STAT3 is a PTPRD substrate in the liver and regulates peroxisomal fatty acid metabolism. (IMAGE)
Caption
(a) PTPRD and STAT3 target gene expression along the cholangiocyte-LPC-hepatocyte pseudotime trajectory (GSE185477). (b) PTPRD expression inversely correlates (Spearman’s r=−0.46) with STAT3 target gene expression in the human liver. (c) Genetic deletion of Ptprd is associated with a significantly (Kruskal-Wallis test) increased STAT3 Y705 phosphorylation (pSTAT3) in the liver of C57BL/6 mice as assessed by western blot analysis and quantified by band densitometry. Data are presented as means±SD. (d) pSTAT3 is a binding partner of PTPRD in hepatic cells. Co-immunoprecipitation of 5 µg recombinant GST-PTPRD fusion protein (rPTPRD) or GST protein alone was incubated with 1 mg IL-6-stimulated HepaRG lysate. Subsequent immunostaining on the same membrane for stain-free (all proteins), anti-pSTAT3 (Y705) and anti-GST (after stripping). (e) Genomic PTPRD silencing promotes IL-6-induced STAT3 phosphorylation. PTPRD was genetically silenced in undifferentiated HepaRG cells using CRISPR-Cas9 (KD). KD and wild-type PTPRD-expressing cells (WT) were serum-starved overnight prior 30 min IL-6 stimulation and analysed subsequently by immunoblotting. Human PTPRD antibody detects a PTPRD fragment after ectodomain shedding. (f) GSEA of dHepaRG cells silenced for PTPRD, showing an enhanced transcriptional activity of STAT3 signalling and impaired expression of gene sets associated with fatty acid metabolism. (g) Combined silencing of PTPRD and STAT3 in FFA-treated dHepaRG cells is able to reverse the gene expression alterations observed with PTPRD silencing alone, including peroxisomal function and fatty acid metabolism. ABCD, ATP binding cassette subfamily D; ACOX1, acyl-CoA oxidase 1; FFA, free fatty acids; GSEA, gene set enrichment analysis; GST, glutathione-S-transferase; IL, interleukin; LPC, liver progenitor cell; NES, normalised enrichment score; PEX19, peroxisomal biogenesis factor 19; PHYH, phytanoyl-CoA 2-hydroxylase; PTPRD, protein tyrosine phosphatase delta; SOCS3, suppressor of cytokine signalling 3; STAT3, signal transducer and activator of transcription 3; VLCFAs, very long chain fatty acids. *P<0.05, ***p<0.001, ****p<0.0001.
Credit
By Armando Andres Roca Suarez, Frank Jühling, Julien Moehlin et al.
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