Our MALDI/TOF-MS analysis showed that both

Aea-HP-1 and Aea-HP-3 are present in the MAGs and HPLC analysis combined with MALDI/MS and ELISA indicated that Aea-HP-1 is the dominant form. The hydroxylation of Pro in biologically active peptides is unusual and, as far as we are aware, occurs in only three other insect peptides, one of which, interestingly, is the SP of D. melanogaster [10] and [11] and the others being [Hyp3]Met-callatostatin and [Hyp2]Met-callatostatin of the blowfly [11] and [12]. Aea-HP-1 and Aea-HP-3, like many insect regulatory peptides, have an amidated C-terminus and a pyroglutamate at the N-terminus, both modifications render Z-VAD-FMK mouse peptides more resistant to degradation by exopeptidases [16]. Resistance to hydrolysis by peptidases will be important for maintaining biological activity during transfer to the female since the MAGs and seminal fluid of A. aegypti are known to contain several exopeptidases [36]. Indeed, we have shown in the present study that MAGs contain peptide-degrading PR-171 cost peptidase activity and that Aea-HP-1 is relatively

stable in the presence of these hydrolytic enzymes. Aea-HP-1 has been tested for myogenic and behavior modifying activity in A. aegypti. The peptide did not stimulate contractions of isolated oviduct and hindgut of female mosquitoes [31], but did alter behavior when injected into non-öogenic females by inhibiting host-seeking behavior [4]. This reduction in host-seeking lasted for up to 5 h and the effect was possibly time limited by the rapid clearance of the peptide from the mosquito hemolymph – only around 17% of the peptide remained in the circulation after 30 min [4]. Aea-HP-3 did not elicit host-seeking inhibitory MYO10 behavior when injected into females indicating that the presence of a hydroxyl group on Pro4 is important for this activity [4]. MAGs of A. aegypti are composed of a thin muscle sheaf surrounding a single layer of secretory cells that form distinct anterior and posterior regions with different modes of secretion [9]. Immunohistochemistry using antibodies that cross-react with Aea-HP-1 identified the

anterior region of the MAG as the likely source of the peptide. These cells make up around two-thirds of the MAG and release their contents into the lumen by an apocrine mechanism involving the pinching off of apical parts of the cell [9]. Aea-HP-1 is generated by limited proteolysis of the preprohormone that comprises a secretory signal peptide and three copies of the peptide precursor sequence [38]. Further post-translational processing will generate either Aea-HP-1 or Aea-HP-3. We were able to detect Aea-HP-1 in fluid emanating from the MAGs, indicating that the peptide is present in the secretions and is a component of the seminal fluid that is eventually passed to the female during mating. This was confirmed by demonstrating that Aea-HP-1 is present in the female reproductive tissues soon after copulation, but not in tissues of virgins.