Animals produce different types of mucus for different purposes. Although previous studies have looked at individual components contained in mucus, especially the proteins, little is known about the overall composition of various mucuses and how that composition affects function.
“It’s remarkable how little we know about this material that’s ubiquitous and central to life,” says Adam B. Braunschweig of the Advanced Science Research Center at the Graduate Center of the City University of New York.
Braunschweig and coworkers have now done a comparative analysis of three types of mucus produced by the common garden snail Cornu aspersum (Nat. Commun. 2023, DOI: 10.1038/s41467-023-41094-z). An adhesive mucus secreted by the snail’s foot helps the animal stick to surfaces. A lubricating mucus, also produced by the foot, helps the snail glide along surfaces. A third mucus on the snail’s back protects the animal from predators.
The researchers analyzed multiple components from each mucus, including proteins, glycans, and ions. They also determined mechanical properties of the secretions. They detected 71 proteins, 18 of which were previously unknown and for which functions could not be assigned via database searches. In each mucus, 40% to 50% of the proteins were extracellular matrix proteins, including 11 different collagens. In addition, the researchers found a previously unknown class of mollusk proteins with nearly identical N-terminal regions but variable C-terminal regions.
A major difference between the three mucuses is in the concentration of calcium ions, which are known to promote crosslinking of the mucus. “The stiff barrier and the adhesive mucus are full of calcium,” Braunschweig says. “The lubricating mucus has the lowest calcium concentration, as well as proteins to sequester calcium. It just tries to keep calcium out, so those proteins can slide along each other and lubricate very well.”
“The study is important for the penetrating analyses in both chemical and mechanical arenas as well as correlating between the two,” J. Herbert Waite, an expert on mollusk adhesives at the University of California, Santa Barbara, writes in an email. “I like the fact that the investigators chose to compare 3 functionally different mucus materials in a simple garden snail where the popular tendency has been to dismiss all slug and snail mucuses as the ‘same icky mess.’”
Snail mucus is already being used in some skin-care products. “Prior to this published study, it was unclear exactly what land snail mucus consisted of, and therefore it was hard to gauge what, if anything, may contribute to skin regeneration,” Scott F. Cummins, who studies snails and other mollusks at the University of the Sunshine Coast, writes in an email. “Now that we recognize that the mucus actually consists of a large variety of proteins and small molecules, of which many are known to play a role in defense/protection and lubrication, it makes things clearer as to how they could be beneficial for our skin.”
Braunschweig and coworkers plan to use their mucomic approach to analyze mucuses from other species. “What we’re doing now is looking at mucuses from different animals with the same behavior and seeing what commonalities they have. The goal is to obtain identical types of data sets so that we can compare them one-to-one and isolate commonalities and differences,” Braunschweig says.