Department of Ophthalmology, Duke University Medical Center , Durham, NC 27710 , USA.
Biol Open. 2012 Feb 15;1(2):140-60. doi: 10.1242/bio.2011489. Epub 2011 Dec 30.
Mutations affecting the retinitis pigmentosa GTPase regulator-interacting protein 1 (RPGRIP1) interactome cause syndromic retinal dystrophies. RPGRIP1 interacts with the retinitis pigmentosa GTPase regulator (RPGR) through a domain homologous to RCC1 (RHD), a nucleotide exchange factor of Ran GTPase. However, functional relationships between RPGR and RPGRIP1 and their subcellular roles are lacking. We show by molecular modeling and analyses of RPGR disease-mutations that the RPGR-interacting domain (RID) of RPGRIP1 embraces multivalently the shared RHD of RPGR(1-19) and RPGR(ORF15) isoforms and the mutations are non-overlapping with the interface found between RCC1 and Ran GTPase. RPGR disease-mutations grouped into six classes based on their structural locations and differential impairment with RPGRIP1 interaction. RPGRIP1α(1) expression alone causes its profuse self-aggregation, an effect suppressed by co-expression of either RPGR isoform before and after RPGRIP1α(1) self-aggregation ensue. RPGR(1-19) localizes to the endoplasmic reticulum, whereas RPGR(ORF15) presents cytosolic distribution and they determine uniquely the subcellular co-localization of RPGRIP1α(1). Disease mutations in RPGR(1) (-19), RPGR(ORF15), or RID of RPGRIP1α(1), singly or in combination, exert distinct effects on the subcellular targeting, co-localization or tethering of RPGRIP1α(1) with RPGR(1-19) or RPGR(ORF15) in kidney, photoreceptor and hepatocyte cell lines. Additionally, RPGR(ORF15), but not RPGR(1-19), protects the RID of RPGRIP1α(1) from limited proteolysis. These studies define RPGR- and cell-type-dependent targeting pathways with structural and functional plasticity modulating the expression of mutations in RPGR and RPGRIP1. Further, RPGR isoforms distinctively determine the subcellular targeting of RPGRIP1α(1,) with deficits in RPGR(ORF15)-dependent intracellular localization of RPGRIP1α(1) contributing to pathomechanisms shared by etiologically distinct syndromic retinal dystrophies.
影响视网膜炎色素变性 GTP 酶调节蛋白相互作用蛋白 1（RPGRIP1）相互作用组的突变导致综合征性视网膜营养不良。RPGRIP1 通过与视网膜炎 GTP 酶调节蛋白（RPGR）相互作用的结构域（RHD）与 RCC1（RHD）相互作用，RCC1 是 Ran GTP 酶的核苷酸交换因子。然而，RPGR 和 RPGRIP1 之间的功能关系及其亚细胞作用尚不清楚。通过分子建模和对 RPGR 疾病突变的分析，我们表明 RPGRIP1 的 RPGR 相互作用结构域（RID）多价地包含 RPGR（1-19）和 RPGR（ORF15）同工型的共享 RHD，并且突变与在 RCC1 和 Ran GTP 酶之间发现的界面不重叠。根据其结构位置和与 RPGRIP1 相互作用的差异损伤，将 RPGR 疾病突变分为六类。单独表达 RPGRIP1α(1)会导致其大量自身聚集，这种效应被 RPGR 同工型的共表达抑制，随后 RPGRIP1α(1) 自身聚集发生。RPGR(1-19)定位于内质网，而 RPGR(ORF15)呈现细胞质分布，它们唯一决定 RPGRIP1α(1)的亚细胞共定位。RPGR(1) (-19)、RPGR(ORF15)或 RPGRIP1α(1)的 RID 中的疾病突变，单独或组合使用，对 RPGRIP1α(1)在肾、光感受器和肝细胞系中的亚细胞靶向、共定位或与 RPGR(1-19)或 RPGR(ORF15)的连接有不同的影响。此外，RPGR(ORF15)而不是 RPGR(1-19)可保护 RPGRIP1α(1)的 RID 免受有限的蛋白水解。这些研究定义了 RPGR 和细胞类型依赖性靶向途径，具有结构和功能可塑性，调节 RPGR 和 RPGRIP1 突变的表达。此外，RPGR 同工型独特地决定了 RPGRIP1α(1)的亚细胞靶向，而 RPGR(ORF15)依赖性 RPGRIP1α(1)的细胞内定位缺陷导致不同病因的综合征性视网膜营养不良共享的病理机制。
