Gpr137b is an orphan G-protein-coupled receptor associated with M2 macrophage polarization

• Published in: Biochemical and biophysical research communications 2019-02, Vol.509 (3), p.657-663
• Main Authors: Islam, Zohirul, Inui, Takashi, Ishibashi, Osamu
• Format: Article
• Language: English
• Subjects: Animals; Cell Polarity; CRISPR-Cas Systems; CRISPR/Cas9; Gene Expression; GPCR; Interleukin-4 - immunology; Lipopolysaccharides - immunology; Macrophage; Macrophage polarization; Macrophages - cytology; Macrophages - immunology; Macrophages - metabolism; Mice; RAW 264.7 Cells; Receptors, G-Protein-Coupled - genetics; Receptors, G-Protein-Coupled - immunology
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/j.bbrc.2018.12.140

Macrophages are classified mainly into two subtypes, M1 and M2, which exhibit distinct phenotypes, based on their microenvironment. Although recent studies have suggested that G-protein-coupled receptors (GPCRs) are associated with M1/M2 macrophage polarization, available information on GPCR-mediated macrophage polarization is still limited. In the present study, we identified Gpr137b as an orphan GPCR abundantly expressed in RAW264, a mouse macrophage cell line, and illuminated its role in M2 macrophage polarization. We generated Gpr137b-knockout (Gpr137b-KO) clones of RAW264 cells using the CRISPR/Cas9 genome editing system. Two independent Gpr137b-KO clones were isolated, which were demonstrated to have frameshifting 188-nucleotide deletions at a region containing the ATG start codon of Gpr137b. Consistently, qRT-PCR analysis revealed that the deleted region is not transcribed. We then treated the Gpr137b-KO and wildtype RAW264 cells with interleukin-4 (IL-4) to induce M2 macrophage polarization. Microarray analysis revealed that the IL-4-induced gene expression of representative M2 macrophage markers was significantly reduced in the Gpr137b-KO cells, and this was validated by qRT-PCR analysis. By contrast, M1 macrophage marker gene expression induced by lipopolysaccharide was unaffected by Gpr137b-KO. Collectively, the current study shows that Gpr137b is a possible regulator of M2 macrophage polarization. •Macrophages are classified mainly into two subtypes, M1 and M2.•G-protein-coupled receptors (GPCRs) are involved in many pathophysiological events.•The orphan GPCR Gpr137b is abundantly expressed in a macrophage cell line, RAW264.•Gpr137b is involved in interleukin-4-induced M2 macrophage polarization.•Gpr137b is not involved in lipopolysaccharide-induced M1 macrophage polarization.