scaf encodes Scarface, a secreted Drosophila protein with an N-terminal Scarface-type CLIP domain and a C-terminal trypsin-like (peptidase S1) domain in which the catalytic histidine and the Ser195/oxyanion-hole motif are replaced, making it a noncatalytic serine protease homolog (SPH). scaf is a transcriptional target of JNK signaling in leading-edge and other epithelial cells, and the secreted protein acts back as an extracellular antagonist of JNK pathway output in a negative-feedback loop; Egfr signaling represses scaf in the lateral epidermis, which limits this antagonism and the downstream Dpp response. Scarface is required for germ-band retraction, embryonic dorsal closure (including amnioserosa attachment and polarized Laminin A localization at the basement membrane), male genitalia rotation, thorax closure, and radiation-induced hinge-to-pouch fate change in the wing disc. Its direct extracellular target is unknown.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004252 serine-type endopeptidase activity | IKR NOT PMID:12568721 Serine proteases and their homologs in the Drosophila melano... | ACCEPT | Summary: Accepted as a negated catalytic annotation: Scaf is an S1-family serine-protease homolog rather than an active serine endopeptidase. Reason: Ross et al. classified Drosophila serine proteases and homologs by catalytic-triad conservation (only the abstract is cached, and it is not Scaf-specific). The NOT claim holds on independent grounds: Rousset et al. state that Scaf bears an inactive catalytic site, UniProt's curated caution notes loss of the conserved triad residues, and the re-review alignment against bovine chymotrypsinogen A (with active Persephone as a positive control) shows His57 replaced by Ser465 and the GDSGGP Ser195/oxyanion-hole motif replaced by FDVGSA, while Asp102 is retained. Loss of the catalytic histidine alone precludes the charge-relay mechanism of serine endopeptidases. No biochemical assay has been reported, so this is a sequence-based negation, which is what IKR asserts. Supporting Evidence: PMID:20530545 Some proteins of this family, like Scaf, bear an inactive catalytic site, representing a subgroup of serine protease homologues (SPH) file:DROME/scaf/scaf-bioinformatics/RESULTS.md Scarface retains the S1 fold but lacks the catalytic His and an intact Ser195/oxyanion-hole motif |
| GO:0004252 serine-type endopeptidase activity | IKR NOT PMID:30367934 Building a platform for predicting functions of serine prote... | ACCEPT | Summary: Accepted as a negated catalytic annotation supported by the 2018 S1-family reclassification of Drosophila SPs and SPHs. Reason: Cao and Jiang classified Drosophila S1-family proteins as SPs or SPHs by presence or absence of the His-Asp-Ser triad; the cached text does not name Scaf in a quotable sentence, so the gene-level call is supported independently. UniProt's curated caution records loss of the conserved triad residues, and the re-review alignment shows the catalytic His and the Ser195 motif are substituted while the S1 fold is retained. This is consistent with the other negated catalytic rows. Supporting Evidence: PMID:30367934 based on the presence or absence of the His-Asp-Ser catalytic triad as described file:DROME/scaf/scaf-uniprot.txt Lacks the conserved residues within the catalytic triad, probably resulting in a loss of proteolytic activity. file:DROME/scaf/scaf-bioinformatics/RESULTS.md The His57 motif reads LSSASC in Scaf where active S1 proteases have the TAAHC motif, so the catalytic histidine is replaced by serine. |
| GO:0005576 extracellular region | EXP PMID:15342518 A piggyBac transposon gene trap for the analysis of gene exp... | ACCEPT | Summary: Accepted: a PBss Scarface-EGFP protein trap supports inference of the trapped protein's extracellular localization. Reason: Bonin and Mann established the PBss system in which predicted protein-EGFP fusions report the localization of the trapped wild-type product. Later Scaf studies used that trap and direct tagged-protein experiments to show a signal sequence, extracellular distribution and secretory behavior, so the curator-assigned experimental extracellular annotation is consistent with subsequent Scaf-specific evidence. Supporting Evidence: PMID:15342518 In those instances where protein-EGFP fusions are predicted to occur, the subcellular localization of the wild-type protein can be inferred from the localization of the EGFP fusion protein. PMID:25737837 Scarface protein contains a signal sequence and has been demonstrated to be a secreted protein |
