Assay provider results from the probe development effort to identify dual inhibitors of LYPLA1 and LYPLA2: Fluorescence-based biochemical gel-based ABPP inhibition of recombinant and endogenous enzyme
Name: Assay provider results from the probe development effort to identify dual inhibitors of LYPLA1 and LYPLA2: Fluorescence-based biochemical gel-based ABPP inhibition of recombinant and endogenous enzyme. ..more
BioActive Compounds: 3
Source (MLPCN Center Name): The Scripps Research Institute Molecular Screening Center (SRIMSC)
Center Affiliation: The Scripps Research Institute (TSRI)
Assay Provider: Benjamin Cravatt, TSRI
Network: Molecular Libraries Probe Production Centers Network (MLPCN)
Grant Proposal Number: 1 R01 CA132630
Grant Proposal PI: Benjamin Cravatt, TSRI
External Assay ID: LYPLA1_INH_FLUO_GEL_1X%INH
Name: Assay provider results from the probe development effort to identify dual inhibitors of LYPLA1 and LYPLA2: Fluorescence-based biochemical gel-based ABPP inhibition of recombinant and endogenous enzyme.
Protein palmitoylation is an essential post-translational modification necessary for trafficking and localization of regulatory proteins that play key roles in cell growth and signaling. Numerous proteins have been identified as targets of palmitoylation, including cytoskeletal proteins, kinases, receptors, and other proteins involved in various aspects of cellular signaling and homeostasis (1). Using a global chemo-proteomic method for the metabolic incorporation and identification of palmitoylated proteins, we were able to identify hundreds of palmitoylated proteins, revealing palmitoylation as a widespread post-translational modification (PTM) (2). Palmitoylation involves an acyl-thioester linkage to specific cysteines (3,4). Given the labile properties of thioesters, palmitoylation is potentially reversible and may be regulated in a manner analogous to other PTMs (e.g., phosphorylation). As such, identification of proteins responsible for the dynamic modulation of palmitoylation is paramount to understanding its patho/physiological roles. For example, multiple oncogenes, including HRAS and SRC, require palmitoylation for malignant transformation (5), suggesting protein palmitoyl thioesterases may have tumor suppressor activity required to repress aberrant growth signaling. More than a decade ago, the cytosolic serine hydrolase acyl-protein thioesterase 1 (APT1) was identified as an in vitro HRAS palmitoyl thioesterase (6). Initially classified as lysophospholipase 1 (LYPLA1) (7), the enzyme has since been demonstrated to have several hundred-fold higher activity as a protein thioesterase. While the in vitro data (6,8) provided an intriguing clue to its possible role in vivo, prior to our studies, little was known about the in vivo thioesterase activity of LYPLA1. Upon retroviral shRNA knockdown of LYPLA1, we found that HRAS was robustly hyper-palmitoylated, providing the first evidence that the endogenous enzyme is a functional protein palmitoyl thioesterase capable of regulating HRAS palmitoylation in mammalian cells. However, shRNA resulted in only an 80% reduction in LYPLA1 expression (unpublished). LYPLA2 (a.k.a. APT2) is 65% identical to LYPLA1, and also exhibits lysophospholipase activity in vitro, but its potential role as a thioesterase is unknown (9). shRNA knockdown studies of LYPLA2 revealed only partial knockdown of the enzyme, making substrate identification inconclusive (unpublished). A principle goal of post-genomic research is the determination of the molecular and cellular role of uncharacterized enzymes like LYPLA1 and LYPLA2. As such, a dual inhibitor selective for both LYPLA1 and LYPLA2 would greatly aid investigations into the biological function of these related enzymes. Several inhibitors of LYPLA1 have been described (10,11), but none of these agents have proven capable of inhibiting LYPLA1 activity in cells, and no selective inhibitors of LYPLA2 have been reported to date. To comprehensively identify LYPLA1 and LYPLA2 substrates and functionally test the role of these enzymes in dynamic de-palmitoylation and tumorigenesis, development of a high affinity inhibitor, capable of achieving temporal and more complete control over activity, is critical.
1. Smotrys, J.E. and Linder, M.E. PALMITOYLATION OF INTRACELLULAR SIGNALING PROTEINS: Regulation and Function. Annual Review of Biochemistry, 2004. 73: 559-587.
2. Martin, B.R. and Cravatt, B.F. Large-scale profiling of protein palmitoylation in mammalian cells. Nat Methods, 2009. 6: 135-138.
3. Magee, A.I., Koyama, A.H., Malfer, C., Wen, D. and Schlesinger, M. J. Release of fatty acids from virus glycoproteins by hydroxylamine. Biochimica et Biophysica Acta (BBA) - General Subjects, 1984. 798: 156-166.
4. Rose, J.K., Adams, G.A. and Gallione, C.J. The presence of cysteine in the cytoplasmic domain of the vesicular stomatitis virus glycoprotein is required for palmitate addition. Proc Natl Acad Sci USA, 1984. 81: 2050-2054.
5. Willumsen, B.M., Cox, A.D., Solski, P.A., Der, C.J. and Buss, J.E. Novel determinants of H-Ras plasma membrane localization and transformation. Oncogene, 1996. 13: 1901-1909.
6. Duncan, J.A. and Gilman, A.G. A Cytoplasmic Acyl-Protein Thioesterase That Removes Palmitate from G Protein alpha Subunits and p21RAS. J Biol Chem, 1998. 273: 15830-15837.
