C5L2 and C5aR interaction in adipocytes and macrophages: Insights into adipoimmunology

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• 作者：Pegah Poursharifi^a ; ^b ; Marc Lapointe^a ; Darlaine Pé ; trin^c ; Dominic Devost^c ; Danny Gauvreau^a ; ^b ; Terence E. Hé ; bert^c ; Katherine Cianflone^a ; ^b ; ^{katherine.cianflone@criucpq.ulaval.ca}
• 关键词：ASP ; acylation-stimulating protein ; BRET ; bioluminescence resonance energy transfer ; C5L2 ; C5aR-like receptor 2 ; GPCR ; G protein-coupled receptor ; TGS ; triglyceride synthesis
• 刊名：Cellular Signalling
• 出版年：2013
• 出版时间：April, 2013
• 年：2013
• 卷：25
• 期：4
• 页码：910-918
• 全文大小：1130 K

文摘

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 (Ser⁴⁷³) 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.