Hagfish slime gland thread cells. II. Isolation and characterization of intermediate filament components associated with the thread.

Abstract

The slime glands of hagfish have two major cell types, gland thread cells (GTCs) and gland mucous cells (GMCs), both of which upon contact with water contribute to the formation of an abundant quantity of viscous mucus. In previous studies we reported a method for the isolation of GTCs and showed that each ellipsoidal thread cell normally contains a single tapered thread which is uniquely coiled into a space-saving conformation and occupies most of the cell volume . Subsequently, the developing thread was found to consist mainly of intermediate filaments (IFs) aligned in parallel not only to one another but also to a far fewer number of interspersed microtubules (see accompanying paper). In the present report, urea extracts of GTCs were purified and characterized to establish the properties of thread components. One major (a) and two minor (ß, y) components prepared by anion exchange chromatography were shown to have similar apparent molecular weights of 63,500 ± 500 daltons but different isoelectric pH values (a, 7.56 ; ß, 5.67 ; y, 5.31). Although the amino acid content of a differed significantly from ß and y, each of the three was highest in Gly, relatively high in Glx, Ser, Thr, Asx, Ala, Val, and Leu, and relatively low in Cys/2 and Trp. The amino acid compositions of ß and y were very similar, and only ß showed evidence of carbohydrate . The threonine content of the a component was higher than has been reported for IFs of different origin, and the high content of hydroxyamino acids (18, 19 residues per 100) in a, ß, and ,y has been approached only by several IF polypeptides from human or bovine epidermal keratins. Mixtures of the purified components formed 9-11-nm filaments in vitro . The results indicate that the hagfish thread cell is a rich source of IFs, which have a structure that facilitates formation of macrofibrils within the cell .The hagfishes are very primitive vertebrates, as judged by numerous morphological and physiological criteria (1), and have a notable ability to secrete large quantities ofmucus (2-7). The mucus-synthesizing capacity is attributable in part to three epidermal cell types which collectively approach 98% of total cells in middorsal-lateral regions of the integument (4). The mass ofthe mucus, however, and most ofthe mucous proteins are products of the numerous epidermally derived slime glands located along both ventro-lateral regions of the integument (1,5,6). Exclusive of the surrounding capsular material, each gland mainly contains gland mucous cells 670 (GMCs)' and gland thread cells (GTCs), both of which when expelled through the pore of the gland rupture upon contact with water and quickly interact to form viscous mucus (5, 6). We have previously described (5, 6) the potential usefulness of the hagfish as an experimental model for studying the biology of mucus and we have reported a procedure for isolation ofintact GTCs and vesicles from GMCs. The mature 'Abbreviations used in this paper: DT-r, dithiothreitol; GMC, gland mucous cell; GTC, gland thread cell; IF,...

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

“…While much is known about the structure, biochemistry and physical properties of the two slime components (Downing et al, 1981;Fernholm, 1981;Fudge et al, 2005;Fudge et al, 2009;Koch et al, 1991a;Koch et al, 1991b;Koch et al, 1994;Spitzer et al, 1984), relatively little is known about the mechanisms involved in the deployment of the slime. In most slimy secretions, deployment involves exocytosis of mucin granules from goblet cells and their subsequent hydration and swelling (Verdugo, 1991).…”

“…The slime, which can comprise 3-4% of the animal's total body mass, originates in epidermally derived slime glands that line the ventro-lateral sides of the animal (Downing et al, 1981;Fernholm, 1981;Fudge et al, 2005). The slime glands contain large quantities of two cell types that develop from undifferentiated cells lining the periphery of the slime gland (Fernholm, 1981;Spitzer et al, 1984). The first are ellipsoid-shaped cells known as gland thread cells (GTCs), which are entirely unique to hagfish (order Myxinoidei) (Newby, 1946).…”

“…1). The second type of cells are gland mucous cells (GMCs), which produce large numbers of membrane-bound mucin vesicles that contain mucin-like glycoproteins (Fernholm, 1981;Fudge et al, 2005;Leppi, 1968;Spitzer et al, 1984). Contraction of the musculature surrounding the slime glands causes the expulsion of these two slime constituents into the surrounding environment (Fernholm, 1981).…”

“…The first are ellipsoid-shaped cells known as gland thread cells (GTCs), which are entirely unique to hagfish (order Myxinoidei) (Newby, 1946). Within the GTC a highly condensed coil (or 'skein') of cytoskeletal elements known as 'intermediate filaments' is assembled in preparation for secretion (Downing et al, 1981;Fernholm, 1981;Newby, 1946;Spitzer et al, 1984) (Fig. 1).…”

Composition, morphology and mechanics of hagfish slime

“…The slime is formed when specialized slime glands eject coiled threads (or 'skeins') and mucin vesicles into seawater (Fig.·2). While considerable work has been done on the slime threads and their constituent proteins (Downing et al, , 1981bKoch et al, 1995Koch et al, , 1994Spitzer et al, 1984); very little is known about the mucin component or how the mucins and threads function together in whole slime.…”