Effect of human very low-density lipoproteins on cardiotrophin-like cytokine factor 1 (CLCF1) activity

Sarah Pasquin,Mukut Sharma,Roger Bosse,Catherine Martel,Gregory J Warner,Przemyslaw Sapieha,Virginia Savin,Agnieszka Dejda,Aurélie Tormo,Salma Chehboun,Gaétan Mayer,Jean-François Gauchat,Yasmine Meliani

doi:10.1038/s41598-018-22400-y

Abstract

The cytokines CLCF1 and CNTF are ligands for the CNTF receptor and the apolipoprotein E (ApoE) receptor sortilin. Both share structural similarities with the N-terminal domain of ApoE, known to bind CNTF. We therefore evaluated whether ApoE or ApoE-containing lipoproteins interact with CLCF1 and regulate its activity. We observed that CLCF1 forms complexes with the three major isoforms of ApoE in co-immunoprecipitation and proximity assays. FPLC analysis of mouse and human sera mixed with CLCF1 revealed that CLCF1 co-purifies with plasma lipoproteins. Studies with sera from ApoE−/− mice indicate that ApoE is not required for CLCF1-lipoprotein interactions. VLDL- and LDL-CLCF1 binding was confirmed using proximity and ligand blots assays. CLCF1-induced STAT3 phosphorylation was significantly reduced when the cytokine was complexed with VLDL. Physiological relevance of our findings was asserted in a mouse model of oxygen-induced retinopathy, where the beneficial anti-angiogenic properties of CLCF1 were abrogated when co-administrated with VLDL, indicating, that CLCF1 binds purified lipoproteins or lipoproteins in physiological fluids such as serum and behave as a “lipocytokine”. Albeit it is clear that lipoproteins modulate CLCF1 activity, it remains to be determined whether lipoprotein binding directly contributes to its neurotrophic function and its roles in metabolic regulation.

Highlights

Cardiotrophin-like cytokine (CLCF1) is an IL-6 family cytokine[1,2] efficiently secreted as a complex with the soluble cytokine receptor cytokine-like factor 1 (CRLF1)[3,4]
The role of CLCF1 as a key ciliary neurotrophic factor receptor (CNTFR) ligand during development is corroborated by similarities in the phenotypes of CLCF1, CRLF1 and CNTFR deficient mice[19,23,24,25] and the overlap between the syndromes associated with mutations in CLCF1, CRLF1 and LIFRβ genes[4,26,27,28]
To exclude possibility that the VLDL-effect is linked to a characteristic of the Ba/F3 pro-B cell line, we investigated the effect of the lipoproteins on the binding of CLCF1 to IMR-32 human neuroblastoma cells or the 3T3-L1 mouse pre-adipocytes both expressing CNTFR5,14

Summary

Introduction

Cardiotrophin-like cytokine (CLCF1) is an IL-6 family cytokine[1,2] efficiently secreted as a complex with the soluble cytokine receptor cytokine-like factor 1 (CRLF1)[3,4]. The effects of CNTF are believed to be both central and systemic, as CNTFR is expressed in the region of the brain controlling energy balance, in adipose tissues and in skeletal muscle[12,14,15,16] Thanks to these promising preclinical results, a CNTF derivative was tested in clinical trials in which significant weight loss was observed[17,18], indicating that activation of the CNTFR can regulate food intake and metabolism. Mutations in CRLF1 and CLCF1 genes result in Crisponi (MIM 601378) and cold-induced sweating (CISS; MIM 272430 and 610313) syndromes, two rare overlapping recessive conditions[4,26,27,29] Infants with these conditions manifest marked disinterest in food[4,26,27,29] suggesting CLCF1, alike CNTF can regulate food intake. We identified CLCF1 in the serum of FSGS patients and observed that CLCF1 activates the STAT3 signaling in glomeruli and podocytes and induces albuminuria in mice and proteinuria in rats[33], indicating that this cytokine could represent such factor

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Conclusion