Upload
philip-bourne
View
915
Download
3
Tags:
Embed Size (px)
DESCRIPTION
Presentation made at PepTalk 2011 in San Diego on Jan. 13, 2011. The emphasis is on computational methods to explore global and local structure similarities in determining the possible promiscuity of drugs to bind to multiple protein receptors.
Citation preview
High-throughput Computational Strategies for Proteomics
Philip E. BourneUniversity of California San Diego
[email protected]://www.sdsc.edu/pb
PepTalk – January 13, 2011
As Applied to Drug Discovery
High-throughput Computation Can Be Applied on Three Axes
Target
Disease
Drug
Cheminfomatics
HTS
Docking
One to Multiple TargetsBioinformatics
Associative Transfer of Indications
Here I will focus mostly on the notion of multiple targets
Why We Think This is Important
• Ehrlich’s philosophy of magic bullets targeting individual chemoreceptors has not been realized in most cases – witness the recent success of big pharma
• Stated another way – The notion of one drug, one target, to treat one disease is a little naïve in a complex system
A.L. Hopkins Nat. Chem. Biol. 2008 4:682-690
Multiple Drugs Multiple Targets
• Gene knockouts only effect phenotype in 10-20% of cases , why? – redundant functions – alternative network routes – robustness of interaction networks
• 35% of biologically active compounds bind to more than one target
Paolini et al. Nat. Biotechnol. 2006 24:805–815
Polypharmacology - One Drug Binds to Multiple Targets
• Tykerb – Breast cancer
• Gleevac – Leukemia, GI cancers
• Nexavar – Kidney and liver cancer
• Staurosporine – natural product – alkaloid – uses many e.g., antifungal antihypertensive
Collins and Workman 2006 Nature Chemical Biology 2 689-700Motivation
7
PKA
Phosphoinositide-3 Kinase Phosphoinositide-3 Kinase (D) and Actin-Fragmin (D) and Actin-Fragmin Kinase (E)Kinase (E)
ChaK (“Channel Kinase”)ChaK (“Channel Kinase”)
Scheeff & Bourne 2005 PLoS Comp. Biol. 1(5): e49.
8
Can We Propose an Evolutionary History for the Protein Kinase-Like Superfamily? •Bayesian inference of phylogeny (MrBayes)
•Manual structure alignment produces very high-quality sequence alignment of diverse homologues
•But, sequence information too degraded to produce branching with sufficient support (i.e. a high posterior probability)
•Addition of a matrix of structural characteristics (similar to morphological characteristics) produces a well supported combined model
•Neither sequence structural characteristics sufficient to alone produce resolved tree, must be used in combination.
1BO1 Atypical 0 0 0 0 1
1IA9 Atypical 1 1 1 1 0
1E8X Atypical 1 0 1 1 1
1CJA Atypical 1 0 1 1 1
1NW1 Atypical 1 0 1 0 0
1J7U Atypical 1 0 1 0 1
1CDK AGC 1 1 1 0 1
1O6L AGC 1 1 1 0 1
1OMW AGC 1 1 1 0 1
1H1W AGC 1 1 1 0 1
1MUO Other 1 1 1 0 1
1TKI CAMK 1 0 1 0 1
1JKL CAMK 1 0 1 0 1
1A06 CAMK 1 0 1 0 1
1PHK CAMK 1 0 1 0 1
1KWP CAMK 1 0 1 0 1
1IA8 CAMK 1 0 1 0 0
1GNG CMGC 1 0 1 0 1
1HCK CMGC 1 0 1 0 1
1JNK CMGC 1 0 1 0 1
1HOW CMGC 1 0 1 0 1
1LP4 Other 1 0 1 0 1
1F3M STE 1 0 1 0 1
1O6Y Other 1 0 1 0 1
1CSN CK1 1 0 1 0 1
1B6C TKL 1 0 1 0 1
2SRC TK 1 0 1 0 1
1LUF TK 1 0 1 0 1
1IR3 TK 1 0 1 0 1
1M14 TK 1 0 1 0 1
1GJO TK 1 0 1 0 1
Example columns:
1) Ion pair analogous to K72-E91 in PKA
2) α-Helix B present
3) State of α-Helix C (0: kinked, 1: straight)
4) State of Strand 4 (0: kinked, 1: straight)
5) α-Helix D present
1 2 3 4 5
Scheeff & Bourne 2005 PLoS Comp. Biol. 1(5): e49.
