Document Detail


Molecular and biochemical characterization of folate transport proteins in retinal Müller cells.
MedLine Citation:
PMID:  20053979     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
PURPOSE: To analyze the mechanisms of folate uptake in retinal Müller cells.
METHODS: RT-PCR and Western blot analysis were performed in freshly isolated neural retina and RPE/eyecup, primary mouse Müller cells, and rMC-1 cells for the three known folate transport proteins folate receptor alpha (FRalpha), proton-coupled folate transporter (PCFT), and reduced folate carrier (RFC). Laser scanning confocal microscopy (LSCM) and immunoelectron microscopy were used to determine the subcellular location of FRalpha and PCFT in primary Müller cells. The pH dependence of the uptake of [(3)H]-methyltetrahydrofolate ([(3)H]-MTF) was assayed in Müller cells in the presence/absence of thiamine pyrophosphate, an inhibitor of RFC.
RESULTS: FRalpha and PCFT are expressed abundantly in the retina in several cell layers, including the inner nuclear layer; they are present in primary mouse Müller cells and rMC-1 cells. LSCM localized these proteins to the plasma membrane, nuclear membrane, and perinuclear region. Immunoelectron microscopic studies revealed the colocalization of FRalpha and PCFT on the plasma membrane and nuclear membrane and within endosomal structures. Müller cell uptake of [(3)H]-MTF was robust at pH 5.0 to 6.0, consistent with PCFT activity, but also at neutral pH, reflecting RFC function. RFC was expressed in mouse Müller cells that had been allowed to proliferate in culture, but not in freshly isolated primary cells.
CONCLUSIONS: FRalpha and PCFT are expressed in retinal Müller cells and colocalize in the endosomal compartment, suggesting that the two proteins may work coordinately to mediate folate uptake. The unexpected finding of RFC expression and activity in cultured Müller cells may reflect the upregulation of this protein under proliferative conditions.
Authors:
B Renee Bozard; Preethi S Ganapathy; Jennifer Duplantier; Barbara Mysona; Yonju Ha; Penny Roon; Robert Smith; I David Goldman; Puttur Prasad; Pamela M Martin; Vadivel Ganapathy; Sylvia B Smith
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural     Date:  2010-01-06
Journal Detail:
Title:  Investigative ophthalmology & visual science     Volume:  51     ISSN:  1552-5783     ISO Abbreviation:  Invest. Ophthalmol. Vis. Sci.     Publication Date:  2010 Jun 
Date Detail:
Created Date:  2010-05-20     Completed Date:  2010-06-11     Revised Date:  2011-05-11    
Medline Journal Info:
Nlm Unique ID:  7703701     Medline TA:  Invest Ophthalmol Vis Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  3226-35     Citation Subset:  IM    
Affiliation:
Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, Georgia 30912-2000, USA.
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MeSH Terms
Descriptor/Qualifier:
Animals
Blotting, Western
Cells, Cultured
Endosomes / metabolism
Folate Receptor 1
Gene Expression Regulation / physiology
Hydrogen-Ion Concentration
Membrane Transport Proteins / genetics,  metabolism*,  ultrastructure
Mice
Mice, Inbred BALB C
Microscopy, Confocal
Microscopy, Immunoelectron
Neuroglia / drug effects,  metabolism*,  ultrastructure
Proton-Coupled Folate Transporter
Receptors, Cell Surface / genetics,  metabolism*,  ultrastructure
Reduced Folate Carrier Protein
Retina / metabolism
Reverse Transcriptase Polymerase Chain Reaction
Tetrahydrofolates / metabolism*
Thiamine Pyrophosphate / pharmacology
Grant Support
ID/Acronym/Agency:
R01 EY 012830/EY/NEI NIH HHS; R01 EY012830-09/EY/NEI NIH HHS
Chemical
Reg. No./Substance:
0/Folate Receptor 1; 0/Folr1 protein, mouse; 0/Membrane Transport Proteins; 0/Proton-Coupled Folate Transporter; 0/Receptors, Cell Surface; 0/Reduced Folate Carrier Protein; 0/Slc19a1 protein, mouse; 0/Slc46a1 protein, mouse; 0/Tetrahydrofolates; 134-35-0/5-methyltetrahydrofolate; 154-87-0/Thiamine Pyrophosphate

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