Duvoisin Robert M, Haley Tammie L, Ren Gaoying, Strycharska-Orczyk Iwona, Bonaparte James P, Morgans Catherine W
Department of Physiology and Pharmacology, Oregon Health & Science University, Portland, Oregon, United States.
Invest Ophthalmol Vis Sci. 2017 May 1;58(5):2732-2738. doi: 10.1167/iovs.17-21443.
Melanoma-associated retinopathy (MAR) is a paraneoplastic syndrome associated with malignant melanoma and the presence of anti-retinal autoantibodies, including autoantibodies against transient receptor potential melanopsin 1 (TRPM1), a cation channel expressed by both melanocytes and retinal bipolar cells. The goal of this study was to further map the antigenic epitope.
Patient sera were tested by immunofluorescence and Western blotting on HEK293 cells transfected with enhanced green fluorescent protein (EGFP)-TRPM1 fusion constructs and mouse retina sections.
The epitope recognized by MAR patient sera was mapped to a region encoded by exons 9 and 10 of the human TRPM1 gene. This region of TRPM1 is highly conserved with TRPM3, and indeed MAR sera were found to cross-react with TRPM3, a closely related channel expressed in the retinal pigment epithelium (RPE).
These results indicate that TRPM1 autoantibodies in MAR patient sera recognize a short, intracellular segment of TRPM1. Cross-reactivity with TRPM3 in the RPE may account for other visual symptoms that are experienced by some MAR patients such as retinal and RPE detachments. We propose that TRPM1 autoantibodies are generated in response to abnormal TRPM1 polypeptides encoded by an alternate mRNA splice variant expressed by malignant melanocytes.
黑色素瘤相关性视网膜病变（MAR）是一种副肿瘤综合征，与恶性黑色素瘤以及抗视网膜自身抗体的存在有关，这些自身抗体包括针对瞬时受体电位黑素视蛋白1（TRPM1）的自身抗体，TRPM1是一种由黑素细胞和视网膜双极细胞表达的阳离子通道。本研究的目的是进一步定位抗原表位。
采用免疫荧光和蛋白质印迹法，对转染了增强型绿色荧光蛋白（EGFP）-TRPM1融合构建体的HEK293细胞和小鼠视网膜切片进行患者血清检测。
MAR患者血清识别的表位被定位到人TRPM1基因第9和第10外显子编码的区域。TRPM1的这一区域与TRPM3高度保守，事实上发现MAR血清与TRPM3发生交叉反应，TRPM3是一种在视网膜色素上皮（RPE）中表达的密切相关通道。
这些结果表明，MAR患者血清中的TRPM1自身抗体识别TRPM1的一个短的细胞内片段。与RPE中的TRPM3发生交叉反应可能解释了一些MAR患者出现的其他视觉症状，如视网膜和RPE脱离。我们提出，TRPM1自身抗体是由恶性黑素细胞表达的一种可变mRNA剪接变体编码的异常TRPM1多肽产生的。