9
AFK
PI3K
CK
APH
ChaK
PIPKIIβ
AGC
CAMK
CMGC
CK1 TK
TKL
Proposed Evolutionary History for the Protein Kinase-Like Superfamily
•Atypical kinase families: Blue
•Typical protein kinase groups (subfamilies): Red
•Branch labels: posterior probability of branch
• Suggests distinctive history for atypical kinases, as opposed to intermittent divergence from the typical protein kinases (TPKs)
• TPK portion of tree shows high degree of agreement with Manning tree
• Branching is supported by species representation of kinase families
0.97
1.0
0.78
0.85
0.64
Scheeff & Bourne 2005 PLoS Comp. Biol. 1(5): e49.
What That Study Told Us
• Structure comparison algorithms are still not good enough or comprehensive enough to provide the level of detail we need for large scale studies….
• We are starting to address this through our research and the RCSB PDB
A Quick Aside – RCSB PDB Pharmacology/Drug View 2010-2011
• Establish linkages to drug resources (FDA, PubChem, DrugBank, ChEBI, BindingDB etc.)
• Create query capabilities for drug information
• Provide superposed views of ligand binding sites
• Analyze and display protein-ligand interactions
Drug Name Asp
Aspirin
Has Bound Drug% Similarity to Drug Molecule 100
Mockups of drug view features
RCSB PDB Ligand View RCSB PDB Team
This begins to address the issue of multiple targets that share global similarity.. but
often that is not the case .. we need to focus on binding site
similarity
Our Approach
• We can characterize a known protein-ligand binding site from a 3D structure (primary site) and search for that site on a proteome wide scale independent of global structure similarity
Which Means …
• We could perhaps find alternative binding sites (off-targets) for existing pharmaceuticals and NCEs?
• If we can make this high throughput we could rationally explore a large network of protein-ligands interactions
What Have These Off-targets and Networks Told Us So Far?
Some Examples…1. Nothing2. A possible explanation for a side-effect of a drug
already on the market (SERMs - PLoS Comp. Biol., 2007 3(11) e217)
3. The reason a drug failed (Torcetrapib - PLoS Comp Biol 2009 5(5) e1000387)
4. How to optimize a NCE (NCE against T. Brucei PLoS Comp Biol. 2010 6(1): e1000648)
5. A multi-target/drug strategy to attack a pathogen (TB-drugome PLoS Comp Biol 2010 6(11): e1000976)
6. A possible repositioning of a drug (Nelfinavir) to treat a completely different condition (under review)
Our Stories
Need to Start with a 3D Drug-Receptor Complex - The PDB Contains Many
ExamplesGeneric Name Other Name Treatment PDBid
Lipitor Atorvastatin High cholesterol 1HWK, 1HW8…
Testosterone Testosterone Osteoporosis 1AFS, 1I9J ..
Taxol Paclitaxel Cancer 1JFF, 2HXF, 2HXH
Viagra Sildenafil citrate ED, pulmonary arterial hypertension
1TBF, 1UDT, 1XOS..
Digoxin Lanoxin Congestive heart failure
1IGJ
Computational Methodology
A Reverse Engineering Approach to Drug Discovery Across Gene FamiliesCharacterize ligand binding site of primary target (Geometric Potential)
Identify off-targets by ligand binding site similarity(Sequence order independent profile-profile alignment)
Extract known drugs or inhibitors of the primary and/or off-targets
Search for similar small molecules
Dock molecules to both primary and off-targets
Statistics analysis of docking score correlations
…
Computational MethodologyXie and Bourne 2009 Bioinformatics 25(12) 305-312
• Initially assign C atom with a value that is the distance to the environmental boundary
• Update the value with those of surrounding C atoms dependent on distances and orientation – atoms within a 10A radius define i
0.2
0.1)cos(
0.1
i
Di
PiPGP
neighbors
Conceptually similar to hydrophobicity or electrostatic potential that is dependant on both global and local environments
Characterization of the Ligand Binding Site - The Geometric Potential
Xie and Bourne 2007 BMC Bioinformatics, 8(Suppl 4):S9Computational Methodology
Discrimination Power of the Geometric Potential
0
0.5
1
1.5
2
2.5
3
3.5
4
0 11 22 33 44 55 66 77 88 99
Geometric Potential
binding site
non-binding site
• Geometric potential can distinguish binding and non-binding sites
100 0
Geometric Potential Scale
Computational Methodology Xie and Bourne 2007 BMC Bioinformatics, 8(Suppl 4):S9
Local Sequence-order Independent Alignment with Maximum-Weight Sub-Graph Algorithm
L E R
V K D L
L E R
V K D L
Structure A Structure B
• Build an associated graph from the graph representations of two structures being compared. Each of the nodes is assigned with a weight from the similarity matrix
• The maximum-weight clique corresponds to the optimum alignment of the two structures
Xie and Bourne 2008 PNAS, 105(14) 5441Computational Methodology
Similarity Matrix of Alignment
Chemical Similarity• Amino acid grouping: (LVIMC), (AGSTP), (FYW), and
(EDNQKRH)• Amino acid chemical similarity matrix
Evolutionary Correlation• Amino acid substitution matrix such as BLOSUM45• Similarity score between two sequence profiles
ia
i
ib
ib
i
ia SfSfd
fa, fb are the 20 amino acid target frequencies of profile a and b, respectivelySa, Sb are the PSSM of profile a and b, respectively Computational Methodology Xie and Bourne 2008 PNAS, 105(14) 5441
The Future as a High Throughput Approach…..
