Silva Fernando A A, Costa Gabriel C A, Parizi Luís F, Silva Vaz Junior Itabajara da, Tanaka Aparecida S
Departamento de Bioquímica, Escola Paulista de Medicina, Universidade de Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil.
Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), RS, Brazil.
Exp Parasitol. 2023 Nov;254:108616. doi: 10.1016/j.exppara.2023.108616. Epub 2023 Sep 9.
Sphingomyelinase D is a toxin present in venomous spiders and bacteria and is associated with infection symptoms in patients affected by spider bites. It was observed that in Ixodes scapularis ticks, sphingomyelinase-like protein secreted in saliva can modulate the host immune response, affecting the transmission of flavivirus to the host via exosomes. In this work, a sphingomyelinase D-like protein (RmSMase) from R. microplus, a tick responsible for economic losses and a vector of pathogens for cattle, was investigated. The amino acid sequence revealed the lack of important residues for enzymatic activity, but the recombinant protein showed sphingomyelinase D activity. RmSMase shows Ca and Mg dependence in acidic pH, differing from IsSMase, which has Mg dependence in neutral pH. Due to the difference between RmSMase and other SMases described, the data suggest that RmSMase belongs to SMase D class IIc. RmSMase mRNA transcription levels are upregulated during tick feeding, and the recombinant protein was recognized by host antibodies elicited after heavy tick infestation, indicating that RmSMase is present in tick saliva and may play a role in the tick feeding process.
鞘磷脂酶D是一种存在于有毒蜘蛛和细菌中的毒素，与蜘蛛叮咬患者的感染症状有关。据观察，在肩突硬蜱中，唾液中分泌的鞘磷脂酶样蛋白可调节宿主免疫反应，影响黄病毒通过外泌体向宿主的传播。在这项研究中，对微小牛蜱（一种造成经济损失的蜱虫和牛病原体的传播媒介）中的一种鞘磷脂酶D样蛋白（RmSMase）进行了研究。氨基酸序列显示缺乏酶活性的重要残基，但重组蛋白表现出鞘磷脂酶D活性。RmSMase在酸性pH下表现出对钙和镁的依赖性，这与在中性pH下对镁有依赖性的肩突硬蜱鞘磷脂酶（IsSMase）不同。由于RmSMase与其他已描述的鞘磷脂酶之间存在差异，数据表明RmSMase属于IIc类鞘磷脂酶D。在蜱虫取食过程中，RmSMase的mRNA转录水平上调，重组蛋白被重度蜱虫感染后产生的宿主抗体识别，表明RmSMase存在于蜱虫唾液中，可能在蜱虫取食过程中发挥作用。
