title: C5L2 and C5aR interaction in adipocytes and macrophages: insights into adipoimmunology.
abstract: Obesity is associated with inflammation characterized by increased infiltration of macrophages into adipose tissue. C5aR-like receptor 2 (C5L2) has been identified as a receptor for acylation-stimulating protein (ASP) and the inflammatory factor C5a, which also binds C5aR. The present study examines the effects of ligands ASP and C5a on interactions between the receptors C5L2 and C5aR in 3T3-L1 adipocytes and J774 macrophages. BRET experiments indicate that C5L2 and C5aR form homo- and heterodimers in transfected HEK 293 cells, which were stable in the presence of ligand. Cell surface receptor levels of C5L2 and C5aR increased during 3T3-L1 adipocyte differentiation; both receptors are also highly expressed in J774 macrophages. Using confocal microscopy to evaluate endogenous receptors in adipocytes following stimulation with ASP or C5a, C5L2 is internalized with increasing perinuclear colocalization with C5aR. There is little C5a-dependent colocalization in macrophages. While adipocyte-conditioned medium (ACM) increased C5L2-C5aR colocalization in macrophages, this was blocked by C5a. ASP stimulation increased Akt (Ser(473)) phosphorylation in both cell types; C5a induced slight Akt phosphorylation in adipocytes with less effect in macrophages. ASP, but not C5a, increased fatty acid uptake/esterification in adipocytes. C5L2-C5aR homodimerization versus heterodimerization may thus contribute to differential responses obtained following ASP vs C5a stimulation of adipocytes and macrophages, providing new insights into the complex interaction between these two cell types within adipose tissue. Studying the mechanisms involved in the differential responses of C5L2-C5aR activation based on cell type will further our understanding of inflammatory processes in obesity.
authors.affiliation: Centre de Recherche de Institut Universitaire de Cardiologie et de Pneumologie de Québec (CRIUCPQ), Québec, QC, Canada.
authors.forename: Pegah
authors.initials: P
authors.lastname: Poursharifi
authors.forename: Marc
authors.initials: M
authors.lastname: Lapointe
authors.forename: Darlaine
authors.initials: D
authors.lastname: Pétrin
authors.forename: Dominic
authors.initials: D
authors.lastname: Devost
authors.forename: Danny
authors.initials: D
authors.lastname: Gauvreau
authors.forename: Terence E
authors.initials: TE
authors.lastname: Hébert
authors.forename: Katherine
authors.initials: K
authors.lastname: Cianflone
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D003176:Complement C3; D015936:Complement C5a / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D019281:Dimerization; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D044087:Receptor, Anaphylatoxin C5a; D019707:Receptors, Chemokine / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D011951:Receptors, Complement / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000494:pharmacology
chemical_list: C038245:C3 protein, human; C488033:C5AR1 protein, human; C000594938:C5ar2 protein, mouse; D003176:Complement C3; D017077:Culture Media, Conditioned; D036341:Intercellular Signaling Peptides and Proteins; D044087:Receptor, Anaphylatoxin C5a; D019707:Receptors, Chemokine; D011951:Receptors, Complement; D011994:Recombinant Proteins; D015936:Complement C5a; D051057:Proto-Oncogene Proteins c-akt