Silencing of threeAmblyomma americanum(L.) insulin-like growth factor binding protein-related proteins prevents ticks from feeding to repletion

Abstract

SUMMARYThe insulin-like growth factor (IGF) binding proteins (IGFBP) family is the regulatory arm of the IGF signaling system that control mitogenic and anabolic actions of IGF peptide hormones. This study describes cloning and biological characterization of three Amblyomma americanum (L.) (Aam) proteins that show amino-terminal sequence and secondary structure similarity to the IGFBP superfamily. The three molecules here provisionally identified as AamIGFBP-rP1 and short (S) and long (L) AamIGFBP-rP6 are expressed in multiple tick organs and are responsive to tick feeding activity with the former being upregulated and the latter being downregulated. We show that they regulate tick physiological functions that may be related to A. americanum tick feeding success as revealed by RNAi-mediated dual silencing of AamIGFBP-rP6S and AamIGFBP-rP6L or AamIGFBP-rP1 alone, which caused a reduction in blood meal size compared to the controls. Additionally, in the case of AamIGFBP-rP1 silencing, 47% of ticks died while attempting to feed and those that did survive and spontaneously detached from the host failed to lay eggs. Although AamIGFBP-rP6S and AamIGFBP-rP6L show overall identities of 49% and 59%, respectively, to Rhipicephalus microplus C protein, the identity level jumps to ~84% when the comparison is restricted to first 70 amino acids of the mature protein. Similarly, the AamIGFBP-rP1 mature protein is ~72%, 87%, 88% and 92% identical to that of Ixodes scapularis S, R. microplus, R. appendiculatus N and A. variegatum F, respectively. The observed across-tick-species conservation suggests that the three molecules (AamIGFBP-rP1, AamIGFBP-rP6S and AamIGFBP-rP6L) represent target for development of vaccines to protect animals against multiple tick species. The data are discussed with reference to advances in tick molecular biology and the potential of the three proteins as targets for immunizing animals against tick feeding.

Insulin-like growth factor binding protein 7, a member of insulin-like growth factor signal pathway, involved in immune response of small abalone Haliotis diversicolor

“…Analysis of conserved domains revealed the presence of an IGFBP N-terminal domain (IB) between amino acids 22 and 88, a kazal-type serine proteinase inhibitor domain (KI) between amino acids 89 and 128, and an immunoglobulin-like C2 domain (IgC2) between amino acids 144 and 223, is consistent with human IGFBP7, spider CsaIGFBP7 and tick AamIGFBP7 sequence features [8,22,32]. Additionally, two IGFBP7 characteristic motifs were identified from the putative amino acid sequence of saIGFBP7: IB domain signature (xCGCCxxC) and KI domain signature (CGxDxxTYxN) (Fig.…”

Dual silencing of long and short Amblyomma americanum acidic chitinase forms weakens the tick cement cone stability

“…Our quantitative RT-PCR analysis data are suggestive of the possibility that AamAch-L proteins could be associated with tick feeding physiology at the salivary gland level, and not at the mid-gut level. In tick research, genes that are upregulated in response to feeding are thought to be associated with blood meal feeding (Mulenga et al, 2007;Aljamali et al, 2009;Mulenga and Khumthong, 2010;Konnai et al, 2011) and those that are down-regulated are believed to play other roles in tick biology, and are not associated with blood meal feeding (Umemiya et al, 2008;Aljamali et al, 2009). Given that AamAch-L mRNA abundance in the SG did not apparently change with feeding could signal the importance of this protein in unfed and during the parasitic stages of A. americanum.…”

Ixodes scapularistick saliva proteins sequentially secreted every 24h during blood feeding

“…According to previously described classifications of I. scapularis proteins [136], CA, CB, and CD clusters are Sequentially Secreted Ixodes scapularis Saliva Proteins respectively classified as basic tail (group 1, n = 15) or tailless proteins (group 2, n = 10), GPIIb/IIIa antagonist (group 9, n = 7), and 7-9 kDa family (group 7, n = 11). TSPs in CC cluster (n = 7) have insulin binding-like proteins motifs [141], while CE cluster proteins are leucine rich (n = 9) as revealed by sequence inspection. On the basis of amino acid motifs, Ribeiro et.…”