Receptor UNC-40 Research Articles

SRC-1 controls growth cone polarity and protrusion with the UNC-6/Netrin receptor UNC-5 in Caenorhabditis elegans.

The Polarity/Protusion model of UNC-6/Netrin function in axon repulsion does not rely on a gradient of UNC-6/Netrin. Instead, the UNC-5 receptor polarizes the VD growth cone such that filopodial protrusions are biased to the dorsal leading edge. UNC-5 then inhibits growth cone protrusion ventrally based upon this polarity, resulting in dorsally-biased protrusion and dorsal migration away from UNC-6/Netrin. While previous studies have shown that UNC-5 inhibits growth cone protrusion by destabilizing actin, preventing microtubule + end entry, and preventing vesicle fusion, the signaling pathways involved are unclear. The SRC-1 tyrosine kinase has been previously shown to physically interact with and phosphorylate UNC-5, and to act with UNC-5 in axon guidance and cell migration. Here, the role of SRC-1 in VD growth cone polarity and protrusion is investigated. A precise deletion of src-1 was generated, and mutants displayed unpolarized growth cones with increased size, similar to unc-5 mutants. Transgenic expression of src-1(+) in VD/DD neurons resulted in smaller growth cones, and rescued growth cone polarity defects of src-1 mutants, indicating cell-autonomous function. Transgenic expression of a putative kinase-dead src-1(D831A) mutant caused a phenotype similar to src-1 loss-of-function, suggesting that this is a dominant negative mutation. The D381A mutation was introduced into the endogenous src-1 gene by genome editing, which also had a dominant-negative effect. Genetic interactions of src-1 and unc-5 suggest they act in the same pathway on growth cone polarity and protrusion, but might have overlapping, parallel functions in other aspects of axon guidance. src-1 function was not required for the effects of activated myr::unc-5, suggesting that SRC-1 might be involved in UNC-5 dimerization and activation by UNC-6, of which myr::unc-5 is independent. In sum, these results show that SRC-1 acts with UNC-5 in growth cone polarity and inhibition of protrusion.

TIAM-1 regulates polarized protrusions during dorsal intercalation in the Caenorhabditis elegans embryo through both its GEF and N-terminal domains.

Mediolateral cell intercalation is a morphogenetic strategy used throughout animal development to reshape tissues. Dorsal intercalation in the Caenorhabditis elegans embryo involves the mediolateral intercalation of two rows of dorsal epidermal cells to create a single row that straddles the dorsal midline, and thus is a simple model to study cell intercalation. Polarized protrusive activity during dorsal intercalation requires the C. elegans Rac and RhoG orthologs CED-10 and MIG-2, but how these GTPases are regulated during intercalation has not been thoroughly investigated. In this study, we characterized the role of the Rac-specific guanine nucleotide exchange factor (GEF) TIAM-1 in regulating actin-based protrusive dynamics during dorsal intercalation. We found that TIAM-1 can promote formation of the main medial lamellipodial protrusion extended by intercalating cells through its canonical GEF function, whereas its N-terminal domains function to negatively regulate the generation of ectopic filiform protrusions around the periphery of intercalating cells. We also show that the guidance receptor UNC-5 inhibits these ectopic filiform protrusions in dorsal epidermal cells and that this effect is in part mediated via TIAM-1. These results expand the network of proteins that regulate basolateral protrusive activity during directed rearrangement of epithelial cells in animal embryos.

