Patent ID: 8569057

Claim:
A method of determining an effect of a compound on trafficking of a target peptide, comprising: a. providing a cell having an endoplasmic reticulum (“ER”), said cell comprising therein i. a first fusion protein comprising the target peptide fused to a first β-galactosidase fragment wherein the target peptide has a mutation causing retention of the first fusion protein in the ER; and ii. a second fusion protein comprising a protein localized to an endosome compartment fused to a second β-galactosidase fragment; b. wherein said first and second β-galactosidase fragments have an affinity for each other to complement and produce an active β-galactosidase enzyme only when the first and second β-galactosidase units are in close proximity; c. adding to said cell a compound that affects release of the target peptide from the ER; and d. evaluating said cell for active β-galactosidase activity to determine whether the first and second fusion protein interact in said sub-cellular compartment as a result of release of the target peptide from the ER being affected by the compound.