Recombinant Human Intelectin Binds Bovine Lactoferrin and Its Peptides

Abstract

Intelectin (IntL), a lectin that exists on the brush border membrane of the small intestine, plays a role in the innate immune response and also acts as a receptor for lactoferrin (LF), an iron-binding glycoprotein found in milk and other secretions. Similar to human LF (hLF), bovine LF (bLF) has been shown to induce proliferation and differentiation of human enterocytes and to modulate their cytokine productions. To evaluate the interaction between human IntL (hIntL) and bLF, recombinant hIntL (rhIntL) conjugated with a tag sequence was examined for its ligand-binding capacity by using microtiter plates coated with LF or other proteins. Interestingly, rhIntL showed higher binding for bLF than hLF. It also bound pepsin hydrolysate of bLF, but to a lower degree than native bLF. A very low binding of rhIntL was observed for bovine serum albumin or transferrin. These findings suggest that hIntL acts as a receptor for bLF and its digested fragments.

Intelectin-1 Is a Prominent Protein Constituent of Pathologic Mucus Associated with Eosinophilic Airway Inflammation in Asthma

“…This binding was inhibited by heparin, suggesting a charge-based interaction between ITLN-1 and lactoferrin's basic N-terminal region (15), and increased by methyl galactofuranoside. Galactofuranoside is found in many microbial polysaccharides and is recognized as a preferred glycan ligand for ITLN-1 (7,16). Our data suggest that ITLN-1 binding to galactofuranosyl residues on microorganisms might improve its ability to bind lactoferrin and target it to regions of high microorganism burden.…”

“…The host defense roles of ITLN-1 may result from its ability to bind structures expressed by microorganisms in a carbohydrate-dependent manner (5). ITLN-1 is also a binding partner for lactoferrin (6), and ITLN-1 may cooperate with lactoferrin in host defense (6,7).…”

Lactoferrin inhibits E. coli O157:H7 growth and attachment to intestinal epithelial cells

“…Ovotransferrin was more effective than human and bovine lactoferrin in preventing attachment and entry of Chlamydophila psittaci to avian macrophages (Beeckman et al, 2007). On the other hand, uptake of bLF in Caco-2 cells might be more effective than hLF as demonstrated by Shin et al (2008), who studied the interaction between human and bovine LF and intelectin, a lectin present on the brush border of intestinal cells. Thus, internalized bLF could no longer prevent bacterial attachment to host cells.…”

The effect of carbohydrate moiety structure on the immunoregulatory activity of lactoferrin in vitro

“…It is plausible that mammals have not developed specific receptors for LF because it is capable of interacting with its host cell receptors through various peptide or carbohydrate regions [16]. LF uses low-and high-affinity receptors that evolved to recognize structures on viruses, bacteria, and fungi: toll-like receptors [17,18], heparan sulfate-containing proteoglycans [19,20], CD14 [21], nucleolin [22], intelectin [23], C-type lectins [24], and sialic acid-binding immunoglobulin superfamily lectins (siglecs) [25]. In the C-type lectin family, LF uses mannose receptor [26] and DC-SIGN [27].…”