Hazim Roni A, Williams David S
Department of Ophthalmology and Stein Eye Institute, Los Angeles, CA, United States.
Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States.
Front Cell Dev Biol. 2022 Mar 4;10:852468. doi: 10.3389/fcell.2022.852468. eCollection 2022.
The retinal pigment epithelium (RPE) is a uniquely polarized epithelium that lies adjacent to the photoreceptor cells in the retina, and is essential for photoreceptor function and viability. Two major motile organelles present in the RPE are the melanosomes, which are important for absorbing stray light, and phagosomes that result from the phagocytosis of the distal tips of the photoreceptor cilium, known as the photoreceptor outer segment (POS). These organelles are transported along microtubules, aligned with the apical-basal axis of the RPE. Although they undergo a directional migration, the organelles exhibit bidirectional movements, indicating both kinesin and dynein motor function in their transport. Apical melanosome localization requires dynein; it has been suggested that kinesin contribution might be complex with the involvement of more than one type of kinesin. POS phagosomes undergo bidirectional movements; roles of both plus- and minus-end directed motors appear to be important in the efficient degradation of phagosomes. This function is directly related to retinal health, with defects in motor proteins, or in the association of the phagosomes with the motors, resulting in retinal degenerative pathologies.
视网膜色素上皮（RPE）是一种独特的极化上皮细胞，位于视网膜中的光感受器细胞附近，对光感受器的功能和生存能力至关重要。RPE中存在的两种主要运动细胞器是黑素体，其对吸收杂散光是重要的，以及吞噬体，其由光感受器纤毛的远端（称为光感受器外段（POS））的吞噬作用产生。这些细胞器沿着与RPE顶-基轴对齐的微管运输。尽管它们经历定向迁移，但细胞器表现出双向运动，表明驱动蛋白和动力蛋白在其运输中均发挥作用。顶端黑素体定位需要动力蛋白；有人提出驱动蛋白的作用可能很复杂，涉及不止一种类型的驱动蛋白。POS吞噬体进行双向运动；正向和负向驱动马达的作用在吞噬体的有效降解中似乎都很重要。这种功能与视网膜健康直接相关，运动蛋白或吞噬体与马达的关联出现缺陷会导致视网膜退行性病变。
