Croquemort-scavenger receptor class B 2 (scrbq2) gene in Anopheles stephensi: Molecular characterization and...

SCRBQ2 is a croquemort-scavenger receptor class B family protein. The identification of SCRBQ2 in the detergentresistantmembrane of the Anopheles stephensi midgut suggests its role as an ookinete-interacting protein, positioning it as a potential target for transmission-blocking vaccine development. The Asscrbq2 gene was characterized in the Indian urban malaria vector A. stephensi. It was amplified and submitted to GenBankwith accession IDON817188. The gene consists of a coding sequence (CDS) of 2922 bp and encodes a protein of 973 amino acids. The AsSCRBQ2 protein contains two merged CD36 domains, which are conserved across various mosquito species. A similar evolutionary merging of these domains has also been observed in Anopheles culicifacies, Anopheles maculipennis, Anopheles minimus, Anopheles dirus, and Anopheles aquasalis.AsSCRBQ2domain I shows 91.02% similarity with SCRBQ1of Anopheles gambiae,whereas domain II shows 88.68%similarity withSCRBQ2of A. gambiae.The similarity between humanCD36 and AsSCRBQ2 highlights the functional versatility of AsSCRBQ2 in mediating immune responses and facilitating Plasmodium falciparum transmission in malaria vectors. Its dual interactions with PfEMP1 and TLR4 position AsSCRBQ2 as a promising target for transmission-blocking vaccine development and vector control strategies. Codon optimization and in silico cloning showed that the Asscrbq2 gene is highly expressed in the Escherichia coli strain K12. The relative expression pattern shows that the Asscrbq2 gene is highly expressed in the midgut than in the fat body, followed by the salivary glands and ovaries. After blood feeding, upregulation was observed in themidgut at 24 h post bloodmeal (PBM), suggesting a role in blood digestion, and in the fat body at 48 h PBM, indicating a possible role in immunity. Previous studies have suggested a role for SCRBQ2 in Plasmodium invasion of the mosquito midgut; however, this remains to be investigated and validated specifically in A. stephensi.