Inhibition effect of SUMOylation of peroxisome proliferator activated receptor γ1 on macrophage M2 polarization / 上海交通大学学报（医学版）

ABSTRACT

Objective • To investigate the role and the regulation mechanism of SUMOylation of peroxisome proliferator activated receptor γ1 (PPARγ1) in macrophage M2 polarization induced by interleukin-4 (IL-4). Methods • To investigate the SUMOylation of PPARγ1 and identify its SUMOylated site, immunoprecipitation (IP) with anti-FLAG/HA antibody and Western blotting were used after plasmids FLAG-PPARγ1-WT/mutant and HA-SUMO1 being co-transfected into HEK293T cells. To determine SENP1 can de-SUMOylate PPARγ1, IP was used when HEK293T cells were co-transfected by FLAG-PPARγ1-WT, HA-SUMO1 and RGS-SENP1-WT, or SENP1 mutant plasmids. The change of the endogenous SUMOylation of PPARγ1 during M2 polarization was checked by IP and Western blotting by using PPARγ or SUMO1 antibodies in cell lysates of RAW264.7 cells and primary peritoneal macrophages induced by IL-4. The expression of some M2 related marker genes were detected by real-time quantitative polymerase chain reaction in PPARγ1-WT/mutants stably-overexpressed RAW264.7 cells. Chromatin immunoprecipitation (ChIP) experiment was used to confirm the different ability of binding to the promoter of arginase (Arg1) between PPARγ1-WT and PPARγ1-K77R. Results • It has been identified that the major SUMOylated site of PPARγ1 was Lys77, which could be de-SUMOylated by SENP1. The endogenous SUMOylation of PPARγ1 decreased when macrophage polarized to M2 macrophage induced by IL-4. The expression of Arg1 increased in PPARγ1-K77R stably-overexpressed RAW264.7 cells. PPARγ1-K77R easily bound to the promoter of Arg1 gene, showing more transcription activity. Conclusion • De-SUMOylation of PPARγ1 at Lys77 can enhance its transcription activity by promoting the expression of Arg1 gene, which is involved in the regulation of macrophage M2 polarization.