Department of Radiation Sciences, Oncology, Umeå University, SE-901 87, Umeå, Sweden.
Department of Radiation Sciences, Oncology, Umeå University, SE-901 87, Umeå, Sweden.
Lung Cancer. 2018 Nov;125:174-184. doi: 10.1016/j.lungcan.2018.09.017. Epub 2018 Sep 24.
The human leucine-rich repeats and immunoglobulin-like domains (LRIG) protein family comprises the integral membrane proteins LRIG1, LRIG2 and LRIG3. LRIG1 is frequently down-regulated in human cancer, and high levels of LRIG1 in tumor tissue are associated with favorable clinical outcomes in several tumor types including non-small cell lung cancer (NSCLC). Mechanistically, LRIG1 negatively regulates receptor tyrosine kinases and functions as a tumor suppressor. However, the details of the molecular mechanisms involved are poorly understood, and even less is known about the functions of LRIG2 and LRIG3. The aim of this study was to further elucidate the functions and molecular interactions of the LRIG proteins.
A yeast two-hybrid screen was performed using a cytosolic LRIG3 peptide as bait. In transfected human cells, co-immunoprecipitation and co-localization experiments were performed. Proximity ligation assay was performed to investigate interactions between endogenously expressed proteins. Expression levels of LMO7 and LIMCH1 in normal and malignant lung tissue were investigated using qRT-PCR and through in silico analyses of public data sets. Finally, a clinical cohort comprising 355 surgically treated NSCLC cases was immunostained for LMO7.
In the yeast two-hybrid screen, the two paralogous proteins LMO7 and LIMCH1 were identified as interaction partners to LRIG3. LMO7 and LIMCH1 co-localized and co-immunoprecipitated with both LRIG1 and LRIG3. Endogenously expressed LMO7 was in close proximity of both LRIG1 and LRIG3. LMO7 and LIMCH1 were highly expressed in normal lung tissue and down-regulated in malignant lung tissue. LMO7 immunoreactivity was shown to be a negative prognostic factor in LRIG1 positive tumors, predicting poor patient survival.
These findings suggest that LMO7 and LIMCH1 physically interact with LRIG proteins and that expression of LMO7 is of clinical importance in NSCLC.
人类亮氨酸丰富重复和免疫球蛋白样结构域（LRIG）蛋白家族包括整合膜蛋白 LRIG1、LRIG2 和 LRIG3。LRIG1 在人类癌症中经常下调，肿瘤组织中高表达 LRIG1 与几种肿瘤类型（包括非小细胞肺癌（NSCLC））的良好临床结果相关。从机制上讲，LRIG1 负调控受体酪氨酸激酶，发挥肿瘤抑制作用。然而，涉及的分子机制的细节了解甚少，对 LRIG2 和 LRIG3 的功能知之甚少。本研究旨在进一步阐明 LRIG 蛋白的功能和分子相互作用。
使用胞质 LRIG3 肽作为诱饵进行酵母双杂交筛选。在转染的人细胞中进行共免疫沉淀和共定位实验。进行邻近连接测定以研究内源性表达蛋白之间的相互作用。使用 qRT-PCR 和公共数据集的计算分析研究正常和恶性肺组织中 LMO7 和 LIMCH1 的表达水平。最后，对包含 355 例接受手术治疗的 NSCLC 病例的临床队列进行 LMO7 免疫染色。
在酵母双杂交筛选中，两个平行蛋白 LMO7 和 LIMCH1 被鉴定为与 LRIG3 的相互作用伙伴。LMO7 和 LIMCH1 与 LRIG1 和 LRIG3 共定位并共免疫沉淀。内源性表达的 LMO7 与 LRIG1 和 LRIG3 接近。LMO7 和 LIMCH1 在正常肺组织中高表达，在恶性肺组织中下调。LMO7 免疫反应性被证明是 LRIG1 阳性肿瘤的一个负面预后因素，预测患者生存不良。
这些发现表明 LMO7 和 LIMCH1 与 LRIG 蛋白物理相互作用，并且 LMO7 的表达在 NSCLC 中具有临床重要性。
