Molecular characterization of a blood‐induced serine carboxypeptidase from the ixodid tick Haemaphysalis longicornis

Abstract

Ticks feed exclusively on blood to obtain their nutrients, but the gene products that mediate digestion processes in ticks remain unknown. We report the molecular characterization and possible function of a serine carboxypeptidase (HlSCP1) identified in the midgut of the hard tick Haemaphysalis longicornis. HlSCP1 consists of 473 amino acids with a peptidase S10 family domain and shows structural similarity with serine carboxypeptidases reported from other arthropods, yeasts, plants and mammals. Endogenous HlSCP1 is strongly expressed in the midgut and is supposed to localize at lysosomal vacuoles and on the surface of epithelial cells. Endogenous HlSCP1, identified as a 53 kDa protein with pI value of 7.5, was detected in the membrane/organelle fraction isolated from the midgut, and its expression was upregulated during the course of blood‐feeding. Enzymatic functional assays revealed that a recombinant HlSCP1 (rHlSCP1) expressed in yeast efficiently hydrolyzed the synthetic substrates specific for cathepsin A and thiol protease over a broad range of pH and temperature values. Furthermore, rHlSCP1 was shown to cleave hemoglobin, a major component of the blood‐meal. Our results suggest that HlSCP1 may play a vital role in the digestion of the host's blood‐meal.

Hlcyst-1 and Hlcyst-2 are Potential Inhibitors of HlCPL-A in the Midgut of the Ixodid Tick Haemaphysalis longicornis

“…Exopeptidases act on the peptides released by the action of the endopeptidases activity of cathepsin B and the amino-dipeptidase activity of cathepsin C. Metallopeptidases might participate in the liberation of free amino acids [10]. Midgut proteolytic enzymes including aspartic protease (longepsin) [7], serine carboxypeptidase (HlSCP) [17] and legumain (HlLgm) [5] have been ascribed to play roles in the degradation of Hb to peptides in the Haemaphysalis longicornis. Accordingly, the present data and those available for other tick species suggest that an enzyme cascade for the proteolysis of Hb operates in the midgut of the ticks [10].…”

Characterization of a Serine Carboxypeptidase Hoscp from Holotrichia Oblita Faldermann (Coleoptera: Scarabaeoidea)

“…A serine carboxypeptidase (HlSCP1) identified in the midgut of the hard tick Haemaphysalis longicornis is strongly expressed in the midgut and is supposed to localize at lysosomal vacuoles and on the surface of epithelial cells. Its expression is upregulated during the course of blood-feeding, which imply that HlSCP1 may function as a lysosomal protease in the process of blood digestion [5]. In our study, we provide the first report of a serine carboxypeptidase in the midgut of H. oblita larvae.…”

“…Currently, SCPs cDNA sequences from a few insects species have been cloned including the Haemaphysalis longicornis [5], the Sitodiplosis mosellana [6], and the Aedes aegypti [7]. The scarab beetle, Holotrichia oblita Faldermann (Coleoptera: Scarabaeidae), are recognized as one of the most destructive pasture pests in the northern parts of China and cause considerable loss of agriculture production and economic income.…”

Some hydrolase activities from the tickHyalomma lusitanicumKoch, 1844 (Ixodoidea: Ixodida)

“…Multiple proteolytic activities have been detected at acidic pH in midguts of adult engorged females of Boophilus microplus (Mendiola et al, 1996) and a tendency to increased values of aspartic-proteinase activity per milligram of total weight was observed during the development of adult female ticks (Mendiola et al, 2001). Other studies indicate that expression of some peptidases is induced or upregulated by a blood-feeding process (Mulenga et al, 2003;Hatta et al, 2006;Motobu et al, 2007).…”