PRR5L degradation promotes mTORC2-mediated PKC-δ phosphorylation and cell migration downstream of Gα12

Mammalian target of rapamycin complex 2 (mTORC2) phosphorylates AGC protein kinases including protein kinase C (PKC) and regulates cellular functions such as cell migration. However, its regulation remains poorly understood. Here we show that lysophosphatidic acid (LPA) induces two phases of PKC-δ hydrophobic motif phosphorylation. The late phase is mediated by Gα 12 , which specifically activates ARAF, leading to upregulation of the RFFL E3 ubiquitin ligase and subsequent ubiquitylation and degradation of the PRR5L subunit of mTORC2. Destabilization of PRR5L, a suppressor of mTORC2-mediated hydrophobic motif phosphorylation of PKC-δ, but not AKT, results in PKC-δ hydrophobic motif phosphorylation and activation. This Gα 12 -mediated signalling pathway for mTORC2 regulation is critically important for fibroblast migration and pulmonary fibrosis development. Wu and colleagues delineate an mTORC2-dependent cell migration pathway. They show that stimulation of the Gα 12 protein subunit induces the ARAF/ERK-mediated expression of the RFFL E3 ubiquitin ligase. RFFL, in turn, targets the inhibitory PRR5L subunit of the mTORC2 complex for ubiquitylation and degradation, enabling mTORC2 to phosphorylate PKC-δ and promote cell migration.