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FRAZZLED/DCC REGULATES SYNAPTOGENESIS AT A DROSOPHILA GIANT SYNAPSE
Title
FRAZZLED/DCC REGULATES SYNAPTOGENESIS AT A DROSOPHILA GIANT SYNAPSE.
Creator
Lopez, Juan, Murphey, Rodney, Florida Atlantic University, Department of Biological Sciences, Charles E. Schmidt College of Science
Abstract/Description
Synaptogenesis is a requirement for cellular communication, but the specific molecular mechanisms underlying synaptogenesis are unclear. Here, we investigate and show the role of the protein Frazzled in synaptogenesis using the transheterozygous Frazzled loss-of-function (LOF) mutant in Drosophila. Leveraging the UAS-GAL4 expression system, we drove expression of various Frazzled/DCC gene constructs in the Giant Fibers (GF) of flies and found changes to synaptogenesis and axon pathfinding. We...
Show moreSynaptogenesis is a requirement for cellular communication, but the specific molecular mechanisms underlying synaptogenesis are unclear. Here, we investigate and show the role of the protein Frazzled in synaptogenesis using the transheterozygous Frazzled loss-of-function (LOF) mutant in Drosophila. Leveraging the UAS-GAL4 expression system, we drove expression of various Frazzled/DCC gene constructs in the Giant Fibers (GF) of flies and found changes to synaptogenesis and axon pathfinding. We identified decreases in electrical synaptogenesis and distinct axon pathfinding errors in Frazzled LOF mutants. Strikingly, the expression of Frazzled intracellular domain (ICD) significantly rescues both phenotypes, while full-length Frazzled protein only partially rescues these phenotypes, prompting us to explore the role of different domains within the protein. Deleting the P1 and P2 domains of Frazzled does not rescue axon pathfinding but did partially rescue synaptogenesis while deleting the P3 domain failed to rescue either phenotype. Moreover, when we drive expression Frazzled with a point-mutated P3 domain, silencing its transcriptional activation domain, it fails to rescue both synaptogenesis and axon pathfinding. These results strongly suggest that Frazzled regulates both synaptogenesis and axon pathfinding in the GFs and is necessary for synaptogenesis of the mixed electrochemical GF synapse. Our results provide novel insights into the molecular mechanisms governing neural circuit assembly and highlight Frazzled as a key player in axon guidance and synaptic development.
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Date Issued
2023
PURL
http://purl.flvc.org/fau/fd/FA00014310
Subject Headings
Drosophila, Synapses, Gap Junctions, Receptors, Cell Surface
Format
Document (PDF)
The effects of Toll-like receptor (TLR) agonists on human nicDC-NK mediated memory/effector T-cell development
Title
The effects of Toll-like receptor (TLR) agonists on human nicDC-NK mediated memory/effector T-cell development.
Creator
Tamjidi, Saba, Nouri-Shirazi, Mahyar, Florida Atlantic University, Charles E. Schmidt College of Medicine, Department of Biomedical Science
Abstract/Description
There is compelling evidence that smokers are less responsive to vaccination. We reported that both therapeutic and prophylactic vaccines fail to protect and cure animals from disease due to negative effects of nicotine on DCs’ ability to generate effector T cells. We have been investigating whether vaccine formulated with TLR agonist(s) could potentially overcome the immunosuppressive effects of nicotine on human DC-NK cross-talk essential for effector T cell generation. Monocyte-derived DCs...