| GO:0005576 extracellular region | IBA GO_REF:0000033 | ACCEPT | Summary: Accepted: the PAINT node PANTHER:PTN000667087 transfers the conserved secreted/extracellular localization of CLIP-domain serine protease homologs to Scaf. Reason: Scaf is experimentally observed as a secreted/extracellular protein by the original protein trap and by direct Scaf studies. The target's own FlyBase gene, FB:FBgn0033033, appears in the WITH/FROM list because its experimental localization helped seed the ancestral node; this is the expected self-seed pattern for an IBA, not circular evidence. The inherited extracellular-region assertion is therefore sound for Q7K5M0. Propagation Review Root cause: NO FAILURE CORE Sources checked: PANTHER:PTN000667087 SUPPORTS TRANSFER Proximate PAINT node from the GOA WITH/FROM list. Scaf itself has direct extracellular evidence among the descendants, and the target self-seed is legitimate experimental grounding of the inherited node assertion. Supporting Evidence: PMID:25737837 Scarface protein contains a signal sequence and has been demonstrated to be a secreted protein PMID:42531335 These results are consistent with Scaf being a secreted protein. |
| GO:0005576 extracellular region | IDA PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | ACCEPT | Summary: Accepted: Sorrosal et al. directly support Scaf as a secreted extracellular serine-protease-like protein in embryos. Reason: Sorrosal et al. analyzed Scaf as a secreted serine-protease-like protein and linked its extracellular action to polarized Laminin A localization. The row records the functional site, while the endosomal colocalization rows from the same paper capture trafficking compartments. Supporting Evidence: PMID:20379222 Here, in Drosophila, we analyse the role of the secreted serine protease-like protein Scarface in germ-band retraction and dorsal closure-morphogenetic processes that rely on the activity of integrins and laminins. |
| GO:0005576 extracellular region | IDA PMID:20530545 The Drosophila serine protease homologue Scarface regulates ... | ACCEPT | Summary: Accepted: Rousset et al. identify scaf as encoding a secreted SPH during JNK-regulated epithelial morphogenesis. Reason: The 2010 Development paper places Scaf in a secreted negative-feedback loop downstream of JNK. Together with independent embryonic, wing-disc and regeneration studies, this supports extracellular region as the main action site for the gene product. Supporting Evidence: PMID:20530545 Here, we show that scaf is a general transcriptional target of the JNK pathway coding for a secreted SPH. PMID:42531335 Scaf was the other ECM protein we found with a role in hinge-to-pouch fate change and translocation. |
| GO:0005576 extracellular region | IEA GO_REF:0000044 | ACCEPT | Summary: Accepted: UniProtKB-SubCell transfer of extracellular localization agrees with Scaf's signal peptide and direct secretion/localization experiments. Reason: This automatic mapping is broad but biologically correct for Q7K5M0. Multiple independent experimental studies describe Scaf as secreted or extracellular, so the UniProtKB-SubCell assertion is aligned with the literature rather than an isolated prediction. Supporting Evidence: PMID:25737837 Scarface protein contains a signal sequence and has been demonstrated to be a secreted protein |
| GO:0005737 cytoplasm | IDA PMID:25737837 Regulation of a serine protease homolog by the JNK pathway d... | KEEP AS NON CORE | Summary: Kept as non-core: Scarface protein trap signal was predominantly cytoplasmic in producing peripodial cells, but this is not its final extracellular site of action. Reason: Srivastava and Dong observed Scarface-GFP in the wing-disc hinge, peripodial stalk and peripodial membrane, and reported cytoplasmic signal excluded from nuclei in peripodial cells. Because Scaf is secreted, the intracellular signal most likely reflects synthesis and trafficking. Supporting Evidence: PMID:25737837 Confocal scans of wing discs from the protein trap demonstrated that the Scarface protein is expressed in the hinge region PMID:25737837 In these peripodial cells, Scarface is excluded from the nucleus and is found predominantly in the cytoplasm |
