spz5 (DNT2, neurotrophin 2) encodes a secreted SpΓ€tzle-family cystine-knot protein. Its prepro-protein is cleaved by furin, and it is secreted mainly as the mature cystine-knot domain. DNT2 is a neurotrophin: it binds the Toll-family receptors Toll-6 and Toll-7 and the kinase-less Trk-like receptor Kek-6, and activates NF-kappaB (Dorsal/Dif) and ERK pro-survival signaling. Together with DNT1 it maintains neuronal survival in the embryonic CNS and contributes to motor axon targeting. Produced by muscle, it acts as a retrograde factor at the larval neuromuscular junction, where with Kek-6 and Toll-6 it regulates NMJ growth and structural synaptic plasticity. In the adult brain DNT2 neurons connect with dopaminergic neurons, and DNT2 with Toll-6 and Kek-6 maintains dopaminergic neuron survival, dendrite growth and synaptogenesis, influencing locomotion and long-term memory; in the visual system it promotes neuronal survival together with Toll-2. Spz5 is also a ligand of Toll-1 that contributes to Toll-1 ligand activity in larvae, and apoptotic neurons release processed Spz5 to activate Toll-6 signaling in glia that primes them for engulfment.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0002225 positive regulation of antimicrobial peptide production | IMP PMID:30361090 Characterization of Spz5 as a novel ligand for Drosophila To... | KEEP AS NON CORE | Summary: Nonaka et al. (2018) characterised Spz5 as a Toll-1 ligand using a spz5 null mutant. The cached record is abstract only; the curator annotated an antimicrobial peptide production phenotype from the full text. Reason: Consistent with Spz5 acting as a Toll-1 ligand and with Spz5 cystine-knot activation of the drosomycin promoter through Toll-1 or Toll-7 (Chowdhury et al. 2019). The full text was not available here, so the curator's IMP is deferred to; the immune role is secondary to the neurotrophic function of Spz5. Supporting Evidence: PMID:30361090 Here, we demonstrate that Spz5, a member of the Spz family of proteins, functions as a ligand for the Toll-1 receptor. PMID:30361090 By generating a spz5 null mutant, we further showed that the Toll-1 ligand activity of larva-derived extract is mainly derived from Spz5. PMID:31088910 Results indicated that the cystine knots for Spz-1, -2, and -5 activated the drosomycin promoter in S2 cells expressing full-length Toll-1 492-, 188-, and 122-fold |
| GO:0005121 Toll binding | IBA GO_REF:0000033 | MODIFY | Summary: IBA from PAINT node PTN002354018 (PTHR23199), seeded by spz, spz5, spz6 and NT1. Spz5 binds Toll-6, Toll-7 and Toll-1. Reason: Spz5/DNT2 is a secreted ligand, and Toll binding is the first step of its ligand activity. Under the ligand convention (projects/LIGANDS_IN_SIGNALING.md) the MF of a ligand is receptor ligand activity or a child; the same PAINT node carries growth factor activity (GO:0008083), which fits a neurotrophin and is the replacement. The node placement is sound and spz5 has its own binding evidence. Propagation Review Root cause: TERM SCOPING PROBLEM Failure modes: GRANULARITY MISMATCH Sources checked: PANTHER:PTN002354018 SUPPORTS TRANSFER The node is seeded by experimental Toll-binding annotations of spz, spz5, spz6 and NT1; the binding claim transfers correctly, but for ligands the ligand-activity term carried by the same node (growth factor activity) is the appropriate MF. Proposed replacements: growth factor activity Supporting Evidence: PMID:23892553 Together, these data demonstrate that DNT1 binds Toll-7 and DNT2 binds promiscuously Toll-6 and Toll-7. PMID:28846707 Kek-6 is expressed in the CNS, interacts genetically with DNTs and can bind DNT2 in signaling assays and co-immunoprecipitations. |
