is described in more detail elsewhere [9]. The combi-nation of LCM with high-throughput profiling techniquesoffers the opportunity to obtain precise genetic finger-prints of individual neurons, thus enabling the compari-son of normal and pathological states [10]. LCM has beenused with cDNA microarrays to profile gene expression of adjacent neuronal subtypes [11]. Expression profiles

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Figure 1. Intracellular pathways underlying gene expression in the CNS. CREB, cAMP responsiveelement binding protein; cAMP, cyclic adenosine monophosphate; cGMP, cyclic guanosinemonophosphate.

TARGETS

Receptorse.g. GPCRs

1st messengersNeurotransmitter

2nd messengerscAMP, cGMP

Target genesIon channel receptorsIntracellular signaling proteinsCytoskeletal proteins

3rd messengerse.g. phosphoproteins

Proteinkinases

CREB-likeproteins

Fos-likeproteins

Cytoplasm

Nucleus

Box 1. Use of protein microarrays/biochip forCNS drug discovery

• Biochips containing genes encoding CNS proteins canuncover disease pathways

• To identify promising drug targets in brain tissue• To identify biomarkers in CSF• Rapid assessment of how a drug may affect the CNS• Target mRNA and protein expression can be inhibited

using antisense oligonucleotides

generated with this integration are useful for screeningcDNAs as well as for producing databases of cell-type-specific gene expression. Coordinate gene expression canindicate functional coupling between the encoded proteinsand facilitates the determination of function of most of thecDNAs now cloned. A detailed analysis of individual celltypes, such as hippocampal glial cells, is necessary wheninvestigating a novel putative therapeutic target; this canbe achieved by LCM. A variant of LCM – microbeam laserpressure catapulting – can be used for the selective cata-pulting of single neurons to study degenerative neurologi-cal disorders such as Alzheimer’s disease. It is possible tocapture single plaques or amyloid deposits for proteomicanalysis.

Alzheimer’s disease and Down’s syndromeAlzheimer’s disease (AD) is a progressive neurodegenera-tive disorder. Although it accounts for about half of all dementias, its pathomechanism is not well understood.There are genetic similarities between AD and Down’s syn-drome (DS) and it is possible that the two diseases share acommon factor in pathogenesis. Proteomic studies pro-vide a unique snapshot illustrating the complexity of interrelated disease mechanisms at work in a complex,multifactorial disease such as AD, and show that compara-tive proteome analysis has the power to develop impor-tant new insights into pathogenic mechanisms in the dementias. The main features of neuropathology in braintissue from people with DS are deteriorated migration, ax-onal pathfinding and wiring of the brain, however, infor-mation on the underlying mechanisms is still limited.One group has carried out a considerable amount of workon CNS proteomics in the areas of both AD and DS [12].Proteomic techniques, such as 2D electrophoresis withMALDI (Matrix-Assisted Laser Desorption/Ionization),have been used to detect differences in protein expressionbetween controls, DS and AD brains. Studies of the abnor-malities of expression of brain proteins in DS and AD areshown in Table 1.

Hippocampal proteomes have been visualized by 2D GEof homogenized postmortem hippocampal tissue from thebrains of schizophrenic, AD and control individuals [21].One protein, which was decreased in concentration inboth diseases, was characterized as diazepam binding inhibitor by N-terminal sequence analysis. Diazepam binding inhibitor can regulate the action of the GABAA

receptor. Protein changes involved 6% of the assessed ADhippocampal proteome, whereas in schizophrenia proteinchanges involved less than 1% of the assessed hippocampalproteome. These findings show that schizophrenia has a sub-tle neuropathological presentation and that comparative

proteome analysis is a viable means by which to investigatediseases of the brain at the molecular level.

