CG4793 (SPH208/cSPH128) encodes a 910-residue secretory-pathway serine protease homolog with an N-terminal protease-like domain and a long repetitive C-terminal region. Its catalytic-site substitutions support a nonenzymatic regulatory role rather than serine endopeptidase activity. CG4793 is a JAK/STAT-responsive regulator of cellular immunity: depletion in lamellocytes increases parasitoid-egg encapsulation, whereas depletion in a constitutively active JAK tumour model suppresses melanotic tumour formation. Its direct molecular partners and mechanism are unresolved.
Summary: The negated peptidase annotation is consistent with the disrupted catalytic machinery of CG4793.
Reason: This is a NOT annotation, not a positive enzyme assignment. Independent alignment of the exact Q8IP30 sequence to two active trypsin controls identifies glycine at the catalytic serine position, with additional substitutions at the aligned His/Asp positions. The controls retain the intact triad. This supports loss of conventional S1 peptidase activity and agrees with the published SPH classification; it does not exclude noncatalytic regulation of other proteases.
Global domain alignments to active trypsins P00760 and P00761 map the catalytic His, Asp and Ser to Q8IP30 Glu145, Asn191 and Gly290, respectively. In particular, the catalytic serine is replaced by glycine in the conserved local segment TCKGDGGAPLA.
IKRNOT PMID:12568721 Serine proteases and their homologs in the Drosophila melano...
ACCEPT
Summary: The negated peptidase annotation is consistent with the disrupted catalytic machinery of CG4793.
Reason: This is a NOT annotation, not a positive enzyme assignment. Independent alignment of the exact Q8IP30 sequence to two active trypsin controls identifies glycine at the catalytic serine position, with additional substitutions at the aligned His/Asp positions. The controls retain the intact triad. This supports loss of conventional S1 peptidase activity and agrees with the published SPH classification; it does not exclude noncatalytic regulation of other proteases.
Global domain alignments to active trypsins P00760 and P00761 map the catalytic His, Asp and Ser to Q8IP30 Glu145, Asn191 and Gly290, respectively. In particular, the catalytic serine is replaced by glycine in the conserved local segment TCKGDGGAPLA.
IKRNOT PMID:30367934 Building a platform for predicting functions of serine prote...
ACCEPT
Summary: The negated peptidase annotation is consistent with the disrupted catalytic machinery of CG4793.
Reason: This is a NOT annotation, not a positive enzyme assignment. Independent alignment of the exact Q8IP30 sequence to two active trypsin controls identifies glycine at the catalytic serine position, with additional substitutions at the aligned His/Asp positions. The controls retain the intact triad. This supports loss of conventional S1 peptidase activity and agrees with the published SPH classification; it does not exclude noncatalytic regulation of other proteases.
Global domain alignments to active trypsins P00760 and P00761 map the catalytic His, Asp and Ser to Q8IP30 Glu145, Asn191 and Gly290, respectively. In particular, the catalytic serine is replaced by glycine in the conserved local segment TCKGDGGAPLA.
Summary: Extracellular localization is a well-supported sequence and phylogenetic inference.
Reason: The existing PAINT inference is consistent with the independently predicted N-terminal signal peptide in the exact Q8IP30 sequence. The architecture supports entry into the secretory pathway and an extracellular role for this protease homolog. This is inferred localization; the gene-specific RNAi phenotype does not itself demonstrate secretion.
Supporting Evidence:
file:DROME/CG4793/CG4793-uniprot.txt
FT SIGNAL 1..18 FT /evidence="ECO:0000256|SAM:SignalP"
Summary: Participation in proteolysis is unresolved for this inactive protease homolog.
Reason: The target lacks the conventional serine nucleophile, so its S1 domain cannot justify intrinsic peptide-bond hydrolysis. Proteolysis is a biological process, however, and a pseudoenzyme could participate noncatalytically by regulating an active protease. The cellular-immunity experiments do not identify such a proteolytic mechanism for CG4793. Target-specific catalytic loss challenges transfer of enzymatic activity, but does not alone refute this broader process assertion.
Global domain alignments to active trypsins P00760 and P00761 map the catalytic His, Asp and Ser to Q8IP30 Glu145, Asn191 and Gly290, respectively. In particular, the catalytic serine is replaced by glycine in the conserved local segment TCKGDGGAPLA.
However, a detailed mechanistic understanding of how these S1A family genes regulate cellular immunity and how their activity may be linked to JAK-STAT pathway signaling remain to be established.
Summary: Participation in proteolysis is unresolved for this inactive protease homolog.
Reason: The target lacks the conventional serine nucleophile, so its S1 domain cannot justify intrinsic peptide-bond hydrolysis. Proteolysis is a biological process, however, and a pseudoenzyme could participate noncatalytically by regulating an active protease. The cellular-immunity experiments do not identify such a proteolytic mechanism for CG4793. Target-specific catalytic loss challenges transfer of enzymatic activity, but does not alone refute this broader process assertion.