The TB-Drugome
1. Determine the TB structural proteome
2. Determine all known drug binding sites from the PDB
3. Determine which of the sites found in 2 exist in 1
4. Call the result the TB-drugome
A Multi-target/drug Strategy Kinnings et al 2010 PLoS Comp Biol 6(11): e1000976
1. Determine the TB Structural Proteome
284
1, 446
3, 996 2, 266
TB proteome
homology
models
solve
d
structu
res
• High quality homology models from ModBase (http://modbase.compbio.ucsf.edu) increase structural coverage from 7.1% to 43.3%
A Multi-target/drug Strategy Kinnings et al 2010 PLoS Comp Biol 6(11): e1000976
2. Determine all Known Drug Binding Sites in the PDB
• Searched the PDB for protein crystal structures bound with FDA-approved drugs
• 268 drugs bound in a total of 931 binding sites
No. of drug binding sites
MethotrexateChenodiol
AlitretinoinConjugated estrogens
DarunavirAcarbose
A Multi-target/drug Strategy Kinnings et al 2010 PLoS Comp Biol 6(11): e1000976
Map 2 onto 1 – The TB-Drugomehttp://funsite.sdsc.edu/drugome/TB/
Similarities between the binding sites of M.tb proteins (blue), and binding sites containing approved drugs (red).
From a Drug Repositioning Perspective
• Similarities between drug binding sites and TB proteins are found for 61/268 drugs
• 41 of these drugs could potentially inhibit more than one TB protein
No. of potential TB targets
raloxifenealitretinoin
conjugated estrogens &methotrexate
ritonavir
testosteronelevothyroxine
chenodiol
A Multi-target/drug Strategy Kinnings et al 2010 PLoS Comp Biol 6(11): e1000976
Top 5 Most Highly Connected Drugs
Drug Intended targets Indications No. of connections TB proteins
levothyroxine transthyretin, thyroid hormone receptor α & β-1, thyroxine-binding globulin, mu-crystallin homolog, serum albumin
hypothyroidism, goiter, chronic lymphocytic thyroiditis, myxedema coma, stupor
14
adenylyl cyclase, argR, bioD, CRP/FNR trans. reg., ethR, glbN, glbO, kasB, lrpA, nusA, prrA, secA1, thyX, trans. reg. protein
alitretinoin retinoic acid receptor RXR-α, β & γ, retinoic acid receptor α, β & γ-1&2, cellular retinoic acid-binding protein 1&2
cutaneous lesions in patients with Kaposi's sarcoma 13
adenylyl cyclase, aroG, bioD, bpoC, CRP/FNR trans. reg., cyp125, embR, glbN, inhA, lppX, nusA, pknE, purN
conjugated estrogens estrogen receptor
menopausal vasomotor symptoms, osteoporosis, hypoestrogenism, primary ovarian failure
10
acetylglutamate kinase, adenylyl cyclase, bphD, CRP/FNR trans. reg., cyp121, cysM, inhA, mscL, pknB, sigC
methotrexatedihydrofolate reductase, serum albumin
gestational choriocarcinoma, chorioadenoma destruens, hydatidiform mole, severe psoriasis, rheumatoid arthritis
10
acetylglutamate kinase, aroF, cmaA2, CRP/FNR trans. reg., cyp121, cyp51, lpd, mmaA4, panC, usp
raloxifeneestrogen receptor, estrogen receptor β
osteoporosis in post-menopausal women 9
adenylyl cyclase, CRP/FNR trans. reg., deoD, inhA, pknB, pknE, Rv1347c, secA1, sigC
What Have These Off-targets and Networks Told Us So Far?
