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Published on: April 20, 2011
Biochemical characterization of a novel sphingomyelinase-like protein from the Rhipicephalus microplus tick
Fernando A A Silva1, Gabriel C A Costa1, Luís F Parizi2
1Departamento de Bioquímica, Escola Paulista de Medicina, Universidade de Federal de São Paulo (UNIFESP), São Paulo, SP, Brazil.
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.
Insights
Researchers investigated a sphingomyelinase D-like protein (RmSMase) from Rhipicephalus microplus ticks. This protein, found in tick saliva, exhibits enzymatic activity and may play a role in the tick feeding process.
Area of Science:
- Biochemistry
- Molecular Biology
- Veterinary Entomology
Background:
- Sphingomyelinase D (SMase D) is a toxin found in spiders and bacteria, linked to spider bite infections.
- SMase D-like proteins in tick saliva can modulate host immunity and influence pathogen transmission.
- Rhipicephalus microplus (Rm) is a significant cattle tick vector of pathogens, causing economic losses.
Purpose of the Study:
- To characterize the sphingomyelinase D-like protein (RmSMase) from Rhipicephalus microplus.
- To investigate the enzymatic activity, biochemical properties, and biological role of RmSMase.
Main Methods:
- Amino acid sequence analysis of RmSMase.
- Recombinant protein expression and purification.
- Enzymatic activity assays under varying pH and ion conditions (Ca2+, Mg2+).
- Analysis of RmSMase mRNA transcription levels during tick feeding.
- Detection of host antibodies against RmSMase post-infestation.
Main Results:
- The amino acid sequence suggested a lack of key residues for enzymatic activity, yet the recombinant RmSMase exhibited sphingomyelinase D activity.
- RmSMase activity is dependent on Ca2+ and Mg2+ at acidic pH, distinct from other known SMases.
- RmSMase mRNA levels increase during tick feeding.
- Host antibodies confirm RmSMase presence in tick saliva and its potential role during feeding.
Conclusions:
- RmSMase represents a novel class (SMase D class IIc) of sphingomyelinase D.
- RmSMase is secreted in Rhipicephalus microplus saliva and likely contributes to the tick feeding process.
- Understanding RmSMase function could offer insights into tick-host interactions and disease transmission.