| GO:0005121 Toll binding | IDA PMID:31088910 Toll family members bind multiple SpΓ€tzle proteins and activ... | MODIFY | Summary: Co-IP: the Spz-5 cystine knot binds the Toll-1 and Toll-7 ectodomains in S2 cell assays (Chowdhury et al. 2019). Reason: Binding is real but is the binding step of a ligand activity; the same assay shows reporter activation through full-length Toll-1 and Toll-7, which supports receptor ligand activity (GO:0048018), already carried by spz5 from this paper. The split from the IBA row (replaced by its child, growth factor activity) is deliberate; each row is refined to what its own evidence shows, and this reporter assay has no growth or survival readout. Proposed replacements: receptor ligand activity Supporting Evidence: PMID:31088910 Focusing on Toll-1 and Toll-7, our co-IP assays indicate the ectodomains of each bind Spz-1, -2, and -5, but not other family members, while also suggesting that binding of Spz-1, -2, and -5 to full-length Toll-1 or Toll-7 results in activation of the drosomycin promoter. PMID:23892553 Together, these data demonstrate that DNT1 binds Toll-7 and DNT2 binds promiscuously Toll-6 and Toll-7. |
| GO:0005576 extracellular region | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002354018: SpΓ€tzle-family members are secreted cystine-knot proteins. Reason: Spz5 has a signal peptide and is secreted as the cleaved cystine-knot form; it acts as a retrograde, muscle-derived factor at the NMJ. Supporting Evidence: PMID:23892553 whereas DNT2 is consistently secreted from S2 cells as a mature, cleaved form consisting of the cystine-knot domain PMID:28846707 Altogether, our data demonstrate that DNT2 is a retrograde ligand for Kek-6 at the NMJ and that DNT2 and Kek-6 are required together for synaptic structure and NMJ growth. |
| GO:0005576 extracellular region | IDA PMID:31088910 Toll family members bind multiple SpΓ€tzle proteins and activ... | ACCEPT | Summary: Spz-5 cystine knot expressed as a secreted protein recovered from S2 culture medium. Reason: Secretion of DNT2 is independently shown by McIlroy et al. (2013). Supporting Evidence: PMID:23892553 whereas DNT2 is consistently secreted from S2 cells as a mature, cleaved form consisting of the cystine-knot domain |
| GO:0005576 extracellular region | IEA GO_REF:0000117 | ACCEPT | Summary: ARBA electronic mapping to extracellular region. Reason: Correct; consistent with experimental secretion data for DNT2. Supporting Evidence: PMID:23892553 whereas DNT2 is consistently secreted from S2 cells as a mature, cleaved form consisting of the cystine-knot domain |
| GO:0008045 motor neuron axon guidance | IMP PMID:19018662 Drosophila neurotrophins reveal a common mechanism for nervo... | KEEP AS NON CORE | Summary: DNT2 mutant embryos show mild ISNb/d and SNa motor axon targeting defects, enhanced in DNT1 DNT2 double and DNT1 DNT2 spz triple mutants (Zhu et al. 2008). Reason: The phenotype is real but mild in single mutants and mostly revealed in combination with DNT1 and spz; motor axon targeting is a downstream output of DNT2-Toll signaling rather than its core role. Supporting Evidence: PMID:19018662 Both ISNb/d and SNa projections are mildly affected in DNT2e03444/Df(3L)exel6092 mutant embryos. |
| GO:0008063 Toll signaling pathway | IDA PMID:30361090 Characterization of Spz5 as a novel ligand for Drosophila To... | KEEP AS NON CORE | Summary: Nonaka et al. (2018): Spz5 acts as a Toll-1 ligand, and Toll-1 ligand activity of larval extract depends mainly on Spz5. Reason: GO:0008063 is defined by ligand binding to the receptor Toll (Toll-1). Unlike DNT1, Spz5 has Toll-1 evidence from two laboratories: Nonaka et al. (2018) identified Spz5 as a furin-independent Toll-1 ligand and showed with a spz5 null mutant that it supplies most Toll-1 ligand activity of larval extract, and Chowdhury et al. (2019) showed Toll-1 binding and drosomycin activation in S2 cells. The claim is therefore kept, but as non-core: the physiological in vivo function of Spz5 established by multiple groups is neurotrophic signaling through Toll-6, Toll-7 and Kek-6, which is captured by the NEW neurotrophin signaling pathway row. Supporting Evidence: PMID:30361090 Here, we demonstrate that Spz5, a member of the Spz family of proteins, functions as a ligand for the Toll-1 receptor. PMID:30361090 By generating a spz5 null mutant, we further showed that the Toll-1 ligand activity of larva-derived extract is mainly derived from Spz5. |