The replacement of a single amino acid can destabilizenative proteins and trigger the aggregation of amyloid fibres, which characterize a range of lethal neurodegenera-tive diseases. Neurodegenerative diseases associated withthe accumulation of amyloid in the brain, includingHuntington’s disease and Alzheimer’s disease, share certainfeatures despite the fact that different proteins are impli-cated in each disease. Neurodegenerative diseases resultingfrom expanded repeat sequences of glutamine residues areassociated with the formation of protein aggregates in thecell nuclei of the affected neurons [22]. Nucleation of theaggregates is the controlling step in the progression ofthese diseases. One potential therapy for neurodegenera-tive diseases would be to use computational methods tofind proteins that stabilize the native structure and counterthe destabilizing effect of the glutamine repeats.

SchizophreniaProteomic technology has been used to survey postmortemtissue to identify changes linked to the various neuropsy-chiatric diseases such as schizophrenia [23]. 2D GE andmass spectrometric sequencing of proteins has enabled thecomparison of subsets of expressed proteins among a largenumber of samples. Protein species that display disease-specific alterations in level in the frontal cortex includeforms of glial fibrillary acidic protein (GFAP), dihydropy-rimidinase-related protein 2 and ubiquinone cytochrome Creductase core protein 1. Thus, proteomic analysis mightidentify novel pathogenic mechanisms of human neuro-psychiatric diseases.

Protein targets for CNS drug discoveryMany of the pharmaceutically important regulation sys-tems operate through proteins (i.e. post-translationally).Major drugs act by binding to proteins. Proteomics is,therefore, important for the study of pharmacology anddrug discovery. In the past, drugs were discovered by asso-ciating a disease with specific proteins in a non-systemicmanner, or simply by serendipity. Application of proteomictechnologies has enabled the prediction of all possible pro-tein-coding regions and the choice of the best candidatesamong novel drug targets. This approach has providedneuropharmacology with powerful tools to dissect novelmolecular pathways involved in health and disease and toidentify new drug targets.

Proteomic technologies are now being integrated intothe drug discovery process to complement genomic ap-proaches. This offers the scientists the ability to integrateinformation from the genome, expressed mRNAs and their

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respective proteins as well a subcellular localization. Aneffective target discovery system would therefore enablethe detection of genes that encode for proteins expressedin specific tissues at low abundance, thereby permittingthe rapid identification of proteins, which are likely to betargets for therapeutic and diagnostic development. Drugdiscovery also involves protein–protein interaction studies.

Important drug targets relevant to neurological disordersthat have been studied by proteomic technologies includereceptors for neurotransmitters, G-protein-coupled receptorsand N-methyl-D-aspartate. Other important targets are cellsignalling pathways and protein kinases.

G-protein-coupled receptorsGPCRs are an important class of drug target. They exist asproteins on the surface membranes of all cells and are alsoreferred to as 7-TM (transmembrane) or serpentine recep-tors because they cross the membrane seven times. TheGPCRs are a superfamily of proteins accounting for ~1% ofthe human genome and are associated with a wide range

of therapeutic categories, including CNS diseases. Purifiedmultiple GPCRs in a functional form can be used for theidentification of tight-binding ligands. There are thoughtto be approximately 2000 GPCRs within the human bodywith potential availability as drug discovery targets. GPCRshave historically been valuable drug targets but, to date,there are only around 100 well-characterized GPCRs withknown ligands, of which only about 50 are targets ofcommercial drugs. Approximately 60% of all currentlyavailable prescription drugs interact with these receptors.

Nearly all molecules known to signal cells via G proteinshave been assigned a cloned GPCR gene. Functions havebeen elucidated for approximately 160 of these receptors,and approximately 140 receptors have been left without afunction or a ligand – the so-called ‘orphan’ receptors.Several of these novel neuropeptide receptor systems havebeen identified by NeoGene’s proprietary orphan receptorstrategy [24].

