Knorr Debbra Y, Hartung Denise, Schneider Kristin, Hintz Luzia, Pies Hanna S, Heinrich Ralf
Department of Cellular Neurobiology, Johann-Friedrich-Blumenbach Institute for Zoology and Anthropology, Georg-August-University Göttingen, Göttingen, Germany.
Front Physiol. 2021 Apr 9;12:648245. doi: 10.3389/fphys.2021.648245. eCollection 2021.
The cytokine receptor-like factor 3 (CRLF3) is an evolutionary conserved class 1 cytokine receptor present in all major eumetazoan groups. Endogenous CRLF3 ligands have not been identified and the physiological responses mediated by mammalian CRLF3 are poorly characterized. Insect CRLF3 is activated by erythropoietin (Epo) and several related molecules that protect mammalian neurons from stress-induced apoptosis. However, insects neither express Epo nor "classical" Epo receptor. Cell-protective effects of insect hemolymph have been described for several species. In this study, we explored the possibility that the endogenous CRLF3 ligand is contained in locust hemolymph. PCR analyses confirmed expression of -transcripts in neurons and hemocytes of and . Survival of locust hemocytes in primary cultures was significantly increased by supplementation of culture medium with locust hemolymph serum. Locust primary neuron cultures were also protected by locust hemolymph, though preceding exposure to fetal bovine serum changed the hemolymph dose-dependency of neuroprotection. Direct comparison of 10% hemolymph serum with recombinant human Epo in its optimal neuroprotective concentration revealed equivalent anti-apoptotic effects on hypoxia-exposed locust neurons. The same concentration of locust hemolymph serum also protected hypoxia-exposed neurons. This indicates that the neuroprotective factor in locust hemolymph is sufficiently conserved in insects to allow activation of neuroprotective receptors in different species. Locust hemolymph-induced neuroprotection in both and was abolished after RNAi-mediated suppression of -expression. In summary, we report the presence of a conserved endogenous cytokine in locust hemolymph that activates CRLF3 and connected anti-apoptotic processes in hemocytes and neurons. Identification and characterization of the CRLF3 ligand will promote knowledge about cytokine evolution and may unravel cell-protective agents with potential clinical application.
细胞因子受体样因子3（CRLF3）是一种在所有主要真后生动物类群中都存在的进化保守的1类细胞因子受体。内源性CRLF3配体尚未被鉴定，哺乳动物CRLF3介导的生理反应也鲜有特征描述。昆虫CRLF3可被促红细胞生成素（Epo）及几种保护哺乳动物神经元免受应激诱导凋亡的相关分子激活。然而，昆虫既不表达Epo，也不表达“经典”的Epo受体。已有多个物种报道了昆虫血淋巴的细胞保护作用。在本研究中，我们探讨了蝗虫血淋巴中含有内源性CRLF3配体的可能性。PCR分析证实了蝗虫中该转录本在神经元和血细胞中的表达。用蝗虫血淋巴血清补充培养基可显著提高原代培养的蝗虫血细胞的存活率。蝗虫原代神经元培养物也受到蝗虫血淋巴的保护，不过预先暴露于胎牛血清会改变血淋巴神经保护作用的剂量依赖性。将10%血淋巴血清与其最佳神经保护浓度下的重组人Epo进行直接比较，发现对缺氧暴露的蝗虫神经元具有同等的抗凋亡作用。相同浓度的蝗虫血淋巴血清也保护缺氧暴露的神经元。这表明蝗虫血淋巴中的神经保护因子在昆虫中具有足够的保守性，能够激活不同物种中的神经保护受体。RNA干扰介导的该基因表达抑制后，蝗虫血淋巴诱导的蝗虫和神经元的神经保护作用均被消除。总之，我们报道了蝗虫血淋巴中存在一种保守的内源性细胞因子，它能激活CRLF3并在血细胞和神经元中连接抗凋亡过程。CRLF3配体的鉴定和表征将促进对细胞因子进化的了解，并可能揭示具有潜在临床应用价值的细胞保护剂。
