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The Drosophila cell adhesion molecule Neuroglian regulates Lissencephaly-1 localisation in circulating immunosurveillance cells.

Williams MJ - BMC Immunol. (2009)

Bottom Line: Interestingly in plasmatocytes from Nrg mutants the nucleokinesis regulating protein Lissencephaly-1 (Lis1) fails to localise properly around the nucleus and is instead found diffuse throughout the cytoplasm and at unidentified perinuclear structures.After attaching to the wasp egg control plasmatocytes extend filopodia laterally from their cell periphery; as well as extending lateral filopodia plasmatocytes from Nrg mutants also extend many filopodia from their apical surface.At the cell periphery of haemocytes Neuroglian may be involved in cell-cell interactions, while at the cell centre Neuroglian regulates the localisation of the nucleokinesis complex protein lissencephaly-1.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, UK. m.j.williams@abdn.ac.uk

ABSTRACT

Background: When the parasitoid wasp Leptopilina boulardi lays its eggs in Drosophila larvae phagocytic cells called plasmatocytes and specialized cells known as lamellocytes encapsulate the egg. This requires these circulating immunosurveillance cells (haemocytes) to change from a non-adhesive to an adhesive state enabling them to bind to the invader. Interestingly, attachment of leukocytes, platelets, and insect haemocytes requires the same adhesion complexes as epithelial and neuronal cells.

Results: Here evidence is presented showing that the Drosophila L1-type cell adhesion molecule Neuroglian (Nrg) is required for haemocytes to encapsulate L. boulardi wasp eggs. The amino acid sequence FIGQY containing a conserved phosphorylated tyrosine is found in the intracellular domain of all L1-type cell adhesion molecules. This conserved tyrosine is phosphorylated at the cell periphery of plasmatocytes and lamellocytes prior to parasitisation, but dephosphorylated after immune activation. Intriguingly, another pool of Nrg located near the nucleus of plasmatocytes remains phosphorylated after parasitisation. In mammalian neuronal cells phosphorylated neurofascin, another L1-type cell adhesion molecule interacts with a nucleokinesis complex containing the microtubule binding protein lissencephaly-1 (Lis1) 1. Interestingly in plasmatocytes from Nrg mutants the nucleokinesis regulating protein Lissencephaly-1 (Lis1) fails to localise properly around the nucleus and is instead found diffuse throughout the cytoplasm and at unidentified perinuclear structures. After attaching to the wasp egg control plasmatocytes extend filopodia laterally from their cell periphery; as well as extending lateral filopodia plasmatocytes from Nrg mutants also extend many filopodia from their apical surface.

Conclusion: The Drosophila cellular adhesion molecule Neuroglian is expressed in haemocytes and its activity is required for the encapsulation of L. boularli eggs. At the cell periphery of haemocytes Neuroglian may be involved in cell-cell interactions, while at the cell centre Neuroglian regulates the localisation of the nucleokinesis complex protein lissencephaly-1.

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Sequence alignments (A) Sequence alignment of three Drosophila proteins containing Dcx-domains and human doublecortin. Underlined sequences indicated Dcx domains, filled circles indicate the three amino acids shown to be necessary for doublecortin to interact with neurofascin. (B) Sequence alignment comparing the FIGQY domains of Human L1-CAM, Human Neurofascin and Drosophila Neuroglian with Drosophila Echinoid.
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Figure 8: Sequence alignments (A) Sequence alignment of three Drosophila proteins containing Dcx-domains and human doublecortin. Underlined sequences indicated Dcx domains, filled circles indicate the three amino acids shown to be necessary for doublecortin to interact with neurofascin. (B) Sequence alignment comparing the FIGQY domains of Human L1-CAM, Human Neurofascin and Drosophila Neuroglian with Drosophila Echinoid.