Netrin-1 ve Reseptörlerinin Çeşitli Kanserlerdeki Rolü

ABSTRACT
 Netrin-1 is a laminin-like protein that is secreted. It plays a role in the development of the nervous system and is also involved in processes such as cell migration, proliferation, angiogenesis, differentiation, apoptosis, metastasis, and invasion. DCC, neogenin, and UNC5 receptor families form the main receptors of netrin-1. These receptors have a dual role depending on the presence or absence of netrin-1. Netrin-1 influences carcinogenesis through signaling pathways such as PI3K/AKT, ERK/MAPK, Notch, and NF-kB. Netrin-1 receptor interactions are effective in cancer cell viability and carcinogenesis mechanisms. Overall, overexpression of netrin-1 and loss of its receptors promote carcinogenesis. Netrin-1 is involved in apoptosis through different receptors. Changes in the expression of DCC and UNC5H receptors affect cancer cell growth and metastasis. Loss of expression in dependent receptors is observed in advanced stages of various tumors. Neogenin is associated with migration and metastasis in tumors. Studies have shown that netrin-1 influences tumor development in various cancers such as gastric cancer, pancreatic ductal adenocarcinoma, colorectal cancer, and glioblastoma. Overexpression of netrin-1 is associated with poor prognosis and decreased overall survival. Netrin-1 levels are reported to be higher in patient groups compared to healthy control groups and decrease with chemotherapy. The mechanism of netrin-1 and its receptors in tumor development is not clear due to their different effects. This article summarizes research findings presenting the role and position of netrin-1 in various cancers.

A short isoform of the UNC-6/Netrin receptor UNC-5 is required for growth cone polarity and robust growth cone protrusion in Caenorhabditis elegans.

Introduction: UNC-6/Netrin is a conserved bi-functional guidance cue which regulates dorsal-ventral axon guidance in C. elegans. In the Polarity/Protrusion model of UNC-6/Netrin mediated dorsal growth away from UNC-6/Netrin, The UNC-5 receptor first polarizes the VD growth cone such that filopodial protrusions are biased dorsally. Based on this polarity, the UNC-40/DCC receptor stimulates growth cone lamellipodial and filopodial protrusion dorsally. The UNC-5 receptor maintains dorsal polarity of protrusion, and inhibits growth cone protrusion ventrally, resulting in net dorsal growth cone advance. Methods: Growth cone imaging in mutants, combined with Cas9 genome editing and genetic analysis, were used to analyze the role of a novel short isoform on unc-5 in growth cone polarity and protrusion. Results: Work presented here demonstrates a novel role of a previously undescribed, conserved short isoform of UNC-5 (UNC-5B). UNC-5B lacks the cytoplasmic domains of UNC-5 long, including the DEATH domain, the UPA/DB domain, and most of the ZU5 domain. Mutations that specifically affect only the unc-5 long isoforms were hypomorphic, suggesting a role of unc-5B short. A mutation specifically affecting unc-5B caused loss of dorsal polarity of protrusion and reduced growth cone filopodial protrusion, the opposite of unc-5 long mutations. Transgenic expression of unc-5B partially rescued unc-5 axon guidance defects, and resulted in large growth cones. Tyrosine 482 (Y482) in the cytoplasmic juxtamembrane region has been shown to be important for UNC-5 function, and is present in both UNC-5 long and UNC-5B short. Results reported here show that Y482 is required for the function of UNC-5 long and for some functions of UNC-5B short. Finally, genetic interactions with unc-40 and unc-6 suggest that UNC-5B short acts in parallel to UNC-6/Netrin to ensure robust growth cone lamellipodial protrusion. Discussion: These results demonstrate a previously-undescribed role for the UNC-5B short isoform, which is required for dorsal polarity of growth cone filopodial protrusion and to stimulate growth cone protrusion, in contrast to the previously-described role of UNC-5 long in inhibiting growth cone protrusion.

TOM-1/tomosyn acts with the UNC-6/netrin receptor UNC-5 to inhibit growth cone protrusion in Caenorhabditis elegans.