The mGluR subtypes that are coupled to the hydrolysis ofphosphoinositide contribute both to synaptic plasticity and

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Table 1. Abnormalities of expression of brain proteins in Down's syndrome (DS) and Alzheimer's disease (AD)

Protein abnormalities Significance Ref

2-D electrophoresis detected decreases of mRNA levels ofdihydropyrimidinase-2 in four brain regions of patients with Down'ssyndrome but not in those with AD as compared with controls

This finding along with deteriorated protein expressionof semaphorin/collapsin family may help to explainderanged migration and histogenesis in DS brain

[13]

Four-fold increase of glial fibrillary acidic protein (GFAP) has been found inthe brains of patients with AD

GFAP is a marker of neuronal damage [14]

1.5-fold increase in levels of 14–3-3γ and 14–3-3ε proteins were reportedin brains of patients with AD and DS

These proteins play a complex role in signaltransduction pathway and decreased levels indicateimpaired signaling and apoptosis

[15]

Immunoprecipitation studies in human brain confirmed that nicastrinspecifically interacts with presenilin 1 as well as presenilin 2 and binds withC-terminal derivatives of β-amyloid precursor protein thus alteringγ-secretase cleavage, which modulates the production of the amyloidβ-protein

Drugs, which bind to nicastrin and inhibit theprocessing of β-amyloid precursor protein into thetoxic derivative β-amyloid peptide, may be helpful asa treatment or prevention of AD

[16]

The protease domain of the membrane protein memapsin 2 cDNA hasbeen expressed in Escherichia coli and purified. Recombinant memapsin 2specifically cleaves the β-secretase site of β-amyloid precursor proteinand fits all of the criteria of β-secretase

β-amyloid precursor protein is involved in theprogression of AD. This finding has a potentialapplication in developing drugs for the preventionand treatment of AD

[17]

Quantitative proteome analysis of postmortem brain tissues from personswith AD and those from age-matched nondemented control tissuesshowed that numerous proteins were differentially expressed inAD cerebellum, cingulate gyrus, and sensorimotor cortex

The identification of these proteins was is relevant tochanges in key pathogenic pathways in AD

[18]

Total VDAC (voltage-dependent anion-selective channel protein)-1 wassignificantly decreased in frontal cortex and thalamus and VDAC-2 wassignificantly elevated in temporal cortex in post mortem brains frompatients with AD. In DS cerebellum, total VDAC-1 protein was elevatedsignificantly whereas VDAC-2 did not show any significant alterations

These results indicate derangement of voltage-dependent anion-selective channel function andreflect impaired glucose, energy, and intermediarymetabolism as well as apoptotic mechanisms

[19]

Comparison of 2-D electrophoresis patterns of cerebrum extracts ofGSK3β [S9A] in AD transgenic mice with those of wild-type micerevealed spots that differed in intensity by at least a factor of 1.5.The spots were subsequently identified by mass spectrometry

Identification of several proteins linked to signaltransduction pathways in which GSK3β plays a role.This may contribute to filling the gaps betweenGSK3β, its substrates and finally the phosphorylationof tau

[20]

to glutamate-mediated excitotoxicity in neurons. G-protein-coupled receptor kinases (GRKs) desensitize a variety ofGPCRs. GRKs contribute to the regulation of both constitu-tive and agonist-stimulated mGluR1a activity and, thereby,might prevent mGluR1a-mediated excitotoxicity associatedwith mGluR1a overactivation. Furthermore, GRK2-dependentmGluR1a desensitization protected against mGluR1a-medi-ated cell death, at least in part by blocking mGluR1a-stimu-lated apoptosis. One study shows that mGluR1a serves as asubstrate for GRK-mediated phosphorylation, and that GRK-dependent ‘feedback’ modulation of mGluR1a responsivenessprotects against pathophysiological mGluR1a signalling [25].

GPCRs are not the only natural substrates for GRKs. Thediscovery that GRKs also phosphorylate tubulin raised thepossibility of additional GRK substrates, such as synucleins(α, β, γ and synoretin), which are highly expressed in brainbut also found in numerous other tissues. α-synuclein hasbeen linked to the development of Alzheimer’s andParkinson’s diseases. GRK-mediated phosphorylation inhibitsthe interaction of synuclein both with phospholipids andwith phospholipase D2 (PLD2), suggesting that GPCRsmight – indirectly – be able to stimulate PLD2 activity viatheir ability to regulate GRK-promoted phosphorylation ofsynuclein [26].