| GO:0005769 early endosome | IDA PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | KEEP AS NON CORE | Summary: Kept as non-core: early-endosome colocalization marks Scaf trafficking, not the final extracellular functional compartment. Reason: Sorrosal et al. experimentally examined Scaf during secretion and endosomal trafficking while studying how it regulates Laminin A polarity. The early endosome row should be preserved as direct trafficking evidence, but extracellular region is the core localization. Supporting Evidence: PMID:20379222 We propose that Scarface has a key role in regulating the polarized localization of laminin A in this developmental context. |
| GO:0005770 late endosome | IDA PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | KEEP AS NON CORE | Summary: Kept as non-core: late-endosome colocalization is compatible with secretory/endosomal routing of a protein whose key role is extracellular. Reason: The 2010 EMBO Reports paper connects Scaf to polarized Laminin A localization and used endosomal colocalization to probe trafficking. Keeping this row captures that direct localization assay without elevating late endosomes over the extracellular epithelial environment. Supporting Evidence: PMID:20379222 We propose that Scarface has a key role in regulating the polarized localization of laminin A in this developmental context. |
| GO:0006508 proteolysis | IEA GO_REF:0000002 | REMOVE | Summary: Removed: the InterPro trypsin-domain mapping asserts proteolysis for catalytically inactive Scaf despite accepted NOT peptidase annotations. Reason: The IPR001254 mapping infers proteolysis from the retained trypsin/peptidase-S1 fold, but Scaf's GOA set also carries multiple accepted NOT peptidase annotations because Scaf lacks the catalytic residue set needed for peptide-bond hydrolysis. A noncatalytic SPH could regulate an extracellular protease cascade, but the cached Scaf literature has not shown Scaf hydrolyzing peptide bonds or participating directly in proteolysis. This positive IEA should therefore be removed rather than retained as a broad process annotation. Supporting Evidence: file:DROME/scaf/scaf-bioinformatics/RESULTS.md the His57 substitution alone is sufficient to rule out the canonical charge-relay mechanism PMID:20530545 We finally demonstrate that scaf acts as an antagonist by negatively regulating JNK activity. |
| GO:0007390 germ-band shortening | IMP PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | ACCEPT | Summary: Accepted: scaf mutant embryos have germ-band retraction and closure phenotypes tied to defective Laminin A polarity. Reason: Germ-band shortening is one of the morphogenetic events disrupted in scaf mutant embryos in the same Laminin-polarity study. Scaf functions as a secreted regulator of cell-matrix organization in the epithelial context that executes this process, so the annotation should remain. Supporting Evidence: PMID:20379222 Here, in Drosophila, we analyse the role of the secreted serine protease-like protein Scarface in germ-band retraction and dorsal closure-morphogenetic processes that rely on the activity of integrins and laminins. PMID:20379222 scarface mutant embryos show defects in these morphogenetic processes |
| GO:0007391 dorsal closure | IMP PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | ACCEPT | Summary: Accepted: Sorrosal et al. directly implicate Scaf in embryonic dorsal closure through secreted control of Laminin A polarity. Reason: The same scaf mutant phenotype that perturbs germ-band retraction also disrupts dorsal closure, and the paper links those process defects to abnormal apical Laminin A accumulation before epithelial polarity is lost. This is a direct developmental role rather than a distant pleiotropic consequence. Supporting Evidence: PMID:20379222 scarface mutant embryos show defects in these morphogenetic processes PMID:20379222 Anomalous accumulation of laminin A on the apical surface of epithelial cells was observed in these embryos before a loss of epithelial polarity was induced. |
| GO:0007391 dorsal closure | IMP PMID:20530545 The Drosophila serine protease homologue Scarface regulates ... | ACCEPT | Summary: Accepted: an independent JNK-feedback study showed that scaf loss-of-function disrupts embryonic dorsal closure. Reason: Rousset et al. identified scaf as a JNK-induced secreted SPH and observed defects in JNK-controlled morphogenesis, including embryonic dorsal closure, in scaf loss-of-function animals. This independently reinforces the Sorrosal et al. Laminin-polarity phenotype. Supporting Evidence: PMID:20530545 scaf loss-of-function induces defects in JNK-controlled morphogenetic events such as embryonic dorsal closure and adult male terminalia rotation. |
