CHARACTERIZATION OF A NEW RETINAL AUTOANTIGEN GENE CORRESPONDING WITH CANCER-ASSOCIATED RETINOPATHY

(1)从人视网膜c DNA文库中分离到多嘧啶结合蛋白(PTB)的人同源基因，该蛋白可能是癌症相关视网膜病变(CAR)的一种自身抗原。该同源物命名为PTB样蛋白(PTBLP)，编码532个氨基酸残基，具有四个RNA识别基序(RRMS)。第三和第四个RRMS是RNA结合能力所必需的。CAR血清识别PTBLP，PTBLP的抗原决定簇定位在C-末端的12个氨基酸内。该多肽序列包括在第四个RRM序列中。副肿瘤性神经系统疾病患者血清中的自身抗体与多种神经元特异性蛋白发生反应。这些蛋白质可分为三类：(1)细胞表面蛋白，例如电压门控性钙通道；(2)胞浆蛋白，例如Recoverin和TULP1；以及(3)核rna结合蛋白，例如含有Rrm结构域的Hu家族蛋白和含有KH Domai…的NovA蛋白PTBLP是第三组的新成员。本研究利用抗神经元RNA结合蛋白的抗体扩大了对副肿瘤性疾病发病机制的认识。(2)我们利用PC12细胞研究了PTBLP在神经元分化中的作用。在神经生长因子诱导PC12细胞向神经元分化的过程中，PTBLP-L(长型，含四个RRMS)下调，而PTBLP-S(短型，N-末端仅含两个RRMS)表达上调。将PTBLP-L基因导入PC12细胞后，细胞分化受到抑制。然而，在PTBLP-S转基因细胞中，这种抑制作用并不明显。当PTBLP-L和PTBLP-S共转染时，PTBLP-L的抑制作用减弱。在分化细胞中，PTBLP-S定位于胞核，PTBLP-L散在分布于胞浆和神经元生长锥内。这些发现表明，PTBLP-L是神经元分化的负调控因子，而PTBLP-S是PTBLP-L的竞争对手。较少

(1) Human homologue of polypyrimidine tract binding protein (PTB), a possible autoantigen for cancer-associated retinopathy (CAR), was isolated from a human retinal cDNA library. This homologue, named PTB-like protein (PTBLP), encodes a 532 amino acid residue protein and has four RNA recognition motifs (RRMs). The third and fourth RRMs are required for RNA binding ability. CAR serum recognized the PTBLP, the antigenic determinant of the PTBLP was localized within 12 amino acids of the C-terminal region. The sequence of the peptide was included in the fourth RRM sequence. Autoantibodies in the sera of the patients with paraneoplastic neurologic disorders react to a variety of neuron specific proteins. These proteins can be classified into three groups : (1) cell surface protein, e.g., voltage-gated calcium channels, (2) cytosolic proteins, e.g., recoverin and TULP1 ; and (3) nuclear RNA binding proteins, e.g., Hu-family proteins containing RRM domain and NOVA protein containing KH domai … More n. The PTBLP is a new member of the third group. This study expands the understanding of the pathogenesis of paraneoplastic disorders with antibodies against neuronal RNA binding proteins.(2) We have studied whether PTBLP plays a role in neuronal differentiation using PC12 cells. During the process of NGF-induced neuronal differentiation of PC12 cells, PTBLP-L (long form containing four RRMs) was down-regulated whereas PTBLP-S (short form containing only two RRMs in the N-terminal region) was up-regulated. Transfection of PTBLP-L into PC12 cells led to the suppression of neuronal differentiation. In PTBLP-S transfected cells, however, this suppression was not evident. When both PTBLP-L and PTBLP-S were co-transfected, the suppressive effect of PTBLP-L decreased. In differentiated cells, PTBLP-S localized in the nucleus and PTBLP-L was found dispersed throughout the cytoplasm and neuronal growth cone. These findings suggest that PTBLP-L acts as a negative regulator of neuronal differentiation and PTBLP-S acts as a competitor of PTBLP-L. Less