Mammalian target of rapamycin complex 1 signaling opposes the effects of anchorage loss, leading to activation of Cdk4 and Cdc6 stabilization

Abstract 

When deprived of an anchorage to the extracellular matrix, fibroblasts arrest in the G₁ phase with inactivation of Cdk4/6 and Cdk2 and destruction of Cdc6, the assembler of prereplicative complexes essential for S phase onset. How cellular anchorages control these kinases and Cdc6 stability is poorly understood. Here, we report that in rat embryonic fibroblasts, activation of mammalian target of rapamycin complex 1 by a Tsc2 mutation or overexpression of a constitutively active mutant Rheb overrides the absence of the anchorage and stabilizes Cdc6 at least partly via activating Cdk4/6 that induces Emi1, an APC/C^Cdh1 ubiquitin ligase inhibitor.

Structured summary

MINT-7890626: cdc27 (uniprotkb:Q4V8A2) physically interacts (MI:0915) with Cyclin-A (uniprotkb:Q6AY13) by anti bait coimmunoprecipitation (MI:0006)

Abbreviations: mTORC1, mammalian target of rapamycin complex 1, ECM, extracellular matrix, S6K1, S6 kinase 1, Rb, retinoblastoma protein, REF, rat embryonic fibroblast, Eker REF, Eker (Tsc2^−/−) rat embryonic fibroblast, 4EBP, eIF4E binding protein, ALLN, N-acetyl-leucinyl-leucinyl-norleucinal, zVAD, benzyloxycarbonyl-valinyl-alaninyl-aspartyl fluoromethyl ketone, MC, methylcellulose medium

Keywords: Anchorage, Mammalian target of rapamycin complex 1, Eker, Rheb, Cdc6, Cdk4, Emi1, APC/C^Cdh1