AIGR Deep Research — K9IFT7 (DESRO): beta-defensin orthology and CCR6 binding OpenScientist openscientist-autonomous 4 artifacts 2026-09-21T01:15:47.419244

OpenScientist final report (text/html)

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OpenScientist K9IFT7 GO decision table (text/csv)

OpenScientist K9IFT7 evidence matrix (text/csv)

AIGR Deep Research — K9IFT7 (DESRO): beta-defensin orthology and CCR6 binding

Gene: K9IFT7 / Desmodus rotundus (vampire bat, NCBITaxon:9430) — GenBank JAA44743.1, RefSeq XP_071076263.1
Focus: function_assignment — does K9IFT7 directly have GO:0031731 "CCR6 chemokine receptor binding"?
Source: genes/DESRO/K9IFT7/K9IFT7-ai-review.yaml (free-text seed)

Executive Judgment

Verdict: PARTIALLY SUPPORTED (homology-plausible but unverified; not the core function).

Orthology to the beta-defensin-1 (DEFB1) subfamily is well supported. K9IFT7 is a canonical 67-aa beta-defensin (Pfam PF00711, InterPro IPR001855, PANTHER PTHR21388:SF9 "BETA-DEFENSIN 1", SUPFAM SSF57392), with the intact 6-cysteine motif (inter-Cys gaps 7-5-10-7-1), cationic net charge (+4), and highest mature-peptide identity to human DEFB1 (hBD-1, 59.1%) among the human panel tested (hBD-3 53.7%, DEFB118 52.3%, hBD-2 40.9%, hBD-4 36.4%). Identity is only moderate, and bat beta-defensins are an expanded, fast-evolving multigene family, so strict 1:1 orthology to DEFB1 is not proven.
CCR6 binding (GO:0031731) is a phylogenetic prediction, evidence code IEA:TreeGrafter — grafted onto the DEFB1 subfamily. There is no direct assay of K9IFT7 or any bat defensin.
The prediction is plausible because the closest human ortholog, DEFB1, has direct experimental CCR6 interaction (PMID 25122636), and K9IFT7 retains a documented CCR6-chemotaxis determinant (N-terminal Leu; PMID 20022113).
But it is contested and non-core. Whether CCR6 is a genuine functional beta-defensin receptor has been directly challenged (PMID 17705135), beta-defensins also use CCR2 (PMID 20483750), and receptor usage varies by defensin/cell type (hBD-1 ≠ hBD-2 for neutrophils, PMID 15009427). The gene's documented role (Vampirome, PMID 23411029) is salivary-gland antimicrobial defense, not chemotaxis.

Bottom line for the curator: the CCR6-binding term is defensible only as a low-confidence, homology-transferred (IEA), non-core molecular function. Do not upgrade it to an experimental code; do not treat the absence of a bat assay as refutation. The best-supported annotations are antimicrobial defense response and extracellular localization.