Some Examples…1. Nothing2. A possible explanation for a side-effect of a drug
already on the market (SERMs - PLoS Comp. Biol., 2007 3(11) e217)
3. The reason a drug failed (Torcetrapib - PLoS Comp Biol 2009 5(5) e1000387)
4. How to optimize a NCE (NCE against T. Brucei PLoS Comp Biol. 2010 6(1): e1000648)
5. A multi-target/drug strategy to attack a pathogen (TB-drugome PLoS Comp Biol 2010 6(11): e1000976)
6. A possible repositioning of a drug (Nelfinavir) to treat a completely different condition (under review)
Our Stories
Nelfinavir
• Nelfinavir may have the most potent antitumor activity of the HIV protease inhibitors
Joell J. Gills et al, Clin Cancer Res, 2007; 13(17) Warren A. Chow et al, The Lancet Oncology, 2009, 10(1)
• Nelfinavir can inhibit receptor tyrosine kinase• Nelfinavir can reduce Akt activation
• Our goal: • to identify off-targets of Nelfinavir in the human
proteome• to construct an off-target binding network • to explain the mechanism of anti-cancer activity
Possible Nelfinavir Repositioning
Possible Nelfinavir Repositioning
binding site comparison
protein ligand docking
MD simulation & MM/GBSABinding free energy calculation
structural proteome
off-target?
network construction & mapping
drug target
Clinical Outcomes
1OHR
Possible Nelfinavir Repositioning
Binding Site Comparison
• 5,985 structures or models that cover approximately 30% of the human proteome are searched against the HIV protease dimer (PDB id: 1OHR)
• Structures with SMAP p-value less than 1.0e-3 were retained for further investigation
• A total 126 Structures have significant p-values < 1.0e-3
Possible Nelfinavir Repositioning
Enrichment of Protein Kinases in Top Hits
• The top 7 ranked off-targets belong to the same EC family - aspartyl proteases - with HIV protease
• Other off-targets are dominated by protein kinases (51 off-targets) and other ATP or nucleotide binding proteins (17 off-targets)
• 14 out of 18 proteins with SMAP p-values < 1.0e-4 are protein kinases
Possible Nelfinavir Repositioning
p-value < 1.0e-3
p-value < 1.0e-4
Distribution of Top Hits on the Human Kinome
Manning et al., Science, 2002, V298, 1912
Possible Nelfinavir Repositioning
1. Hydrogen bond with main chain amide of Met793 (without it 3700 fold loss of inhibition)2. Hydrophobic interactions of aniline/phenyl with gatekeeper Thr790 and other residues
H-bond: Met793 with quinazoline N1 H-bond: Met793 with benzamidehydroxy O38
EGFR-DJKCo-crys ligand
EGFR-Nelfinavir
Interactions between Inhibitors and Epidermal Growth Factor Receptor (EGFR) – 74% of binding site resides
are comparable
DJK = N-[4-(3-BROMO-PHENYLAMINO)-QUINAZOLIN-6-YL]-ACRYLAMIDE
Off-target Interaction Network
Identified off-target
Intermediate protein
Pathway
Cellular effect
Activation
Inhibition
Possible Nelfinavir Repositioning
Summary
• The HIV-1 drug Nelfinavir appears to be a broad spectrum low affinity kinase inhibitor
• Most targets are upstream of the PI3K/Akt pathway
• Findings are consistent with the experimental literature
• More direct experiment is needed
Possible Nelfinavir Repositioning
The Future as a Dynamical Network Approach
Computational Evaluation of Drug Off-Target Effects
Proteome
Drug binding site alignments
SMAP
Predicted drug targets
Drug and endogenous substrate binding site analysis
Competitively inhibitable targets
Inhibition simulations in context-specific model
COBRA Toolbox
Predicted causal targets and genetic risk factors
Metabolicnetwork
Scientificliterature
Tissue and biofluid localization data
Gene expression
data
Physiologicalobjectives
System exchange constraints
Flux states optimizing objective
Physiological context-specific
model
Influx
Efflux
Drug response phenotypes
Dru
g ta
rget
s
Physiologicalobjectives
Causal drug targets
All targets
336 genes1587 reactions
Plos Comp. Biol. 2010 6(9): e1000938
Acknowledgements
Sarah Kinnings
Lei Xie
Li Xie
http://funsite.sdsc.eduhttp://www.slideshare.net/pebourne/ucl120810
Roger ChangBernhard Palsson