Wnt1 Up-regulates CD36 Expression Via TCF4 And PPAR-γ In Macrophages And MIR-29a Promotes SRA Expression By Targeting QKI In Macrophages

Article one:wntl postively regulates CD36 expression via TCF4 and PPAR-y in macrophagesBackgroundScavenger receptors including CD36 control the phagocytosis of oxidized low-density lipoprotein and play an important role in macrophage physiology, but the underlying molecular mechanism by which CD36 is regulated in macrophages remains to be determined.ObjectiveWe aim to investigate the role of wntl in macrophage physiology and further explore the molecular mechanism through which wntl regulates CD36. We also want to understand the regulatory mechanism of wntl upregulation during monocyte-macrophage differentiation.MethodsHere, we investigated the relationship between Wntl and CD36 in macrophage derived from GM-CSF stimulated monocytes. CD36 was suppressed following knockdown of Wntl by siRNA, while it was increased by ectopic overexpression of Wntl in macrophages. Using a P-catenin inhibitor, pcroxisome proliferator-activated receptor gamma (PPAR-y) siRNA, and transcription factor 4 (TCF4) siRNA, we demonstrated that Wntl regulates the expression of CD36 through TCF4 and PPAR-y. Co-immunoprecipitation, chromatin immunoprecipitation, and immunofluorescence experiments showed that P-catenin interacted with PPAR-y and that PPAR-y and TCF4 colocalized in the nucleus. Furthermore, Pax3 upregulating Wntl during monocyte-macrophage differentiation was demonstated by western blots.ResultsOur study demonstrated that wntl promotes CD36 expression via activation of PPAR-y and TCF4 in macrophages derived from GM-CSF stimulated monocytes.ConclusionsOur findings suggest that Wntl plays an important role in macrophage physiology via activation of the canonical Wnt pathway.Article two:MiR-29a promotes scavenger receptor A expression by targeting QKI (quaking) during monocyte-macrophage differentiationBackgroundMonocyte differentiation into macrophages results in upregulation of miR-29a and scavenger receptor A (SRA) expression, while the expression of RNA binding protein, QKI is downregulated. Since SRA is a functionally important protein in atherosclerosis, it is imperative to understand the various mechanisms involved in its regulation specially the mechanism of miR-29a mediated SRA regulation. There are individual studies linking miR-29a to SRA or QKI to monocyte differentiation, but there is no evidence of any linkage among them.ObjectivesAim to explore the detail mechanism of miR-29a upregulated SRA, We also want to understand the relationship among miR-29a, QKI and SRA during monocyte-macrophage differentiation.MethodsIn this study, we firstly validated the upregulation of miR-29a and inhibition of QKI during monocyte-macrophage differentiation. QKI expression was detected when the differentiated macrophages were treated with miR-29a and its inhibitor. Combined with luciferase reporter techonology, QKI is demonstrated to be a direct target of mir-29a. In addition, it was observed by bioinformatics analysis that 3’UTR in SRA mRNA, has QKI binding site. So, we attempted to further understand QKI’s role in SRA regulation. The macrophages were manipulated either with overexpression of QKI or by its ablation and it was observed that QKI suppressed SRA at the transcriptional level. Moreover, with the help of luciferase reporter vector, it was established that QKI inhibited SRA transcription though binding to QRE of 3’UTR in SRA mRNA. Furthermore, to link the QKI mediated regulation of SRA expression with its functional activity; we analyzed lipid uptake capacity of macrophages transfected with either ectopic OKI plasmid or ablated for QKI.ResultsWe showed that miR-29a inhibited QKI expression through binding to 3’UTR of QKI mRNA. And, QKI inhibited SRA expression through binding to QRE region of SRA mRNA and promoting degradation of SRA mRNA.ConclusionsMiR-29a plays an important role in SRA expression during monocyte-macrophage differentiation through targeting RNA binding protein-QKI.