A series of observations suggests a potential applicationfor mGlu5 receptor antagonists in chronic neurodegenera-tive disorders, such as amylotrophic lateral sclerosis andAlzheimer’s disease. mGlu2 and mGlu3 receptor agonistsinhibit glutamate release and also promote the synthesisand release of neurotrophic factors in astrocytes [27].

Using a proteomic approach based on peptide affinitychromatography followed by mass spectrometry and im-munoblotting, 15 proteins have been identified that inter-act with the C-terminal tail of the 5-HT2C receptor – a GPCR[28]. These proteins include several synaptic multidomainproteins, proteins of the actin/spectrin cytoskeleton andsignalling proteins. Co-immunoprecipitation experimentsshowed that the 5-HT2C receptor is associated with proteinnetworks that are important for its synaptic localizationand its coupling to the signalling machinery. Examples ofCNS drugs interacting with GPCRs are shown in Table 2.

N-methyl-D-aspartate receptorsN-methyl-D-aspartate (NMDA) receptors are excitatory neu-rotransmitter receptors that play a crucial role in synapticplasticity and neuronal development in the mammalianbrain. They are found highly concentrated in the postsynap-tic membrane of glutamatergic synapses. The yeast two-hybrid system has been used to investigate the molecularmechanisms underlying NMDA receptor localization and toidentify proteins expressed in the brain that interact with

the NMDA receptor subunit NR1, an important glutamate-gated ion channel [29]. The results of this research demon-strate the splice variant-specific association of NR1 with neu-rofilaments and suggest a possible mechanism for anchoringor localizing NMDA receptors in the neuronal plasma mem-brane. Proteomic technologies such as mass spectrometryhave been used to characterize multiprotein complexes ofNMDA receptors isolated from mouse brain [30]. Several ofthese proteins are encoded by activity-dependent genes. TheNMDA receptor consists of 75 or more proteins, which canbe grouped into five classes: neurotransmitter receptors,cell adhesion proteins, adaptors, signalling enzymes andcytoskeletal proteins. Proteomic technologies, along withgenomic data and gene expression profiles, will providepossible molecular interactions within neuronal networks.An understanding of these networks and their disruption indisease will provide new explanations for behaviour [31].

Cell signalling pathwaysAbout one-fifth of all human genes encode proteins involvedin signal transduction. Large-scale proteomics projects nowin progress seek to better define crucial components of signaltransduction networks to enable more intelligent design oftherapeutic agents that can correct disease-specific sig-nalling alterations by targeting individual proteins. Thereare instances in which protein interaction technologies havebeen adapted to identify small molecule agents that regulateprotein response in physiologically desirable ways that arerelevant to future drug discovery efforts. Protein kinases arethe most important substrates in cell signalling pathwaysrelevant to neuropsychiatric disorders.

Protein kinasesProtein kinases are coded by more than 2000 genes andthus constitute the largest single enzyme family in thehuman genome. In fact, most cellular processes are regu-lated by the reversible phosphorylation of proteins onserine, threonine and tyrosine residues. At least 30% of allproteins are thought to contain covalently bound phos-phate. Scientists at MDS Proteomics have reported a novel

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Table 2. Examples of CNS drugs interactingwith GPCRs

Product Receptor(s) Indication

Zyprexa (Eli Lilly and Co) 5-HT2 /dopamine (D)

Schizophrenia

Risperdal (Johnson & Johnson) 5-HT2 Schizophrenia

Imigran (GlaxoSmithKline) 5-HT1B/1D Migraine

BuSpar (Bristo-Myers-Squib) 5-HT1A Anti-depressant

method to determine whether drugs and drug targets areeffective in combating disease by identifying the key regu-latory protein ‘switches’ (phosphorylation sites) insidehuman cells [32]. This discovery enables the accurate distinction between healthy and diseased cells, which inturn uncovers the key protein targets against which newdrugs will be made. This technology will accelerate thedrug development process.

