Mucin disulfide cross-links

Mucin disulfide cross-links are the fundamental structural connections that define the viscoelastic properties of the airway mucus gel [1]. These covalent bonds form between the cysteine-rich terminal domains of large, gel-forming mucin glycoproteins, specifically MUC5AC and MUC5B, creating a complex three-dimensional polymer network [2]. In a healthy respiratory system, this network is essential for trapping inhaled particulates and pathogens, which are then removed via mucociliary clearance [5]. However, in pathological states such as cystic fibrosis, asthma, and chronic obstructive pulmonary disease (COPD), the density of these cross-links increases significantly due to mucin hypersecretion and oxidative stress, resulting in thick, stagnant mucus that obstructs the airways [3]. Therapeutic intervention typically involves the use of mucolytic agents, such as N-acetylcysteine, which function as reducing agents to break these disulfide bridges through thiol-disulfide exchange [4]. By reducing the degree of polymerization, these drugs lower mucus viscosity and elasticity, thereby improving airway clearance and respiratory function [4].

Other names

Mucin disulfide bondsInter-mucin disulfide bridgesMucin polymer cross-linksMucin-mucin disulfide linkages

Reduction of intermolecular disulfide bonds via thiol-disulfide exchange, leading to the depolymerization of mucin networks and reduction of mucus viscosity [3, 4].