Discoverx Corporation

Eurofins Discoverx Corporation

William Raab

Thomas S Wehrman

Daniel Bassoni

Wei Feng

Keith R Olson

Chin Yee Loh

Philip Achacoso

Thomas Wehrman

Methods and materials are disclosed for use in an enzyme fragment complementation assay using complementary fragments of &#x3b2;-galactosidase to study the trafficking of proteins in a cell. Compounds that bind to a target peptide have been found to affect protein folding and therefore trafficking. &#x3b2;-Galactosidase fragments, an enzyme donor (ED) and an enzyme acceptor (EA), are fused to a target peptide and to an intracellular compartment protein, wherein the compartment is involved in intracellular trafficking. Contacting the cell with a compound that binds to the target peptide results in enhanced movement of the protein through the cellular trafficking pathway comprised of the endoplasmic reticulum, Golgi apparatus, the plasma membrane, endosomes, etc. Using this approach, compounds that bind to a target peptide and alter its ability to traffic through the normal cellular pathway can be readily detected.

Monitoring protein trafficking using beta-galactosidase reporter fragment complementation

Methods and compositions are provided to measure the binding of a test compound to a target peptide by measuring the effect of the compound on the abundance of the target peptide inside a cell. The target peptide may bind the test compound at an active site or an allosteric site, and it has been found that such binding may stabilize the target peptide against cellular degradation. The target peptide will preferably comprise a destabilizing mutation which shortens the half life of the target peptide within the cell, typically a mammalian cell. Test compounds, including small molecules, have been found to stabilize target peptides. Also provided are systems and kits for use in practicing the methods.

Detection of intracellular binding events by measuring protein abundance

A method for determining ligand activation of receptors using cells expressing genetic constructs of a fusion protein of at least a binding domain of an auxiliary protein and a fragment of &#x3b2;-galactosidase, a fusion protein of an endosome-associated protein and a complementary fragment of &#x3b2;-galactosidase, and a wild-type receptor. The receptors are characterized by binding to the auxiliary protein-binding domain upon activation by an agonist and then endocytosing associated with an endosome to which the endosome-associated protein binds. Cells are incubated with a candidate ligand followed by lysis with a lysing medium comprising a substrate for the &#x3b2;-galactosidase. The enzyme product is then detected as a measure of the activation of the receptor.

Wild-type receptor assays

Methods for detecting phosphorylation of receptor tyrosine kinases ('RTKs') upon activation are provided. The method employs cells comprising two fusion products: (1) an RTK fused to a small fragment of &#x3b2;-galactosidase and (2) a phosphotyrosine binding peptide fused to the large fragment of &#x3b2;-galactosidase, where the 2 fragments weakly complex to form an active enzyme, and optionally a construct for a cytosolic RTK phosphorylating kinase, when the RTK does not autophosphoryate. To detect phosphorylation a &#x3b2;-galactosidase substrate is added to the cells, whereby product formation indicates the occurrence of phosphorylation.

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San Francisco, CA, United States of America

William Raab