Stabilization and swelling of hagfish slime mucin vesicles

Abstract

SUMMARYWhen agitated, Atlantic hagfish (Myxine glutinosa) produce large quantities of slime that consists of hydrated bundles of protein filaments and membrane-bound mucin vesicles from numerous slime glands. When the slime exudate contacts seawater, the thread bundles unravel and the mucin vesicles swell and rupture. Little is known about the mechanisms of vesicle rupture in seawater and stabilization within the gland, although it is believed that the vesicle membrane is permeable to most ions except polyvalent anions. We hypothesized that the most abundant compounds within the slime gland exudate have a stabilizing effect on the mucin vesicles. To test this hypothesis, we measured the chemical composition of the fluid component of hagfish slime exudate and conducted functional assays with these solutes to test their ability to keep the vesicles in a condensed state. We found K + concentrations that were elevated relative to plasma, and Na + , Cl -and Ca 2+ concentrations that were considerably lower. Our analysis also revealed high levels of methylamines such as trimethylamine oxide (TMAO), betaine and dimethylglycine, which had a combined concentration of 388 mmol l -1 in the glandular fluid. In vitro rupture assays demonstrated that both TMAO and betaine had a significant effect on rupture, but neither was capable of completely abolishing mucin swelling and rupture, even at high concentrations. This suggests that some other mechanism such as the chemical microenvironment within gland mucous cells, or hydrostatic pressure is responsible for stabilization of the vesicles within the gland.

Defensive slime formation in Pacific hagfish requires Ca2+ and aquaporin mediated swelling of released mucin vesicles

“…We found that Pacific hagfish vesicles exposed to SSW exhibited two distinct categories of swelling behaviour, a pattern also found in Atlantic hagfish Myxine glutinosa (Herr et al, 2010). When the vesicle membrane was disrupted by Triton X-100, swelling behaviour was homogenized.…”

“…Slime exudate samples were collected from anaesthetized hagfish as described in Herr et al (Herr et al, 2010), and were stored in a stabilization buffer {SB; 0.9 mol l −1 sodium citrate + 0.1 mol l −1 PIPES buffer [piperazine-N,N′-bis(ethanesulfonic acid)], pH 6.7} (Downing et al, 1981;Fudge et al, 2003). Stabilized slime was filtered to separate mucin vesicles from thread skeins, and samples of isolated vesicles were quantified and standardized using the linear relationship between vesicle number and absorbance (350 nm) (Downing et al, 1981).…”

“…Mucin vesicle rupture assays followed the methods described in Herr et al (Herr et al, 2010). Drug/solution effects on mucin vesicles were quantified by calculating the percentage of mucin vesicles that ruptured when exposed to each solution for 120 s. Vesicle swelling rates were measured by recording videos of vesicle rupture at ~14 frames s , and analyzing the rate at which vesicle area increased, frame-by-frame as a percentage of the initial area.…”

Introducing a novel mechanism to control heart rate in the ancestral pacific hagfish

“…Beyond their basal position in vertebrate evolution, hagfishes are biologically intriguing because of their anoxia tolerance and their legendary ability to produce copious amounts of slime (Hansen and Sidell, 1983;Stecyk and Farrell, 2006;Cox et al, 2010;Herr et al, 2010). More recently, hagfish have been proposed as champions of CO 2 tolerance (Baker et al, 2015).…”

Spontaneous unraveling of hagfish slime thread skeins is mediated by a seawater-soluble protein adhesive

“…This unique process allows the tiny volume of exudate released from the glands to transform into about a liter of slime in a fraction of a second. Although the mechanisms underlying mucin vesicle rupture have been investigated to some extent (Luchtel et al, 1991;Herr et al, 2010), little is known about the mechanisms involved in skein unraveling. Winegard and Fudge (Winegard and Fudge, 2010) demonstrated that the presence of mucin vesicles as well as mixing forces are required for skein unraveling in the slime of the Atlantic hagfish (Myxine glutinosa).…”