Preservation of folate transport activity with a low-pH optimum in rat IEC-6 intestinal epithelial cell lines that lack reduced folate carrier function

American Journal of Physiology. Cell Physiology
Yanhua WangRongbao Zhao

Abstract

Intestinal folate transport has been well characterized, and rat small intestinal epithelial (IEC-6) cells have been used as a model system for the study of this process on the cellular level. The major intestinal folate transport activity has a low-pH optimum, and the current paradigm is that this process is mediated by the reduced folate carrier (RFC), despite the fact that this carrier has a neutral pH optimum in leukemia cells. The current study addressed the question of whether constitutive low-pH folate transport activity in IEC-6 cells is mediated by RFC. Two independent IEC-6 sublines, IEC-6/A4 and IEC-6/PT1, were generated by chemical mutagenesis followed by selective pressure with antifolates. In IEC-6/A4 cells, a premature stop resulted in truncation of RFC at Gln(420). A green fluorescent protein (GFP) fusion with the truncated protein was not stable. In IEC-6/PT1 cells, Ser(135) was deleted, and this alteration resulted in the failure of localization of the GFP fusion protein in the plasma membrane. In both cell lines, methotrexate (MTX) influx at neutral pH was markedly decreased compared with wild-type IEC-6 cells, but MTX influx at pH 5.5 was not depressed. Transient transfection of the GFP-mutated RFC construct...Continue Reading

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Citations

Jun 29, 2013·Animal : an International Journal of Animal Bioscience·M JingJ D House
Oct 9, 2009·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Beihua Zhong, Donna H Wang
Oct 14, 2016·American Journal of Physiology. Renal Physiology·Oleg PalyginAlexander Staruschenko
Aug 12, 2006·Canadian Journal of Physiology and Pharmacology·Elisa KeatingFátima Martel
Feb 20, 2007·Molecular Cancer Therapeutics·Shrikanta ChattopadhyayI David Goldman
Mar 1, 2006·Molecular Cancer Therapeutics·Shrikanta ChattopadhyayI David Goldman
Jul 21, 2007·The American Journal of Pathology·Leon MoussaPeter G Tipping

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