| GO:0008063 Toll signaling pathway | IDA PMID:31088910 Toll family members bind multiple SpΓ€tzle proteins and activ... | KEEP AS NON CORE | Summary: Chowdhury et al. (2019): the Spz-5 cystine knot binds the Toll-1 ectodomain and activates a drosomycin reporter through full-length Toll-1 in S2 cells. Reason: GO:0008063 is defined by ligand binding to the receptor Toll (Toll-1). Unlike DNT1, Spz5 has Toll-1 evidence from two laboratories: Nonaka et al. (2018) identified Spz5 as a furin-independent Toll-1 ligand and showed with a spz5 null mutant that it supplies most Toll-1 ligand activity of larval extract, and Chowdhury et al. (2019) showed Toll-1 binding and drosomycin activation in S2 cells. The claim is therefore kept, but as non-core: the physiological in vivo function of Spz5 established by multiple groups is neurotrophic signaling through Toll-6, Toll-7 and Kek-6, which is captured by the NEW neurotrophin signaling pathway row. Supporting Evidence: PMID:31088910 Focusing on Toll-1 and Toll-7, our co-IP assays indicate the ectodomains of each bind Spz-1, -2, and -5, but not other family members, while also suggesting that binding of Spz-1, -2, and -5 to full-length Toll-1 or Toll-7 results in activation of the drosomycin promoter. PMID:31088910 Results indicated that the cystine knots for Spz-1, -2, and -5 activated the drosomycin promoter in S2 cells expressing full-length Toll-1 492-, 188-, and 122-fold |
| GO:0008063 Toll signaling pathway | IGI PMID:30361090 Characterization of Spz5 as a novel ligand for Drosophila To... | KEEP AS NON CORE | Summary: Nonaka et al. (2018): genetic interaction between spz and spz5 in developmental processes. Reason: GO:0008063 is defined by ligand binding to the receptor Toll (Toll-1). Unlike DNT1, Spz5 has Toll-1 evidence from two laboratories: Nonaka et al. (2018) identified Spz5 as a furin-independent Toll-1 ligand and showed with a spz5 null mutant that it supplies most Toll-1 ligand activity of larval extract, and Chowdhury et al. (2019) showed Toll-1 binding and drosomycin activation in S2 cells. The claim is therefore kept, but as non-core: the physiological in vivo function of Spz5 established by multiple groups is neurotrophic signaling through Toll-6, Toll-7 and Kek-6, which is captured by the NEW neurotrophin signaling pathway row. Supporting Evidence: PMID:30361090 Finally, we found a genetic interaction between spz and spz5 in terms of developmental processes. PMID:30361090 Here, we demonstrate that Spz5, a member of the Spz family of proteins, functions as a ligand for the Toll-1 receptor. |
| GO:0008083 growth factor activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN002354018, seeded by spz, spz5 and NT1 experimental annotations. Reason: Growth factor activity is a child of receptor ligand activity and is the best-fitting ligand term for a neurotrophin that promotes neuronal survival, neurite growth and synaptogenesis. spz5 is within the clade and has its own experimental support. Supporting Evidence: PMID:23892553 Together, these data demonstrate that DNT1 binds Toll-7 and DNT2 binds promiscuously Toll-6 and Toll-7. PMID:39704728 Loss of function for DNT-2 or its receptors Toll-6 and kinase-less Trk-like kek-6 caused DAN and synapse loss, impaired dendrite growth and connectivity, decreased synaptic sites, and caused locomotion deficits. |
