Ohlsson M, Jonsson R, Brokstad K A
The Broegelmann Research Laboratory, Department of Microbiology and Immunology, The Gade Institute, University of Bergen, Bergen, Norway.
Scand J Immunol. 2002 Nov;56(5):456-69. doi: 10.1046/j.1365-3083.2002.01072_79.x.
The Ro52, Ro60 and La48 autoantigens are associated with Sjögren's syndrome (SS) and systemic lupus erythematosus (SLE). The mechanisms behind tolerance breakdown of these self-peptides remain unclear; however, apoptosis has been proposed to cause their presentation to the immune system. We have examined the localization of transiently expressed enhanced green fluorescent protein (EGFP)-tagged Ro52, Ro60 and La48 autoantigens in a human salivary gland (HSG) cell line by laser confocal microscopy under normal growth conditions and during apoptosis. Surface exposure of Ro52, Ro60 and La48 was demonstrated on nonfixed apoptotic cells with monoclonal antibodies (MoAbs) or with primary SS patient antisera. Laser scanning cytometry determined the apoptotic frequency. EGFP alone was studied as control. We found that Ro52 mainly is cytoplasmic, Ro60 both nuclear and cytoplasmic, while La48 only resides in the nucleus under normal conditions. During early apoptosis, La48 is dramatically redistributed to the cytoplasm, while the localization of Ro52 and Ro60 is maintained. All three autoantigens filled apoptotic blebs and covered TUNEL (terminal-deoxynucleotidyl-transferase-mediated dUTP-digoxigenin nick end labelling)-positive apoptotic bodies. Identical results were obtained in COS-7 cells. We have developed a transfection system to study the intracellular localization of the three autoantigens Ro52, Ro60 and La48, without antibody detection. During apoptosis, there is an intracellular redistribution of endogenous and EGFP-tagged Ro52, Ro60 and La48, leading to surface exposure. These findings may indicate a role for apoptosis in the induction and facilitation of humoral responses to Ro52, Ro60 and La48 in the autoimmune exocrinopathy of SS.
Ro52、Ro60和La48自身抗原与干燥综合征（SS）及系统性红斑狼疮（SLE）相关。这些自身肽耐受破坏背后的机制尚不清楚；然而，有观点认为细胞凋亡会导致它们呈递给免疫系统。我们通过激光共聚焦显微镜，在正常生长条件及细胞凋亡过程中，研究了瞬时表达的增强型绿色荧光蛋白（EGFP）标记的Ro52、Ro60和La48自身抗原在人唾液腺（HSG）细胞系中的定位。用单克隆抗体（MoAbs）或原发性SS患者抗血清在未固定的凋亡细胞上证实了Ro52、Ro60和La48的表面暴露。激光扫描细胞术测定了凋亡频率。单独研究EGFP作为对照。我们发现，在正常条件下，Ro52主要位于细胞质中，Ro60位于细胞核和细胞质中，而La48仅存在于细胞核中。在早期细胞凋亡过程中，La48显著重新分布到细胞质中，而Ro52和Ro60的定位保持不变。所有三种自身抗原都填充凋亡小泡并覆盖TUNEL（末端脱氧核苷酸转移酶介导的dUTP-地高辛标记）阳性的凋亡小体。在COS-7细胞中获得了相同的结果。我们开发了一种转染系统，无需抗体检测即可研究三种自身抗原Ro52、Ro60和La48的细胞内定位。在细胞凋亡过程中，内源性和EGFP标记的Ro52、Ro60和La4出现细胞内重新分布，导致表面暴露。这些发现可能表明细胞凋亡在SS自身免疫性外分泌病中对Ro52、Ro60和La48的体液反应的诱导和促进中起作用。
