Deregulated expression of the MYC oncoprotein contributes to the genesis of many human tumours, yet strategies to exploit this for a rational tumour therapy are scarce. MYC promotes cell growth and proliferation, and alters cellular metabolism to enhance the provision of precursors for phospholipids and cellular macromolecules 1,2 . Here we show in human and murine cell lines that oncogenic levels of MYC establish a dependence on AMPK-related kinase 5 (ARK5; also known as NUAK1) for maintaining metabolic homeostasis and for cell survival. ARK5 is an upstream regulator of AMPK and limits protein synthesis via inhibition of the mammalian target of rapamycin 1 (mTORC1) signalling pathway. ARK5 also maintains expression of mitochondrial respiratory chain complexes and respiratory capacity, which is required for efficient glutamine metabolism. Inhibition of ARK5 leads to a collapse of cellular ATP levels in cells expressing deregulated MYC, inducing multiple pro-apoptotic responses as a secondary consequence. Depletion of ARK5 prolongs survival in MYC-driven mouse models of hepatocellular carcinoma, demonstrating that targeting cellular energy homeostasis is a valid therapeutic strategy to eliminate tumour cells that express deregulated MYC.To identify kinases that are specifically required for the viability of cells expressing deregulated MYC, we used U2OS cells expressing c-MYC fused to the oestrogen receptor ligand binding domain (MYC-ER) (Fig. 1a). Activation of MYC-ER by 4-hydroxytamoxifen (OHT) had little effect on apoptosis when cells were grown at low density in the presence of growth factors. Under these conditions, we performed a short interfering (si)RNA screen of the human kinome, using automated microscopy to identify siRNAs that induced poly-ADP-ribose-polymerase cleavage specifically in the presence of OHT. This screen yielded two hits, ARK5 and AMPK (Supplementary Table 1).Depletion of ARK5 induced the accumulation of MYC-expressing cells that stained positive for annexin V and propidium iodide (Fig. 1a and Supplementary Fig. 1a). Similarly, expressing different short hairpin (sh)RNAs targeting ARK5 induced levels of MYC-dependent death that correlated with the degree of knockdown (Fig. 1b). Titration of OHT revealed that levels of MYC that cause a dependence on ARK5 are higher than those required to promote proliferation ( Supplementary Fig. 1b). Depletion of ARK5 induced death in U2OS cells constitutively expressing MYC and suppressed propagation of MRC5 fibroblasts in a MYCdependent manner (Fig. 1c and Supplementary Fig. 1c). Expression of murine ARK5, which is not targeted by the shRNAs used, prevented death upon depletion of human ARK5 (Fig. 1d). This rescue required LKB1-dependent phosphorylation of T212, but not AKT-dependent phosphorylation of S601 (refs 3, 4). Mutation of K85 within the ATPbinding domain blocked the ability of murine ARK5 to prevent death, demonstrating that rescue requires ARK5 catalytic activity. Accordingly, a small-molecule inhibitor of ARK5, BX795, mimicked the effects o...

Chlamydia trachomatis is an important human pathogen that replicates inside the infected host cell in a unique vacuole, the inclusion. The formation of this intracellular bacterial niche is essential for productive Chlamydia infections. Despite its importance for Chlamydia biology, a holistic view on the protein composition of the inclusion, including its membrane, is currently missing. Here we describe the host cell-derived proteome of isolated C. trachomatis inclusions by quantitative proteomics. Computational analysis indicated that the inclusion is a complex intracellular trafficking platform that interacts with host cells’ antero- and retrograde trafficking pathways. Furthermore, the inclusion is highly enriched for sorting nexins of the SNX-BAR retromer, a complex essential for retrograde trafficking. Functional studies showed that in particular, SNX5 controls the C. trachomatis infection and that retrograde trafficking is essential for infectious progeny formation. In summary, these findings suggest that C. trachomatis hijacks retrograde pathways for effective infection.