| GO:0008083 growth factor activity | IMP PMID:19018662 Drosophila neurotrophins reveal a common mechanism for nervo... | ACCEPT | Summary: Expression of the DNT2 cystine knot in neurons rescues naturally occurring cell death, and DNT1 DNT2 double mutants have more apoptosis (Zhu et al. 2008). Reason: Core molecular function: DNT2 is a secreted neurotrophic ligand of Toll-6, Toll-7 and Kek-6 that promotes neuronal survival, dendrite growth and synaptogenesis. Supporting Evidence: PMID:19018662 Expressing DNT2 or activated Toll in all CNS neurons also rescues NOCD. PMID:19018662 indicating redundancy between DNT1 and DNT2 for cell survival PMID:39704728 Loss of function for DNT-2 or its receptors Toll-6 and kinase-less Trk-like kek-6 caused DAN and synapse loss, impaired dendrite growth and connectivity, decreased synaptic sites, and caused locomotion deficits. |
| GO:0021556 central nervous system formation | IBA GO_REF:0000033 | MARK AS OVER ANNOTATED | Summary: IBA from PTN002354018, seeded by NT1 and spz5 IMP rows from Zhu et al. (2008). Reason: The seed phenotypes are late neuronal apoptosis and motor axon misrouting, with some abnormal embryos in a minority of mutants; DNT loss does not prevent the CNS from forming. Specific terms (negative regulation of neuron apoptotic process, motor neuron axon guidance) capture the function. Propagation Review Root cause: SOURCE WEAK OR INFERRED Failure modes: SOURCE EVIDENCE WEAK GRANULARITY MISMATCH Sources checked: PANTHER:PTN002354018 SOURCE WEAK OR INFERRED The IBD for central nervous system formation is seeded only by the NT1 and spz5 IMP rows from Zhu et al. 2008, whose phenotypes are late neuronal apoptosis and axon misrouting rather than failed CNS formation. Supporting Evidence: PMID:19018662 Loss of DNT1, spz, Toll, or DNT2 function does not cause massive CNS neuronal death either. PMID:19018662 Both ISNb/d and SNa projections are mildly affected in DNT2e03444/Df(3L)exel6092 mutant embryos. |
| GO:0021556 central nervous system formation | IMP PMID:19018662 Drosophila neurotrophins reveal a common mechanism for nervo... | MARK AS OVER ANNOTATED | Summary: Zhu et al. (2008): DNT2 mutants show increased CNS apoptosis, mild axon targeting defects, and some embryos with abnormal morphology and CNS defects. Reason: Central nervous system formation overstates the phenotype; the abnormal-morphology embryos are a minority and the main defects are late neuronal death and targeting errors, annotated with specific terms. Supporting Evidence: PMID:19018662 Some stage 13β16 spz2 and DNT2e03444 mutant embryos have abnormal morphology and CNS defects PMID:19018662 Loss of DNT1, spz, Toll, or DNT2 function does not cause massive CNS neuronal death either. |
| GO:0031637 regulation of neuronal synaptic plasticity in response to neurotrophin | IMP PMID:19018662 Drosophila neurotrophins reveal a common mechanism for nervo... | ACCEPT | Summary: Annotated from Zhu et al. (2008). Later work shows DNT2 is a muscle-derived retrograde ligand that regulates NMJ growth and structural synaptic plasticity with Kek-6 and Toll-6, and drives synaptogenesis in an adult dopaminergic circuit. Reason: The claim that DNT2 regulates neuronal synaptic plasticity as a neurotrophin is well supported by Ulian-Benitez et al. (2017) and Sun et al. (2024), although the cited 2008 paper shows survival and targeting rather than plasticity. Supporting Evidence: PMID:28846707 Altogether, our data demonstrate that DNT2 is a retrograde ligand for Kek-6 at the NMJ and that DNT2 and Kek-6 are required together for synaptic structure and NMJ growth. PMID:28846707 Instead, Kek-6 and Toll-6 interact physically, and together regulate structural synaptic plasticity and homeostasis. PMID:39704728 Loss of function for DNT-2 or its receptors Toll-6 and kinase-less Trk-like kek-6 caused DAN and synapse loss, impaired dendrite growth and connectivity, decreased synaptic sites, and caused locomotion deficits. |
