Scavenger receptor B1 facilitates the endocytosis of Escherichia coli via TLR4 signaling in mammary gland infection

Abstract

SCARB1 belongs to class B of Scavenger receptors (SRs) that are known to be involved in binding and endocytosis of various pathogens. SRs have emerging role in regulating innate immunity and host-pathogen interactions by acting in co-ordination with Toll-like receptors. Little is known about the function of SCARB1 in milk-derived mammary epithelial cells (MECs). This study reports the role of SCARB1 in infection and its potential association in TLR4 signaling on bacterial challenge in Goat mammary epithelial cells (GMECs). The novelty in the establishment of MEC culture lies in the method that aims to enhance the viability of the cells with intact characteristics upto a higher passage number. We represent MEC culture to be used as a potential infection model for deeper understanding of animal physiology especially around the mammary gland. On E.coli challenge the expression of SCARB1 was significant in induced GMECs at 6 h. Endoribonuclease- esiRNA based silencing of SCARB1 affects the expression of TLR4 and its pathways i.e. MyD88 and TRIF pathways on infection. Knockdown also affected the endocytosis of E.coli in GMECs demonstrating that E.coli uses SCARB1 function to gain entry in cells. Furthermore, we predict 3 unique protein structures of uncharacterized SCARB1 (Capra hircus) protein. Overall, we highlight SCARB1 as a main participant in host defence and its function in antibacterial advances to check mammary gland infections.

Mannose-functionalization of reconstituted high-density lipoprotein nanoparticles improves payload delivery and enhances M2-to-M1 phenotype reprogramming of RAW 264.7 macrophages polarized by B16-F10 melanoma cells

“…Pre-treatment with mannose did not significantly prevent the NR uptake by the cells from the rHDL-DSPE-PEG-NR NPs, also suggesting that the mannose moiety is important for the involvement of the mannose receptor in the cellular NR uptake (Figure 5D). While reports show that CD206 mediates uptake of particles via endocytosis (van der Zande et al, 2021), both endocytic and non-endocytic mechanisms have been noted for the SR-B1-mediated uptake of HDL contents or extracellular objects (Silver et al, 2001;Nieland et al, 2005;Pagler et al, 2006;Zhang et al, 2019;Plochberger et al, 2020;Taban et al, 2023). To investigate the payload uptake mechanism, the macrophages were pre-treated with cytochalasin D (CytD), an actin polymerization inhibitor which targets macropinocytosis, phagocytosis, clathrin-mediated endocytosis and clathrin-independent endocytosis (Francia et al, 2019).…”