title: Leukocyte immunoglobulin-like receptor B4 regulates key signalling molecules involved in FcγRI-mediated clathrin-dependent endocytosis and phagocytosis.
abstract: FcγRI cross-linking on monocytes may trigger clathrin-mediated endocytosis, likely through interaction of multiple intracellular molecules that are controlled by phosphorylation and dephosphorylation events. However, the identity of phospho-proteins and their regulation are unknown. We proposed the leukocyte immunoglobulin-like receptor B4 (LILRB4) that inhibits FcγRI-mediated cytokine production via Tyr dephosphorylation of multiple kinases, may also regulate endocytosis/phagocytosis through similar mechanisms. FcγRI and/or LILRB4 were antibody-ligated on THP-1 cells, lysates immunoprecipitated using anti-pTyr antibody and peptides sequenced by mass spectrometry. Mascot Search identified 25 Tyr phosphorylated peptides with high confidence. Ingenuity Pathway Analysis revealed that the most significantly affected pathways were clathrin-mediated endocytosis and Fc-receptor dependent phagocytosis. Tyr phosphorylation of key candidate proteins in these pathways included common γ-chain of the Fc receptors, Syk, clathrin, E3 ubiquitin protein ligase Cbl, hepatocyte growth factor-regulated tyrosine kinase substrate, tripartite motif-containing 21 and heat shock protein 70. Importantly, co-ligation of LILRB4 with FcγRI caused significant dephosphorylation of these proteins and was associated with suppression of Fc receptor-dependent uptake of antibody-opsonised bacterial particles, indicating that LILRB4. These results suggest that Tyr phosphorylation may be critical in FcγRI-dependent endocytosis/phagocytosis that may be regulated by LILRB4 by triggering dephosphorylation of key signalling proteins.
authors.affiliation: Inflammation and Infection Research Centre, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW 2052, Australia.
authors.forename: Mijeong
authors.initials: M
authors.lastname: Park
authors.affiliation: Bioanalytical Mass Spectrometry Facility, Department of Medicine, University of NSW, Sydney, NSW 2052, Australia.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Raftery
authors.affiliation: Inflammation and Infection Research Centre, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW 2052, Australia.|Department of Respiratory Medicine, Prince of Wales Hospital, Sydney, NSW 2031, Australia.
authors.forename: Paul S
authors.initials: PS
authors.lastname: Thomas
authors.affiliation: Inflammation and Infection Research Centre, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW 2052, Australia.
authors.forename: Carolyn L
authors.initials: CL
authors.lastname: Geczy
authors.affiliation: Inflammation and Infection Research Centre, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW 2052, Australia.
authors.forename: Katherine
authors.initials: K
authors.lastname: Bryant
authors.affiliation: Inflammation and Infection Research Centre, School of Medical Sciences, Faculty of Medicine, University of NSW, Sydney, NSW 2052, Australia.
authors.forename: Nicodemus
authors.initials: N
authors.lastname: Tedla
mesh_terms: D002966:Clathrin / Q000378:metabolism*; D004705:Endocytosis; D006801:Humans; D008562:Membrane Glycoproteins; D009000:Monocytes / Q000276:immunology*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D017452:Receptors, IgG / Q000378:metabolism*; D011971:Receptors, Immunologic; D000074084:THP-1 Cells
chemical_list: D002966:Clathrin; C489017:FCGR1A protein, human; C107907:LILRB4 protein, human; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D017452:Receptors, IgG; D011971:Receptors, Immunologic