Evidence Matrix

Citation	Evidence type	Supports/Refutes/Qualifies/Competing	Claim tested	Key finding	Context	Confidence & limitations
UniProt K9IFT7 (DB record)	computational/database	Qualifies	Term provenance	GO:0031731 is IEA:TreeGrafter (phylogenetic graft to PANTHER SF9 "beta-defensin 1"); no experimental code	D. rotundus TrEMBL entry	High that it is IEA; weakest GO evidence tier
This report (NW alignment)	structural/evolutionary (computational)	Supports (orthology)	Which human defensin is closest	Mature K9IFT7 most identical to DEFB1/hBD-1 (59.1%); canonical 6-Cys motif, net +4, N-term Leu	in-silico vs human panel	Moderate; simple global alignment, not a phylogeny/tree reconciliation
PMID 23411029 (Vampirome)	localization/expression (primary)	Qualifies/Competing	Documented function	Bat salivary accessory submandibular gland antimicrobial (with lysozyme, lactotransferrin); no CCR6 assay	D. rotundus glands, RNA-seq + LC-MS/MS	High for antimicrobial/secreted role; silent on CCR6
PMID 10521347 (Yang 1999, Science)	direct assay/binding (primary)	Supports (family-level)	Beta-defensin–CCR6 binding	Human beta-defensin chemotactic via CCR6; competitively displaced ¹²⁵I-LARC/CCL20 on CCR6 transfectants (foundational MF evidence)	CCR6-transfected cells, iDC, memory T cells	High; peptide used was primarily hBD-2, not DEFB1/hBD-1
PMID 25122636 (Diao 2014)	direct interaction (primary)	Supports	Ortholog CCR6 binding	Human DEFB1 interacts with CCR6 and triggers Ca²⁺ mobilization	Human sperm	High for DEFB1; different tissue/species than K9IFT7
PubMed (no hits)	absence of evidence	Qualifies	Bat defensin function	No functional characterization of any chiropteran/bat beta-defensin (CCR6 or antimicrobial assay) was found	Chiroptera	Confirms annotation rests entirely on cross-mammal homology
PMID 29207656	direct assay (primary)	Supports	CCR6 as DEFB1-linked receptor	CCR6 required for ligand-induced CatSper activation	Human sperm	Corroborates DEFB1–CCR6 axis
PMID 20022113 (Tyrrell 2010)	mutant/structure-function (primary)	Supports (plausibility)	CCR6 determinants	N-terminal Leu/Ile essential for CCR6 chemotaxis; K9IFT7 mature N-term = Leu	Defb14 peptide derivatives	Determinant present in K9IFT7 = plausibility, not proof
PMID 17705135 (Soruri 2007)	direct assay (primary)	Competing/Refutes (family-level)	Is CCR6 a real beta-defensin receptor	"CCR6 is not a functional receptor for beta-defensins"; CCR6-transfectants unresponsive to hBD-2/-3	Human/murine cells, CCR6 transfectants	Direct conflict; challenges the whole annotation basis
PMID 20483750 (Röhrl 2010)	direct interaction (primary)	Qualifies/Competing	Receptor exclusivity	hBD-2/-3 (and mouse orthologs) bind CCR2, not only CCR6	HEK293-CCR2, human monocytes	Shows multiple receptors; CCR6 not sole/obligate
PMID 15009427 (Niyonsaba 2004)	direct assay (primary)	Qualifies	hBD-1 vs hBD-2 receptor usage	"hBD-2, but not hBD-1" chemoattracts neutrophils via CCR6	TNF-treated human neutrophils	Receptor/activity is defensin- and cell-type-specific
PMID 21434867 (Morgera 2011)	cellular assay (primary)	Qualifies	CCR6 dependence	iDC responses to hBD2 occur via "CCR6-dependent and -independent" mechanisms	Human iDC/monocytes	CCR6 partial contributor

GO Curation Implications

GO:0031731 "CCR6 chemokine receptor binding" (MF): Evidence supports retaining it only as a low-confidence, homology-based (IEA) prediction flagged non-core. It should not be generalized to bare "protein binding" (uninformative) nor promoted to an experimental code. A curator may reasonably choose to (a) keep the IEA as-is with a not-core note, or (b) down-weight/remove it given the direct family-level conflict (PMID 17705135) and the lack of any bat/DEFB1-ortholog-specific salivary assay. Lead, requires curator verification.
Better-supported annotations to prioritize: GO:0050830 / GO:0050829 (defense response to Gram-positive/negative bacterium, BP), GO:0002227 (innate immune response in mucosa, BP), GO:0005576 (extracellular region, CC) — all consistent with the primary Vampirome evidence (PMID 23411029) and the Pfam/InterPro defensin identity. These represent the gene product's core function.
If any experimental-code MF for receptor binding is ever added, it must derive from an assay of K9IFT7 (or a demonstrated bat DEFB1 ortholog), not transfer from human DEFB1.

Mechanistic Scope

The tested molecular function is direct binding of the secreted mature beta-defensin peptide to the CC chemokine receptor CCR6 (a GPCR), which for human beta-defensins couples to Gαi and drives chemotaxis of immature dendritic cells / memory T cells and Ca²⁺ mobilization. This is distinct from, and must be separated from:
- Antimicrobial activity (membrane-disruptive killing of bacteria/fungi) — the evidenced core role in bat saliva.
- Salivary/glandular expression (localization, not activity).
- Chemotaxis via other receptors (CCR2, or CCR6-independent membrane effects).
For K9IFT7 specifically, CCR6 binding is inferred by homology, not demonstrated; the antimicrobial role is documented.

Conflicts and Alternatives

Family-level receptor conflict: PMID 17705135 directly reports CCR6 is not a functional beta-defensin receptor — a fundamental challenge to the annotation's premise.
Multiple/alternative receptors: CCR2 usage (PMID 20483750) and CCR6-independent mechanisms (PMID 21434867) mean "CCR6 binding" may overstate specificity.
Defensin-specific variability: hBD-1 behaves differently from hBD-2 (PMID 15009427); transferring a CCR6 phenotype across the whole SF9 subfamily risks paralog over-annotation.
Orthology uncertainty: 59% mature identity to DEFB1 with an expanded bat beta-defensin repertoire means K9IFT7 may be a bat-specific paralog rather than a true DEFB1 ortholog; TreeGrafter subfamily assignment can misplace fast-evolving lineage-specific defensins.
Context mismatch: the strongest DEFB1–CCR6 evidence is in human sperm (PMID 25122636/29207656), a context unrelated to a bat salivary antimicrobial.

