HY8

Amino Acid Sequence

3D Structure (/structures/AF-P01116-F1-model_v6.cif)

Function

Signal transducer in the Ras-MAPK signaling pathway that regulates cell proliferation and survival Ras proteins bind GDP/GTP and possess intrinsic GTPase activity. Activates MAPK1/MAPK3 resulting in phosphorylation and ultimately degradation of GJA1 Plays a role in promoting oncogenic events by inducing transcriptional silencing of tumor suppressor genes (TSGs) in colorectal cancer (CRC) cells in a ZNF304-dependent manner Recognized by LZTR1 that mediates its ubiquitination by a BCR (BTB-CUL3-RBX1) E3 ubiquitin-protein ligase complex

Mechanism

The ubiquitin-proteasome pathway (UPP) constitutes the principal pathway for protein degradation in eukaryotic cells, mediating the breakdown of target proteins through ubiquitin tagging and subsequent proteasomal degradation. In an ATP-dependent manner, the ubiquitin-activating enzyme (E1) activates ubiquitin (Ub) and conjugates it to a ubiquitin-conjugating enzyme (E2). E3 ligase subsequently catalyzes the transfer of Ub to the target protein, leading to the formation of a polyubiquitin chain that completes the ubiquitination mark. The 19S regulatory particle of the 26S proteasome recognizes this ubiquitination signal and, after deubiquitination, mediates the ATP-dependent delivery of the substrate into the 20S proteasome for degradation

Description

Encouraged by the obvious increase in the ubiquitin level in the HY8-treated group, we further performed rescue assays (Figures 4D and S5). Cotreatment with the proteasome inhibitor MG132 blocked KRAS degradation, indicating that the engagement of proteasome pathway is required. In contrast, cotreatment with the lysosomal inhibitor bafilomycin A1 (Baf A1) had no effect on KRAS degradation, suggesting the autophagy/lysosome pathway is not involved in carborane-induced KRAS degradation

Description

Subsequently, all of the conjugates were examined by Western blotting to evaluate their ability to induce KRASG12C degradation in cells (Figure2). Analysis of the correlation between cytotoxicity and KRAS G12C degradation indicates that target degradation does not necessarily result in cytotoxicity. Partial degradation of the target protein (approximately 60% degradation of KRAS G12C upon HY8 treatment) may be insufficient to induce cytotoxic effects, particularly in KRAS-driven cancer cells that exhibit strong pathway redundancy