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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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Neuroglian167 intracellular domain showing the conserved FIGQY sequence (underline) and the two predicted tyrosine phosphorylation sites (arrows). The location of the inserted GFP sequence is also indicated. Phosphorylation of the conserved tyrosines was predicted using the Netphos 2.0 program.
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Figure 9: Neuroglian167 intracellular domain showing the conserved FIGQY sequence (underline) and the two predicted tyrosine phosphorylation sites (arrows). The location of the inserted GFP sequence is also indicated. Phosphorylation of the conserved tyrosines was predicted using the Netphos 2.0 program.

Mentions: In NrgG00305 mutants the FIGQY tyrosine is still phosphorylated yet Lis1 mislocalises in the mutant plasmatocytes. This leads to the possibility that phosphorylation of the FIGQY tyrosine is not sufficient for interaction of Nrg with the Lis1 complex. In the study where neurofascin was shown to interact with doublecortin, it was shown that doublecortin only slightly bound to L1-CAM, and not at all to NRCAM, even though they also contain phospho-FIGQY [1]. There is another conserved tyrosine found in all L1-family members upstream of the FIGQY sequence (Figure 9). This tyrosine is predicted to be phosphorylated in both Neuroglian and neurofascin, but not in L1-CAM or NRCAM. The GFP sequence the NrgG00305 allele is incorporated between these two conserved tyrosines and may disrupt their interaction with the Lis1 complex. Also, even though it was shown that phospho-FIGQY was necessary for the interaction of neurofascin with doublecortin in vivo, it may not be sufficient [1]. Another possibility is insertion of GFP into the Nrg open reading frame may change the conformation of the intracellular domain blocking the interaction of Nrg with the Lis1 complex even though the conserved FIGQY tyrosine is phosphorylated.


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

Williams MJ - BMC Immunol. (2009)

Neuroglian167 intracellular domain showing the conserved FIGQY sequence (underline) and the two predicted tyrosine phosphorylation sites (arrows). The location of the inserted GFP sequence is also indicated. Phosphorylation of the conserved tyrosines was predicted using the Netphos 2.0 program.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 9: Neuroglian167 intracellular domain showing the conserved FIGQY sequence (underline) and the two predicted tyrosine phosphorylation sites (arrows). The location of the inserted GFP sequence is also indicated. Phosphorylation of the conserved tyrosines was predicted using the Netphos 2.0 program.
Mentions: In NrgG00305 mutants the FIGQY tyrosine is still phosphorylated yet Lis1 mislocalises in the mutant plasmatocytes. This leads to the possibility that phosphorylation of the FIGQY tyrosine is not sufficient for interaction of Nrg with the Lis1 complex. In the study where neurofascin was shown to interact with doublecortin, it was shown that doublecortin only slightly bound to L1-CAM, and not at all to NRCAM, even though they also contain phospho-FIGQY [1]. There is another conserved tyrosine found in all L1-family members upstream of the FIGQY sequence (Figure 9). This tyrosine is predicted to be phosphorylated in both Neuroglian and neurofascin, but not in L1-CAM or NRCAM. The GFP sequence the NrgG00305 allele is incorporated between these two conserved tyrosines and may disrupt their interaction with the Lis1 complex. Also, even though it was shown that phospho-FIGQY was necessary for the interaction of neurofascin with doublecortin in vivo, it may not be sufficient [1]. Another possibility is insertion of GFP into the Nrg open reading frame may change the conformation of the intracellular domain blocking the interaction of Nrg with the Lis1 complex even though the conserved FIGQY tyrosine is phosphorylated.

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