Lactoferrin and its hydrolysate bind directly to the oleate‐activated form of the lipolysis stimulated lipoprotein receptor

Abstract

The hepatic removal of triglyceride-rich chylomicrons during the postprandial phase represents an important step towards determining the bioavailability of dietary lipids amongst the peripheral tissues. Indeed, elevated postprandial lipemia is often associated with obesity and increased risk of coronary heart disease. The milk protein, lactoferrin, has been shown to inhibit hepatic chylomicron remnant removal by the liver, resulting in increased postprandial lipemia. Despite numerous studies on potential targets for lactoferrin, the molecular mechanisms underlying the effect of lactoferrin remain unclear. We recently demonstrated that the lipolysis stimulated lipoprotein receptor (LSR) contributes to the removal of triglyceride-rich lipoproteins during the postprandial phase. Here, we report that while lactoferrin does not have any significant effect on LSR protein levels in mouse Hepa1-6 cells, this protein colocalizes with LSR in cells but only in the presence of oleate, which is needed to obtain LSR in its active form as lipoprotein receptor. Ligand blotting using purified LSR revealed that lactoferrin binds directly to the receptor in the presence of oleate and prevents the binding of triglyceride-rich lipoproteins. Both C-and N-lobes of lactoferrin as well as a mixture of peptides derived from its hydrolysis retained the ability to bind LSR in its active form. We propose then that the elevated postprandial lipemia observed upon lactoferrin treatment in vivo is mediated in part by its direct interaction with free fatty acid activated LSR, thus preventing clearance of chylomicrons and their remnants through the LSR pathway. Abbreviations apoE, apolipoprotein E; FFA, free fatty acid; HPRT, hypoxanthine guanine phosphoribosyltransferase; LDL, low-density lipoprotein; LDL-R, LDL receptor; Lf, lactoferrin; LRP, LDL-R-related protein; LSR, lipolysis stimulated lipoprotein receptor; TG, triglyceride; VLDL, very-low-density lipoprotein.

The Role of Lipolysis Stimulated Lipoprotein Receptor in Breast Cancer and Directing Breast Cancer Cell Behavior

“…While additional studies are warranted, the possibility exists that tissue specific factors may promote a more generalized membrane-signaling role for LSR in breast tissue, and that activation of LSR signaling drives a re-programming of the transcriptome potentially through the downstream activation of transcription factors. Indeed LSR has been shown to bind to 14-3-3s in HEK293 cells using affinity capture and proteomic analysis [30], and was shown to directly bind lactoferrin in ligand blot assays [31] highlighting a multitude of signaling possibilities for LSR in a tissue specific context.…”

Intracellular Retention and Subsequent Release of Bovine Milk Lactoferrin Taken Up by Human Enterocyte-Like Cell Lines, Caco-2, C2BBe1 and HT-29

“…29) In respect of the subsequently released LF fragments, a peptide fragment at the LF Nterminus, called lactoferricin, is known to show higher anti-bacterial activity than LF, 30) and both the N-and Clobes of LF have recently been reported to bind to an LF receptor, the lipolysis-stimulated lipoprotein receptor, of hepatocytes and thereby to inhibit the hepatic uptake of triglyceride-rich lipoproteins. 31) LF fragmentation by enterocyte subcellular proteolysis may therefore enhance the anti-microbial activity and inhibitory activity toward lipoprotein uptake. Further studies are needed to characterize the released LF fragments and the polarized apical-or basolateral-release from the cell monolayers to understand the physiological significance of subcellular processing of LF by the intestinal epithelial cells.…”

Inhibitory Action of Benzo[α]pyrene on Hepatic Lipoprotein Receptors In Vitro and on Liver Lipid Homeostasis in Mice

“…Rat liver plasma membranes were prepared as previously described [36]. LDL (1.025< density ( d ) <1.055 g/mL) and VLDL ( d <1.006 g/mL) were isolated from pooled human plasma [8].…”