Differentiation-dependent regulation of the intestinal folate uptake process: studies with Caco-2 cells and native mouse intestine

Abstract

Subramanian VS, Reidling JC, Said HM. Differentiationdependent regulation of the intestinal folate uptake process: studies with Caco-2 cells and native mouse intestine. Am J Physiol Cell Physiol 295: C828 -C835, 2008. First published July 23, 2008 doi:10.1152/ajpcell.00249.2008.-Differentiation of intestinal epithelial cells is accompanied by alterations in levels of expression of many genes, including those involved in nutrient uptake. Effects of differentiation of intestinal epithelial cells on the physiological and molecular parameters of the intestinal folate uptake process are not well characterized. To address this issue, we used two models, Caco-2 cells and native mouse intestine. Studies with Caco-2 cells showed a significant increase in the initial rate of carrier-mediated folic acid uptake during differentiation (i.e., as the cells transitioned from preconfluent to confluent and then to postconfluent stages). This increase was associated with an increase in the level of expression of the human reduced folate carrier (hRFC) and the human protoncoupled folate transporter (hPCFT) both at the protein and mRNA levels with differentiation; it was also associated with a significant increase in activity of the hRFC and hPCFT promoters. Studies with native mouse intestine showed a significantly higher folate uptake in villus compared with crypt cells, which was again associated with a significantly higher level of expression of the mouse RFC and PCFT at the protein and mRNA levels. Together, these studies demonstrate that the intestinal folate uptake process undergoes differentiationdependent regulation and that this regulation is mediated via changes in the level of expression of both the RFC and PCFT. In addition, the studies suggest the possible involvement (at least in part) of a transcriptional mechanism(s) in this type of regulation of the intestinal folate uptake process. transport; epithelial transport; reduced folate carrier; proton-coupled folate transporter FOLATE IS ESSENTIAL FOR NORMAL cellular proliferation, growth, and functions. The coenzyme derivatives of folic acid are required for the synthesis of precursors of DNA and RNA and the metabolism of several amino acids including homocysteine (6,21,26,42). An adequate supply of folate is therefore necessary for normal human health and well-being. This is demonstrated by the variety of clinical abnormalities that result from folate deficiency (e.g., megaloblastic anemia, growth retardation, and neurological disorders) (7,15,17,26) and by the health benefits attained by optimizing folate body homeostasis [e.g

Vitamin D3 and Its Nuclear Receptor Increase the Expression and Activity of the Human Proton-Coupled Folate Transporter

“…It has been reported that vitamin D 3 -induced gene expression increases as Caco-2 cells differentiate (Cui et al, 2009). Thus, our current findings on VDRmediated regulation of PCFT expression provide a possible molecular mechanism for a prior observation that folate uptake into Caco-2 cells is enhanced upon confluence-associated differentiation (Subramanian et al, 2008b).…”

“…PCFT promoter activity has been shown possibly to be epigenetically regulated by its methylation status in human tumor cell lines (Gonen et al, 2008). Furthermore, both the PCFT mRNA expression levels and PCFT promoter activity positively correlate with the level of differentiation of colon-derived Caco-2 cells (Subramanian et al, 2008b).…”

Intestinal Absorption Of Folates

“…Studies in mouse and rat intestines revealed higher mRNA and PCFT and RFC protein levels in the villus tip compared with expression in the crypt base (122,123). Similarly, as Caco-2 cells became confluent and differentiated, expression of both transporters increased (122).…”

“…Similarly, as Caco-2 cells became confluent and differentiated, expression of both transporters increased (122). Although vitamin D 3 promotes differentiation (124,125), it is uncertain whether the increase in PCFT expression that occurs with the differentiation of Caco-2 cells, or in the villus tip versus crypt cells, is related specifically to vitamin D 3 regulation.…”

Post-hatching ontogeny of intestinal proton-coupled folate transporter and reduced folate carrier in broiler chickens

“…The observed reductions in folate uptake with maturation were associated with a decrease in both the mRNA and protein abundance of RFC, possibly mediated through transcriptional mechanisms. Recently, Subramanian et al (2008) reported that the differentiation of enterocytes was associated with an upregulation in carrier-mediated folate uptake, which was associated with an increase in the abundance of mRNA and protein for both the RFC and PCFT in the intestine.…”