Mentions: In neurons it has been shown that the L1-family member neurofascin interacts with doublecortin and this interaction is necessary for neuronal migration [1]. Doublecortin is a microtubule-associated protein involved in neuronal migration [29], and along with the microtubule array and neurofascin, doublecortin interacts with lissencephaly-1 (LIS1). In both mammalian and Drosophila neurogenesis, Lis-1 is necessary for neuroblast proliferation and migration [36-38]. The doublecortin-Lis1 interaction is necessary for nucleokinesis during neuronal migration [39]. It is speculated that the interaction with neurofascin may be necessary to anchor the Lis1 complex to generate the force necessary for nucleokinesis, and without the signal from neurofascin nucleokinesis and cell migration cannot occur [1,36]. It may be that phosphorylation of the Nrg-FIGQY tyrosine at the plasmatocyte cell centre is necessary for Nrg to interact with a Drosophila doublecortin domain (Dcx) containing protein, to allow for nuclear anchoring. In an NrgG00305 mutant plasmatocyte Nrg may not be able to interact with a Dcx-domain protein, thus the Dcx-Lis1 complex cannot interact properly with the nuclear membrane and ends up at the unidentified perinuclear centriole-like structures or diffuse in the cytoplasm. There is no obvious homolog of mammalian doublecortin in Drosophila, but there are three proteins that contain Dcx domains, two of which are very similar to other doublecortin domain proteins called doublecortin-like kinase-1 and -2 in mammals. In a study to define the interaction of doublecortin with neurofascin, three amino acids in doublecortin were discovered to be important for this interaction [1]. Interestingly, all three of these amino acids are conserved in the Drosophila doublecortin-like kinase homolog CG17528 and the Dcx-domain protein CG42247, while two are conserved in the doublecortin-like kinase homolog CG10177 (Figure 8A). The possibility that Nrg interacts with one of these Dcx-domain containing proteins to anchor the nucleus during plasmatocyte spreading is currently under investigation. Of further interest is the observation that CG42247 was found to interact with another cell adhesion molecule Echinoid in a yeast-two hybrid screen [40]. Though Echinoid does not contain the FIGQY sequence found in L1-family molecules it does contain a similar sequence, FEGEY, in its intracellular domain near the C-terminus (Figure 8B).


The Drosophila cell adhesion molecule Neuroglian regulates Lissencephaly-1 localisation in circulating immunosurveillance cells.

Williams MJ - BMC Immunol. (2009)

Sequence alignments (A) Sequence alignment of three Drosophila proteins containing Dcx-domains and human doublecortin. Underlined sequences indicated Dcx domains, filled circles indicate the three amino acids shown to be necessary for doublecortin to interact with neurofascin. (B) Sequence alignment comparing the FIGQY domains of Human L1-CAM, Human Neurofascin and Drosophila Neuroglian with Drosophila Echinoid.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2667480&req=5

Figure 8: Sequence alignments (A) Sequence alignment of three Drosophila proteins containing Dcx-domains and human doublecortin. Underlined sequences indicated Dcx domains, filled circles indicate the three amino acids shown to be necessary for doublecortin to interact with neurofascin. (B) Sequence alignment comparing the FIGQY domains of Human L1-CAM, Human Neurofascin and Drosophila Neuroglian with Drosophila Echinoid.
Mentions: In neurons it has been shown that the L1-family member neurofascin interacts with doublecortin and this interaction is necessary for neuronal migration [1]. Doublecortin is a microtubule-associated protein involved in neuronal migration [29], and along with the microtubule array and neurofascin, doublecortin interacts with lissencephaly-1 (LIS1). In both mammalian and Drosophila neurogenesis, Lis-1 is necessary for neuroblast proliferation and migration [36-38]. The doublecortin-Lis1 interaction is necessary for nucleokinesis during neuronal migration [39]. It is speculated that the interaction with neurofascin may be necessary to anchor the Lis1 complex to generate the force necessary for nucleokinesis, and without the signal from neurofascin nucleokinesis and cell migration cannot occur [1,36]. It may be that phosphorylation of the Nrg-FIGQY tyrosine at the plasmatocyte cell centre is necessary for Nrg to interact with a Drosophila doublecortin domain (Dcx) containing protein, to allow for nuclear anchoring. In an NrgG00305 mutant plasmatocyte Nrg may not be able to interact with a Dcx-domain protein, thus the Dcx-Lis1 complex cannot interact properly with the nuclear membrane and ends up at the unidentified perinuclear centriole-like structures or diffuse in the cytoplasm. There is no obvious homolog of mammalian doublecortin in Drosophila, but there are three proteins that contain Dcx domains, two of which are very similar to other doublecortin domain proteins called doublecortin-like kinase-1 and -2 in mammals. In a study to define the interaction of doublecortin with neurofascin, three amino acids in doublecortin were discovered to be important for this interaction [1]. Interestingly, all three of these amino acids are conserved in the Drosophila doublecortin-like kinase homolog CG17528 and the Dcx-domain protein CG42247, while two are conserved in the doublecortin-like kinase homolog CG10177 (Figure 8A). The possibility that Nrg interacts with one of these Dcx-domain containing proteins to anchor the nucleus during plasmatocyte spreading is currently under investigation. Of further interest is the observation that CG42247 was found to interact with another cell adhesion molecule Echinoid in a yeast-two hybrid screen [40]. Though Echinoid does not contain the FIGQY sequence found in L1-family molecules it does contain a similar sequence, FEGEY, in its intracellular domain near the C-terminus (Figure 8B).

