Human Retinal Pigment Epithelial Cells Prefer Proline As a Nutrient and Transport Metabolic Intermediates to the Retinal Side

Overview

Journal J Biol Chem

Specialty Biochemistry

Date 2017 Jun 16

PMID 28615447

Citations 57

Authors

Jennifer R Chao

Kaitlen Knight

Abbi L Engel

Connor Jankowski

Yekai Wang

Megan A Manson

Haiwei Gu

Danijel Djukovic

Daniel Raftery

James B Hurley

Jianhai Du

Affiliations

Soon will be listed here.

Abstract

Metabolite transport is a major function of the retinal pigment epithelium (RPE) to support the neural retina. RPE dysfunction plays a significant role in retinal degenerative diseases. We have used mass spectrometry with C tracers to systematically study nutrient consumption and metabolite transport in cultured human fetal RPE. LC/MS-MS detected 120 metabolites in the medium from either the apical or basal side. Surprisingly, more proline is consumed than any other nutrient, including glucose, taurine, lipids, vitamins, or other amino acids. Besides being oxidized through the Krebs cycle, proline is used to make citrate via reductive carboxylation. Citrate, made either from C proline or from C glucose, is preferentially exported to the apical side and is taken up by the retina. In conclusion, RPE cells consume multiple nutrients, including glucose and taurine, but prefer proline, and they actively synthesize and export metabolic intermediates to the apical side to nourish the outer retina.

Citing Articles

Retinal Protective Effect of Mono-Ethyl Fumarate in Experimental Age-Related Macular Degeneration via Anti-Oxidative and Anti-Apoptotic Alterations.

Lee H, Zhang S, Ahn H, Kim T, Kim J, Lee H Int J Mol Sci. 2025; 26(4).

PMID: 40003880 PMC: 11855399. DOI: 10.3390/ijms26041413.

Less Is More: The RPE Cell Culture Medium Additive THT Mildly Impairs RPE Health.

Hass D, Pandey K, Robbings B, Lim R, Chao J, Hurley J Adv Exp Med Biol. 2025; 1468:333-337.

PMID: 39930218 DOI: 10.1007/978-3-031-76550-6_55.

Novel Insights Into Gyrate Atrophy of the Choroid and Retina (GACR): A Cohort Study.

Balfoort B, Van den Broeck F, Boon C, Brouwers M, Diederen R, Dhillon P J Inherit Metab Dis. 2025; 48(1):e12842.

PMID: 39761806 PMC: 11703598. DOI: 10.1002/jimd.12842.

"Energetics of the outer retina I: Estimates of nutrient exchange and ATP generation".

Prins S, Kiel C, Foss A, Zouache M, Luthert P PLoS One. 2024; 19(12):e0312260.

PMID: 39739933 PMC: 11687866. DOI: 10.1371/journal.pone.0312260.

Eye on the horizon: The metabolic landscape of the RPE in aging and disease.

Hansman D, Du J, Casson R, Peet D Prog Retin Eye Res. 2024; 104:101306.

PMID: 39433211 PMC: 11833275. DOI: 10.1016/j.preteyeres.2024.101306.

References

Wood J, Chidlow G, Graham M, Osborne N . Energy substrate requirements of rat retinal pigmented epithelial cells in culture: relative importance of glucose, amino acids, and monocarboxylates. Invest Ophthalmol Vis Sci. 2004; 45(4):1272-80. DOI: 10.1167/iovs.03-0693. View

Hurley J, Lindsay K, Du J . Glucose, lactate, and shuttling of metabolites in vertebrate retinas. J Neurosci Res. 2015; 93(7):1079-92. PMC: 4720126. DOI: 10.1002/jnr.23583. View

ODonnell J, SANDMAN R, Martin S . Gyrate atrophy of the retina: inborn error of L-ornithin:2-oxoacid aminotransferase. Science. 1978; 200(4338):200-1. DOI: 10.1126/science.635581. View

Ando A, Ueda M, Uyama M, Masu Y, Okumura T, Ito S . Heterogeneity in ornithine cytotoxicity of bovine retinal pigment epithelial cells in primary culture. Exp Eye Res. 2000; 70(1):89-96. DOI: 10.1006/exer.1999.0750. View