Show moreThere is compelling evidence that smokers are less responsive to vaccination. We reported that both therapeutic and prophylactic vaccines fail to protect and cure animals from disease due to negative effects of nicotine on DCs’ ability to generate effector T cells. We have been investigating whether vaccine formulated with TLR agonist(s) could potentially overcome the immunosuppressive effects of nicotine on human DC-NK cross-talk essential for effector T cell generation. Monocyte-derived DCs and nicDCs were stimulated with individual and combined TLR agonists prior to co-culture with purified T cells. The phenotypes and cytokine profiles of T cell were assessed using Flow Cytometry and ELISA, respectively. We found nicDCs cultured with TLR-8/7 alone or in combination with TLR-3 produce quantitatively and qualitatively similar IFN-γ producing effector T cells when compared to control DCs. Our data suggest that the addition of appropriate TLR agonist to vaccine formulation could potentially overcome the immunosuppression seen in smokers, thereby containing the spread of infectious disease to vulnerable population
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Date Issued
2015
PURL
http://purl.flvc.org/fau/fd/FA00004469, http://purl.flvc.org/fau/fd/FA00004469
Subject Headings
Cell membranes, Cell receptors, Evidence based medicine, Immune system, Molecular biology, T cells -- Receptors, Tobacco -- Physiological effects
Format
Document (PDF)
Chitin Microparticles (CMPs) Induce M1 Macrophage Activation via Intracellular TLR2 Signaling Mechanism
Title
Chitin Microparticles (CMPs) Induce M1 Macrophage Activation via Intracellular TLR2 Signaling Mechanism.
Creator
Davis, Spring, Shibata, Yoshimi, Florida Atlantic University, Charles E. Schmidt College of Medicine, Department of Biological Sciences
Abstract/Description
Chitin Microparticles (CMPs, 1-10um), a special form of the ubiquitous and nontoxic polysaccharide Chitin (GlcNAc), is capable of inducing a switch in macrophages from the wound-healing M2 phenotype to the classically activated pro-inflammatory M1 phenotype; which has therapeutic implications in allergy and cancer. We hypothesized that TLR2 forms a complex with CMPs and Chitin-Binding Proteins (CBPs) at the surface of peritoneal macrophages and remains with that complex after internalization...
Show moreChitin Microparticles (CMPs, 1-10um), a special form of the ubiquitous and nontoxic polysaccharide Chitin (GlcNAc), is capable of inducing a switch in macrophages from the wound-healing M2 phenotype to the classically activated pro-inflammatory M1 phenotype; which has therapeutic implications in allergy and cancer. We hypothesized that TLR2 forms a complex with CMPs and Chitin-Binding Proteins (CBPs) at the surface of peritoneal macrophages and remains with that complex after internalization to initiate downstream signaling events, leading to the production of the M1 cytokine, TNFalpha. Our results from experiments performed in RAW 264.7 cells show that TLR2 and TLR1, but not TLR6, are associated with the CMP binding fraction, and that both TLR1 and TLR2 might be important for M1 activation as a result of CMP phagocytosis. This project sheds light on CMP as a potential therapeutic agent and provides more evidence for a phagocytosis-dependent TLR2 signaling pathway.
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Date Issued
2016
PURL
http://purl.flvc.org/fau/fd/FA00004762, http://purl.flvc.org/fau/fd/FA00004762
Subject Headings
Biopharmaceutics., Macrophages., Cell receptors., Ligands (Biochemistry), High performance processors.
Format
Document (PDF)
Adult olfactory neuron turnover and the asscociation between fractalkine and microglia
Title
Adult olfactory neuron turnover and the asscociation between fractalkine and microglia.
Creator
Mello, Rebecca Femandes, Guthrie, Kathleen M.
Date Issued
2013-04-05
PURL
http://purl.flvc.org/fcla/dt/3361154
Subject Headings
Olfactory Receptor Neurons, Olfactory Bulb--physiology, Cell death, Microglia, Chemokines
Format
Document (PDF)
Elucidating the role of Semaphorin 7A in breast cancer
Title
Elucidating the role of Semaphorin 7A in breast cancer.
Creator
Garcia-Areas, Ramon A., lragavarapu-Charyulu, Vijaya, Florida Atlantic University, Charles E Schmidt College of Science, Department of Biomedical Science
Abstract/Description
Solid tumors can hijack many of the same programs used in neurogenesis to enhance tumor growth and metastasis, thereby generating a plethora of neurogenesis-related molecules including semaphorins Among them, we have identified Semaphorin7A (SEMA7A) in breast cancer We first used to the DA-3 mammary tumor model to determine the effect of tumor-derived SEMA7A on immune cells We found that tumor-derived SEMA7A can modulate the production of proangiogenic chemokines CXCL2/MIP-2 and CXCL 1, and...