7. Sugimoto, H., Hayashi, H. & Yamashita, S. Purification, cDNA cloning, and regulation of lysophospholipase from rat liver. J Biol Chem, 1996. 271: 7705-7711.
8. Hirano, T. et al. Thioesterase activity and subcellular localization of acylprotein thioesterase 1/lysophospholipase 1. Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 2009. 1791: 797-805.
9. Toyoda, T., Sugimoto, H. and Yamashita, S. Sequence, expression in Escherichia coli, and characterization of lysophospholipase II. Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids, 1999. 1437: 182-193.
10. Biel, M., Deck, P., Giannis, A. and Waldmann, H. Synthesis and Evaluation of Acyl Protein Thioesterase 1 (APT1) Inhibitors. Chemistry - A European Journal, 2006. 12: 4121-4143.
11. Deck, P. et al. Development and Biological Evaluation of Acyl Protein Thioesterase 1 (APT1) Inhibitors. Angewandte Chemie International Edition, 2005. 44: 4975-4980.
assay provider, LYPLA1, lysophospholipase 1, LYPLA2, lysophospholipase 2, APT1, acyl-protein thioesterase 1, APT2, acyl-protein thioesterase 2, serine hydrolase, palmitoylation, inhibitor, recombinant enzyme, recombinant human enzyme, endogenous enzyme, mouse proteome, mouse proteomic lysate, activity-based protein profiling, ABPP, gel-based ABPP, fluorophosphonate rhodamine, FP-Rh, Scripps, Scripps Research Institute Molecular Screening Center, SRIMSC, Molecular Libraries Probe Production Centers Network, MLPCN
Assays (see Protocol for details)
§ Panel component ID.
The purpose of this assay is to determine whether test compounds can inhibit LYPLA1 and LYPLA2 in a complex proteomic lysate using an activity-based proteomic profiling (ABPP) assay. In this assay, a complex proteome, containing endogenous and spiked-in recombinant forms of LYPLA1 or LYPLA2, is incubated with test compound followed by reaction with a rhodamine-conjugated fluorophosphonate (FP-Rh) activity-based probe. The reaction products are separated by SDS-PAGE and visualized in-gel using a flatbed fluorescence scanner. The percentage activity remaining is determined by measuring the integrated optical density (IOD) of the bands. As designed, test compounds that act as LYPLA1 and/or LYPLA2 inhibitors will prevent enzyme-probe interactions, thereby decreasing the proportion of bound fluorescent probe, giving lower fluorescence intensity in the band in the gel. Percent inhibition is calculated relative to a DMSO (no compound) control.
To soluble (Assay 1) or membrane (Assays 2-4) proteome prepared from mouse brain (1 mg/ml in DPBS) is added either 20 nM purified recombinant human (rh) LYPLA1 (Assays 1 and 3) or 20 nM purified rhLYPLA2 (Assays 2 and 4). For each Assay, proteome was treated with 20 uM test compound (1 uL of a 50x stock in DMSO) for 30 minutes at 25 C (50 uL reaction volume). FP-Rh (1 uL of 50x stock in DMSO) was added to a final concentration of 2 uM. The reaction was incubated for 30 minutes at 25 C, quenched with 2x SDS-PAGE loading buffer, separated by SDS-PAGE and visualized by in-gel fluorescent scanning. The percentage activity remaining was determined by measuring the integrated optical density of the target bands: rhLYPLA1 (Assay 1), rhLYPLA2 (Assay 2), endogenous mouse (em) LYPLA1 (Assay 3) and emLYPLA2 (Assay 4) relative to a DMSO-only (no compound) control.
% Inhibition = ( 1- ( IOD_Test_Compound - IOD_Low_Control ) / ( IOD_High_Control - IOD_Low_Control ) ) * 100
Test_Compound is defined as target treated with test compound.
High_Control is defined as target treated with DMSO only (no compound).
Low_Control is defined as background in a blank region of the gel.
If band resolution was too low to determine % inhibition accurately, % inhibiton is not reported.
PubChem Activity Outcome and Score:
The following applies to each panel in this assay:
Compounds with greater than or equal to 30% inhibition of target band in each assay were considered active.
The reported PubChem Activity Score has been normalized to 100% of the observed inhibition.
Assay 1 Score: The PubChem Activity Score range for active compounds is 100-31, and for inactive compounds 29-0.
Assay 2 Score: The PubChem Activity Score range for active compounds is 100-39, and for inactive compounds 36-0.
Assay 3 Score: The PubChem Activity Score range for active compounds is 100-35, and for inactive compounds 30-0.
Assay 4 Score: The PubChem Activity Score range for active compounds is 100-100, and for inactive compounds 42-42.
Overall Outcome and Score:
Compounds that were active in all four panel assays are considered active overall.
The overall score is taken as the fraction of panels where the compound is active, multiplied by 100.
The PubChem Activity Score range for active compounds is 100-100, and for inactive compounds 75-0.
List of Reagents:
Soluble and membrane proteomes prepared from mouse brain
rhLYPLA1 and rhLYPLA2 (provided by Assay Provider)
FP-Rh (provided by the Assay Provider)
DPBS (Cellgro 20-031-CV)
This assay was performed by the assay provider with MLSMR compounds aliquoted in DMSO.
Categorized Comment - additional comments and annotations
** Test Concentration. § Panel component ID.