In the polarity/protrusion model of growth cone repulsion from UNC-6/netrin, UNC-6 first polarizes the growth cone of the VD motor neuron axon via the UNC-5 receptor, and then regulates protrusion asymmetrically across the growth cone based on this polarity. UNC-6 stimulates protrusion dorsally through the UNC-40/DCC receptor, and inhibits protrusion ventrally through UNC-5, resulting in net dorsal growth. Previous studies showed that UNC-5 inhibits growth cone protrusion via the flavin monooxygenases and potential destabilization of F-actin, and via UNC-33/CRMP and restriction of microtubule plus-end entry into the growth cone. We show that UNC-5 inhibits protrusion through a third mechanism involving TOM-1/tomosyn. A short isoform of TOM-1 inhibited protrusion downstream of UNC-5, and a long isoform had a pro-protrusive role. TOM-1/tomosyn inhibits formation of the SNARE complex. We show that UNC-64/syntaxin is required for growth cone protrusion, consistent with a role of TOM-1 in inhibiting vesicle fusion. Our results are consistent with a model whereby UNC-5 utilizes TOM-1 to inhibit vesicle fusion, resulting in inhibited growth cone protrusion, possibly by preventing the growth cone plasma membrane addition required for protrusion.

Notch-dependent binary fate choice regulates the Netrin pathway to control axon guidance of Drosophila visual projection neurons

Notch-dependent binary fate choice between sister neurons is one of the mechanisms to generate neural diversity. How these upstream neural fate specification programs regulate downstream effector genes to control axon targeting and neuropil assembly remains less well understood. Here, we report that Notch-dependent binary fate choice in Drosophila medulla neurons is required to regulate the Netrin axon guidance pathway, which controls targeting of transmedullary (Tm) neurons to lobula. In medulla neurons of Notch-on hemilineage composed of mostly lobula-targeting neurons, Notch signaling is required to activate theexpression of Netrin-B and repress the expression of its repulsive receptor Unc-5. Turning off Unc-5 is necessary for Tm neurons to target lobula. Furthermore, Netrin-B provided by Notch-on medulla neurons is required for correct targeting of Tm axons from later-generated medulla columns. Thus, the coordinate regulation of Netrin pathway components by Notch signaling ensures correct targeting of Tm axons and contributes to the neuropil assembly.

A Ligand-Gated Association between Cytoplasmic Domains of UNC5 and DCC Family Receptors Converts Netrin-Induced Growth Cone Attraction to Repulsion

A Ligand-Gated Association between Cytoplasmic Domains of UNC5 and DCC Family Receptors Converts Netrin-Induced Growth Cone Attraction to Repulsion

The PH/MyTH4/FERM molecule MAX-1 inhibits UNC-5 activity in the regulation of VD growth cone protrusion in Caenorhabditis elegans.

UNC-6/Netrin is a secreted conserved guidance cue that regulates dorsal-ventral axon guidance of Caenorhabditis elegans and in the vertebral spinal cord. In the polarity/protrusion model of VD growth cone guidance away from ventrally expressed UNC-6 (repulsion), UNC-6 first polarizes the growth cone via the UNC-5 receptor such that filopodial protrusions are biased dorsally. UNC-6 then regulates a balance of protrusion in the growth cone based upon this polarity. UNC-5 inhibits protrusion ventrally, and the UNC-6 receptor UNC-40/DCC stimulates protrusion dorsally, resulting in net dorsal growth cone outgrowth. UNC-5 inhibits protrusion through the flavin monooxygenases FMO-1, 4, and 5 and possible actin destabilization, and inhibits pro-protrusive microtubule entry into the growth cone utilizing UNC-33/CRMP. The PH/MyTH4/FERM myosin-like protein was previously shown to act with UNC-5 in VD axon guidance utilizing axon guidance endpoint analysis. Here, we analyzed the effects of MAX-1 on VD growth cone morphology during outgrowth. We found that max-1 mutant growth cones were smaller and less protrusive than wild type, the opposite of the unc-5 mutant phenotype. Furthermore, genetic interactions suggest that MAX-1 might normally inhibit UNC-5 activity, such that in a max-1 mutant growth cone, UNC-5 is overactive. Our results, combined with previous studies suggesting that MAX-1 might regulate UNC-5 levels in the cell or plasma membrane localization, suggest that MAX-1 attenuates UNC-5 signaling by regulating UNC-5 stability or trafficking. Alternately, MAX-1 might inhibit UNC-5 independent of this known mechanism. We also show that the effects of MAX-1 in growth cone protrusion are independent of UNC-40/DCC, UNC-33/CRMP, and UNC-34/Enabled. In summary, in the context of growth cone protrusion, MAX-1 inhibits UNC-5, demonstrating the mechanistic insight that can be gained by analyzing growth cones during outgrowth in addition to axon guidance endpoint analysis.

