Fig. 6

EphA4-null BMDMs show enhanced efferocytosis regulated by ERK/ Stat6/MERTK. A–I EphA4 deletion improves the efferocytosis efficiency of BMDMS in vitro. A–H Representative images showing the engulfment of the pHrodo-stained apoptotic (but not live) Jurkat cells (red) by GFP + untreated WT (A–D) and EphA4 KO (E–H) BMDMS. I Quantification of the efferocytosis efficiency of WT and EphA4 KO BMDMS after stimulation with LPS and HMGB1 for 4 h. J Efferocytosis of EphA4 KO BMDMSs is mediated by the blockade of forward EphA4, not reverse ephrin signals. Treatment of WT and EphA4 KO BMDMS with clustered EphA4-FC to activate reverse ephrin signals did not reduce the efferocytosis of EphA4 KO BMDMS. K–M mRNA expression of Mertk (K), Gas6 (L), and Pros1 (M) with and without engulfment of apoptotic Jurkat cells. EphA4 KO BMDMSs have higher expression of Mertk and Gas6 than WT. N The use of MERTK inhibitor reduced efferocytosis of both WT and EphA4 KO BMDMS; however, Stat6 and ERK inhibitors selectively reduced efferocytosis in EphA4 KO BMDMS. O Stat6 inhibitor reduced Mertk and Gas6 expression, and ERK inhibitor reduced Gas6 expression in KO BMDMS engulfing apoptotic Jurkat cells. P Suggested pathway for the regulation of efferocytosis by EphA4. N = 5–6 mice/group. Ns = non-significant; *P < 0.05; **P < 0.01; ***P < 0.001, ****P < 0.0001. Two-way ANOVA followed by Šídák’s multiple comparisons test (I–N) or one-way ANOVA followed by Tukey’s multiple comparisons test (O). Scale bar = 50 µm in A–H