Elevated Choline Kinase α–Mediated Choline Metabolism Supports the Prolonged Survival of TRAF3-Deficient B Lymphocytes

Abstract

Specific deletion of the tumor suppressor TRAF3 from B lymphocytes in mice leads to the prolonged survival of mature B cells and expanded B cell compartments in secondary lymphoid organs. In the current study, we investigated the metabolic basis of TRAF3-mediated regulation of B cell survival by employing metabolomic, lipidomic, and transcriptomic analyses. We compared the polar metabolites, lipids, and metabolic enzymes of resting splenic B cells purified from young adult B cell–specific Traf3−/− and littermate control mice. We found that multiple metabolites, lipids, and enzymes regulated by TRAF3 in B cells are clustered in the choline metabolic pathway. Using stable isotope labeling, we demonstrated that phosphocholine and phosphatidylcholine biosynthesis was markedly elevated in Traf3−/− mouse B cells and decreased in TRAF3-reconstituted human multiple myeloma cells. Furthermore, pharmacological inhibition of choline kinase α, an enzyme that catalyzes phosphocholine synthesis and was strikingly increased in Traf3−/− B cells, substantially reversed the survival phenotype of Traf3−/− B cells both in vitro and in vivo. Taken together, our results indicate that enhanced phosphocholine and phosphatidylcholine synthesis supports the prolonged survival of Traf3−/− B lymphocytes. Our findings suggest that TRAF3-regulated choline metabolism has diagnostic and therapeutic value for B cell malignancies with TRAF3 deletions or relevant mutations.

ChoK-Full of Potential: Choline Kinase in B Cell and T Cell Malignancies

“…However, given the lack of CHKA gene amplification, it remained unknown what oncogenic alterations and signaling pathways cause the elevated expression of CHKA in B cell malignancies. Addressing this gap in knowledge, we recently made an interesting finding that deletion of the tumor suppressor gene TRAF3 leads to up-regulation of Chka at mRNA and protein levels in both mouse and human models of B cell malignancies [ 59 ].…”

“…In an effort to elucidate the metabolic basis of TRAF3-mediated regulation of mature B cell survival, we performed metabolomic, lipidomic and transcriptomic profiling to compare the metabolism of resting splenic B cells purified from young adult B- Traf3 −/− and littermate control mice. We found that multiple metabolites, lipids and enzymes regulated by TRAF3 in B cells are clustered in the choline metabolic pathway [ 59 ]. Using stable isotope labeling, we showed that the biosynthesis of P-Cho and PC species (32:2 and 34:3) is increased in Traf3 −/− B cells, which is mediated by the up-regulated expression of Chkα [ 59 ].…”

“…We found that multiple metabolites, lipids and enzymes regulated by TRAF3 in B cells are clustered in the choline metabolic pathway [ 59 ]. Using stable isotope labeling, we showed that the biosynthesis of P-Cho and PC species (32:2 and 34:3) is increased in Traf3 −/− B cells, which is mediated by the up-regulated expression of Chkα [ 59 ]. We also demonstrated that CHKA is consistently up-regulated in human MM cells that contain TRAF3 deletions or inactivating mutations [ 59 ].…”

“…Using stable isotope labeling, we showed that the biosynthesis of P-Cho and PC species (32:2 and 34:3) is increased in Traf3 −/− B cells, which is mediated by the up-regulated expression of Chkα [ 59 ]. We also demonstrated that CHKA is consistently up-regulated in human MM cells that contain TRAF3 deletions or inactivating mutations [ 59 ]. Furthermore, the reconstitution of TRAF3 in these MM cells results in decreased CHKα protein levels, reduced biosynthesis of P-Cho and PC species (32:2 and 34:3), and increased apoptosis [ 59 ].…”

“…We also demonstrated that CHKA is consistently up-regulated in human MM cells that contain TRAF3 deletions or inactivating mutations [ 59 ]. Furthermore, the reconstitution of TRAF3 in these MM cells results in decreased CHKα protein levels, reduced biosynthesis of P-Cho and PC species (32:2 and 34:3), and increased apoptosis [ 59 ]. Taken together, our findings revealed that loss of the tumor suppressor TRAF3 is a common oncogenic alteration leading to up-regulated CHKα expression and elevated choline metabolism in human and mouse B cell malignancies.…”