BAP1 regulates AMPK-mTOR signalling pathway through deubiquitinating and stabilizing tumour-suppressor LKB1.

Liver kinase B1 (LKB1), a tumour suppressor, participates in many cellular processes, including cell survival, growth, apoptosis, transformation, and metabolism. Upon performing yeast two-hybrid screening, co-immunoprecipitation, and GST pull-down, we identified that BRCA1-associated protein 1 (BAP1), a deubiquitinase, interacts with LKB1. Immunoblotting was performed to examine the effect of BAP1 on the activation of 5' AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR), downstream of LKB1. The relationship between BAP1 deficiency and cancer cell proliferation was examined using cell survival assay and soft agar assay. qRT-PCR and oil red O staining were performed to evaluate lipid synthesis. Our findings reveal that BAP1 deubiquitinates LKB1, inhibits its degradation, and stabilises it, thereby affecting AMPK activation and downstream mTOR activity. BAP1 deficiency may enhance cellular proliferation as well as lipid synthesis.