EFFECTS OF LIPID COMPOSITION, CURVATURE, AND MUTATIONS ON CONNEXIN DYNAMICS

Connexins (Cxs) are a conserved family of transmembrane proteins that assemble into intercellular channels enabling direct communication between neighboring cells. These structures, known as gap junctions (GJs), consist of two hemichannels (HCs), or connexons, each formed by six connexin monomers. Through these channels, cells coordinate electrical activity, metabolic exchange, and signaling processes across tissues.

Cx46 and Cx50 are the main connexins expressed in the eye lens, where membrane composition is strongly enriched in cholesterol. High cholesterol levels have been proposed to reduce hydrophobic barrier formation, limit lipid oxidation, and preserve lens transparency during aging. Cx43 is another widely expressed and extensively studied connexin, playing central roles in cardiac tissue, the brain, and epithelia.

Using Molecular Dynamics simulations, this presentation explores two complementary aspects of connexin hemichannel organization and dynamics. First, in lens connexins Cx46 and Cx50, we analyze how lipid composition and point mutations affect hemichannel stability. Results show that cholesterol preferentially binds to the protein surface, potentially increasing local membrane rigidity and contributing to channel stabilization, suggesting that age-related changes in membrane composition could directly impact gap junction function in the lens.

Second, for Cx43, we examine the influence of membrane environment and extracellular disulfide bridges on hexameric hemichannel organization. Despite differences between bilayer and nanodisc systems, the overall intersubunit organization remains highly conserved. In contrast, extracellular disulfide bridges induce local rearrangements in extracelular regions, reducing regional flexibility and modifying pore-neck geometry without disrupting the global hexameric architecture.

Overall, these findings highlight how membrane composition and covalent modulation contribute to connexin stability and dynamics, providing a molecular framework to understand how changes in the cellular environment may impact gap junction function.