Promoter methylation-mediated repression of UNC5 receptors and the associated clinical significance in human colorectal cancer

BackgroundDeregulated methylation of tumor suppressor genes is a hallmark event in colorectal cancer (CRC) carcinogenesis. UNC5 receptors, down-regulated in various human malignancies due to epigenetic alterations, have been proposed as putative tumor suppressor genes. In this study, we focused on the methylation-mediated inhibition of UNC5 receptors and the associated clinical significance in CRC.MethodsMethylation and expression analysis was performed in TCGA datasets. And the results were confirmed in vitro in CRC cell lines treated with 5-aza-deoxycytidine. Then, the expression and epigenetic alterations of UNC5 receptors were evaluated in clinical specimens. Moreover, the diagnostic and prognostic values of the methylation alterations were also analyzed.ResultsMethylation-mediated repression was observed in UNC5C and UNC5D, but not in UNC5A and UNC5B, which was confirmed in CRC cell lines. Except for UNC5B, significantly elevated methylation was observed in UNC5A, UNC5C, and UNC5D in CRC. The discrimination efficiency of the three receptors was comparable with that of SEPT9. Kaplan–Meier curve survival analysis showed that hypermethylation of UNC5A, UNC5C and UNC5D was associated with poor progression-free and overall survival. Moreover, methylation levels of UNC5C and UNC5D were independent predictors of CRC progression-free (P = 0.001, P = 0.003, respectively) and overall survival (P = 0.008, P = 0.004, respectively).ConclusionsHypermethylation of UNC5C and UNC5D mediates the repression and has promising diagnostic and prognostic values in CRC.

Repulsive guidance molecule acts in axon branching in Caenorhabditis elegans

Repulsive guidance molecules (RGMs) are evolutionarily conserved proteins implicated in repulsive axon guidance. Here we report the function of the Caenorhabditis elegans ortholog DRAG-1 in axon branching. The axons of hermaphrodite-specific neurons (HSNs) extend dorsal branches at the region abutting the vulval muscles. The drag-1 mutants exhibited defects in HSN axon branching in addition to a small body size phenotype. DRAG-1 expression in the hypodermal cells was required for the branching of the axons. Although DRAG-1 is normally expressed in the ventral hypodermis excepting the vulval region, its ectopic expression in vulval precursor cells was sufficient to induce the branching. The C-terminal glycosylphosphatidylinositol anchor of DRAG-1 was important for its function, suggesting that DRAG-1 should be anchored to the cell surface. Genetic analyses suggested that the membrane receptor UNC-40 acts in the same pathway with DRAG-1 in HSN branching. We propose that DRAG-1 expressed in the ventral hypodermis signals via the UNC-40 receptor expressed in HSNs to elicit branching activity of HSN axons.

FLRT2 and FLRT3 Cooperate in Maintaining the Tangential Migratory Streams of Cortical Interneurons during Development.

