title: Biotin supplementation decreases the expression of the SERCA3 gene (ATP2A3) in Jurkat cells, thus, triggering unfolded protein response.
abstract: Protein folding in the endoplasmic reticulum (ER) depends on Ca(2+); uptake of Ca(2+) into the ER is mediated by sarco/endoplasmic reticulum Ca(2+)-ATPase 3 (SERCA3). The 5'-flanking region of the SERCA3 gene (ATP2A3) contains numerous binding sites for the transcription factors Sp1 and Sp3. Biotin affects the nuclear abundance of Sp1 and Sp3, which may act as transcriptional activators or repressors. Here we determined whether biotin affects the expression of the SERCA3 gene and, thus, protein folding in human lymphoid cells. Jurkat cells were cultured in media containing 0.025 nmol/L biotin (denoted "deficient") or 10 nmol/L biotin ("supplemented"). The transcriptional activity of the full-length human SERCA3 promoter was 50% lower in biotin-supplemented cells compared to biotin-deficient cells. Biotin-dependent repressors bind to elements located 731-1312 bp upstream from the transcription start site in the SERCA3 gene. The following suggest that low expression of SERCA3 in biotin-supplemented cells impaired folding of secretory proteins in the ER, triggering unfolded protein response: (i) sequestration of Ca(2+) in the ER decreased by 14-24% in response to biotin supplementation; (ii) secretion of interleukin-2 into the extracellular space decreased by 75% in response to biotin supplementation; (iii) the nuclear abundance of stress-induced transcription factors increased in response to biotin supplementation; and (iv) the abundance of stress-related proteins such ubiquitin activating enzyme 1, growth arrest and DNA damage 153 gene, X-box binding protein 1 and phosphorylated eukaryotic translation initiation factor 2alpha increased in response to biotin supplementation. Collectively, this study suggests that supplements containing pharmacological doses of biotin may cause cell stress by impairing protein folding in the ER.
authors.affiliation: Department of Nutrition and Health Sciences, University of Nebraska at Lincoln, 68583-0806, USA.
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Griffin
authors.forename: Rocio
authors.initials: R
authors.lastname: Rodriguez-Melendez
authors.forename: Leonard
authors.initials: L
authors.lastname: Dode
authors.forename: Frank
authors.initials: F
authors.lastname: Wuytack
authors.forename: Janos
authors.initials: J
authors.lastname: Zempleni
mesh_terms: D001710:Biotin / Q000008:administration & dosage*; D019921:Biotinylation; D002118:Calcium / Q000032:analysis; D000252:Calcium-Transporting ATPases / Q000235:genetics*; D019735:Carbon-Carbon Ligases / Q000378:metabolism; D003593:Cytoplasm / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D009687:Nuclear Proteins / Q000235:genetics; D017510:Protein Folding; D011766:Pyruvate Carboxylase / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D000071701:Regulatory Factor X Transcription Factors; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D014157:Transcription Factors
chemical_list: D004268:DNA-Binding Proteins; D007376:Interleukin-2; D009687:Nuclear Proteins; D012333:RNA, Messenger; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D001710:Biotin; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D019735:Carbon-Carbon Ligases; D011766:Pyruvate Carboxylase; C021573:methylcrotonoyl-CoA carboxylase; C506949:ATP2A3 protein, human; D000252:Calcium-Transporting ATPases; D002118:Calcium