PT  - JOURNAL ARTICLE
AU  - Rebecca Harris
AU  - Ming Yang
AU  - Christina Schmidt
AU  - Sarbjit Singh
AU  - Amarnath Natarajan
AU  - Christian Frezza
AU  - Heike Laman
TI  - Fbxo7 promotes Cdk6 activity to inhibit PFKP and glycolysis in T cells
AID  - 10.1101/2021.11.05.467417
DP  - 2021 Jan 01
TA  - bioRxiv
PG  - 2021.11.05.467417
4099  - http://biorxiv.org/content/early/2021/11/05/2021.11.05.467417.short
4100  - http://biorxiv.org/content/early/2021/11/05/2021.11.05.467417.full
AB  - Deregulated Fbxo7 expression is associated with many pathologies, including anaemia, male sterility, cancer, and Parkinson’s disease, demonstrating its critical role in a variety of cell types. Although Fbxo7 is an F-box protein that recruits substrates for SCF-type E3 ubiquitin ligases, it also promotes the formation of cyclin D/Cdk6/p27 complexes in an E3-ligase independent fashion. We discovered PFKP, the major gatekeeper of glycolysis, in a screen for Fbxo7 substrates. PFKP has been previously shown to be a critical substrate of Cdk6 for the viability of T-ALL cells. We investigated the molecular relationships between Fbxo7, Cdk6 and PFKP, and the functional effect Fbxo7 has on T cell metabolism, viability, and activation. Fbxo7 promotes Cdk6-independent ubiquitination and Cdk6-dependent phosphorylation of PFKP. Importantly Fbxo7-deficient cells have reduced Cdk6 activity, and haematopoietic and lymphocytic cell lines show a significant dependency on Fbxo7. Compared to WT cells, CD4+ T cells with reduced Fbxo7 expression show increased glycolysis, despite lower cell viability and activation levels. Metabolomic studies of activated CD4+ T cells confirm increased glycolytic flux in Fbxo7-deficient cells, as well as altered nucleotide biosynthesis and arginine metabolism. We show Fbxo7 expression is glucose-responsive at the mRNA and protein level, and we propose Fbxo7 inhibits PFKP and glycolysis via its activation of Cdk6.