Molecular Mechanism Studies Of HaCTL3 Promoting Hemocytic Encapsulation Mediated By Ha?-integrin In The Cotton Bollworm (Helicoverpa Armigera)

Insects rely on innate immune system to defend against pathogens, which includes both humoral and cellular immunity. Hemocytes-mediated phagocytosis, nodulation and encapsulation, constitute cellular immunity. Encapsulation is an important defensive reaction against foreign invaders that are too large to be phagocytosed by individual hemocytes in insects. During the process, hemocytes must change their state from non-adhesive to adhesive when they spread on or encapsulate foreign invaders. Our previous studies have shown that a pattern recognition receptor, C-type lectin 3 of Helicoverpa armigera (HaCTL3) promoted hemocytic encapsulation by recruiting hemocytes, but the cell-membrane receptor of HaCTL3 remains unclear. Further,?-integrin has been reported to play crucial roles in spreading and encapsulation in several insects, but the molecular mechanisms are not completely understood. In order to clarify the function of Ha?-integrin in H. armigera, and verify whether HaP-integrin plays a role in hemocytic encapsulation promoted by HaCTL3, we cloned Ha?-integrin gene based on H. armigera transcriptom. Subsequently, recombinant Ha?-integrin was expressed and purified. We further analyzed the expressin profiles of Ha?-integrin and the function of Ha?-integrin. We can conclude that (i) Haf?-integrin was highly expressed in hemocytes and was mainly localized on the membrane of hemocytes. (ii) Ha?-integrin was involved in hemocytic encapsulation. (iii) HaCTL3 could bind to the surface of hemocytes, however, this binding was abolished when knock down of Haf?-integrin,suggesting that Ha?-integrin may serve as a hemocytic receptor of HaCTL3. Further,co-immunoprecipitation assays confirmed that HaCTL3 interacted with Hap-integrin. (iv)Knockdown of Ha?-integrin suppressed HaCTL3-mediated hemocytic encapsulation.In summary, we conclude that Ha(3-integrin may serve as a hemocytic receptor of HaCTL3 during the encapsulation reaction. These results will deepen our understanding of the molecular mechanisms of hemocytic encapsulation and provide new clues for pests control.