Chao Jennifer R, Knight Kaitlen, Engel Abbi L, Jankowski Connor, Wang Yekai, Manson Megan A, Gu Haiwei, Djukovic Danijel, Raftery Daniel, Hurley James B, Du Jianhai
Department of Ophthalmology, University of Washington, Seattle, Washington 98109.
Department of Ophthalmology, University of Washington, Seattle, Washington 98109.
J Biol Chem. 2017 Aug 4;292(31):12895-12905. doi: 10.1074/jbc.M117.788422. Epub 2017 Jun 14.
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.
代谢物转运是视网膜色素上皮（RPE）支持神经视网膜的一项主要功能。RPE功能障碍在视网膜退行性疾病中起重要作用。我们使用带有碳示踪剂的质谱法系统地研究了培养的人胎儿RPE中的营养物质消耗和代谢物转运。液相色谱-串联质谱法（LC/MS-MS）检测到来自顶侧或基底侧培养基中的120种代谢物。令人惊讶的是，脯氨酸的消耗量比任何其他营养物质都多，包括葡萄糖、牛磺酸、脂质、维生素或其他氨基酸。除了通过三羧酸循环被氧化外，脯氨酸还通过还原羧化作用用于生成柠檬酸。由碳标记的脯氨酸或碳标记的葡萄糖生成的柠檬酸优先被转运到顶侧并被视网膜摄取。总之，RPE细胞消耗多种营养物质，包括葡萄糖和牛磺酸，但更倾向于脯氨酸，并且它们积极合成代谢中间产物并将其转运到顶侧以滋养外视网膜。