| GO:0007394 dorsal closure, elongation of leading edge cells | IMP PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | ACCEPT | Summary: Accepted: Scaf acts in the dorsal-closure epithelial program assayed by leading-edge and Laminin A polarity phenotypes. Reason: The term is a specific sub-process of the Scaf-dependent dorsal-closure phenotype reported in scaf mutant embryos. The evidence is tied to epithelial sheet morphogenesis and cell-matrix organization, which is the recurring direct role for secreted Scaf. Supporting Evidence: PMID:20379222 scarface mutant embryos show defects in these morphogenetic processes |
| GO:0007560 imaginal disc morphogenesis | IMP PMID:25737837 Regulation of a serine protease homolog by the JNK pathway d... | ACCEPT | Summary: Accepted: scaf knockdown in wing imaginal disc domains causes thoracic cleft phenotypes that phenocopy defective JNK-dependent disc morphogenesis. Reason: Srivastava and Dong showed that Scarface is expressed in the developing wing disc under JNK control and that RNAi in Apterous- or Pannier-positive thoracic tissue produces cleft thorax phenotypes. The annotation is broad but still directly describes the affected imaginal-disc morphogenesis. Supporting Evidence: PMID:25737837 down-regulation of scarface results in a thoracic-cleft phenotype that phenocopies the JNK pathway defect. PMID:42531335 Functional validation using RNA interference revealed that secreted Matrix Metalloprotease 1 (Mmp1) and the related secreted protease homolog Scarface (Scaf) are required in hinge cells for IR-induced cell fate conversion and translocation. |
| GO:0008233 peptidase activity | IKR NOT GO_REF:0000047 | ACCEPT | Summary: Accepted: the key-residue rule correctly negates generic peptidase activity for catalytically inactive Scaf. Reason: Scaf retains a peptidase S1 domain but lacks the catalytic residue set needed for peptide-bond hydrolysis. The NOT assertion is consistent with the more specific negated serine-type endopeptidase rows and with the PTHR24250 review. Supporting Evidence: PMID:30367934 SPHs are enzymatically inactive due to the lack of catalytic residue(s) but some of them (e.g. Masquerade) have known regulatory functions |
| GO:0016324 apical plasma membrane | IDA PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | KEEP AS NON CORE | Summary: Kept as non-core: apical membrane colocalization reflects trafficking or a local pool of Scaf observed while Laminin A becomes mislocalized. Reason: Sorrosal et al. investigated Scaf secretion and membrane/endosomal trafficking in the context of apical Laminin A misaccumulation. The apical colocalization row should be retained as direct assay evidence, while the extracellular matrix-facing secreted protein is the core functional species. Supporting Evidence: PMID:20379222 Anomalous accumulation of laminin A on the apical surface of epithelial cells was observed in these embryos before a loss of epithelial polarity was induced. |
| GO:0045087 innate immune response | IBA GO_REF:0000033 | UNDECIDED | Summary: Undecided: PTN000667087 transfers innate immune response from CLIP/S1 immune descendants, but leaf evidence does not yet settle whether this process was inherited by Scaf. Reason: PTN000667087 is an ecdysozoan-level node (taxon:1206794). Its immune IBD is seeded by Drosophila Toll- and melanization-cascade CLIP proteases (psh, grass, SPE, modSP, MP1 and others) and by Anopheles CLIPA8 (A0A1S4H5S2), a catalytically inactive CLIP-SPH. Because a noncatalytic SPH is among the donors, Scaf's loss of the catalytic His does not by itself place Scaf outside the inherited function. Scaf has a CLIP domain and direct cached evidence for extracellular epithelial morphogenesis, JNK feedback, Laminin A polarity, thorax closure and radiation-induced hinge plasticity, but no cached Scaf paper or FlyBase experimental BP row reports an innate-immune phenotype. Scaf orthologs carry a lineage-specific Scarface-type CLIP domain (Pfam PF18399) and their PANTHER placement is unstable (UniProt PTHR24250:SF27; PANTHER 