Figure 2. The sodium bicarbonate carrier SLC4A7 provides cellular bicarbonate for de novo purine and pyrimidine synthesis.

(A) Genes coessential with the sodium bicarbonate carrier SLC4A7.

(B) CERES dependency score for the de novo purine, pyrimidine synthesis and bicarbonate transporter enzymes. A CERES score less than 0 indicates a higher likelihood that the gene of interest is essential in a given cell line. A score of 0 indicates a gene is not essential (NE Genes: Non-essential genes).

(C) Immunoblots of HeLa cells transfected with siRNA targeting SLC4A7 or nontargeting controls, and measurement of intracellular pH (pHi) and NaHCO₃ uptake.

(D, E) Purine and pyrimidine levels measured via LC-MS/MS in HeLa cells transfected as in (C)

(F) Normalized peak areas of ¹⁵N-glutamine levels measured as in (D) in HeLa cells treated as in (C) and labeled with ¹⁵N-amide-glutamine for 1 h.

(G, H) Normalized peak areas of ¹⁵N-labeled nucleotide intermediates from HeLa cells measured and treated as in (F).

(I, J) Radiolabeling was performed for 6 h in HeLa cells transfected as in (C) to measure de novo purine synthesis (¹⁴C-glycine) (I) or pyrimidine synthesis activity (¹⁴C-aspartate) (J).

(C)-(J) The data are graphed as the means ± SDs of biological triplicates and are representative of at least two independent experiments. *p < 0.05, by two-tailed Student’s t-test for pairwise comparisons.