Knowledge Gaps

Gap	What was checked	Why it matters	Resolving evidence
No assay of K9IFT7 (or any bat defensin) vs CCR6	PubMed; Vampirome	Annotation rests entirely on homology transfer	Direct binding/chemotaxis assay of recombinant K9IFT7 on CCR6⁺ cells
True orthology (DEFB1 vs bat-specific paralog)	NW identity, PANTHER SF9	Determines validity of subfamily transfer	Phylogenetic tree reconciliation of chiropteran beta-defensin cluster; synteny
Correct mature N-terminus / cleavage	UniProt Chain 24-67 vs domain 34-66	N-terminal Leu is a CCR6 determinant; propiece removal could alter it	Proteomic N-terminal sequencing of the salivary peptide
Whether CCR6 is a genuine receptor at all	PMID 17705135 vs 25122636	Field disagreement undermines the term	Reproducible receptor-transfectant binding across labs

Discriminating Tests

Direct receptor assay: recombinant/synthetic K9IFT7 (correctly folded, 3 disulfides) in a CCR6-transfectant binding + chemotaxis/Ca²⁺-flux assay, with CCR6-knockout and CCL20 competition controls.
Receptor panel: test CCR2 and CCR6 side-by-side to establish specificity vs the known CCR2 cross-reactivity.
Antimicrobial vs chemotactic split: MIC assays (Gram±) to anchor the core function; compare potency to chemotactic EC50.
Phylogenomics: reconcile the D. rotundus beta-defensin cluster against human DEFB1/DEFB4/DEFB103 to confirm or refute DEFB1 orthology and detect lineage-specific expansion.
Structure: AlphaFold model (AlphaFoldDB K9IFT7 exists) + electrostatics to check the CCR6-binding surface and N-terminal helix.

Curation Leads (require curator verification)

Action lead: Keep GO:0031731 only as IEA/homology, non-core, or down-weight/remove; add an explicit note that the sole basis is TreeGrafter transfer from human DEFB1 and that CCR6 as a beta-defensin receptor is contested. Do not replace with generic "protein binding."
Candidate references to attach/verify:
PMID 25122636 — direct human DEFB1–CCR6 interaction (supports, ortholog).
PMID 17705135 — CCR6 not a functional beta-defensin receptor (conflict/caveat).
PMID 20483750 — CCR2 as alternative receptor (caveat).
PMID 20022113 — N-terminal Leu/Ile CCR6 determinant (plausibility).
PMID 23411029 — primary source; salivary antimicrobial role (core function).
Candidate core-function terms to prioritize (better supported): GO:0050830, GO:0050829, GO:0002227 (BP, defense/innate immunity); GO:0005576 (CC).
Suggested curator questions: Is a phylogenetic-only MF receptor-binding term desired on a lineage-specific TrEMBL bat defensin? Should the annotation be qualified with a "non-core"/"inferred" note pending a direct assay?
Suggested experiment: recombinant K9IFT7 CCR6-transfectant binding + chemotaxis assay (see Discriminating Tests).

Provenance Artifacts

Computed tables saved alongside the gene directory (genes/DESRO/K9IFT7/):
- K9IFT7_GO_decision_table.csv — per-term curation leads (MF/BP/CC, evidence codes, basis).
- K9IFT7_evidence_matrix.csv — literature evidence matrix with stance tally.

Orthology identities were computed by Needleman–Wunsch alignment of the K9IFT7 mature peptide against a UniProt-fetched human/mouse beta-defensin panel (executed in-session; DEFB1 59.1% > hBD-3 53.7% > DEFB118 52.3%). The 6-cysteine motif (inter-Cys gaps 7-5-10-7-1), net charge +4, and N-terminal Leu were computed directly from the sequence.

Limitations

TrEMBL (unreviewed) entry; no functional data exist for any chiropteran/bat beta-defensin (PubMed returned no hits), so every functional claim is cross-mammal homology transfer. Orthology inference used a simple global-alignment identity rather than a full phylogeny, and the human mature-peptide boundaries were not cleanly parsed for all panel members (alignments partly include propieces); nonetheless the DEFB1-closest ranking was stable across both runs, with hBD-3 (53.7%) and DEFB118 (52.3%) as near neighbors — i.e., subfamily assignment is confident but exact DEFB1 orthology is only moderately supported. The foundational beta-defensin–CCR6 evidence (Yang 1999, PMID 10521347) used hBD-2; direct DEFB1–CCR6 evidence (Diao 2014, PMID 25122636) is human sperm, a non-salivary context. All computational orthology statements are inference, clearly distinguished from the primary literature.