{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nSLC52A1, which encodes riboflavin transporter‐1 (RFVT1; formerly known as hRFT1/GPR172B), was first identified as a novel riboflavin carrier expressed in several tissues including the placenta and intestine, where it localizes to the plasma membrane to mediate the cellular uptake of vitamin B2 (riboflavin). Initial molecular cloning studies characterized SLC52A1 as a 448–450 amino acid protein that functions in riboflavin transport, and subsequent reviews established its nomenclature and classification into the newly defined SLC52 family. These studies also showed that SLC52A1 is abundantly expressed in tissues such as the placenta and plays a crucial role in riboflavin homeostasis."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nTranscriptional regulation studies have further dissected the control of SLC52A1 expression. Analysis of its 5’-flanking promoter region revealed a TATA-less, GC-rich core containing cis-regulatory elements, particularly an Sp1 binding site that is crucial for basal transcription. Moreover, investigations in intestinal epithelial models demonstrated that both differentiation and inflammatory signals, such as tumor necrosis factor-α, modulate the expression and promoter activity of SLC52A1, thereby influencing riboflavin uptake under physiological and pathophysiological conditions."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nFunctionally, SLC52A1 plays a central role in maintaining riboflavin levels required for multiple redox reactions and mitochondrial energy production. Its activity in enterocytes has been linked to efficient intestinal absorption of riboflavin, with potential implications in disease contexts such as colorectal cancer. At the cellular level, SLC52A1-derived riboflavin uptake appears to mitigate mitochondrial dysfunction and suppress stress-induced senescence by modulating the AMPK–p53 pathway. Clinically, pathogenic variants in SLC52A1 have been associated with transient multiple acyl-CoA dehydrogenation deficiency and variable symptomatology ranging from infancy to adulthood, thereby expanding the spectrum of riboflavin transporter 1 deficiency."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "7", "end_ref": "10"}]}, {"type": "t", "text": ""}]}]}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Atsushi Yonezawa, Satohiro Masuda, Toshiya Katsura, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "Differentiation-dependent regulation of intestinal vitamin B(2) uptake: studies utilizing human-derived intestinal epithelial Caco-2 cells and native rat intestine."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Am J Physiol Gastrointest Liver Physiol (2013)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1152/ajpgi.00018.2013"}], "href": "https://doi.org/10.1152/ajpgi.00018.2013"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "23413253"}], "href": "https://pubmed.ncbi.nlm.nih.gov/23413253"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Atsushi Yonezawa, Ken-ichi Inui "}, {"type": "b", "children": [{"type": "t", "text": "Novel riboflavin transporter family RFVT/SLC52: identification, nomenclature, functional characterization and genetic diseases of RFVT/SLC52."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Mol Aspects Med (2013)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.mam.2012.07.014"}], "href": "https://doi.org/10.1016/j.mam.2012.07.014"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "23506902"}], "href": "https://pubmed.ncbi.nlm.nih.gov/23506902"}]}, {"type": "r", "ref": 5, "children": [{"type": "t", "text": "Subrata Sabui, Abhisek Ghosal, Hamid M Said "}, {"type": "b", "children": [{"type": "t", "text": "Identification and characterization of 5'-flanking region of the human riboflavin transporter 1 gene (SLC52A1)."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Gene (2014)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.gene.2014.10.001"}], "href": "https://doi.org/10.1016/j.gene.2014.10.001"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "25284511"}], "href": "https://pubmed.ncbi.nlm.nih.gov/25284511"}]}, {"type": "r", "ref": 6, "children": [{"type": "t", "text": "Kasin Yadunandam Anandam, Omar A Alwan, Veedamali S Subramanian, et al. 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