SQSTM1/p62-mediated PD-L1 biomolecular condensate formation promotes lung tumorigenesis.
Journal
Journal of advanced research
ISSN
2090-1224
Date Issued
2026-02-21
Author(s)
Lin, Yen-Cheng
Lin, Yu-Wei
Wang, Rou-Hsin
Pang, Jiun-Yu
Hsiao, Meng-Chi
Wang, Hsien-Mien
Wu, Shwu-Yuan
Chiang, Cheng-Ming
Chao, Jui-I
Abstract
Biomolecular condensates are membraneless organelles functionally involved in diverse processes, including cancer progression. Sequestosome-1 (SQSTM1)/p62 regulates liquid-liquid phase separation to drive biomolecular condensates, while programmed death-ligand 1 (PD-L1) promotes cancer cell growth. Although SQSTM1 has been shown to form condensates with several complexes, its full range of partners remains incompletely characterized.
This study aimed to investigate the role of SQSTM1 in mediating PD-L1 condensate formation and its contribution to lung tumorigenesis.
The SQSTM1-PD-L1 interaction and condensate colocalization were examined by immunoprecipitation and immunofluorescence. Truncated SQSTM1 constructs validate the interacting domain with PD-L1, which is supported by computational AlphaFold3 analysis. We applied 1,6-hexanediol, FDA-approved PD-L1 antibody Atezolizumab, and CRISPR/Cas9-based SQSTM1 knockout to disrupt SQSTM1/PD-L1 biomolecular condensates, along with in vitro and in vivo experiments. The Survivin levels were analyzed using real-time quantitative PCR and immunoblotting. Clinical correlations of SQSTM1 and PD-L1 expression with prognosis were assessed using public datasets.
Our research demonstrate that SQSTM1, by its Phox1 and Bem1 (PB1) domain, directly interacts with PD-L1 to facilitate the SQSTM1/PD-L1 biomolecular condensate formation. The formation of SQSTM1/PD-L1 condensates prevents PD-L1 from ubiquitin-proteasome-mediated degradation and stabilizes PD-L1 levels. Deletion of the PB1 domain in SQSTM1 inhibits the formation of PD-L1 biomolecular condensates and induces PD-L1 K48 ubiquitination for protein degradation. Disruption of SQSTM1/PD-L1 condensates with 1,6-hexanediol induces PD-L1 proteolysis and reduces cell viability. Knockout of SQSTM1 disrupts PD-L1 condensate formation, downregulates PD-L1 protein levels, and attenuates tumor growth. Treatment with PD-L1 antibody drug Atezolizumab inhibits SQSTM1/PD-L1 condensates and suppresses tumor formation. Clinically, high SQSTM1 and PD-L1 expression correlated with poor prognosis in lung cancer patients.
Together, the SQSTM1 directly interacts with non-membrane-associated PD-L1 to drive the formation of SQSTM1/PD-L1 biomolecular condensates, which prevent PD-L1 degradation, promote lung tumorigenesis, and serve as a potential therapeutic target in lung cancers.
Subjects
Biomolecular condensate
PB1 domain
PD-L1
SQSTM1
Tumorigenesis
Type
text::journal::journal article