Costantini Todd W, Dang Xitong, Yurchyshyna Maryana V, Coimbra Raul, Eliceiri Brian P, Baird Andrew
Department of Surgery, University of California San Diego Health Sciences, San Diego, California, United States of America.
Cardiovascular Research Center, Luzhou Medical College, Luzhou, Sichuan, China.
Mol Med. 2015 Apr 3;21(1):323-36. doi: 10.2119/molmed.2015.00018.
The human genome contains a variant form of the α7-nicotinic acetylcholine receptor (α7nAChR) gene that is uniquely human. This CHRFAM7A gene arose during human speciation and recent data suggests that its expression alters ligand tropism of the normally homopentameric human α7-AChR ligand-gated cell surface ion channel that is found on the surface of many different cell types. To understand its possible significance in regulating inflammation in humans, we investigated its expression in normal human leukocytes and leukocyte cell lines, compared CHRFAM7A expression to that of the CHRNA7 gene, mapped its promoter and characterized the effects of stable CHRFAM7A overexpression. We report here that CHRFAM7A is highly expressed in human leukocytes but that the levels of both CHRFAM7A and CHRNA7 mRNAs were independent and varied widely. To this end, mapping of the CHRFAM7A promoter in its 5'-untranslated region (UTR) identified a unique 1-kb sequence that independently regulates CHRFAM7A gene expression. Because overexpression of CHRFAM7A in THP1 cells altered the cell phenotype and modified the expression of genes associated with focal adhesion (for example, FAK, P13K, Akt, rho, GEF, Elk1, CycD), leukocyte transepithelial migration (Nox, ITG, MMPs, PKC) and cancer (kit, kitL, ras, cFos cyclinD1, Frizzled and GPCR), we conclude that CHRFAM7A is biologically active. Most surprisingly however, stable CHRFAM7A overexpression in THP1 cells upregulated CHRNA7, which, in turn, led to increased binding of the specific α7nAChR ligand, bungarotoxin, on the THP1 cell surface. Taken together, these data confirm the close association between CHRFAM7A and CHRNA7 expression, establish a biological consequence to CHRFAM7A expression in human leukocytes and support the possibility that this human-specific gene might contribute to, and/or gauge, a human-specific response to inflammation.
人类基因组包含一种独特的人类α7烟碱型乙酰胆碱受体（α7nAChR）基因变体形式。这个CHRFAM7A基因在人类物种形成过程中出现，最近的数据表明，它的表达改变了正常同五聚体人类α7-AChR配体门控细胞表面离子通道的配体嗜性，该离子通道存在于许多不同细胞类型的表面。为了了解其在调节人类炎症方面的潜在意义，我们研究了它在正常人白细胞和白细胞细胞系中的表达，将CHRFAM7A的表达与CHRNA7基因的表达进行比较，绘制其启动子图谱并表征稳定过表达CHRFAM7A的影响。我们在此报告，CHRFAM7A在人类白细胞中高度表达，但CHRFAM7A和CHRNA7 mRNA的水平是独立的，且差异很大。为此，在其5'非翻译区（UTR）对CHRFAM7A启动子进行图谱分析，确定了一个独特的1 kb序列，该序列独立调节CHRFAM7A基因表达。由于在THP1细胞中过表达CHRFAM7A改变了细胞表型，并改变了与粘着斑相关基因（例如FAK、P13K、Akt、rho、GEF、Elk1、CycD）、白细胞跨上皮迁移（Nox、ITG、MMPs、PKC）和癌症（kit、kitL、ras、cFos cyclinD1、Frizzled和GPCR）相关基因的表达，我们得出结论CHRFAM7A具有生物学活性。然而，最令人惊讶的是，在THP1细胞中稳定过表达CHRFAM7A会上调CHRNA7，这反过来又导致特异性α7nAChR配体银环蛇毒素在THP1细胞表面的结合增加。综上所述，这些数据证实了CHRFAM7A与CHRNA7表达之间的密切关联，确立了CHRFAM7A在人类白细胞中表达的生物学后果，并支持这种人类特异性基因可能促成和/或衡量人类对炎症的特异性反应的可能性。
