Worm Breeder's Gazette 11(2): 91
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
C. elegans cuticles are impervious to metabolites, and biochemically relatively inactive. However, in Iymphatic filarial and other tissue dwelling nematodes, the cuticle plays a significant role in nutrition. For example, the cuticle of Brugia species is permeable to sugars, amino acids, nucleotide precursors and other metabolites. Surface radioiodinaton techniques have been used to define two sets of 'surface antigens' in many parasitic nematodes. The first is only solubilized by -mercaptoethanol and comprises (in the main) the cuticle collagens. These collagens are the structural basis of the hydroskeleton. The second set is detergent- or PBS-soluble and non- collagenous. The function of most of these antigens is unknown, but they may play a role in trans-cuticular uptake or modification of their immediate environment, the host, C. elegans is often used as a 'model' nematode, substituting for parasitic species which are difficult to handle. Encouraged by Sam Politz, I decided to take some of the standard techniques used for the analysis of parasitic nematode cuticular molecules and apply them to C. elegans. Analysis by reducing SDS-PAGE and autoradiography of whole surface-labelled adults boiled in -me reveals only four major labelled molecules. Three higher molecular weight species (35, 65 and 90-105kDa) are cuticle collagens: they are digested to completion by Clostridial collagenase. The pattern is very similar to the surface labelled collagens of Brugia filarial nematodes (see Selkirk et al [1989] Mol. Biochem. Parasitol. 32, 229-246). The remaining surface molecule has a molecular weight of 15kDa and incorporates about 80% of the label. While it is partially sensitive to collagenase digestion, it does not appear to be a 'proper' collagen: 1: Nematode collagens, from available evidence, are synthesized as 30kDa precursors. The 15kDa is unlikely to be a degradation fragment as the extractions are performed in the presence of a cocktail of protease inhibitors. 2: Collagenase digestion leaves an 11kDa fragment. Thus only 20% of the molecule can be Gly-X-Pro type repeats, and this region must reside next to one of the termini. 3: Homogenization of the worms in PBS alone solubilizes the 15kDa: it does not require -me or DTT to release it from the cuticle, unlike the collagens. The 15kDa is accompanied by a shadow at 16kDa which is also partially collagenase sensitive. It may represent a modified or partially reduced form (although boiling in 5% -me for 30 minutes doesn't remove it). Several parasitic species also have 14-16kDa surface molecules, and I am using specific reagents directed to these to check for homology.