Proteomics and drug discovery for CNS disordersAn insight into the protein-based mechanisms of neuro-logical disorders will provide more relevant targets for drugdiscovery for CNS disorders. As the molecular mechanismsof action of some of the classic drugs that act on the brainare being identified, protein kinase C (PKC) has been implicated in many disorders, such as depression. Valproicacid, used for the treatment of manic-depressive disorders,decreases PKC and this effect coincides with an increase inneuroprotective protein bcl-2 in the CNS [33]. Chroniclithium administration for manic-depressive disorder alsoproduces a reduction in the expression of PKC-α andPKC-ε, as well as a major PKC substrate – MARCKS –which has been implicated in long-term neuroplasticevents in the developing and adult brain. More recently,studies have demonstrated robust effects of lithium onanother kinase system, GSK-3β, and on neuropro-tective/neurotrophic proteins in the brain [34]. These observations have implications for the design of new therapies for neurological disorders.

All four genes definitively linked toinherited forms of Alzheimer’s disease(AD) have been shown to increase theproduction and/or deposition of amy-loid β-protein in the brain. In particu-lar, evidence that the presenilin pro-teins, mutations in which cause themost aggressive form of inherited AD,lead to altered intramembranouscleavage of the β-amyloid precursorprotein by the protease γ-secretase, hasspurred progress towards novel thera-peutics. The finding that presenilinitself might be the long-sought-afterγ-secretase, coupled with the recentidentification of β-secretase, has pro-vided discrete biochemical targets fordrug screening and development [35].Scientists at AlphaGene, Inc. haveidentified two novel genes associatedwith AD – 121181 and 121228 – andhave studied their expression in a

yeast two-hybrid system. The studies showed that gene121228 interacted with several proteins known to beassociated with AD, including ApoG, AMY (non-amyloid,plaque-like structures), GFAP and seven other novel geneproducts that are currently being characterized.

Recent circumstantial evidence from the mouse andDrosophilia model systems suggests that abnormal proteinfolding and aggregation play a key role in the pathogene-sis of both Huntington’s disease and Parkinson’s disease.A detailed understanding of the molecular mechanismsof protein aggregation, and its effect on neuronal cell death, could therefore open new opportunities fortherapy [36].

The role of proteomics in drugs discovery for CNS disor-ders is shown in Fig. 2.

Future prospects of neuroproteomicsA CNS proteome database of primary human neural tissueswould avoid the uncertainties of experimental models andaccelerate pre- and clinical development of more specificdiagnostic and prognostic disease markers and new selec-tive drug targets. The Human Brain Proteome Project inGermany plans to combine the results of proteomics, tran-script profiling, protein interaction studies and bioinfor-matics into a unified database. Information about this pro-ject is limited but should eventually be available throughthe Human Proteome Organization (www.hupo.org).

Expression profiling has an important role to play in drugdiscovery for CNS disorders and it will involve both gene

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Figure 2. Proteomics applications in CNS drug discovery and development. MALDI-TOF-MS,matrix-assisted laser desorption ionization, time-of-flight, mass spectrometry. Reproduced,with permission from Jain PharmaBiotech

TARGETS

CNS diseases with protein pathology

Cerebrospinal fluid:Disease-specific proteins

Brain samplesfor proteomic

studies

CNS tissue:Laser capture microdissection

MALDI-TOF-MSMembrane protein microarrays

Targets and pathwaysdrug discovery

Small molecule inhibitors

Preclinical development

Bio-markers of CNSdiseases

CNS moleculardiagnostics

Clinical development

and protein expression. New technologies for expressionprofiling in CNS drug discovery are shown in Box 2.

Neuroproteomic technologies will enable the combi-nation of diagnostics and therapeutics. Some of the pro-teins found in body fluids, such as the cerebrospinal fluid,will form the basis of molecular diagnostic tests, as well asbeing the target for drugs. Proteomic approaches will com-plement pharmacogenomics and will be important for thedevelopment of personalized medicines for neurologicaldisorders.

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Box 2. New technologies for expression profilingin CNS drug discovery

• Protein microarrays• Protein expression profiles• In vivo brain imaging with SPECT and PET• Use of in vivo reporter genes such as enzymes, receptors,

antigens or transporters• New technologies for the identification of marker or

target proteins• New bioinformatic tools

Documents

Role of neuroproteomics in CNS drug discovery