Neuron migration is a hallmark of nervous system development that allows gathering of neurons from different origins for assembling of functional neuronal circuits. Cortical inhibitory interneurons arise in the ventral telencephalon and migrate tangentially forming three transient migratory streams in the cortex before reaching the final laminar destination. Although migration defects lead to the disruption of inhibitory circuits and are linked to aspects of psychiatric disorders such as autism and schizophrenia, the molecular mechanisms controlling cortical interneuron development and final layer positioning are incompletely understood. Here, we show that mouse embryos with a double deletion of FLRT2 and FLRT3 genes encoding cell adhesion molecules exhibit an abnormal distribution of interneurons within the streams during development, which in turn, affect the layering of somatostatin+ interneurons postnatally. Mechanistically, FLRT2 and FLRT3 proteins act in a noncell-autonomous manner, possibly through a repulsive mechanism. In support of such a conclusion, double knockouts deficient in the repulsive receptors for FLRTs, Unc5B and Unc5D, also display interneuron defects during development, similar to the FLRT2/FLRT3 mutants. Moreover, FLRT proteins are chemorepellent ligands for developing interneurons in vitro, an effect that is in part dependent on FLRT-Unc5 interaction. Together, we propose that FLRTs act through Unc5 receptors to control cortical interneuron distribution in a mechanism that involves cell repulsion.SIGNIFICANCE STATEMENT Disruption of inhibitory cortical circuits is responsible for some aspects of psychiatric disorders such as schizophrenia or autism. These defects include interneuron migration during development. A crucial step during this process is the formation of three transient migratory streams within the developing cortex that determine the timing of interneuron final positioning and the formation of functional cortical circuits in the adult. We report that FLRT proteins are required for the proper distribution of interneurons within the cortical migratory streams and for the final laminar allocation in the postnatal cortex. These results expand the multifunctional role of FLRTs during nervous system development in addition to the role of FLRTs in axon guidance and the migration of excitatory cortical neurons.

Regulation of UNC-40/DCC and UNC-6/Netrin by DAF-16 promotes functional rewiring of the injured axon.

The adult nervous system has a limited capacity to regenerate after accidental damage. Post-injury functional restoration requires proper targeting of the injured axon to its postsynaptic cell. Although the initial response to axonal injury has been studied in great detail, it is rather unclear what controls the re-establishment of a functional connection. Using the posterior lateral microtubule neuron in Caenorhabditis elegans, we found that after axotomy, the regrowth from the proximal stump towards the ventral side and accumulation of presynaptic machinery along the ventral nerve cord correlated to the functional recovery. We found that the loss of insulin receptor DAF-2 promoted 'ventral targeting' in a DAF-16-dependent manner. We further showed that coordinated activities of DAF-16 in neuron and muscle promoted 'ventral targeting'. In response to axotomy, expression of the Netrin receptor UNC-40 was upregulated in the injured neuron in a DAF-16-dependent manner. In contrast, the DAF-2-DAF-16 axis contributed to the age-related decline in Netrin expression in muscle. Therefore, our study revealed an important role for insulin signaling in regulating the axon guidance molecules during the functional rewiring process.

UNC5 dependence receptor family in human cancer: A controllable double-edged sword.

UNC5 receptor family (UNC5A-D) have been identified as dependence receptors whose functions depend on the availability of their ligand netrin-1. Through binding to netrin-1, these receptors transmit signals for cell survival, migration and differentiation, and participate in diverse physiological and pathological processes. In the lack of netrin-1, however, these receptors initiate apoptosis-inducing signal. Accumulating evidence reveals that netrin-1 and its receptors play a role in tumorigenesis and tumor progression. The expression of UNC5 receptor family is down-regulated in a variety of human tumors. Expression aberrance of UNC5 receptor family in tumors is caused by diverse mechanisms including genomic, epigenetic, transcriptional and post-transcriptional regulation. Notably, blocking netrin-1 binding to its receptors induces apoptotic cell death in tumor cells. In this review, we describe the characters and roles of UNC5 family members in tumorigenesis and tumor progression, discussing the regulatory mechanisms underlying down-regulation of UNC5 family members as well as recent implications of targeting netrin-1/UNC5 on potential clinical application for cancer treatment.

The Collagens DPY-17 and SQT-3 Direct Anterior-Posterior Migration of the Q Neuroblasts in C. elegans.

