TEP2 (Thioester-containing protein 2) is a secreted complement-like protein belonging to the alpha-2-macroglobulin/thioester-containing protein family in the African malaria mosquito Anopheles gambiae. TEP2 contains a conserved thioester motif (GCGEQ) that enables covalent attachment to pathogen surfaces, functioning as a predicted opsonin similar to the well-characterized TEP1. The protein is encoded by gene AGAP008366 located in a TEP gene cluster on chromosome arm 3R (29A-30E), near TEP15. While TEP1 has been extensively studied for its role in anti-Plasmodium immunity, TEP2 remains less characterized but is predicted to function similarly based on conserved domain architecture. TEP2 expression is induced ~9-fold in mosGILT-null mosquitoes, indicating responsiveness to immune pathway perturbation. The protein is expected to be secreted into the hemolymph where it circulates until deployment on pathogen surfaces.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0002376 immune system process | IEA GO_REF:0000043 | ACCEPT | Summary: This IEA annotation is derived from the UniProt keyword "Immunity" (KW-0391) through automated mapping. TEP2 is a thioester-containing protein belonging to the TEP family which functions in insect innate immunity. The protein contains an intact thioester motif and is part of the complement-like immune pathway in A. gambiae (Christophides et al., 2002). Expression is significantly induced (~9-fold) in mosGILT-null mosquitoes, demonstrating responsiveness to immune pathway perturbation (Arora et al., 2024). Reason: TEP2 is a member of the thioester-containing protein family which plays essential roles in insect innate immunity. The annotation to "immune system process" is technically correct and appropriate for this complement-like protein, although it is a broad term. The induction of TEP2 in immune-perturbed mosquitoes and its TEP family membership strongly support this annotation. Supporting Evidence: file:ANOGA/TEP2/TEP2-deep-research-falcon.md TEP2 is a distinct An. gambiae TEP gene in a multi-gene cluster on chromosome arm 3R (29A-30E). TEP2 lies very close to TEP15, with other TEPs (TEP12-14) located farther within the same region. TEP2 is annotated with a present thioester (TE) motif, consistent with complement-like opsonin function file:ANOGA/TEP2/TEP2-deep-research-falcon.md In A. gambiae mosGILT-null, TEP2 (AGAP008366) whole-body transcript levels increased ~9-fold versus wild type (p=0.0001), indicating strong inducibility under immune/reproductive pathway perturbation |
| GO:0004866 endopeptidase inhibitor activity | IEA GO_REF:0000002 | REMOVE | Summary: This annotation is derived from InterPro domain mapping (IPR001599 Alpha-2- macroglobulin and IPR002890 MG2 domain) which are shared with protease inhibitors like alpha-2-macroglobulin. However, TEP2 is a thioester-containing protein that belongs to the complement-like branch of this family, not the protease inhibitor branch. Similar to the well-characterized TEP1 in A. gambiae, TEP2 is predicted to function as an opsonin that covalently tags pathogen surfaces via its reactive thioester bond, not as a protease inhibitor (Shokal and Eleftherianos, 2017). There is no experimental evidence that TEP2 acts as an endopeptidase inhibitor. Reason: TEP2 is a thioester-containing protein that functions as a predicted complement-like opsonin in the insect innate immune pathway, not as a protease inhibitor. While it shares alpha-2-macroglobulin domains with protease inhibitors, the TEP family has diverged to function primarily in pathogen opsonization rather than protease inhibition. This is well established for TEP1 in A. gambiae and applies by homology to TEP2. The annotation represents an over-annotation based solely on domain homology without consideration of the functional divergence of the TEP family. This is the same issue identified for TEP1 annotation review. Supporting Evidence: file:ANOGA/TEP2/TEP2-deep-research-falcon.md TEP2 belongs to the A2M/TEP family and contains the conserved thioester motif. By analogy to complement-like TEPs in mosquitoes, the active thioester can mediate covalent attachment to microbial surfaces, serving as an opsonin that promotes downstream effector outcomes such as phagocytosis or killing file:ANOGA/TEP2/TEP2-deep-research-falcon.md Thioester-containing proteins (TEPs): Secreted innate immune effectors with a reactive thioester (GCGEQ) that can form covalent bonds with microbial surfaces. In insects, TEPs are functionally analogous to vertebrate complement factors (e.g., C3), contributing to recognition, opsonization, and clearance by phagocytosis and/or lysis |
| GO:0005576 extracellular region | IEA GO_REF:0000120 | ACCEPT | Summary: This IEA annotation is derived from combined automated methods based on InterPro domains (IPR009048, IPR036595 alpha-macroglobulin receptor-binding domain) and UniProt subcellular location annotations (SL-0243 Secreted). TEP2 is predicted to be a secreted protein based on its TEP family membership and signal peptide features. The well-characterized TEP1 is secreted into the hemolymph, and TEP2 is expected to follow the same localization pattern (Baxter et al., 2010). Reason: The annotation is consistent with TEP family biology. TEP proteins are secreted into the hemolymph (extracellular region in insects) where they circulate until activated and deposited on pathogen surfaces. The UniProt entry confirms secreted localization based on ARBA annotation. While direct experimental evidence for TEP2 localization is lacking, the inference from TEP family membership and conserved architecture is strong. Supporting Evidence: file:ANOGA/TEP2/TEP2-deep-research-falcon.md Mosquito complement-like TEPs (exemplified by TEP1) are secreted into the hemolymph, where they circulate and are activated/targeted to pathogen surfaces. Given TEP2's conserved signal features within the TEP family and genomic clustering with other secreted TEPs, TEP2 is expected to be a secreted hemolymph protein file:ANOGA/TEP2/TEP2-uniprot.txt SUBCELLULAR LOCATION: Secreted {ECO:0000256|ARBA:ARBA00004613} |
