SPACRCAN, a novel human interphotoreceptor matrix hyaluronan-binding proteoglycan synthesized by photoreceptors and pinealocytes
SPACRCAN, a novel human interphotoreceptor matrix hyaluronan-binding proteoglycan synthesized by photoreceptors and pinealocytes
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DOI：
10.1074/jbc.275.10.6945
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发表时间：
2000-03-10
影响因子：
4.8
通讯作者：
Hollyfield, JG
中科院分区：
文献类型：
--
作者：
Acharya, S;Foletta, VC;Hollyfield, JG
光感受器间基质是一种独特的细胞外复合体，位于眼底的光感受器和视网膜色素上皮之间。由于可能在光感受器维持中起支持作用，因此组成分子很可能在光感受器功能中发挥关键作用，并可能成为遗传性视网膜疾病的靶点。在本研究中，我们鉴定并鉴定了该基质中的一种新的软骨素蛋白多糖SPACRCAN。SPACRCAN基因是从人视网膜cDNA文库中克隆出来的，定位于染色体3q11.2。对SPACRCAN mRNA和蛋白的分析表明，SPACRCAN仅由光感受器和松果体细胞表达，由光感受器合成的SPACRCAN定位于光感受器间基质，在视杆和视锥周围，该功能蛋白含有1160个氨基酸，具有较大的中央粘蛋白结构域，三个共同的糖胺聚糖结合位点，两个表皮生长因子样重复序列，一个可能的透明质酸结合基序，以及靠近C末端的一个潜在的跨膜结构域。凝集素和Western blotting显示，软骨素酶ABC消化前的M-R约为40万，软骨素酶ABC消化后的M-R约为230,000。去除N-和O-连接的低聚糖使M-r降低到大约160,000，这表明大约60%的SPACRcan质量是碳水化合物。最后，我们证明了SPACRCAN与透明质酸结合，并提出SPACRCAN和透明质酸之间的联系可能参与了不溶性光感受器基质的组织，特别是当SPACRCAN是该基质中存在的主要蛋白多糖时。
The interphotoreceptor matrix is a unique extracellular complex occupying the interface between photoreceptors and the retinal pigment epithelium in the fundus of the eye. Because of the putative supportive role in photoreceptor maintenance, it is likely that constituent molecules play key roles in photoreceptor function and may be targets for inherited retinal disease. In this study we identify and characterize SPACRCAN, a novel chondroitin proteoglycan in this matrix. SPACRCAN was cloned from a human retinal cDNA library and the gene localized to chromosome 3q11.2. Analysis of SPACRCAN mRNA and protein revealed that SPACRCAN is expressed exclusively by photoreceptors and pinealocytes, SPACRCAN synthesized by photoreceptors is localized to the interphotoreceptor matrix where it surrounds both rods and cones, The functional protein contains 1160 amino acids with a large central mucin domain, three consensus sites for glycosaminoglycan attachment, two epidermal growth factor-like repeats, a putative hyaluronan-binding motif, and a potential transmembrane domain near the C-terminal, Lectin and Western blotting indicate an M-r around 400,000 before and 230,000 after chondroitinase ABC digestion. Removal of N- and O-linked oligosaccharides reduces the M-r to approximately 160,000, suggesting that approximately 60% of the mass of SPACRCAN is carbohydrate. Finally, we demonstrate that SPACRCAN binds hyaluronan and propose that associations between SPACRCAN and hyaluronan may be involved in organization of the insoluble interphotoreceptor matrix, particularly as SPACRCAN is the major proteoglycan present in this matrix.