Cell adhesion molecules and their extracellular ligands control morphogenetic events such as directed cell migration. The migration of neuroblasts and neural crest cells establishes the structure of the central and peripheral nervous systems. In C. elegans, the bilateral Q neuroblasts and their descendants undergo long-range migrations with left/right asymmetry. QR and its descendants on the right migrate anteriorly, and QL and its descendants on the left migrate posteriorly, despite identical patterns of cell division, cell death, and neuronal generation. The initial direction of protrusion of the Q cells relies on the left/right asymmetric functions of the transmembrane receptors UNC-40/DCC and PTP-3/LAR in the Q cells. Here, we show that Q cell left/right asymmetry of migration is independent of the GPA-16/Gα pathway which regulates other left/right asymmetries, including nervous system L/R asymmetry. No extracellular cue has been identified that guides initial Q anterior versus posterior migrations. We show that collagens DPY-17 and SQT-3 control initial Q direction of protrusion. Genetic interactions with UNC-40/DCC and PTP-3/LAR suggest that DPY-17 and SQT-3 drive posterior migration and might act with both receptors or in a parallel pathway. Analysis of mutants in other collagens and extracellular matrix components indicated that general perturbation of collagens and the extracellular matrix (ECM) did not result in directional defects, and that the effect of DPY-17 and SQT-3 on Q direction is specific. DPY-17 and SQT-3 are components of the cuticle, but a role in the basement membrane cannot be excluded. Possibly, DPY-17 and SQT-3 are part of a pattern in the cuticle and/or basement membrane that is oriented to the anterior–posterior axis of the animal and that is deciphered by the Q cells in a left–right asymmetric fashion. Alternatively, DPY-17 and SQT-3 might be involved in the production or stabilization of a guidance cue that directs Q migrations. In any case, these results describe a novel role for the DPY-17 and SQT-3 collagens in directing posterior Q neuroblast migration.

Neurodevelopment: UNC-40/DCC and the Patterning of Neural Circuits

A new study in Caenorhabditis elegans suggests the ubiquitin-proteasome system promotes degradation of the netrin receptor UNC-40 in a particular neuron only in one sex, leading to sex-specific patterns of synaptic connections.

Synaptic Protein Degradation Controls Sexually Dimorphic Circuits through Regulation of DCC/UNC-40

SummarySexually dimorphic circuits underlie behavioral differences between the sexes, yet the molecular mechanisms involved in their formation are poorly understood. We show here that sexually dimorphic connectivity patterns arise in C. elegans through local ubiquitin-mediated protein degradation in selected synapses of one sex but not the other. Specifically, synaptic degradation occurs via binding of the evolutionary conserved E3 ligase SEL-10/FBW7 to a phosphodegron binding site of the netrin receptor UNC-40/DCC (Deleted in Colorectal Cancer), resulting in degradation of UNC-40. In animals carrying an undegradable unc-40 gain-of-function allele, synapses were retained in both sexes, compromising the activity of the circuit without affecting neurite guidance. Thus, by decoupling the synaptic and guidance functions of the netrin pathway, we reveal a critical role for dimorphic protein degradation in controlling neuronal connectivity and activity. Additionally, the interaction between SEL-10 and UNC-40 is necessary not only for sex-specific synapse pruning, but also for other synaptic functions. These findings provide insight into the mechanisms that generate sex-specific differences in neuronal connectivity, activity, and function.

