https://bio.nikkeibp.co.jp/atcl/news/p1/24/12/10/12737/
https://www.nature.com/articles/s41467-024-54308-9
A collaborative research group of the RIKEN Center for Integrative Medical Sciences and the National Institute of Genetics has developed a technology to degrade target proteins in vivo in mice using a degron sequence recognized by the ubiquitin ligase complex. The technology makes it possible to efficiently evaluate drug efficacy and side effects in disease model mice. When there is a candidate molecule that can be a target for antibody drugs or molecular targeted drugs, this system can add a degron sequence to the candidate molecule as a target for treatment, and degrade the target molecule in disease model mice to efficiently evaluate the efficacy and side effects of the drug.
The technology utilizes the degron sequence, an amino acid sequence that serves as a marker for degradation. When an agonist (ligand) of the degron system is added, the degron sequence is recognized by the ubiquitin ligase complex and undergoes ubiquitination. By adding a degron sequence to the target protein to be degraded and then adding an agonist, only the target protein can be degraded. Until now, targeted protein degradation induction technology using degron sequences has been limited to applications such as cultured cells.
The research group developed an in vivo targeted protein degradation technology using degron sequences in mice. First, in order to control the expression of cell type-specific ubiquitin ligase, the researchers introduced components of the ubiquitin ligase complex from the human-derived hCRBN gene and the grass-derived OsTIR1 gene into the mouse genome, and established two mouse strains. The target for degradation was the Satb1 protein present in the nucleus. Satb1 plays a role in controlling the expression of specific genes by regulating the three-dimensional structure of genomic DNA and the epigenome. Mice in which the degradation dynamics of Satb1 can be detected by fluorescence have already been established. A degron sequence recognized by human-derived hCRBN and a degron sequence recognized by grass-derived OsTIR1 were introduced into the Satb1 locus of the mouse genome, and two mouse strains expressing these fusion proteins were created.
To activate the degron system, mice carrying a degron sequence recognized by human-derived hCRBN were intraperitoneally administered pomalidomide, an immunomodulatory drug derived from thalidomide, as an agonist of the degron system. It was confirmed that degradation of the target protein, Satb1, occurred within a few hours of administration. Mice with a degron sequence recognized by OsTIR1 derived from grasses were given a plant hormone auxin derivative as a degron system agonist, and the degron was similarly degraded.
In both mouse strains, the researchers found that Satb1 degradation could be induced in various organs, including the thymus, spleen, lymph nodes, lungs, intestines, and brain, in addition to blood. Although it is difficult to administer a degron system agonist intraperitoneally to fetuses or newborn mice, they found that Satb1 degradation could be induced in fetuses and newborn mice by intraperitoneally administering the agonist to pregnant and lactating mother mice.
Next, the researchers administered a single intraperitoneal dose of a degron system agonist to the mice they created, and then measured the amount of Satb1 protein in blood T cells (lymphocytes) over time. In both mouse strains, the amount of Satb1 protein decreased to about 10% of its original level within a few hours after administration of the degron system agonist.
