Maturation of hagfish gland thread cells: Composition and characterization of intermediate filament polypeptides

Abstract

Previous studies with the hagfish, a primitive vertebrate, have shown that the gland thread cells (GTCs) each contain a single thread (approximately 60 cm long in average-sized cells) in the form of a concisely coiled cytoskeletal entity destined for export by holocrine secretion. The thread in relatively immature GTCs consists almost entirely of intermediate filaments (IFs) bundled in parallel alignment with far fewer microtubules (MTs). The three thread polypeptides described earlier (alpha, basic; beta, acidic; gamma, most acidic; each with a Mr of 63-64 kD) are now further evaluated with respect to in vitro assembly, cross-reactivity with IF polypeptides from higher vertebrates, and peptide sequence homology with known IF polypeptides. The overall results mainly suggest that the hagfish polypeptides are keratinlike substances but lamins or a new type of IF is not ruled out. However, cross-reactivity is weak with mammalian keratins; the 8-11-nm filaments formed from mixtures of alpha and gamma in vitro are generally linear rather than the curvilinear structures usually formed by keratin and nonkeratin IFs; and mixtures of alpha and beta tend to yield 9-12-nm granules or granular strings. Polypeptide analyses on GTCs segregated on the basis of maturational stage show a progressive increase in beta/gamma values which correlates with cell maturation, but the alpha/(beta + gamma) ratios remain near 1. Inasmuch as beta and gamma have many similar properties, the documented increase in the amount of the beta component in aging GTCs might in part be the result of a failure in a posttranslational modification system and may contribute to the ultrastructural changes that accompany thread maturation in preparation for holocrine secretion and subsequent modulation of the viscoelastic properties of mucus.

Deployment of hagfish slime thread skeins requires the transmission of mixing forcesviamucin strands

“…By focusing on mucin vesicles that adhered to the glass slide we could image the mucin vesicles and visualize their response to shear flow. Hagfish slime used in this experiment was collected, as detailed above, but placed into a 10°C stabilization solution (0.9 moll -1 sodium citrate, 0.1moll -1 PIPES) modified from Spitzer et al (Spitzer et al, 1988).…”

Genes coding for intermediate filament proteins closely related to the hagfish “thread keratins (TK)” α and γ also exist in lamprey, teleosts and amphibians

“…Hence, the evolutionary origin of vertebrate keratins still remains largely unclear because a clear evolutionary link to the IF proteins from lower chordates is still missing. We have now discovered that the thread forming keratins (thread keratins; TK) α and γ that several years ago were described and sequenced from the pacific hagfish Eptatretus stoutii [33][34][35][36][37][38] may fill this evolutionary gap between the keratins from vertebrates and lower chordates. Hagfish are members of a very ancient group of chordates that probably branched off from the chordate lineage even before the vertebrate column appeared in the tree of life.…”

Marine Keratins

“…11.3 The slimy hagfi sh (Courtesy: NOAA Fisheries) (Strahan 1959(Strahan , 1963Martini 1998 ;Crystall 2000 ;Fudge 2001 ). Slime glands that line both sides of the hagfi sh's body are responsible for production and ejecting of the slime exudate Spitzer et al 1984Spitzer et al , 1988Spitzer and Koch 1998 ). In the classical paper by John Ferry published in 1941, he wrote about overproduction of colorless and transparent slime by a hagfi sh in sea water during a few seconds.…”