Interphotoreceptor Retinoid-Binding Protein (IRBP) Promotes Retinol Uptake and Release by Rat Muller Cells (rMC-1) In Vitro: Implications for the Cone Visual Cycle
Interphotoreceptor Retinoid-Binding Protein (IRBP) Promotes Retinol Uptake and Release by Rat Muller Cells (rMC-1) In Vitro: Implications for the Cone Visual Cycle
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DOI：
10.1167/iovs.14-14721
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发表时间：
2014-10-01
影响因子：
4.4
通讯作者：
Tsin, Andrew T.
中科院分区：
文献类型：
--
作者：
Betts-Obregon, Brandi S.;Gonzalez-Fernandez, Federico;Tsin, Andrew T.
目的。光感受器间类视黄醇结合蛋白 (IRBP) 在促进视觉周期中视杆细胞和视锥细胞、RPE 和 Muller 细胞之间类视黄醇交换中的作用仍然是个谜。光感受器间视黄醇结合蛋白结合视锥外节和米勒细胞绒毛的细胞周基质的能力表明在视锥视觉周期中全反式和11-顺式视黄醇靶向运输中的功能。我们假设 IRBP 促进全反式视黄醇向大鼠 Muller 细胞 (rMC-1) 的递送和摄取，以及 11-顺式视黄醇从大鼠 Muller 细胞 (rMC-1) 的释放。将大鼠 Muller 细胞与全反式视黄醇和 BSA 或牛 IRBP (bIRBP) 一起孵育。通过高效液相色谱（HPLC）分析细胞匀浆和条件培养基中的类维生素A。结果。用 10 μM 视黄醇和 BSA 孵育的细胞每毫克匀浆蛋白含有 2100 pmol 的全反式视黄醇，而通过 bIRBP 递送视黄醇时为 3450 pmol；当通过 BSA 递送视黄醇时，这些细胞还含有 450 pmol 每毫克全反式视黄酯，而通过 bIRBP 递送视黄醇时，每毫克细胞含有 270 pmol 的全反式视黄酯。来自与 BSA 递送的视黄醇一起孵育的细胞的条件培养基不含 11-顺式视黄醇。然而，通过 bIRBP 递送视黄醇的细胞将 130 pmol/mL 的 11-顺式视黄醇释放到细胞培养基中。与 5.0 mM 去铁胺（一种铁螯合剂）一起孵育可将 IRBP 依赖性 11-顺式视黄醇回收减少 60%。结论。促进 Muller 细胞摄取全反式视黄醇和释放 11-顺式视黄醇是 IRBP 以前未被认识的功能，它可能对视锥细胞功能和完整性至关重要。
PURPOSE. Interphotoreceptor retinoid-binding protein's (IRBP) role in facilitating the exchange of retinoids between rod and cone photoreceptors, RPE, and Muller cells in the visual cycle remains a mystery. Interphotoreceptor retinoid-binding protein's ability to bind the pericellular matrix of the cone outer segment and Muller cell villi suggests a function in all-trans and 11-cis retinol targeted trafficking in the cone visual cycle. We hypothesize that IRBP facilitates delivery and uptake of all-trans retinol to and release of 11-cis retinol from rat Muller cells (rMC-1).METHODS. Rat Muller cells were incubated with all-trans retinol and BSA or bovine IRBP (bIRBP). Retinoids in the cell homogenates and conditioned media were analyzed by high performance liquid chromatography (HPLC).RESULTS. Cells incubated with 10 mu M retinol and BSA had 2100 pmol of all-trans retinol per milligram homogenate protein compared with 3450 pmol when retinol was delivered by bIRBP; these cells also had 450 pmol all-trans retinyl ester per milligram when retinol was delivered by BSA compared with 270 pmol when retinol was delivered by bIRBP. Conditioned media from cells incubated with retinol delivered by BSA did not contain11-cis retinol. However, cells with retinol delivered by bIRBP released 130 pmol/mL of 11-cis retinol into the cell media. Incubation with 5.0 mM deferoxamine (an iron chelator) reduced IRBP-dependent 11-cis retinol retrieval by 60%.CONCLUSIONS. Promoting Muller cell uptake of all-trans retinol and release of 11-cis retinol is a previously unrecognized function of IRBP that may be critical to cone function and integrity.