19.0 PTHR24260:SF145; insect orthologs scattered over PTHR24250/24252/24256/24258), so whether the Scarface clade sits inside the branch that inherited the immune role cannot be settled from the classification alone. There is no target-specific evidence of loss, and no evidence of the function, so the IBA remains undecided rather than removed. Propagation Review Root cause: UNRESOLVED Sources checked: PANTHER:PTN000667087 UNRESOLVED The PTHR24250 PAINT fetch places the immune IBD on the same ancestor as Scaf's extracellular localization IBD. The source evidence supports immune roles in several CLIP/S1 descendants, but direct Scaf evidence is developmental and extracellular, and this pass did not establish whether Scaf inherited or lost the immune role. Supporting Evidence: PMID:30367934 SPHs are enzymatically inactive due to the lack of catalytic residue(s) but some of them (e.g. Masquerade) have known regulatory functions PMID:20379222 Here, in Drosophila, we analyse the role of the secreted serine protease-like protein Scarface in germ-band retraction and dorsal closure-morphogenetic processes that rely on the activity of integrins and laminins. PMID:42531335 Scaf was the other ECM protein we found with a role in hinge-to-pouch fate change and translocation. |
| GO:0045197 establishment or maintenance of epithelial cell apical/basal polarity | IMP PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | ACCEPT | Summary: Accepted: scaf loss disrupts polarized Laminin A localization before epithelial polarity defects emerge. Reason: This captures a mechanistically central phenotype from Sorrosal et al.: secreted Scaf regulates the polarized distribution of Laminin A at the basement membrane. Since the apical Laminin A defect precedes loss of epithelial polarity, Scaf's involvement is close to the cell-matrix event that the GO term describes. Supporting Evidence: PMID:20379222 Anomalous accumulation of laminin A on the apical surface of epithelial cells was observed in these embryos before a loss of epithelial polarity was induced. |
| GO:0048802 notum morphogenesis | IMP PMID:25737837 Regulation of a serine protease homolog by the JNK pathway d... | ACCEPT | Summary: Accepted: scaf RNAi in the notum-forming region of the wing disc causes a thoracic cleft. Reason: The Pannier and Apterous driver experiments knock down scaf in the future-thorax/notum territory and generate thoracic cleft phenotypes. This is the appropriate specific developmental-process annotation for the 2015 thorax-closure result. Supporting Evidence: PMID:25737837 scarface knockdown using the Ap-Gal4 driver resulted in loss of bristles from the medio-lateral region of the thorax and the thorax displayed a mild thoracic cleft PMID:25737837 scarface knockdown using the Pnr-Gal4 driver resulted in a much stronger thoracic cleft and loss of bristles from the medio-lateral region of the thorax |
| GO:0048803 imaginal disc-derived male genitalia morphogenesis | IGI PMID:20530545 The Drosophila serine protease homologue Scarface regulates ... | ACCEPT | Summary: Accepted: genetic interaction evidence places scaf in JNK-regulated pupal genital-disc epithelial fusion and male terminalia rotation. Reason: Rousset et al. reported that scaf loss-of-function perturbs adult male terminalia rotation, a JNK-controlled morphogenetic event analogous to embryonic dorsal closure. The IGI row should be retained as a process-level annotation for that developmental context. Supporting Evidence: PMID:20530545 scaf loss-of-function induces defects in JNK-controlled morphogenetic events such as embryonic dorsal closure and adult male terminalia rotation. |
| GO:0048803 imaginal disc-derived male genitalia morphogenesis | IMP PMID:20530545 The Drosophila serine protease homologue Scarface regulates ... | ACCEPT | Summary: Accepted: scaf mutant phenotypes directly support a role in imaginal-disc-derived male genitalia morphogenesis. Reason: This duplicate GO term is supported by mutant phenotype rather than genetic interaction and should be kept. The 2010 JNK-feedback study directly connects secreted Scaf to the epithelial fusion process that rotates the pupal genital disc. Supporting Evidence: PMID:20530545 Live imaging of the latter process reveals that, like for dorsal closure, JNK directs the dorsal fusion of two epithelial layers in the pupal genital disc. |