Global domain alignments to active trypsins P00760 and P00761 map the catalytic His, Asp and Ser to Q8IP30 Glu145, Asn191 and Gly290, respectively. In particular, the catalytic serine is replaced by glycine in the conserved local segment TCKGDGGAPLA.
However, a detailed mechanistic understanding of how these S1A family genes regulate cellular immunity and how their activity may be linked to JAK-STAT pathway signaling remain to be established.
Summary: The negated peptidase annotation is consistent with the disrupted catalytic machinery of CG4793.
Reason: This is a NOT annotation, not a positive enzyme assignment. Independent alignment of the exact Q8IP30 sequence to two active trypsin controls identifies glycine at the catalytic serine position, with additional substitutions at the aligned His/Asp positions. The controls retain the intact triad. This supports loss of conventional S1 peptidase activity and agrees with the published SPH classification; it does not exclude noncatalytic regulation of other proteases.
Global domain alignments to active trypsins P00760 and P00761 map the catalytic His, Asp and Ser to Q8IP30 Glu145, Asn191 and Gly290, respectively. In particular, the catalytic serine is replaced by glycine in the conserved local segment TCKGDGGAPLA.
GO:0035208 positive regulation of hemocyte proliferation
IGI PMID:20168330 Transcriptional targets of Drosophila JAK/STAT pathway signa...
KEEP AS NON CORE
Summary: Retain the genetic interaction in the activated-JAK haemocyte tumour model as context-dependent biology.
Reason: Bina et al. identify CG4793 in an RNAi screen for effectors of hopTumL-induced melanotic tumours; its depletion suppresses the tumour index. This supports the existing FlyBase IGI inference in that overproliferation model, rather than demonstrating a universal positive effect on normal haemocyte proliferation. Direct circulating-haemocyte counts in the article concern baz, not CG4793. The physiological parasitoid assay instead establishes a negative effect on lamellocyte-mediated encapsulation, a distinct outcome and context.
Conversely, knockdown of CG4793 in lamellocytes resulted in a significant increase in the encapsulation rate.
GO:0140540 negative regulation melanotic encapsulation of foreign target
IMP PMID:33644706 The S1A protease family members CG10764 and CG4793 regulate ...
NEW
Summary: CG4793 restrains lamellocyte-mediated encapsulation of parasitoid eggs.
Reason: Two independent RNAi constructs increase encapsulation when CG4793 is depleted in lamellocytes, with no effect after plasmatocyte depletion. This directly supports negative regulation of the melanotic encapsulation response in the tested Drosophila–Leptopilina clavipes infection model. The experiment is gene-level; it does not establish which CG4793 isoform or molecular partner mediates the effect.
Conversely, knockdown of CG4793 in lamellocytes resulted in a significant increase in the encapsulation rate.
Core Functions
Restrains lamellocyte-mediated melanotic encapsulation of parasitoid eggs through an unresolved noncatalytic mechanism. The molecular activity is not established, so no specific molecular-function term is asserted.
Global domain alignments to active trypsins P00760 and P00761 map the catalytic His, Asp and Ser to Q8IP30 Glu145, Asn191 and Gly290, respectively. In particular, the catalytic serine is replaced by glycine in the conserved local segment TCKGDGGAPLA.
Q: Which extracellular binding partner or protease-regulatory interaction mediates CG4793-dependent control of lamellocyte encapsulation?
Q: Which CG4793 isoform and tissue source mediate the distinct parasitoid-infection and hopTumL tumour phenotypes?
External Prediction Reviews
These computational predictions are reviewed separately from the GOA annotation set used for this review. The assessments below are from this project and do not constitute official GO annotations or endorsement by GO/UniProt. They are not included in the existing annotation review above.
The intrinsic serine-type endopeptidase prediction is contradicted by loss of the catalytic serine in the exact Q8IP30 protease-like domain. CG4793 has experimentally supported immune-regulatory biology, but its direct molecular mechanism is unresolved.
Review rationale: The exact 910-residue Q8IP30 sequence has a protease-like domain with glycine replacing the catalytic serine, supported by substantial-coverage alignments to two active trypsin controls. The controls agree on the additional His-to-Glu and Asp-to-Asn site mappings, although the histidine region is more divergent. These residue observations, rather than the SPH name or an automated domain caution alone, refute conventional serine endopeptidase catalysis. Four existing GOA NOT annotations are concordant negative annotations, not evidence that the positive prediction is correct or non-novel. The source gives model score 0.99 and phmmer donor Q7Z410 with score 226.0; donor similarity cannot restore the missing nucleophile. Gene-specific RNAi establishes cellular immune regulation, without assaying purified-protein proteolysis or resolving a direct mechanism.
Supporting Evidence:
file:DROME/CG4793/CG4793-bioinformatics/RESULTS.md: "Global domain alignments to active trypsins P00760 and P00761 map the catalytic His, Asp and Ser to Q8IP30 Glu145, Asn191 and Gly290, respectively. In particular, the catalytic serine is replaced by glycine in the conserved local segment TCKGDGGAPLA."
PMID:33644706: "CG4793 is an SPH gene and encodes a protein that is predicted to be catalytically inactive."