Show moreSolid tumors can hijack many of the same programs used in neurogenesis to enhance tumor growth and metastasis, thereby generating a plethora of neurogenesis-related molecules including semaphorins Among them, we have identified Semaphorin7A (SEMA7A) in breast cancer We first used to the DA-3 mammary tumor model to determine the effect of tumor-derived SEMA7A on immune cells We found that tumor-derived SEMA7A can modulate the production of proangiogenic chemokines CXCL2/MIP-2 and CXCL 1, and prometastatic MMP-9 in macrophages We next aimed to determine the expression and function of SEMA7A in mammary tumor cells We found that SEMA7A is highly expressed in both metastatic human and murine breast cancer cells We show that both TGF-β and hypoxia elicits the production of SEMA 7 A in mammary cells SEMA7 A shRNA silencing in 4T1 cells resulted in decreased mesenchymal markers MMP-3, MMP-13, Vimentin and TGF-β) SEMA7A silenced cells show increased stiffness with reduced migratory and proliferative potential In vivo, SEMA7A silenced 4T1 tumor bearing mice showed decreased tumor growth and metastasis Genetic ablation of host-derived SEMA7A synergized to further decrease the growth and metastasis of 4T1 cells Our findings suggest novel functional roles for SEMA7A in breast cancer and that SEMA7A could be a novel therapeutic target to limit tumor growth and metastasis
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Date Issued
2016
PURL
http://purl.flvc.org/fau/fd/FA00004802
Subject Headings
Breast--Cancer--Diagnosis, Semaphorins, Protein precursors, Cellular signal transduction, Cell receptors
Format
Document (PDF)
Synaptic Rearrangements and the Role of Netrin-Frazzled Signaling in Shaping the Drosophila Giant Fiber Circuit
Title
Synaptic Rearrangements and the Role of Netrin-Frazzled Signaling in Shaping the Drosophila Giant Fiber Circuit.
Creator
Lloyd, Brandon N., Murphey, Rodney K., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description
In the developing CNS, presynaptic neurons often have exuberant overgrowth and form excess (and overlapping) postsynaptic connections. Importantly, these excess connections are refined during circuit maturation so that only the appropriate connections remain. This synaptic rearrangement phenomenon has been studied extensively in vertebrates but many of those models involve complex neuronal circuits with multiple presynaptic inputs and postsynaptic outputs. Using a simple escape circuit in...
Show moreIn the developing CNS, presynaptic neurons often have exuberant overgrowth and form excess (and overlapping) postsynaptic connections. Importantly, these excess connections are refined during circuit maturation so that only the appropriate connections remain. This synaptic rearrangement phenomenon has been studied extensively in vertebrates but many of those models involve complex neuronal circuits with multiple presynaptic inputs and postsynaptic outputs. Using a simple escape circuit in Drosophila melanogaster (the giant fiber circuit), we developed tools that enabled us to study the molecular development of this circuit; which consists of a bilaterally symmetrical pair of presynaptic interneurons and postsynaptic motorneurons. In the adult circuit, each presynaptic interneuron (giant fiber) forms a single connection with the ipsilateral, postsynaptic motorneuron (TTMn). Using new tools that we developed we labeled both giant fibers throughout their development and saw that these neurons overgrew their targets and formed overlapping connections. As the circuit matured, giant fibers pruned their terminals and refined their connectivity such that only a single postsynaptic connection remained with the ipsilateral target. Furthermore, if we ablated one of the two giant fibers during development in wildtype animals, the remaining giant fiber often retained excess connections with the contralateral target that persisted into adulthood. After demonstrating that the giant fiber circuit was suitable to study synaptic rearrangement, we investigated two proteins that might mediate this process. First, we were able to prevent giant fibers from refining their connectivity by knocking out highwire, a ubiquitin ligase that prevented pruning. Second, we investigated whether overexpressing Netrin (or Frazzled), part of a canonical axon guidance system, would affect the refinement of giant fiber connectivity. We found that overexpressing Netrin (or Frazzled) pre- & postsynaptically resulted in some giant fibers forming or retaining excess connections, while exclusively presynaptic (or postsynaptic) expression of either protein had no effect. We further showed that by simultaneously reducing (Slit-Robo) midline repulsion and elevating Netrin (or Frazzled) pre- & postsynaptically, we significantly enhanced the proportion of giant fibers that formed excess connections. Our findings suggest that Netrin-Frazzled and Slit-Robo signaling play a significant role in refining synaptic circuits and shaping giant fiber circuit connectivity.
