The cytoskeletal protein smoothelin maintains homologous recombination repair by stabilizing RAD51 in an HUWE1-dependent manner in colorectal cancer

Dysregulation of cytoskeletal proteins has been found in response to DNA damage stress, yet the functional role of cytoskeletal proteins in DNA repair remained unexplored. Here, we found that DNA-damaging agents induced substantial upregulation of smooth muscle-specific cytoskeletal protein smoothelin (SMTN) in colorectal cancer (CRC) cells. Silencing SMTN abrogated G2/M arrest, exacerbated DNA damage, and markedly enhanced the chemosensitivity of CRC cells to various DNA-damaging agents. Notably, SMTN could rapidly accumulate at DNA damage sites within 1 min after laser irradiation, which was indispensable for the initiation of homologous recombination (HR) repair. Mechanistically, SMTN stabilized RAD51 by disrupting its interaction with its E3 ubiquitin ligase HUWE1, thereby maintaining the process of HR repair. To explore the therapeutic role of SMTN, customized cell membrane infused biomimetic liposomes were constructed to ensure rapid delivery of SMTN siRNA specifically into HCT-116 cells, yielding significantly enhanced anti-cancer effects of irinotecan and fuzuloparib both in vitro and in vivo. To summarize, our findings revealed a novel function of SMTN in DNA damage repair and provided a therapeutic strategy of targeting SMTN to enhance the efficacy of DNA damage agents.