Department of Ophthalmology, Horae Gene Therapy Center, UMASS Medical School, Worcester, MA 01605, USA.
Department of Ophthalmology, Horae Gene Therapy Center, UMASS Medical School, Worcester, MA 01605, USA
Biol Open. 2016 Apr 15;5(4):424-8. doi: 10.1242/bio.016816.
Mutations inRPGR(ORF15)(retinitis pigmentosa GTPase regulator) are a major cause of inherited retinal degenerative diseases. RPGR(ORF15)(1152 residues) is a ciliary protein involved in regulating the composition and function of photoreceptor cilia. The mutational hotspot in RPGR(ORF15)is an unusual C-terminal domain encoded by exon ORF15, which is rich in polyglutamates and glycine residues (Glu-Gly domain) followed by a short stretch of basic amino acid residues (RPGR(C2)domain; residues 1072-1152). However, the properties of the ORF15-encoded domain and its involvement in the pathogenesis of the disease are unclear. Here we show that RPGR(ORF15)is glutamylated at the C-terminus, as determined by binding to GT335, which recognizes glutamylated substrates. This reactivity is lost in two mouse mutants ofRpgr, which do not express RPGR(ORF15)due to disease-causing mutations in exon ORF15. Our results indicate that RPGR(ORF15)is posttranslationally glutamylated in the Glu-Gly domain and that the GT335 antibody predominantly recognizes RPGR(ORF15)in photoreceptor cilia.
RPGR（ORF15）（视网膜色素变性 GTP 酶调节因子）中的突变是遗传性视网膜退行性疾病的主要原因。RPGR（ORF15）（1152 个残基）是一种纤毛蛋白，参与调节光感受器纤毛的组成和功能。RPGR（ORF15）中的突变热点是由外显子 ORF15 编码的不寻常的 C 末端结构域，该结构域富含多谷氨酸和甘氨酸残基（Glu-Gly 结构域），其后是短的碱性氨基酸残基（RPGR（C2）结构域；残基 1072-1152）。然而，ORF15 编码结构域的性质及其在疾病发病机制中的作用尚不清楚。在这里，我们表明 RPGR（ORF15）在 C 末端发生谷氨酸化，这是通过与识别谷氨酸化底物的 GT335 结合来确定的。由于外显子 ORF15 中的致病突变，两个 Rpgr 小鼠突变体中都没有表达 RPGR（ORF15），从而丧失了这种反应性。我们的结果表明，RPGR（ORF15）在 Glu-Gly 结构域中发生翻译后谷氨酸化，并且 GT335 抗体主要在光感受器纤毛中识别 RPGR（ORF15）。
