Biochemical characterization of a novel sphingomyelinase-like protein from the Rhipicephalus microplus tick

Fernando A A Silva; Gabriel C A Costa; Luís F Parizi; Itabajara da Silva Vaz Junior; Aparecida S Tanaka

doi:10.1016/j.exppara.2023.108616

Biochemical characterization of a novel sphingomyelinase-like protein from the Rhipicephalus microplus tick

Exp Parasitol. 2023 Nov:254:108616. doi: 10.1016/j.exppara.2023.108616. Epub 2023 Sep 9.

Authors

Fernando A A Silva¹, Gabriel C A Costa¹, Luís F Parizi², Itabajara da Silva Vaz Junior³, Aparecida S Tanaka⁴

Affiliations

¹ Departamento de Bioquímica, Escola Paulista de Medicina, Universidade de Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil.
² Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), RS, Brazil.
³ Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul (UFRGS), RS, Brazil; Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul (UFRGS), RS, Brazil; Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular (INCT-EM), RJ, Brazil.
⁴ Departamento de Bioquímica, Escola Paulista de Medicina, Universidade de Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil; Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular (INCT-EM), RJ, Brazil. Electronic address: astanaka10@unifesp.br.

PMID: 37696328
DOI: 10.1016/j.exppara.2023.108616

Abstract

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 Ca²⁺ and Mg²⁺ dependence in acidic pH, differing from IsSMase, which has Mg²⁺ 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.

Keywords: Lipid; Rhipicephalus microplus; Sphingomyelin; Sphingomyelinase D; Tick.