Glycocalyx crowding with synthetic mucin mimetics strengthens interactions between soluble and virus-associated lectins and cell surface glycan receptors

Abstract

Membrane-associated mucins protect epithelial cell surfaces against pathogenic threats by serving as non-productive decoys that capture infectious agents and clear them from the cell surface and by erecting a physical barrier that restricts their access to target receptors on host cells. However, the mechanisms through which mucins function are still poorly defined due to a limited repertoire of tools available for tailoring their structure and composition in living cells with molecular precision. Using synthetic glycopolymer mimetics of mucins, we modeled the mucosal glycocalyx on red blood cells (RBC) and evaluated its influence on lectin (SNA) and virus (H1N1) adhesion to endogenous sialic acid receptors. The glycocalyx inhibited the rate of SNA and H1N1 adhesion in a size- and density-dependent manner, consistent with current view of the mucins as providing a protective shield against pathogens. Counterintuitively, increasing density of the mucin mimetics enhanced the retention of bound lectins and viruses. Careful characterization of SNA behavior at the RBC surface using a range of biophysical and imaging techniques revealed lectin-induced crowding and reorganization of the glycocalyx with concomitant enhancement in lectin clustering, presumably through the formation of a more extensive glycan receptor patch at the cell surface. Our findings indicate that glycan-targeting pathogens may exploit the biophysical and biomechanical properties of mucins to overcome the mucosal glycocalyx barrier.

Principles of glycocalyx engineering with hydrophobic-anchored synthetic mucins

“…However, based on examining the effect of the wash step, we believe the low MW synMUCs are more readily lost by agitation of the membrane and likely do incorporate similarly to the others. These data were unexpected since Godula et al reported higher efficiency incorporation for a 30mer glucosylated PEG vs. a 140mer or 440mer (Honigfort et al, 2021). The discrepancy could potentially be due to the polymer structure, which in our case is inherently more rigid, the cell type employed, which in their case was red blood cells which have a compact and minimal glycocalyx and do not endocytose, or the structural differences in the cholesterol structures used.…”

“…Study of the cellular glycocalyx is a rapidly growing area in need of tools to precisely probe molecular structure-function relationships. Cell-surface engineering with synthetic mucinmimetic materials has emerged as a strategy which has already provided insights on glycocalyx mechanics, cancer biology, and infection (Paszek et al, 2014;Huang et al, 2017;Delaveris et al, 2020;Honigfort et al, 2021). Though various materials have been used as mucin mimics, a common engineering strategy has been used.…”

“…Consequently, researchers have investigated a variety of synthetic mucin-mimetic structures along with methods to display them on cell-surfaces. These approached have shed light on processes from oncogenesis (Paszek et al, 2014;Woods et al, 2017) and neural development Pulsipher et al, 2014) to infection processes (Delaveris et al, 2020;Honigfort et al, 2021).…”