| GO:0050793 regulation of developmental process | IMP PMID:25737837 Regulation of a serine protease homolog by the JNK pathway d... | MARK AS OVER ANNOTATED | Summary: Marked as over-annotated: the 2015 thorax study is already captured by more informative notum and imaginal-disc morphogenesis rows. Reason: scaf knockdown in wing-disc domains produced thoracic clefts, and the same paper already supports the better-scoped notum morphogenesis and imaginal disc morphogenesis rows. The RNAi phenotype shows that Scaf is required for thorax closure; it does not show Scaf regulating developmental processes in general, and its regulatory role is better expressed by the JNK-antagonist evidence (negative regulation of JNK cascade, proposed as NEW). The generic term is an over-annotation of the phenotype rather than a distinct claim. Supporting Evidence: PMID:25737837 down-regulation of scarface results in a thoracic-cleft phenotype that phenocopies the JNK pathway defect. |
| GO:0055037 recycling endosome | IDA PMID:20379222 Scarface, a secreted serine protease-like protein, regulates... | KEEP AS NON CORE | Summary: Kept as non-core: recycling-endosome colocalization is trafficking evidence for secreted Scaf. Reason: The recycling-endosome signal belongs to the Sorrosal et al. trafficking analysis of how Scaf moves through cells that secrete it. It is useful evidence but not the destination where Scaf's JNK and Laminin-polarity functions are executed. Supporting Evidence: PMID:20379222 We propose that Scarface has a key role in regulating the polarized localization of laminin A in this developmental context. |
| GO:0046329 negative regulation of JNK cascade | IMP PMID:20530545 The Drosophila serine protease homologue Scarface regulates ... | NEW | Summary: New: scaf loss mimics JNK over-activity and scaf over-expression suppresses JNK target output, establishing secreted Scaf as a negative-feedback antagonist of JNK signaling. Reason: This is the best-supported statement of what Scaf does, and it is not captured by any existing row. Rousset et al. conclude that scaf negatively regulates JNK activity, from loss-of-function mimicking JNK over-activity and from enhancement of the puc (JNK phosphatase) genitalia phenotype by ectopic scaf. Kushnir et al. independently show that scaf over-expression suppresses, and scaf loss expands, JNK-dependent dpp expression and pMad in the dorsal ectoderm, and that scaf is epistatic to rhomboid for this output. This is a regulation claim, not participation in the kinase cascade: Scaf is the regulator, acting extracellularly on an unidentified target, which matches the GO usage for secreted pathway antagonists. Comparator check: the intracellular feedback inhibitor puc carries this term; no secreted JNK antagonist other than Scaf is described in Drosophila. Supporting Evidence: PMID:20530545 Genetic data show that scaf loss-of-function mimics JNK over-activity. PMID:20530545 We finally demonstrate that scaf acts as an antagonist by negatively regulating JNK activity. PMID:28628612 These observations support a role for Scaf as a suppressor of Dpp signaling in the dorsal ectoderm. |
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Download this section (compressed HTML)Q: Which extracellular protein, receptor, or protease cascade is the direct target of catalytically inactive Scaf during Laminin A polarization and JNK feedback?
Q: Does radiation-induced Scaf use the same extracellular mechanism as embryonic dorsal closure and thorax closure, or a regeneration-specific branch downstream of JNK?
Experiment: Identify the direct extracellular binding partner of Scaf (for example by affinity purification of tagged secreted Scaf from leading-edge-enriched tissue or S2 conditioned medium followed by mass spectrometry), and test whether candidate receptors or proteases are required for Scaf-mediated suppression of JNK targets.
Hypothesis: Secreted Scaf antagonizes JNK signaling by binding an extracellular ligand, receptor or protease rather than by proteolysis.
Experiment: Test whether the Scaf peptidase S1 domain is sufficient for JNK antagonism, and whether restoring His465 and the Ser195 motif changes activity, to distinguish a noncatalytic binding mechanism from any residual protease function.
Hypothesis: The JNK-antagonist activity of Scaf does not require catalysis.
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