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Date Issued
2016
PURL
http://purl.flvc.org/fau/fd/FA00004758, http://purl.flvc.org/fau/fd/FA00004758
Subject Headings
Drosophila melanogaster--Cytogenetics., Genetic transcription., Transcription factors., Cellular signal transduction., Cellular control mechanisms., Cell receptors.
Format
Document (PDF)
Characterization of receptor protein tyrosine phosphatase PTP69D in the giant fiber circuit
Title
Characterization of receptor protein tyrosine phosphatase PTP69D in the giant fiber circuit.
Creator
Lee, LaTasha Hoskins, Godenschwege, Tanja A., Florida Atlantic University, Charles E. Schmidt College of Science, Department of Biological Sciences
Abstract/Description
PTP69D is a receptor protein tyrosine phosphatase (RPTP) with two intracellular catalytic domains (Cat1 and Cat2), which has been shown to play a role in axon outgrowth and guidance of embryonic motorneurons, as well as targeting of photoreceptor neurons in the visual system of Drosophila melanogaster. Here, we characterized the developmental role of PTP69D in the giant fiber (GF) neurons; two interneurons in the central nervous system (CNS) that control the escape response of the fly. In...
Show morePTP69D is a receptor protein tyrosine phosphatase (RPTP) with two intracellular catalytic domains (Cat1 and Cat2), which has been shown to play a role in axon outgrowth and guidance of embryonic motorneurons, as well as targeting of photoreceptor neurons in the visual system of Drosophila melanogaster. Here, we characterized the developmental role of PTP69D in the giant fiber (GF) neurons; two interneurons in the central nervous system (CNS) that control the escape response of the fly. In addition to guidance and targeting functions, our studies reveal an additional role for PTP69D in synaptic terminal growth in the CNS. We found that inhibition of phosphatase activity in catalytic domain (Cat1) proximal to the transmembrane domain did not affect axon guidance or targeting but resulted in stunted terminal growth of the GFs. Cell autonomous rescue and knockdown experiments demonstrated a function for PTP69D in the GFs, but not its postsynaptic target neurons. In addition,complementation studies and structure-function analyses revealed that for GF terminal growth, Cat1 function of PTP69D requires the immunoglobulin and the Cat2 domain but not the fibronectin type III repeats nor the membrane proximal region. In contrast, the fibronectin type III repeats, but not the immunoglobulin domains, were previously shown to be essential for axon targeting of photoreceptor neurons. Thus, our studies uncover a novel role for PTP69D in synaptic terminal growth in the CNS that is mechanistically distinct from its function during earlier developmental processes.
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Date Issued
2014
PURL
http://purl.flvc.org/fau/fd/FA00004301, http://purl.flvc.org/fau/fd/FA00004301
Subject Headings
Drosophila melanogaster., Protein-tyrosine phosphatase--Metabolism., Protein-tyrosine kinase., Protein kinases--Inhibitors., Phosphoprotein phosphatases., Transcription factors., Cell receptors., Cellular signal transduction.
Format
Document (PDF)