| GO:0043524 negative regulation of neuron apoptotic process | IGI PMID:19018662 Drosophila neurotrophins reveal a common mechanism for nervo... | ACCEPT | Summary: DNT1 DNT2 double mutants have more CNS apoptosis than single mutants, and neuronal DNT2 expression rescues naturally occurring cell death (Zhu et al. 2008). Reason: Neuronal survival is a core DNT2 function, acting through Toll-6 (embryonic CNS; PAM dopaminergic neurons) and Toll-2 (visual system), via NF-kB/ERK signaling. Supporting Evidence: PMID:19018662 indicating redundancy between DNT1 and DNT2 for cell survival PMID:23892553 over-expression of Toll-6CY in all neurons rescued the apoptosis caused by loss of DNT2 function PMID:39704728 Altogether, these data showed that DNT-2 functions via Toll-6 to maintain PAM neuron survival. PMID:42552905 Loss of function for DNT-2 or Toll-2 induced apoptosis, and Toll-2 knock-down prevented the pro-survival function of DNT-2. |
| GO:0045087 innate immune response | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: IBA from PTN002354018, seeded by spz and spz5. Reason: Spz5 is a Toll-1 ligand (Nonaka et al. 2018; Chowdhury et al. 2019) and activates Toll-6 innate-immune-type signaling in glia after neuronal apoptosis (McLaughlin et al. 2019), so an immune-related role is supported, but it is secondary to its neurotrophic function. Supporting Evidence: PMID:30361090 Here, we demonstrate that Spz5, a member of the Spz family of proteins, functions as a ligand for the Toll-1 receptor. PMID:31088910 Results indicated that the cystine knots for Spz-1, -2, and -5 activated the drosomycin promoter in S2 cells expressing full-length Toll-1 492-, 188-, and 122-fold PMID:30745142 Neuronal apoptosis drives processing and activation of the Toll-6 ligand, SpΓ€tzle5. |
| GO:0045087 innate immune response | IMP PMID:30361090 Characterization of Spz5 as a novel ligand for Drosophila To... | KEEP AS NON CORE | Summary: Nonaka et al. (2018) spz5 null mutant analysis of Toll-1 ligand activity; abstract only in the local cache. Reason: Deferring to the curator who read the full text; the Toll-1 ligand role is supported in the abstract and by independent in vitro work. Non-core relative to neurotrophic signaling. Supporting Evidence: PMID:30361090 Here, we demonstrate that Spz5, a member of the Spz family of proteins, functions as a ligand for the Toll-1 receptor. PMID:30361090 By generating a spz5 null mutant, we further showed that the Toll-1 ligand activity of larva-derived extract is mainly derived from Spz5. |
| GO:0048018 receptor ligand activity | IDA PMID:30361090 Characterization of Spz5 as a novel ligand for Drosophila To... | ACCEPT | Summary: Spz5 functions as a ligand for Toll-1, independently of furin processing (Nonaka et al. 2018). Reason: Receptor ligand activity is the correct ligand MF for this Toll-1 assay; it is not a growth-factor readout. Spz5 is a ligand for several receptors (Toll-1, Toll-6, Toll-7, Kek-6); the neurotrophic role is captured more specifically by growth factor activity. Supporting Evidence: PMID:30361090 Here, we demonstrate that Spz5, a member of the Spz family of proteins, functions as a ligand for the Toll-1 receptor. |
| GO:0048018 receptor ligand activity | IDA PMID:31088910 Toll family members bind multiple SpΓ€tzle proteins and activ... | ACCEPT | Summary: Spz-5 cystine knot binds Toll-1/Toll-7 ectodomains and activates drosomycin reporter through full-length Toll-1 or Toll-7. Reason: Binding plus receptor activation shows receptor ligand activity. Supporting Evidence: PMID:31088910 Focusing on Toll-1 and Toll-7, our co-IP assays indicate the ectodomains of each bind Spz-1, -2, and -5, but not other family members, while also suggesting that binding of Spz-1, -2, and -5 to full-length Toll-1 or Toll-7 results in activation of the drosomycin promoter. PMID:31088910 Results indicated that the cystine knots for Spz-1, -2, and -5 activated the drosomycin promoter in S2 cells expressing full-length Toll-1 492-, 188-, and 122-fold |