Bottom Line: Interestingly in plasmatocytes from Nrg mutants the nucleokinesis regulating protein Lissencephaly-1 (Lis1) fails to localise properly around the nucleus and is instead found diffuse throughout the cytoplasm and at unidentified perinuclear structures.After attaching to the wasp egg control plasmatocytes extend filopodia laterally from their cell periphery; as well as extending lateral filopodia plasmatocytes from Nrg mutants also extend many filopodia from their apical surface.At the cell periphery of haemocytes Neuroglian may be involved in cell-cell interactions, while at the cell centre Neuroglian regulates the localisation of the nucleokinesis complex protein lissencephaly-1.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Biological and Environmental Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, UK. m.j.williams@abdn.ac.uk

ABSTRACT

Background: When the parasitoid wasp Leptopilina boulardi lays its eggs in Drosophila larvae phagocytic cells called plasmatocytes and specialized cells known as lamellocytes encapsulate the egg. This requires these circulating immunosurveillance cells (haemocytes) to change from a non-adhesive to an adhesive state enabling them to bind to the invader. Interestingly, attachment of leukocytes, platelets, and insect haemocytes requires the same adhesion complexes as epithelial and neuronal cells.

Results: Here evidence is presented showing that the Drosophila L1-type cell adhesion molecule Neuroglian (Nrg) is required for haemocytes to encapsulate L. boulardi wasp eggs. The amino acid sequence FIGQY containing a conserved phosphorylated tyrosine is found in the intracellular domain of all L1-type cell adhesion molecules. This conserved tyrosine is phosphorylated at the cell periphery of plasmatocytes and lamellocytes prior to parasitisation, but dephosphorylated after immune activation. Intriguingly, another pool of Nrg located near the nucleus of plasmatocytes remains phosphorylated after parasitisation. In mammalian neuronal cells phosphorylated neurofascin, another L1-type cell adhesion molecule interacts with a nucleokinesis complex containing the microtubule binding protein lissencephaly-1 (Lis1) 1. Interestingly in plasmatocytes from Nrg mutants the nucleokinesis regulating protein Lissencephaly-1 (Lis1) fails to localise properly around the nucleus and is instead found diffuse throughout the cytoplasm and at unidentified perinuclear structures. After attaching to the wasp egg control plasmatocytes extend filopodia laterally from their cell periphery; as well as extending lateral filopodia plasmatocytes from Nrg mutants also extend many filopodia from their apical surface.

Conclusion: The Drosophila cellular adhesion molecule Neuroglian is expressed in haemocytes and its activity is required for the encapsulation of L. boularli eggs. At the cell periphery of haemocytes Neuroglian may be involved in cell-cell interactions, while at the cell centre Neuroglian regulates the localisation of the nucleokinesis complex protein lissencephaly-1.

Show MeSH
Related in: MedlinePlus