Biotin Requirements Are Lower in Human Jurkat Lymphoid Cells but Homeostatic Mechanisms Are Similar to Those of HepG2 Liver Cells

Abstract

The following proteins are candidates for maintaining biotin homeostasis in humans: the biotin transporters sodium-dependent multivitamin transporter (SMVT) and monocarboxylate transporter 1, the biotinyl-protein ligase holocarboxylase synthetase (HCS), and the lysine-epsilon-biotin hydrolase biotinidase. Liver cells are supplied through the portal vein with high levels of water-soluble vitamins compared with those of peripheral tissues. We hypothesized that the mechanisms of biotin homeostasis are qualitatively and quantitatively different in cells derived from human liver (HepG2 cells) and lymphoid tissues (Jurkat cells). Cells were cultured in biotin-defined media, representing deficient (D), normal (N), and supplemented (S) individuals. Biotinylation of carboxylases depended on biotin availability in both cell types, but HepG2 cells required 3 times more biotin than Jurkat cells to maintain normal levels of holocarboxylases. The expression of biotin transporters was less in both types in medium S compared with cells in media D and N; in contrast, the expression of HCS was higher in cells in medium S compared with the other cells. The abundance of 3-methylcrotonyl-CoA carboxylase mRNA was lower in cells in medium D than cells in media N and S. The enrichment of biotinylated histones was higher at the SMVT promoter 1 in HepG2 and Jurkat cells in medium S compared with the corresponding cells in media D and N, presumably repressing the SMVT gene. The mechanisms of biotin homeostasis are qualitatively similar but quantitatively different in HepG2 and Jurkat cells; HCS, histone biotinylation, and biotin transporters play a role in homeostasis in both.

Inhibition of acetyl-CoA carboxylases by soraphen A prevents lipid accumulation and adipocyte differentiation in 3T3-L1 cells

“…Relative mRNA expression was quantified by RT-qPCR and the ΔCt protocol as described previously (Kaur Mall et al, 2010) using the primers in Online Supplementary Table 1. Assays were performed in three independent biological replicates and results were normalized to 18S ribosomal RNA.…”

Lysine biotinylation and methionine oxidation in the heat shock protein HSP60 synergize in the elimination of reactive oxygen species in human cell cultures

“…The binding of biotin to lysine residues in proteins is catalyzed by holocarboxylase synthetase [11], which localizes in the cytoplasm, mitochondria, and nuclei in mammalian cells [12-15]. Previous studies suggest that the abundance of protein biotinylation marks depends on biotin supply in human cell cultures and in healthy adults [16, 17]. …”

Three promoters regulate the transcriptional activity of the human holocarboxylase synthetase gene

“…For example, the expression of HLCS depends on biotin availability in well-controlled and homogenous organisms such as rats and human cell cultures [21, 22], whereas no such effect can be reproduced in a biotin-defined, yet heterogeneous population in an outpatient study in adults [50]. We propose that HLCS is a ubiquitously expressed housekeeping gene and that effects of biotin on promoter activity are small, consistent with the absence of a TATA box in any of the three HLCS promoters.…”

“…Previous studies in rats and in human cell cultures suggest that the expression of HLCS depends on a sufficient supply of biotin [15, 21, 22]. However, these findings were not reproduced when investigating HLCS mRNA levels in lymphocytes from healthy adults where the inter-individual variation is large [23].…”