Maminishkis A, Miller S . Experimental models for study of retinal pigment epithelial physiology and pathophysiology. J Vis Exp. 2010; (45). PMC: 3144659. DOI: 10.3791/2032. View

Mitsubuchi H, Nakamura K, Matsumoto S, Endo F . Inborn errors of proline metabolism. J Nutr. 2008; 138(10):2016S-2020S. DOI: 10.1093/jn/138.10.2016S. View

Lindsay K, Du J, Sloat S, Contreras L, Linton J, Turner S . Pyruvate kinase and aspartate-glutamate carrier distributions reveal key metabolic links between neurons and glia in retina. Proc Natl Acad Sci U S A. 2014; 111(43):15579-84. PMC: 4217417. DOI: 10.1073/pnas.1412441111. View

Gu H, Carroll P, Du J, Zhu J, Neto F, Eisenman R . Quantitative Method to Investigate the Balance between Metabolism and Proteome Biomass: Starting from Glycine. Angew Chem Int Ed Engl. 2016; 55(50):15646-15650. PMC: 6238948. DOI: 10.1002/anie.201609236. View

Strunnikova N, Maminishkis A, Barb J, Wang F, Zhi C, Sergeev Y . Transcriptome analysis and molecular signature of human retinal pigment epithelium. Hum Mol Genet. 2010; 19(12):2468-86. PMC: 2876890. DOI: 10.1093/hmg/ddq129. View

10.

Fronk A, Vargis E . Methods for culturing retinal pigment epithelial cells: a review of current protocols and future recommendations. J Tissue Eng. 2016; 7:2041731416650838. PMC: 4959307. DOI: 10.1177/2041731416650838. View

11.

Du J, Yanagida A, Knight K, Engel A, Vo A, Jankowski C . Reductive carboxylation is a major metabolic pathway in the retinal pigment epithelium. Proc Natl Acad Sci U S A. 2016; 113(51):14710-14715. PMC: 5187684. DOI: 10.1073/pnas.1604572113. View

12.

Adijanto J, Philp N . Cultured primary human fetal retinal pigment epithelium (hfRPE) as a model for evaluating RPE metabolism. Exp Eye Res. 2014; 126:77-84. PMC: 4345411. DOI: 10.1016/j.exer.2014.01.015. View

13.

Ambati J, Fowler B . Mechanisms of age-related macular degeneration. Neuron. 2012; 75(1):26-39. PMC: 3404137. DOI: 10.1016/j.neuron.2012.06.018. View

14.

Miyamoto Y, Del Monte M . Na(+)-dependent glutamate transporter in human retinal pigment epithelial cells. Invest Ophthalmol Vis Sci. 1994; 35(10):3589-98. View

15.

Strauss O . The retinal pigment epithelium in visual function. Physiol Rev. 2005; 85(3):845-81. DOI: 10.1152/physrev.00021.2004. View

16.

Lehmann G, Benedicto I, Philp N, Rodriguez-Boulan E . Plasma membrane protein polarity and trafficking in RPE cells: past, present and future. Exp Eye Res. 2014; 126:5-15. PMC: 4502961. DOI: 10.1016/j.exer.2014.04.021. View

17.

Gabrielian K, Wang H, Ogden T, Ryan S . In vitro stimulation of retinal pigment epithelium proliferation by taurine. Curr Eye Res. 1992; 11(6):481-7. DOI: 10.3109/02713689209001804. View

18.

Maenpaa H, Gegelashvili G, Tahti H . Expression of glutamate transporter subtypes in cultured retinal pigment epithelial and retinoblastoma cells. Curr Eye Res. 2004; 28(3):159-65. DOI: 10.1076/ceyr.28.3.159.26244. View

19.

Rattner A, Nathans J . Macular degeneration: recent advances and therapeutic opportunities. Nat Rev Neurosci. 2006; 7(11):860-72. DOI: 10.1038/nrn2007. View

20.

Sonoda S, Spee C, Barron E, Ryan S, Kannan R, Hinton D . A protocol for the culture and differentiation of highly polarized human retinal pigment epithelial cells. Nat Protoc. 2009; 4(5):662-73. PMC: 2688697. DOI: 10.1038/nprot.2009.33. View