The netrin receptor UNC-40/DCC assembles a postsynaptic scaffold and sets the synaptic content of GABAA receptors

Increasing evidence indicates that guidance molecules used during development for cellular and axonal navigation also play roles in synapse maturation and homeostasis. In C. elegans the netrin receptor UNC-40/DCC controls the growth of dendritic-like muscle cell extensions towards motoneurons and is required to recruit type A GABA receptors (GABAARs) at inhibitory neuromuscular junctions. Here we show that activation of UNC-40 assembles an intracellular synaptic scaffold by physically interacting with FRM-3, a FERM protein orthologous to FARP1/2. FRM-3 then recruits LIN-2, the ortholog of CASK, that binds the synaptic adhesion molecule NLG-1/Neuroligin and physically connects GABAARs to prepositioned NLG-1 clusters. These processes are orchestrated by the synaptic organizer CePunctin/MADD-4, which controls the localization of GABAARs by positioning NLG-1/neuroligin at synapses and regulates the synaptic content of GABAARs through the UNC-40-dependent intracellular scaffold. Since DCC is detected at GABA synapses in mammals, DCC might also tune inhibitory neurotransmission in the mammalian brain.

Progress of netrin‐1 in traumatic brain injury

Traumatic brain injury (TBI), as a common disease, usually causes neurological damage, such as cognitive impairments, motor deficits, and neuropsychiatric deficits. As TBI occurs, a cascade reaction in the cellular and molecular levels will cause secondary damage, leading to the apoptosis of neurons and glial cells as well as brain edema, etc. However, the treatment is far from satisfaction owning to the complicated set of factors or pathways that are initiated post‐injury. As a bifunctional axonal guidance cue, netrin‐1 can attract axons via the deleted in colorectal cancer (DCC) receptors and repelling others via Unc5 receptors, but its exact role in the recovery of motor and sensory function after TBI has not well been studied, and the mechanisms remain elusive. Here, collecting the current literatures, we aimed to summarize and predict the exact role of netrin‐1 in TBI.

C-mannosylation supports folding and enhances stability of thrombospondin repeats.

Previous studies demonstrated importance of C-mannosylation for efficient protein secretion. To study its impact on protein folding and stability, we analyzed both C-mannosylated and non-C-mannosylated thrombospondin type 1 repeats (TSRs) of netrin receptor UNC-5. In absence of C-mannosylation, UNC-5 TSRs could only be obtained at low temperature and a significant proportion displayed incorrect intermolecular disulfide bridging, which was hardly observed when C-mannosylated. Glycosylated TSRs exhibited higher resistance to thermal and reductive denaturation processes, and the presence of C-mannoses promoted the oxidative folding of a reduced and denatured TSR in vitro. Molecular dynamics simulations supported the experimental studies and showed that C-mannoses can be involved in intramolecular hydrogen bonding and limit the flexibility of the TSR tryptophan-arginine ladder. We propose that in the endoplasmic reticulum folding process, C-mannoses orient the underlying tryptophan residues and facilitate the formation of the tryptophan-arginine ladder, thereby influencing the positioning of cysteines and disulfide bridging.

Molecular characterization of the netrin-1 UNC-5 receptor in Lucilia sericata larvae.

Larval therapy with Lucilia sericata is a promising strategy in wound healing. Axon guidance molecules play vital roles during the development of the nervous system and also regulate the capacity of neuronal restoration in wound healing. Netrin-1, one of the proteins that larvae secrete, plays a useful role in cell migration and nerve tissue regeneration. The UNC-5 receptor combines with a netrin-1 signal and transmits the signal from one side of the membrane to the other side, initiating a change in cell activity. In the current study, we identified the full length of the UNC-5 receptor mRNA in L. sericata using different sets of primers, including exon junction and specific region primers. The coding sequence (CDS) of the UNC-5 receptor was sequenced and identified to include 633 base-pair nucleic acids, and BLAST analysis on its nucleotide sequence revealed 96% identity with the Lucilia cuprina netrin-1 UNC-5 receptor. The protein residue included 210 amino acids (aa) and coded for a protein with 24 kD weight. This gene lacked the signal peptide. Furthermore, the UPA domain is conserved in UNC-5. It lied at the interval of 26–131 aa. We identified the CDS of netrin-1 UNC-5 receptor in L. sericata. It could be applied to research activities implementing a new essential component design in wound healing.