| GO:0005615 extracellular space | IEA GO_REF:0000120 | ACCEPT | Summary: This IEA annotation is based on InterPro domain mapping (IPR011626 A2M_TED thioester domain) and ARBA rule mapping (ARBA00027728). TEP2 is predicted to circulate in the hemolymph (extracellular space of insects) similar to TEP1, which forms a complex with LRIM1/APL1C in the hemolymph. The extracellular space annotation is appropriate for hemolymph-circulating proteins. Reason: The annotation is consistent with TEP family biology. Hemolymph is the extracellular space in insects where TEP proteins circulate. TEP1 has been demonstrated to circulate in the hemolymph as part of a complex with LRIM1/APL1C, and TEP2 is expected to follow a similar localization pattern based on conserved domain architecture. This annotation is more specific than "extracellular region" and appropriately captures the circulating nature of TEP proteins. Supporting Evidence: file:ANOGA/TEP2/TEP2-deep-research-falcon.md Given TEP2's conserved signal features within the TEP family and genomic clustering with other secreted TEPs, TEP2 is expected to be a secreted hemolymph protein (inference from family and TEP1 data) file:ANOGA/TEP2/TEP2-deep-research-falcon.md In the canonical mosquito complement-like pathway, TEP1 is stabilized and delivered by LRIM1/APL1C until deposition on pathogens |
| GO:0045087 innate immune response | ISS DOI:10.3389/fimmu.2017.00759 | NEW | Summary: TEP2 is predicted to participate in innate immune response based on its membership in the TEP family and conserved thioester motif. The protein shows significant upregulation (~9-fold) in mosGILT-null mosquitoes, demonstrating responsiveness to immune pathway perturbation. Reason: While GO:0002376 "immune system process" is already annotated, this more specific term "innate immune response" better captures the nature of TEP2 function as a complement-like protein. TEPs function in the germline-encoded innate immune system, not adaptive immunity. The term is supported by TEP family membership and immune-regulated expression. Supporting Evidence: file:ANOGA/TEP2/TEP2-deep-research-falcon.md Thioester-containing proteins (TEPs): Secreted innate immune effectors with a reactive thioester (GCGEQ) that can form covalent bonds with microbial surfaces. In insects, TEPs are functionally analogous to vertebrate complement factors (e.g., C3), contributing to recognition, opsonization, and clearance by phagocytosis and/or lysis file:ANOGA/TEP2/TEP2-deep-research-falcon.md In A. gambiae mosGILT-null, TEP2 (AGAP008366) whole-body transcript levels increased ~9-fold versus wild type (p=0.0001) |
| GO:0008228 opsonization | ISS DOI:10.3389/fimmu.2017.00759 | NEW | Summary: TEP2 is predicted to function as an opsonin based on its conserved thioester motif (GCGEQ) and TEP family membership. The reactive thioester enables covalent attachment to pathogen surfaces, marking them for destruction by phagocytosis or melanization. Reason: Opsonization is the predicted primary biological process of TEP2 based on homology to TEP1 and conserved domain architecture. The thioester motif is characteristic of complement-like opsonins. While direct experimental evidence for TEP2-mediated opsonization is lacking, the inference from TEP family function is strong. Supporting Evidence: file:ANOGA/TEP2/TEP2-deep-research-falcon.md TEP2 belongs to the A2M/TEP family and contains the conserved thioester motif. By analogy to complement-like TEPs in mosquitoes, the active thioester can mediate covalent attachment to microbial surfaces, serving as an opsonin that promotes downstream effector outcomes such as phagocytosis or killing |
| GO:0140272 exogenous protein binding | ISS DOI:10.3389/fimmu.2017.00759 | NEW | Summary: TEP2 is predicted to bind to pathogen surfaces via its reactive thioester motif. This molecular function enables opsonization of pathogens for subsequent clearance by phagocytosis or melanization. Reason: As a complement-like opsonin, TEP2 binds to proteins/molecules on pathogen surfaces (exogenous proteins). The thioester motif allows covalent attachment to microbial surfaces. This is the appropriate molecular function term for the opsonin activity. Supporting Evidence: file:ANOGA/TEP2/TEP2-deep-research-falcon.md By analogy to complement-like TEPs in mosquitoes, the active thioester can mediate covalent attachment to microbial surfaces, serving as an opsonin |
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Download this section (compressed HTML)Q: Does TEP2 interact with LRIM1/APL1C heterodimer similar to TEP1, and if so, is this interaction required for stabilization and delivery to pathogen surfaces?
Q: What is the specific role of TEP2 versus TEP1 and other TEPs in the A. gambiae complement-like pathway? Is there functional redundancy or specificity?
Q: Does TEP2 contribute to anti-Plasmodium immunity like TEP1, or does it have different pathogen specificity?
Experiment: RNAi knockdown of TEP2 followed by bacterial or fungal infection challenge to assess immune function.
Hypothesis: TEP2 knockdown will increase pathogen proliferation and reduce mosquito survival, similar to TEP1 knockdown phenotypes.
Experiment: Co-immunoprecipitation studies to determine if TEP2 interacts with LRIM1/APL1C or other hemolymph proteins.
Hypothesis: TEP2 forms a circulating complex with LRIM1/APL1C similar to TEP1.
Experiment: Immunolocalization of TEP2 during pathogen challenge to determine if it deposits on pathogen surfaces.
Hypothesis: TEP2 will accumulate on pathogen surfaces similar to TEP1 opsonization.
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