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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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Nrg necessary for proper encapsulation of L. boulardi eggs (A) Encapsulation capacities of Nrg mutant larvae in response to parasitisation by L. boulardi G486. [(Number of larvae with properly melanized wasp eggs/number of parasitized larvae) × 100)]. Numbers above the bars indicate the number of wasp parasitized larvae examined, numbers in parentheses indicate percentage of larvae that properly encapsulated the L. boulardi G486 eggs (B, C) Encapsulated wasp eggs recovered from larvae 22–24 h after parasitisation, and stained with the plasmatocyte specific protein Nimrod. (B) Control (w1118) and (C) NrgG00305 homozygous mutants. (D, E) Haemocytes 38–40 h post-parasitisation stained with the L1 lamellocyte specific antibody. (D) Control and (E) NrgG00305 homozygous mutants. (F) Control and NrgG00305plasmatocytes attached to L. boulardi G486 eggs. Unlike controls, plasmatocytes from NrgG00305 extend filopodia from their apical side.
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Figure 7: Nrg necessary for proper encapsulation of L. boulardi eggs (A) Encapsulation capacities of Nrg mutant larvae in response to parasitisation by L. boulardi G486. [(Number of larvae with properly melanized wasp eggs/number of parasitized larvae) × 100)]. Numbers above the bars indicate the number of wasp parasitized larvae examined, numbers in parentheses indicate percentage of larvae that properly encapsulated the L. boulardi G486 eggs (B, C) Encapsulated wasp eggs recovered from larvae 22–24 h after parasitisation, and stained with the plasmatocyte specific protein Nimrod. (B) Control (w1118) and (C) NrgG00305 homozygous mutants. (D, E) Haemocytes 38–40 h post-parasitisation stained with the L1 lamellocyte specific antibody. (D) Control and (E) NrgG00305 homozygous mutants. (F) Control and NrgG00305plasmatocytes attached to L. boulardi G486 eggs. Unlike controls, plasmatocytes from NrgG00305 extend filopodia from their apical side.

Mentions: An encapsulation assay was performed on larvae parasitized by the avirulent L. boulardi wasp strain G486. When the avirulent wasp strain G486 parasitizes larvae a darkened cellular capsule is visible in the hemoceol 30–40 h later. While 81% of NrgG00305 heterozygous mutant larvae properly encapsulated and melanised L. boulardi eggs, NrgG00305 homozygous larvae never properly encapsulated the wasp egg (Figure 7A). Similar to NrgG00305 homozygous mutants, none of the larvae expressing Nrg RNAi in haemocytes properly encapsulated the wasp egg (Figure 7A).


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

Williams MJ - BMC Immunol. (2009)

Nrg necessary for proper encapsulation of L. boulardi eggs (A) Encapsulation capacities of Nrg mutant larvae in response to parasitisation by L. boulardi G486. [(Number of larvae with properly melanized wasp eggs/number of parasitized larvae) × 100)]. Numbers above the bars indicate the number of wasp parasitized larvae examined, numbers in parentheses indicate percentage of larvae that properly encapsulated the L. boulardi G486 eggs (B, C) Encapsulated wasp eggs recovered from larvae 22–24 h after parasitisation, and stained with the plasmatocyte specific protein Nimrod. (B) Control (w1118) and (C) NrgG00305 homozygous mutants. (D, E) Haemocytes 38–40 h post-parasitisation stained with the L1 lamellocyte specific antibody. (D) Control and (E) NrgG00305 homozygous mutants. (F) Control and NrgG00305plasmatocytes attached to L. boulardi G486 eggs. Unlike controls, plasmatocytes from NrgG00305 extend filopodia from their apical side.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Nrg necessary for proper encapsulation of L. boulardi eggs (A) Encapsulation capacities of Nrg mutant larvae in response to parasitisation by L. boulardi G486. [(Number of larvae with properly melanized wasp eggs/number of parasitized larvae) × 100)]. Numbers above the bars indicate the number of wasp parasitized larvae examined, numbers in parentheses indicate percentage of larvae that properly encapsulated the L. boulardi G486 eggs (B, C) Encapsulated wasp eggs recovered from larvae 22–24 h after parasitisation, and stained with the plasmatocyte specific protein Nimrod. (B) Control (w1118) and (C) NrgG00305 homozygous mutants. (D, E) Haemocytes 38–40 h post-parasitisation stained with the L1 lamellocyte specific antibody. (D) Control and (E) NrgG00305 homozygous mutants. (F) Control and NrgG00305plasmatocytes attached to L. boulardi G486 eggs. Unlike controls, plasmatocytes from NrgG00305 extend filopodia from their apical side.
Mentions: An encapsulation assay was performed on larvae parasitized by the avirulent L. boulardi wasp strain G486. When the avirulent wasp strain G486 parasitizes larvae a darkened cellular capsule is visible in the hemoceol 30–40 h later. While 81% of NrgG00305 heterozygous mutant larvae properly encapsulated and melanised L. boulardi eggs, NrgG00305 homozygous larvae never properly encapsulated the wasp egg (Figure 7A). Similar to NrgG00305 homozygous mutants, none of the larvae expressing Nrg RNAi in haemocytes properly encapsulated the wasp egg (Figure 7A).

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