A family of serine protease inhibitors (serpins) in the cattle tick Rhipicephalus (Boophilus) microplus

Abstract

Proteins belonging to the serine protease inhibitor (serpin) superfamily play essential roles in many organisms. In arthropods these proteins are involved in innate immune system, morphogenesis and development. In mammals serpins regulate pathways that are essential to life such as blood coagulation, fibrinolysis, inflammation and complement activation, some of which are considered the host's first line of defense to hematophagous and/or blood dueling parasites. Thus, it is hypothesized that ticks use serpins to evade host defense, facilitating parasitism. This study describes eighteen full-length cDNA sequences encoding serpins identified in Rhipicephalus (Boophilus) microplus, here named RmS 1-18 (R. microplus serpin). Spatial and temporal transcriptional profiling demonstrated that R. microplus serpins are transcribed during feeding, suggesting their participation in tick physiology regulation. We speculate that the majority of R. microplus serpins are conserved in other ticks, as indicated by phylogeny analysis. Over half of the 18 RmSs are putatively functional in the extracellular environment, as indicated by putative signal peptides on 11 of 18 serpins. Comparative modeling and structural-based alignment revealed that R. microplus serpins in this study retain the consensus secondary of typical serpins. This descriptive study enlarges the knowledge on the molecular biology of R. microplus, an important tick species.

De novo assembly and annotation of the salivary gland transcriptome of Rhipicephalus appendiculatus male and female ticks during blood feeding

“…Even though RAS-4 and HBPM have low identities compared to the original protein sequences, they are full-length and contain the expected complete functional domains, motifs and signal signatures. The HBPM homolog assembled here has the same abundant male-specific expression profile as the previously published HBPM (Paesen et al, 1999) and the assembled RAS-4 homolog clustered into the expected phylogenetic clade of serpins (Tirloni et al, 2014). The assembled proteins therefore seem to be functional, though their functions remain to be determined.…”

Conserved Amblyomma americanum tick Serpin19, an inhibitor of blood clotting factors Xa and XIa, trypsin and plasmin, has anti-haemostatic functions

“…From this perspective, it is proposed that ticks inject serpins into the host to mediate evasion of host defenses and thus they could be suitable targets for tick vaccines (Mulenga et al, 2001). Several tick serpin-encoding cDNAs have been cloned and characterized, including serpins of A. americanum (Mulenga et al, 2007; Porter et al, 2015), Amblyomma maculatum (Karim et al, 2011), Ixodes scapularis (Ribeiro et al, 2006; Mulenga et al, 2009), Ixodes ricinus (Leboulle et al, 2002; Prevot et al, 2006; Chmelar et al, 2011) , Rhipicephalus microplus (Rodriguez-Valle et al, 2012; Tirloni et al, 2014b), Rhipicephalus appendiculatus (Mulenga et al, 2003a), Rhipicephalus haemaphysaloides (Yu et al, 2013), and Haemaphysalis longicornis (Sugino et al, 2003; Imamura et al, 2005, 2006). As of January 2015, more than 200 tick serpin-encoding cDNAs were available in public databases (Porter et al, 2015).…”

“…Indeed, the presence of serpins in tick saliva was well demonstrated though saliva proteomic studies in Dermacentor andersoni (Mudenda et al, 2014) and R. microplus (Tirloni et al, 2014a) as well as being inferred from transcriptional analysis of salivary glands from A. americanum (Mulenga et al, 2007; Porter et al, 2015), A. maculatum (Karim et al, 2011), Amblyomma triste , Amblyomma parvum , Amblyomma cajennense (Garcia et al, 2014), Amblyomma variegatum (Ribeiro et al, 2011), Hyalomma marginatum rufipes (Francischetti et al, 2011), I. scapularis (Valenzuela et al, 2002; Ribeiro et al, 2006; Mulenga et al, 2009), I. ricinus (Leboulle et al, 2002; Schwarz et al, 2013, 2014), R. appendiculatus (Mulenga et al, 2003a, b), R. microplus (Tirloni et al, 2014b), R. haemaphysaloides (Yu et al, 2013), H. longicornis (Sugino et al, 2003; Imamura et al, 2005), and Antricola delacruzi (Ribeiro et al, 2012). Accordingly, inhibitory tick serpins have been found and characterized in tick saliva, including A. americanum salivary serpin (AAS) 6 (Mulenga et al, 2007; Chalaire et al, 2011), a cross-class inhibitor of papain and trypsin-like proteases able to inhibit blood clotting and complement activation (Mulenga et al, 2013).…”

Gut transcriptome analysis on females of Ornithodoros mimon (Acari: Argasidae) and phylogenetic inference of ticks

“…However, other authors have suggested that inhibitors such as serpin can be used by ticks to regulate endopeptidase activity and hemostasis (MULENGA et al, 2001(MULENGA et al, , 2003PERNER et al, 2016;TIRLONI et al, 2014). Peptidase inhibitors have been mentioned as effective antigens for preparing vaccines, because these genes are essential for the survival of ticks, since they are associated with endogenous processes such as regulation of hemolymph coagulation through controlling proteinase activity (IMAMURA et al, 2005).…”