The authors performed a CRISPR-Cas9 mutagenesis screen in a T-ALL cell line to identify mutations in the PSEN1 gene that could confer resistance to the PSEN1-selective γ-secretase inhibitor MRK-560. They identified three main resistance mechanisms:
Mutations at the enzyme-drug interface that directly disrupt the interaction between MRK-560 and PSEN1, such as insertions around amino acids 421-422 and substitutions affecting the intracellular transmembrane domain 6a (amino acids 275-276). These mutations conferred selective resistance to MRK-560 compared to broad-spectrum γ-secretase inhibitors.
Mutations at the enzyme-substrate interface that cause a shift in the relative binding affinities towards the drug and/or the substrate (NOTCH1). These mutations, such as 139(M>SL), 164(A>AP), and 165(W>C), resulted in resistance to both MRK-560 and broad-spectrum inhibitors.
A mutation at the enzyme-substrate interface, 164(A>AP), that potentially hinders the entrance of MRK-560 to the binding pocket, leading to selective resistance to MRK-560.
The authors validated these resistance mechanisms using mouse embryonic fibroblasts and T-ALL cell lines engineered to express the specific PSEN1 mutations. Their findings provide insights into the PSEN1-selectivity of MRK-560 and can help guide the design of other PSEN1-selective γ-secretase inhibitors to overcome resistance in cancer therapy.
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by Vandersmisse... a las www.biorxiv.org 03-06-2024
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