title: Molecular characterization and functional significance of the Vti family of SNARE proteins in tick salivary glands.
abstract: Exocytosis involves membrane fusion between secretory vesicles and the plasma membrane. The Soluble N-ethylmaleimide-sensitive factor attachment proteins (SNAPs) and their receptor proteins (SNAREs) interact to fuse vesicles with the membrane and trigger the release of their sialosecretome out of the tick salivary gland cells. In this study, we examined the functional significance of the Vti family of SNARE proteins of blood-feeding Amblyomma maculatum and Amblyomma americanum. Vti1A and Vti1B have been implicated in multiple functional roles in vesicle transport. QRT-PCR studies demonstrated that the highest transcriptional expression of vti1a and vti1b genes occurs in unfed salivary glands, suggesting that elevated secretory vesicle formation occurs prior to feeding but continues at low rates after blood feeding commences. Vti1A and Vti1B localize to the secretory vesicles in unfed tick salivary glands in immunofluorescence microscopy studies. Knockdown of vti1a and vti1b by RNA interference resulted in a significant decrease in the engorged tick weight compared to the control during prolonged blood-feeding on the host. RNA interference of vti1a or vti1b impaired oviposition and none of the ticks produced eggs masses. Surprisingly, the double knockdown did not produce a strong phenotype and ticks fed normally on the host and produced egg masses, suggesting a compensatory mechanism exists within the secretory system which may have been activated in the double knockdown. These results suggest an important functional role of the Vti family of SNARE proteins in tick blood feeding and ultimately oviposition. Understanding the basic functions of the Vti family of SNARE proteins in salivary glands may lead to better ways to prevent tick attachment and transmission of tick-borne diseases.
authors.affiliation: Department of Biological Sciences, The University of Southern Mississippi, 118 College Drive # 5018, Hattiesburg, MS 39406, USA.
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Villarreal
authors.forename: Steven W
authors.initials: SW
authors.lastname: Adamson
authors.forename: Rebecca E
authors.initials: RE
authors.lastname: Browning
authors.forename: Khemraj
authors.initials: K
authors.lastname: Budachetri
authors.forename: Muhammad Sohail
authors.initials: MS
authors.lastname: Sajid
authors.forename: Shahid
authors.initials: S
authors.lastname: Karim
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D060829:Arthropod Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018076:DNA, Complementary / Q000032:analysis; D005247:Feeding Behavior; D005260:Female; D005786:Gene Expression Regulation; D015151:Immunoblotting; D026863:Ixodidae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008297:Male; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010058:Oviposition; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D034622:RNA Interference; D012333:RNA, Messenger / Q000032:analysis; D050600:SNARE Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D012469:Salivary Glands / Q000378:metabolism; D022142:Secretory Vesicles / Q000378:metabolism; D016415:Sequence Alignment; D013045:Species Specificity
chemical_list: D060829:Arthropod Proteins; D018076:DNA, Complementary; D012333:RNA, Messenger; D050600:SNARE Proteins