| GO:0048018 receptor ligand activity | IPI PMID:28846707 Kek-6: A truncated-Trk-like receptor for Drosophila neurotro... | ACCEPT | Summary: DNT2 binds Kek-6 in co-IP and signaling assays and acts as its retrograde ligand at the NMJ (Ulian-Benitez et al. 2017). Reason: Kek-6 is a kinase-less Trk-like receptor for DNT2; the ligand activity is supported by binding and by genetic interaction in vivo. Growth factor activity is the more specific neurotrophic term carried elsewhere. Supporting Evidence: PMID:28846707 Kek-6 is expressed in the CNS, interacts genetically with DNTs and can bind DNT2 in signaling assays and co-immunoprecipitations. PMID:28846707 Altogether, our data demonstrate that DNT2 is a retrograde ligand for Kek-6 at the NMJ and that DNT2 and Kek-6 are required together for synaptic structure and NMJ growth. |
| GO:0048167 regulation of synaptic plasticity | IGI PMID:28846707 Kek-6: A truncated-Trk-like receptor for Drosophila neurotro... | ACCEPT | Summary: DNT2 genetically interacts with kek-6 and Toll-6 in regulating NMJ growth, bouton number and active zones (Ulian-Benitez et al. 2017). Reason: Structural synaptic plasticity is a core output of DNT2 neurotrophic signaling at the NMJ and in adult dopaminergic circuits (Sun et al. 2024). Supporting Evidence: PMID:28846707 Altogether, our data demonstrate that DNT2 is a retrograde ligand for Kek-6 at the NMJ and that DNT2 and Kek-6 are required together for synaptic structure and NMJ growth. PMID:28846707 Instead, Kek-6 and Toll-6 interact physically, and together regulate structural synaptic plasticity and homeostasis. PMID:39704728 Loss of function for DNT-2 or its receptors Toll-6 and kinase-less Trk-like kek-6 caused DAN and synapse loss, impaired dendrite growth and connectivity, decreased synaptic sites, and caused locomotion deficits. |
| GO:0038179 neurotrophin signaling pathway | IDA PMID:23892553 Toll-6 and Toll-7 function as neurotrophin receptors in the ... | NEW | Summary: DNT2 binds Toll-6 and Toll-7 and triggers Dif/NF-kB signaling through them in S2 cells; activated Toll-6 rescues DNT2 loss-of-function apoptosis in vivo; mature DNT2 activates NF-kB and ERK pro-survival signaling via Toll-6/7; DNT2 maintains PAM neuron survival via Toll-6. Reason: A ligand is annotated involved_in the pathway it initiates (projects/LIGANDS_IN_SIGNALING.md; GO-CAM signaling receptor guideline). DNT2 does the initiating step of this pathway: it is the neurotrophin that binds and activates the receptors. GOA places spz5 only in the Toll-1 pathway (GO:0008063), whose receptor is Toll-1, so its main signaling role is missing. The receptor side is already placed in this pathway: the Toll-7 review in this repository gives Toll-7 neurotrophin receptor activity in GO:0038179. Neither existing Toll signaling row can be modified into this term because the Toll-1 evidence behind them is genuine. Supporting Evidence: PMID:23892553 Together, these data demonstrate that DNT1 binds Toll-7 and DNT2 binds promiscuously Toll-6 and Toll-7. PMID:23892553 were stimulated with purified DNT2 this triggered a drosomycin-luciferase readout indicative of Dif signalling PMID:23892553 over-expression of Toll-6CY in all neurons rescued the apoptosis caused by loss of DNT2 function PMID:28373203 Collectively, these data show that DNT1 and 2 can activate the prosurvival signaling pathways NF-ΞΊB and ERK via Toll-6 and -7 and that pro-DNT1 can activate the proapoptotic JNK pathway. PMID:39704728 Altogether, these data showed that DNT-2 functions via Toll-6 to maintain PAM neuron survival. |
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Download this section (compressed HTML)spatzle 5 (spz5) encodes one of the paralogs of spz. It is a ligand for Toll-6 and kek6. Together, they can promote neuron survival, axonal and dendritic growth and branching, and structural plasticity of synapses. Alterations in spz5 levels influence behaviour in larvae and adult flies, including in locomotion and long-term memory.
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